Friday, December 21, 2012

Holiday Wishes

I already know that I will not be posting all next week - the holidays and visiting company will ensure that. I'll try for something on New Year's Eve, and then hit it again hard in January.

I hope everyone gets to spend some time with family and loved ones in the next few weeks - we all need it.

Epoxy Resin Art from Klari Reis

I ran across some examples of the epoxy art of Klari Reis.

These are petri dishes filled with colored epoxies, all biologically inspired. You can see more examples in this San Francisco Chronicle article and at her website. I love the way that the epoxies can resemble glass, my favorite medium.

Long-time readers will remember that I mentioned the art work of Momoko Sudo, also epoxy-resin based, just over 2 years ago.

Thursday, December 20, 2012

Copper Thieves Foiled by Plastic

Copper thieves have been active for the past 10 years or so, stealing copper pipes and tubing whenever and wherever they get a chance. Although copper prices peaked back in 2008, there is still enough opportunities for ne'er-do-wells to make a quick buck. Copper is fairly dense (the specific gravity is just under 9), so a little goes a long ways.

Contrast this with plastic tubing. The specific gravity is around 1, give or take (PVC is 1.4), so you need to steal 9 times as much just to have the same mass, and then the pricing is not so favorable either. Locally, scrap copper is going for about $3/lb, (~ 5€/kg), while scrap plastic is far less than a buck a pound. So, 1/9th the mass at say a fifth the price is not a good deal for even the most thick-headed of thieves looking to make a quick buck.

I mention all this as there was a local report yesterday that thieves had stolen copper tubing used to cool an outdoor skating rink here in St. Paul. The tubing will now be replaced, but with plastic tubing. And not just any plastic tubing, but crosslinked high density polyethylene (xHDPE). The crosslinking is great at toughening up the polymer, but worse yet, it makes it very difficult to recycle [*], meaning that even if it is stolen, no one will buy it.

It is important to understand this aspect of the polymer's chemistry, as the statement in the article, "The plastic-based composite material...has little to no scrap value..." could be taken as a broad-brushstroke about recycling plastics in general. Such a generalization would not be true, something I've written about in the past. Plastics can be cost effectively recycled and the demand for recyclable plastics is growing every year. Just not for xHDPE.

[*] This is why recycling tires is so difficult too - the crosslinking prevents the tires from being remelted.

Friday, December 14, 2012

Changes. Big Changes.

Today is my last day at Aspen Research.

This was not an easy decision as the 8 1/2 years I spent at Aspen were fantastic. The people are all great and are a huge part of reason that I stayed here so long here, far longer than any other position in my career. Please continue to use them for your analytical, compounding and technical consulting needs. The company is poised for fantastic growth in 2013 with the new 72 mm twin-screw extruder coming in and so it will be fun to watch all the big plans come true. It's just that I will be doing so from the outside.

The reasons for my move are personal and will be kept that way, but be assured that the separation is quite amicable on both sides. This means the big green Aspen Research logo on the homepage will be coming down [*], my contact information will be changing and a few other details on the pages will be adjusted.

Sadly for my long-suffering readers, I absolutely plan on continuing to blog, but the blog will be much more personally oriented, or closer to the point, the blog will be more clearly dissociated from my employer to the point of not mentioning them at all. This was not the case at present where an important function of the blog was to help sell the capabilities of Aspen. I expect it to take a few days to learn the ropes at the new place, so there might be a lack of posts for a while.

But I am very excited about what awaits me in my new position. It will be less focused on rheology. In fact I won't be running a rheometer at all, so you shouldn't expect too many posts about ketchup rheology. But don't worry, I still have a killer write-up (or at least, I think so!) on the rheology of a certain consumable liquid that most of us love. The report is in fact so good, that it will to be published in the Rheology Bulletin this January. I will let you know when that happens. (It's an open access publication from the Society of Rheology, so you will all be able to read it.)

So it's not goodbye to you readers, just my colleagues here at Aspen. Again, a wonderful bunch of pretty intelligent people whom I will miss.

[*] I still don't like it and no one here is really sure what it is. We are better chemists here than to think it is CH5. We know pentavalent molecules exist, but we seldom work with them. A former supervisor thought that it looked like a squashed cartoon turtle. Well, it certainly is unique, or as we would say here in Minnesota, "That's different".

Thursday, December 13, 2012

BPA and Estrogenic Activity and Lawsuits and...

I'm too busy to write much today, but I do want to point out that PlasticsNews has a nice, 3-part writeup on all the fuss over BPA (bisphenol A) and estrogen activity. This is a subject that I've discussed multiple times in the past, especially with regards to the horrible testing run by Plastipure and Certichem. It so bad that Eastman Chemical is suing them over the results.

For better or worse, I'm heavily quoted at the end of part 3.

Part 1
Part 2
Part 3

Tuesday, December 11, 2012

Is this Duck-ageddon?!?!

Rubber ducks are in the news a lot lately. And they are getting bigger with time.

First, back on December 4th, US Customs seized a shipment of 36,000 rubber ducks that recently arrived from China.
The reason? The duckies were too high in phthalate concentration. (Sorry, no more details than that. What phthalate? And how high is too high?) Since phthalates were being used, I suspect that in fact the duckies were not rubber duckies but were in fact made of vinyl.

Thank goodness these were your run of the mill, bathtub sized rubber ducks. The other ducks in the news were much larger. On December 5th, Oxfam America had a 15-foot inflated duck on the US Capital Mall.
The reason? It's a lame-duck session of Congress.

But the monster-sized duck that invaded England today is the stuff of nightmares (or another Ghostbusters movie). Set your eyes upon the 50-foot tall inflated duck that floated down the river Thames earlier today as a publicity effort for Facebook.
So we've gone from a 3-inch duck to a 15 foot duck overnight, and then to a 50-foot duck in a week. So is this the end? Is this the way that the Mayans predicted our doom? That the earth will be overrun with ever larger ducks?

Fortunately, that doesn't appear to be the case. The plotted data suggests that we are safe for a while:
100 days from now, the ducks will still be just 120 feet tall, not a serious threat to civilization. Even 1000 days out (3 years) the height will only be 180 feet. No, we're safe for a while. But just remember the next time you see a giant duck that you were warned.

Getting something good from Mechanochemistry

Mechanochemical reactions, especially thermomechanical chemical reactions are the bane of my career. Regardless of what I am working with, I know that every process step that a polymer is exposed to will do something to break it down. Even in reactive steps, such as polymerization, crosslinking or chain extending, there is some sort of shear used to ensure good mixing [*]. And that means degradation. The higher the temperature, the greater the degradation. The more the shear, the greater the degradation. The longer the process, the more the degradation.

But few aspects of science are ever pure evil, and that is even the case with mechanochemical reactions. While the value of these reactions have been known for some time (the Wikipedia article suggests that starting a fire with two sticks is the oldest such reaction), studying the fundamentals has always been challenging. Without knowing the fundamentals, monitoring something as simple as the degree of the reaction becomes a trial-and-error project.

That is all changing due to recent work that uses high energy X-rays to monitor the real-time, in situ kinetics of mechanochemical reactions in a ball mill. High energy x-rays from a synchrotron means that you take your reaction to the x-ray source and not the other way around, which further means that this isn't too practical as of yet for just any old lab to run (or even afford). But as technology advances, these techniques or similar ones will become more available.

The obvious appeal of these type of reactions is that they are solvent-free. By not having to add and then later remove solvent, the efficiency of the process is greatly improved.

[*] The only exception that I can think of is photochemistry of thin films and coatings. But even that isn't pristine and pure, as there is always some photodegradation occurring. Granted, it is overwhelmed by the polymerization and/or crosslinking, but photochemistry always has a degradation element to it. Always.

Monday, December 10, 2012

Shrink Wrapping a Cucumber: A Waste of Packaging?

Most cucumbers that I see in the grocery store are shrink-wrapped on a styrofoam [1] tray such as this:
But then there are the occasional odd ones, long and thin [2] that are sold separately with their own shrink-wrap, such as this:
For reasons that are unknown to me, some people (1, 2, 3) are upset about the shrink-wrapped cucumbers. I say unknown as there is far more packaging materials in the former picture than in the latter, but it doesn't matter much as the bigger issue is that there is any packaging around the cucumber. The reasoning is that after all, there is no packaging on other vegetables such as broccoli, tomatoes, avocados, why on a cucumber?

As is typical with packaging, the situation is complicated with many hidden elements - there is more than just the initial appearance. A new book, "Why Shrinkwrap a Cucumber?: The Complete Guide to Environmental Packaging" addresses many of these issues. With regards to the film on the gherkin-wannabe, the authors write
"...research shows that a wrapped cucumber lasts more than three times as long as an unwrapped one. It will also lose just 1.5 per cent of its weight through evaporation after 14 days, compared with 3.5 per cent in just three days for an exposed cucumber. A longer life... means less frequent deliveries, with all their consequent energy costs, and, crucially, less waste. Globally, we throw out as much as 50 per cent of food, often when it perishes. It typically goes to landfill and gives off methane, a greenhouse gas."
The most poignant commentary that I've ever read on the whole packaging issue however, is this:
"Some materials, such as glass, hardly seem to register on [consumer's] environmental radar, while others, particularly plastics, are never off it."
Rational? No. Reality? Yes. And so goes the battle.

[1] Yes, I know that I should be saying expanded polystyrene foam or EPS, as Styrofoam is actually the registered trademark of Dow for their EPS that is used in insulation or floral arrangements. But it is so much easier to say styrofoam and it communicates better too...

[2] For some reason, they seem to be called English hothouse cucumbers and are seedless. Compared to the regular cukes, they are pricey, but a wonderful addition to my wife's šaltas barščiai (the Lithuanian version of cold borscht, made with buttermilk...)

Wednesday, December 05, 2012

Criminals Beware! Plastic Money can Foil Your Plans

Forgive me for being "flushed" with excitement about this story, but it appears that the new plastic 20 dollar bills that the Canadian government recently introduced have an unexpected benefit in catching criminals: they float. Which means that they can't be disposed of as you would normal currency. Not that I am ever predisposed to quickly rid myself of currency or even thought about how to do it when the police are at the front door. So if you are like me (and I do hope you are), you wonder how do criminals try to dispose of bills quickly? Well, the Global Montreal website reports
"When Quebec UPAC officers arrived in Laval in October to and [sic] search the apartment of Gilles Vaillancourt [Editor's note: the former mayor], his cousin, who happens to own the premises, panicked. According to reports, as the police were about to enter the building, Ginette Vaillancourt tried to flush a large wad of cash down the toilet. Unfortunately, she didn't realize that these were the new polymer notes - so instead of disintegrating, the bills floated - and eventually blocked the toilet."
Canadian criminals beware! You now need to find other options for rapid disposal of money. My favorite choice would a 5-gallon/40-liter tank of boiling tetralin, but that's just me being a polymer guy. However, I'm glad that Canadians are realizing a benefit of the new bills, as it doesn't seem like they were otherwise well received by the public.

And lastly, I don't think that the old "paper" bills would have "disintegrated" as the report suggests, or at least not very quickly. The toilet would have still become plugged. If any Canadians are willing to perform the necessary tests, I would be happy to pass on the results, or if you have the cash but are unwilling to perform the tests, I would be happy to run the experiments. "What's that? Now that the experiments are done you want the cash back? Why no, you see what happened was..."

Monday, December 03, 2012

The Return of the "Perfect Polymer"

Oh no, not again. Not another PR blurb about a "perfect polymer". Please tell me I didn't just read this headline:
"In Search of the Perfect Polymer"
We've been through this just over a year ago, and here it comes again. As I said back then,
"We don't have "perfect metals", "perfect ceramics" or "perfect anything". All plastics have their strengths and weaknesses and there is not perfect plastic that can act as an adhesive and a high temperature aerospace material and a low temperature sealant and a structural material and be biodegradable in a landfill (but only once it knows that it is in the landfill) and costs next to nothing to buy and can be processed using an E-Z bake oven and...After all, that would be the perfect plastic in my mind and the mind of many others."

Are the alliterative properties of the phrase "Perfect Plastic" and "Perfect Polymer" really so attractive that all logic needs to be withheld? I can't think of any other reason that this phrase keeps popping up repeatedly.

Comments on "Cool, or Simple and Cheap..." by Whitesides

George Whitesides recently had an excellent editorial published (free access with registration) in the journal Lab on a Chip. The write-up is clearly aimed at academics, as it discusses a number of the non-technical issues associated with product development, issues that are often not well understood by academics looking to capitalize ideas and discoveries from their labs. He has a couple of really good zingers, such as
"The ratio of money spent to invent something, to make the invention into a prototype product, to develop the prototype to the point where it can be manufactured, and to manufacture and sell it at a large scale is, very qualitatively, 1 : 10 : 100 : 1000. We university folks—the inventors at the beginning of the path leading to products—are cheap dates."
To me there are a couple of competing ideas in this idea. First, the invention are indeed cheap, but at the same time very essential, as without the "Eureka!" invention stage, there are no follow up stages. The problem is that this stage is often overvalued and even society as a whole is somewhat to blame. We have built quite a legend around the image of the "lone inventor", the one creative person toiling along in the lab, creating a device so wonderful that "the world will beat a path to his door".

But secondly, what is not realized by most in society is the large investments noted above. More importantly, there is increasing risk aversion that comes with each step. As more and more capital is required to reach the next step, the money is invested by increasingly conservative investors. Making ethanol from the hybrid plant genius speciesific, var. wonderfulae seems like a great idea when oil futures are $100/barrel, but your billion dollar investment is a bust when the futures drop to $80. Are you really go to risk it? You might be better off starting small (meaning it won't be as cheap to make), and selling it to rich Hollywood people who can afford it. This would be a smaller investment but people are more willing to take a bigger risk on a small investment than the other way around.

George also wrote:
"You don’t really know you have solved the problem for someone until they like your solution so much they’re willing to pay you to use it. Writing a check is a very meaningful human interaction."
I love that beautiful phrase which is correct, but it only reaches half of the truth. Getting someone to pay you is essential, but you really don't have a successful business until they pay you twice. It is very easy to get a lot of hype and publicity and excitement at a product launch and have fantastic initial sales, but it isn't until someone has bought the product, used it and then buys it again that you can claim success. You may have fooled them once for the initial sale, but you can't fool them a second time.

Lastly, I strongly disagree with this idea:
"The manufacturers of a putative product...are usually agnostic about its paternity: problem ‘‘pull’’ or technology ‘‘push’’ are equally satisfactory."
"Pull" products are always easier to develop and sell because there is consumer demand - a market or potential market exists. "Push" products are far more challenging because the market doesn't exist and it is difficult to quantify its size. And that means that it is difficult to know if the payback for an investment will ever exist.

Take Post-It notes for instance. This was clear a technology "push". No one knew that they wanted them other then maybe in some very small, clearly limited applications. Who knew the market would be so big? No one. No one at all.

That is because "push" products are often revolutionary. "Pull" products are answering a documented demand, which means that both you and your competitors are working on solutions so the market will already be fractured. But a successful "push" product will blindside everyone - competitors and consumers alike, and that is a great spot to be. It can takes years for competitors to catch up, if ever (try and find Post-It notes made by a competitor of 3M). Just know that the "push" path is risky, really risky. There are plenty of "push" products that have failed because there really was no market for what was being pushed. And as I said above, a risky path is not one that has easy access to large investments. The end result is that all of this make the "push" approach even that much more challenging. So to say that manufacturers are agnostic on "push" vs. "pull"? No, no, no.

Friday, November 30, 2012

Spamming is not Marketing

There's something about this post at Plastics News that bugs me: "If American Moldmakers Marketed Like Chinese Moldmakers". It's about a LinkedIn group discussion in which a automotive parts supplier is looking for a moldmaker in Ohio, only to be inundated with offers from Chinese moldmakers. As you can gather from the title of her post, the author thinks Americans should be similarly aggressive in seeking out quotes.
"I wrote a response that I hope moldmakers in this country will take to heart. What I said was that if U.S. mold manufacturers would market their companies, expertise, and capabilities as much as the Chinese mold manufacturers, OEMs and Tier One suppliers wouldn't have to get in on a LinkedIn group to try and find a good moldmaker."
This is crazy. Any input I've ever received from Chinese moldmakers is something that is NOT seriously marketing "their companies, expertise, and capabilities". Let me show you an example. I get plenty of emails such as this one from my deleted messages file:
Dear Sir,

We would like to be Your Molds supplier in China.

We offer : Mold Design
Mold Manufacture
Rapid Prototype
Injection Molds
Die Casting Molds

Contact [company name deleted] today with any questions you may have regarding consumer electronics, home appliances and other industrial components.

Thanks & Best Regards.
[name deleted]
International Sales
This is spam, plain and simple. It is completely and absolutely useless to me as we do not do ANY injection molding here at Aspen Research. Lacking injection molding capabilities, I have no interest whatsoever in any of these offers. If my junk mail filter doesn't catch these emails, I delete them from my inbox without a second thought. Even if I was interested in mold design and moldmaking, I would still ignore this offer as it is not serious marketing, it is not serious selling nor is it any serious explanation of a company's abilities. Sure, you can admire the energy and drive behind someone looking under every possible rock for a lead (assuming that this email was actually sent under human direction and not by a bot), but no one can suggest with a straight face that this effort will pay off. And to use this as a model for others to emulate, and even worse, embrace it with the name of "marketing" is ridiculous.

Thursday, November 29, 2012

It's Biology, So The Laws of Chemistry Don't Apply, Right?

It is becoming increasingly clear that more and more chemical production in the future will be bio-based in one way or the other. Most likely there will be multiple "bio" steps involved, such as using microbes to ferment a grown crop into something useful. For example, we currently see this in ethanol production, in which corn, sugar cane or some other sugar source is grown, feed into a reactor inoculated with yeasts which then turn the sugar into ethanol. At this point, traditional chemical operations take over to concentrate the ethanol to the desired level of purity.

While this new alchemy may seem magical, the laws of chemistry still apply. In particular, mass balances. If your output is going to have carbon in it, you need carbon as an input. Yes, the microbes already have carbon as part of their biochemical makeup, but they aren't going to sacrifice it for your efforts. Look upon them as a catalyst - they help the reaction proceed, but are not consumed by it.

So when I read articles like this:"Biodegradable Plastic Manufactured From Air And Bacteria", you can understand my frustration. The article discusses an improved process for making polyhydroxy alkanoates (PHAs), and while it is true that the bacteria use air in the process, some of which ends up in the polymer output, PHAs have quite a bit of carbon in them. PHA's are class of polymers with this generic structure:
In all cases, n is 1 or more. [*] The R group can be hydrogen, methyl, ethyl...which means that there is at least 1 carbon for every oxygen atom.

While biological processes are outside of the traditional areas of chemistry and we may not be perfectly comfortable with them, mass balances still apply. And that means atomic mass balances as well. So where is all that carbon in the polymer going to come from? Not only does the article not specify it, but it doesn't even point out that it is required. No, just air and bacteria. It's magic! This is the equivalent to saying that my car runs on air. It most certainly does need air, but it also needs a gasoline as well.

While this may seem like I'm being overly academic, the source of the carbon will have a major impact on how "green" this process is overall. Does the carbon come as waste from some existing process? If so, great! Is it something that needs to be grown especially for this process? That's not so great, particularly is the yield of that feed crop aren't high.

But just as importantly, we need to recognize that the new bio-based chemistries that will be sold to us in the future still have to follow some basic principles, ones that we as technical people already know quite well. We just need to have the confidence to apply them to these knew technologies, even to ones with which we are uncomfortable.

[*] n = 0 is certainly possible and is actually known as polylactic acid (PLA). For reasons that are not very logical, it is not considered a PHA.

Wednesday, November 28, 2012

Cheap Junky Plastic? Think Again

I sadly admit that plastic items are commonly thought of as being cheap and junky. Disposable. Of no monetary value. While I don't agree with any of those descriptors [*], the last one is clearly wrong, as recyclers have been saying for some time that your waste plastic is valuable and they want it.

As is human nature, whenever something is of value, criminal activity will soon follow. And that is happening with waste plastic. I've written before of criminals stealing plastic, but that was virgin resin. Stealing waste plastic for recycling it is something entirely new, but the LA Times is reporting that 47 cases have been prosecuted in the last year. What is most surprising is that these cases are investigated by a 5-person task force which specializes in the crime. Police forces will have specialized task forces for gangs, prostitution, narcotics, and other concerns, but plastics? We have hit the big time.

The article quotes cites that $6 million in stolen plastics was recovered, but I wonder if they are running the numbers "correctly". The stolen plastics are normally not in a ground or pelletized state, so they priced lower than they will be later. Just as the monetary value of drug busts are based on "street value" - how much the drugs will be worth when they are sold for consumption - and not on how much the dealers paid each other, the monetary value of the recovered plastics should also be priced by their street value, or maybe more correctly, their "hopper value".

[*] Well, there are some exceptions

Tuesday, November 27, 2012

Should We Stay or Should We Go Now?

Here are two recent conflicting reports about manufacturing in the US. First, a "Good News" article about reshoring - the moving of manufacturing plants back to the US.
“It’s against the paradigm that people have accepted [about what is made in China]. But people are usually about a decade behind in their perceptions. Anything that’s got a significant amount of money on the bill for shipping to the US, you’ve got to consider making it in the US. The shipping that we’re saving, and the fact that we don’t have to carry so much inventory, frees up cash.”
My experience here at Aspen Research in helping companies reshore has been more from a concern about quality, but the point about carrying inventory on "floating warehouses" is also a real concern. Regardless, I always found it rewarding to know that I directly helped some Americans have jobs and that cheap labor is not the solution to a companies financial problems.

But then on the other hand is news that an American company is encouraging its suppliers to move their facilities out of the US in order to take advantage of cheap labor. That company: Boeing. Granted, they are suggesting Mexico rather than China as a travel destination, and while I realize that a company can do business wherever it wants, Boeing is more than a little indebted to US taxpayers. The company receives a good number of military and other government contracts to the tune of tens of billions of dollars. As expected, this news is not playing too well for many people with "...mostly negative responses to Boeing inviting suppliers to an event that will teach them how to outsource work to Mexico."

Such is the world we now live in.

P.S. I apologize to The Clash for blatantly ripping off the title of one of their songs. I hope their lawyers aren't too bothered. I certainly don't want London calling! (But you should if you don't already.)

Monday, November 26, 2012

Fantasy Images of the Great Garbage Patch

When people hear of the Great Garbage Patch(es), the mental image they have is something like this:

when the reality is much more like this:

I've mentioned before the words of Andrew Blackwell that the afflicted area of the ocean is more of a garbage galaxy than anything else - mostly empty space. This is a sadly ironic situation in that a very concentrated patch would be easy to capture and remove, while the reality is that the concentration of garbage is so low that removing it from the ocean economically is far beyond our present technology.

But even with this reality, some people fantasize in the other direction about the garbage patch being something so big, so grandiose that ... well, it's best if I let the pictures speak for themselves:

Wow. Wow. Wow. What a pile of garbage. Literally and figuratively. This is the first monthly installment in an ongoing series.
"Created by Joe Harris and Martín Morazzo, the book follows the young heir to an oil fortune who seeks to cut his own path by conquering the monstrous gyre, which in Great Pacific is represented as an actual island of refuse twice the size of Texas, and founding his own sovereign nation. Unfortunately for him, what awaits the ambitious young billionaire on the Great Pacific Garbage Patch is much more dangerous than just trash."

If the gyres were anything like that, you would be able to see it from satellite pictures and Google Maps, like in this drawing:
and yet, as (the Scripps Institute notes), nothing of the patches can be seen from the air or space.

Sadly, others have had even more ludicrous thoughts of the garbage being used as living space. Not for a conquering hero is in the graphic novel, but as an actual community complete with high rises, a modern day Venice:

Looks lovely, doesn't it. Until the first tropical storm or typhoon comes along.

Friday, November 16, 2012

Is Ketchup Really Thixotropic? And Does it Matter?

It is becoming common knowledge that ketchup is "thixotropic". More and more people are beginning to talk about it, which means that this is a good time to put the idea to the test. In addition, the Grand CENtral blog is sponsoring a #FoodChem carnival this week, so this is my entry.

What most people have observed is that ketchup is a thick fluid, and in glass bottles in particular, very difficult to get flowing. However, once the flow starts, it flows quite readily, usually leading to too much ketchup ending up on your burger and fries. The question is how do rheologists describe this behavior and is this sudden onset of flow really due to "thixotropy"?

Before we can get into that discussion, there are a few terms that I will define as they all play a role in the rheology of ketchup. But before I can get to those terms, I'm going to discuss what I mean by shear and shear rate. While there are mathematical definitions, I'll skip them for today and just describe these ideas qualitatively.

For any liquid that is flowing, the velocity of the liquid that is right up against the wall is zero [1], while the velocity of the fluid elsewhere is not. This means that the fluid is being sheared. The faster the fluid is moving, the higher the shear rate is, but also, the smaller the gap in which the fluid is moving, the higher the shear rate.

For a run of the mill liquid such as water, the viscosity of it is constant regardless of the shear rate. That makes it a Newtonian liquid. If the viscosity is not constant, then it is a non-Newtonian liquid. Non-Newtonian behavior comes in many flavors, but I'm only to going to discuss three options today.

The first is "shear-thinning". A shear-thinning liquid is one where the viscosity decreases as the shear rate increases.

Second is the le mot du jour, thixotropy, which is similar to shear-thinning but also decidedly different. At a constant shear rate, a thixotropic material will show a decrease in viscosity over time.

Last is "yield stress". This is the idea that certain materials need a minimal amount of force applied to them in order for flow to start. If less force is applied nothing happens.

It is possible for a non-Newtonian fluid to exhibit any combination of these characteristics. Ketchup in fact shows all three behaviors. But enough with the academic terms, let's get on with the show.

Like most places of work with a refrigerator in the cafeteria, there is an old bottle of ketchup sitting in it, bought some time ago for the company picnic that gets used every once in a while to spice up a tater-tot hot dish (a.k.a. tater-tot casserole if you never learned to speak Minnesotan). This morning I grabbed the bottle, got out the big 45 mm plates for the rheometer [2], squirted a portion out and took some data. (So does this qualify for #RealTimeChem too?)

The plot below shows the viscosity of the ketchup as the shear rate increases.
It drops, so you can say ketchup is shear thinning. This an important property for ketchup that is in squeeze bottles, as it makes it easier to dispense through the narrow opening - a region of high shear.

The next plot shows what happens when I subjected the ketchup to a constant shear rate.
Over time, the viscosity drops, so yes, ketchup is thixotropic.

I would have loved to have taken the data for this last plot, but I have the wrong type of rheometer for it [3], so I am borrowing a plot from TA Instruments.
This plot shows that ketchup also has a yield stress. A certain amount of force is needed to get it moving in the first place.

So the question is this: when you get a big glug of ketchup shooting out of the glass bottle, is it due to the shear-thinning, the thixotropy or the yield stress?

Despite the trendiness of the term, the thixotropy is the easiest candidate to eliminate. Look at the small drop in viscosity. It's just not significant. And while the shear-thinning plots shows a large drop in viscosity, you need high shear rates to achieve that and you won't find that in the big part of the bottle - it's just too big a gap. So that leaves yield stress as the winner. Look at the plot of yield stress again. The viscosity suddenly drops by a factor of 1000 just by reaching a critical stress! That's why you suddenly get a massive amount all at once - you finally reached the yield stress.

While ketchup is indeed thixotropic and I am glad that more and more people are becoming familiar with rheology, that phenomenon is the least of your concerns in getting the ketchup out of the bottle.

[1] This is a very fundamental concept in fluid mechanics known as the no-slip boundary condition.

[2] This stuff is a pretty soft gel, so by using larger diameter plates and their associated larger torque, I am generating a larger signal for the instrument to pick up. Also, the plates were coated with 600 grit sandpaper in order to minimize slip at their surface.

[3] My rheometer subjects the sample to a strain (deformation) and measures the stress (force). The type of instrument I need for a yield-stress plot is one that subjects the sample to a stress and measures the strain. Santa, I've been a good little rheologist this year. Can I please have a controlled-stress rheometer for Christmas?

Monday, November 12, 2012

The Difficult of Getting Paid

I think I can probably state that ALL of my readers like to get paid. Even if someone out there is independently wealthy, they still like to get paid when they are owed something (you would certainly never get be independently wealthy if you didn't follow that practice). In most cases, getting paid for an owed debt is fairly simple as there are numerous laws and courts to help..."induce"...the transfer of money, but if the matter involves multiple countries, it can get to be more challenging. Or should I say, far more challenging.

That is what Dow Chemical is finding out. It has been waiting and waiting and waiting for a $2+ billion dollar settlement from the Kuwaiti state company Petrolchemical Industries Company (PIC). This all began back in 2008 when Dow and PIC started a joint venture to be called K-Dow. Dow was contributing assets and PIC was contributing cash for them. PIC was of course planning on using oil revenues to fund their side of the venture, but when the price of oil dropped, the Kuwaitis pulled out. This left Dow holding the bag. That in itself was bad enough, but Dow had already counted its chickens before they were hatched and had put an offer in to buy Rohm & Haas with the money that the Kuwaitis had promised them. One way or the other, Dow was able to complete the deal with Rohm & Haas but still sought compensation from PIC. They won a settlement of over $2 billion, and as of the beginning of this year, were still expecting payment shortly.

Flash forward to now and they are still waiting. So now they are looking at grabbing assets where ever they can find them. Wow. What a mess. What an horrible mess. It's not like grabbing assets is going to be the end of this, as that will lead to still more legal battles around the world. The only ones happy with all this would be the law firms as it means more work for them. Given that since this all began, oil prices have climbed to very high levels for a long period of time, you would have thought that PIC would have had no problem in setting aside a measly $2 billion, but that appears to not be the case.

Friday, November 09, 2012

Friday Fun: Easy to Make Self-Folding Polymer Objects

Here's a fun and simple example of a self-folding polymer, so simple that you can do it at home. Researchers at North Carolina State inkjet printed black lines onto polystyrene (PS) sheets and then exposed them to an IR lamp. The black preferentially absorbed the IR and caused localized heating in the PS leading to localized shrinkage on one side of the sheet. The result of these asymmetric stresses was buckling/folding of the sheet so that a 3-D object could be formed.

Here's several examples of the folding, with the original flat sheet on the left and the resulting folded product on the right:
You can see that by being creative and inking one side or the other that both peaks and valleys could be formed. Better yet, there is a video link at the bottom of the page.

I can see this being an amusing toy for children; further practical applications escape me for the moment, but won't for long. This is too simple a technique to ignore. Well done.

Thursday, November 08, 2012

Plastic Pollution in the Great Lakes - and a Surprising Critic of the Report

While I've always been concerned about plastic pollution in the oceans, commonly wrapped up as the 5 Gyres matter, living near the North American Pole of Inaccessibility has made that pollution a distance concern (pun intended). Any of the plastic bags I see floating down the street will never make it to the ocean.

But when reports came out that the Great Lakes were similarly afflicted with plastic pollution, well, that struck closer to home (again, pun intended). Lake Superior is a beautiful lake less than 3 hours from here, one that I have visited countless times. Lake Michigan is a little farther, but one that I still see with great regularity. The waters are clear, cold and beautiful and need to stay that way.

What is most concerning - and surprising - is that the lakes were reported to have an even higher concentration of pollution than the oceans do. I say surprising, for a couple of reasons. First, the lakes are continually "flushed" as rainwater runs into and out of them, whereas the oceans are at the bottom of the hill. (This is the same reason that oceans are salty and the lakes are not. The salt in the lakes is carried into the oceans and accumulates there.) But secondly, the oceans have well established flow patterns, including gyres, and these gyres are what are necessary for the concentration of pollutants in the ocean. Without them, the pollution would be concentrated near their source - the shorelines. I have yet to see any documentation that the Great Lakes have gyres.

But what really struck me as odd was the criticism that the report received after it was published. Or more accurately, who it was that was criticizing the report: the 5 Gyres Organization. The very same group that supported the research. The criticism can be found here (scroll down to the 3rd comment from Stiv Wilson). In part, he said:
"I took these two samples on the 5 Gyres/Fredonia Great Lakes expedition that yielded so many pieces- but to say this constitutes a higher density than the ocean is false. The average ocean sample has about a third of the individual fragments as the two samples from Lake Erie. But they are way way way smaller than what you find in the ocean, not just smaller than 5mm but smaller than .5mm, so by weight, the concentrations in the Great Lakes are a fraction of what’s in the ocean..."

Stiv and I have crossed paths before (be sure to read the exchange in the comments) so his further comments at the Ecowatch page that " Heck, I’m public enemy number one with the plastics industry, but I work on facts, and this article pushes the bounds of reality and journalistic due diligence." self-referentially pushes the bounds of reality and journalistic due diligence.

What's going on? My guess is that Stiv is concerned that this report would divert focus from the oceans - his predetermined cause - to the Great Lakes. But if that is what the numbers ultimately show, well, someone who "works on facts" will just have to accept that.

Tuesday, November 06, 2012

BPA - The cost of junk science and overhype

I've never been a big fan of the blog "Hands Off My Plastic Stuff", a blog largely if not entirely devoted to the BPA battle, and in this case, taking the position that banning it is wrong. I have no idea who the author is, but he/she admits to a lack of technical training and it shows at time [*]. Parts of the posts often ends up being as emotional as the opponents he/she faces. That said, two recent posts were very good and deserve a larger audience.

The first discusses a recent article pointing out the dangers of junk science - how government resources are diverted from non-junk science to respond to public concerns.

The second is on the UCSD researcher disavowing that university's recent PR blurb about how the real threat from BPA may be in the metabolized products. I written and complained loudly many times in the past of various university PR departments overstating research results, so I am glad to see others joining the efforts.

[*] Statements such as "BPA is short for bisphenol A, which didn’t mean anything to me until I started to look into this topic. Turns out it’s a polycarbonate (I’m still lost at this point, don’t worry) which means it’s a type of plastic" drive me up the wall. For the gazillionth time, BPA is a monomer used to make plastics, such as polycarbonate. Copolymerize it with phosgene and you will have the stuff of CD's and waterbottles. But by itself, it is a white powder.

Monday, November 05, 2012

Job Titles and Business Cards

Over the years, I've had numerous job titles. I won't go into the details, but most large corporations have a whole range of them, often with subtle little nuances that are not apparent to outsiders but mean a whole lot to insiders as to where one stands on the corporate totem pole.

When I first joined Aspen Research, I was told that I could put whatever I wanted on my business card for a job title as we were just too small to care. So I went big: "Principal Polymer Scientist" or some such nonsense. But what I realized in handing the cards out to (potential) clients, was that they were not interested in the "Principal" but in the "Polymer Scientist" aspect.

So when it was time for a new box of cards, I took a chance and went to the opposite extreme: "Polymer Scientist". Nothing more. No "Advanced", "Senior", "Specialist", "Fellow" or anything else.
The response has been even better. "Polymer Scientist. That's just what we're looking for." In this case, stripping the title to the basics does a better a job of communicating.

I realize that the type of person I am generally handing this out to is different than in the past. This card is going to potential clients, whereas in my previous employments, I was usually handing it out to suppliers. I still keep wondering if there is something better to put as a title, but regardless, this has taught me to think about what I put on my cards and not just go for the most impressive title I can lay claim to. What I put there says something about me and it just may not be what I think it is.

Friday, November 02, 2012

Publishing Industrial Research

The topic came up in another forum yesterday about how research articles published by industrial people either "reflect[s] work that is no longer mission critical to the company" or is"well timed [and] heavily scrutinized for IP purposes".

While that is certainly true in some cases (very few I suspect), there are plenty of exceptions. Before I address those criticisms, let me summarize what I have observed about industrial research and its suitability for publication.

First off, even if IP protection and trade secrets and keeping a competitive advantage were overlooked, most of industrial research is completely unsuitable for publication. Some of it is only relevant to the company doing the research, such as "What are the best conditions to run that modified reflux unit off the SW side of the plant when we are making product X-2134?" Does anybody in the world care at all? A competitor would hardly even care since they have an entirely different process or at least a different refluxer for making their version of X-2134.

In other cases, the research is very much oriented towards an end use and not towards advancing science. "What combination of comonomers will give our tape the best adhesion to 316 SSL?" A competitor would certainly want to know as they could then quickly duplicate it, but would publishing this suddenly make Dr. Rhe Surch at Stanvard University change direction in his research? And could you even get this published in a well-respected journal?

A tremendous amount of industrial research is done using designed experiments, a statistical procedure that is great when you have a large number of variables to explore. You are able to change multiple variables at once and still "understand" the results. I say "understand" as the output is a polynomial equation, the form of which is chosen a priori instead of being theoretically derived. As a result, the output does little to advance science since it is only useful in the operating window that was explored. I don't recall ever seeing a DOE published in JACS and doubt a reviewer would ever let it pass. (Well, then again...)

So given this, is it worth the effort to publish? You would either have to add additional experiments to attempt to make the research "science-worthy" or you could publish in a lesser journal. And what does it gain you? Companies reward their workers for developing new products that save money, generate sales,...Publications do none of this, so those industrial researchers who do publish usually do it because it is of personal interest, not of corporate interests.

There are exceptions, and my employer is one of them. While we do very little in actual publications, we do give a number of talks at technical conferences about what research we have done for clients, and we use that as a means to promote sales. Of course, the talks are heavily whitewashed so that we don't reveal any confidential information. We can get away with the lack of details in a talk, but I can't imagine any journals that would accept the equivalent lack of details in a publication.

So now to the criticisms from yesterday. "No longer mission critical"? It depends on how you define mission critical. If you are on mission critical research, you are far more concerned about getting it done than taking the time to write an article. Once the research is done, then there might be time to sit around, reflect and write something up, but in the heat of the battle when big bucks are at stake (and yes, mission critical means mission critical), there is no time for publications.

"Well-timed"? I'm not even sure what that means in this case.

"Heavily scrutinized for IP purposes"? Of course, but even academic research has these concerns given that the Bayh-Dole Act allows Universities to patent the results of their research.

I agree with what I think is the general feeling about published industrial research - it just isn't as exciting as academic research. But this cuts both ways, and the best example is to read the patent literature. Patents by industrial firms can be extremely exciting and revealing, but patents written by academics are some of the worst ones ever published. They are heavily oriented along the lines of a research article (I've read some that were almost verbatim their published research) and they show very little effort or creativity in broadening the claims.

Scientific publications are still devoted to their original mission - to publish scientific results so that other researchers can use them to advance their research and then publish their results so that other researchers...Industrial research is far more applied and so even if it wanted to be part of this cycle, it really wouldn't be a great fit. To complain about whatever research is made available is really missing the point and showing a lack of understanding about industrial research.

Wednesday, October 31, 2012

Shaken, not Stirred

Given the free access from Springer until the end of November for Rheologica Acta [*], I've been scanning some of the journals to see if there are any interesting articles. One article caught my eye in particular, but I was disappointed after reading the article. First, the research and the results:

The authors dissolved various molecular weights of polyethylene oxide (PEO) in water, either by shaking the containers or by stirring them, in both cases over a period of 4 days. Surprise, surprise, the shaken samples had a higher viscosity than the stirred ones due to the mechanical breakdown in molecular weight of the more aggressive process. This only happened with higher molecular weight materials with 35,000 g/mole being the cut off.

As I said, I was pretty disappointed with the article. This is one of those cases where the results were pretty much expected even if they had never been published. Much like those data on the nonlinear rheology of polystyrene that I posted here a couple of weeks ago. It might not be a completely worthless effort to publish them somewhere but a 12-page article is overkill.

But it is pretty apparent that the referees never looked at the article. Consider this blooper on page 1 of the article:
"The specific chemical structure of PEO, HO − [(CH2)n − O]x −H with n = 2, confers to this polymer very unusual interactions with water. Indeed, while poly(methylene oxide) with n = 1 and poly(butylenes oxide) with n = 3 are both hydrophobic and insoluble in water..."
Psst! For n = 3, these would be poly(PROPYL-ene oxides). Oh brother...Thankfully, the quality of the other articles that I am reading is higher.

[*] You are taking advantage of this access, right? It also includes Colloid and Polymer Science,Polymer Bulletin, and Polymer Science Series A

Monday, October 29, 2012

More Open Access articles in Polymers and Rheology

Here's a couple of rather significant chances to access the literature, but these are limited time offers, so act fast.

First up, the AIP is offering access to their publications for the time period 1999 to present. Unfortunately, the access is only until October 31, so move fast. The complete list of journal titles is available here. There are a good number of rheology and polymers articles in Applied Physics Letters and others - you just have to search around a little bit.

Springer is being a quite bit more generous with not only the time range of article available, but also the access window. It seems that for select journals, the entire archive is available until November 30. The list of available journal titles is here. Some of the more relevant journals for readers of this blog are So get reading! [*] This journal goes back to 1907 when it was originally published in German under the name Zeitschift fuer Chemie und Industrie der Kolloid. Gradually over the decades it not only started publishing articles in English, but also even articles about polymers, becoming Kolloid Zeitschrift, Zeitschrift fuer Polymere somewhere along the line, a journal title that I can still type in my sleep as "Kolloid-Z. u. Z. Polymere", having done it endless times in my dissertation.

Friday, October 26, 2012

Pronouncing and Mispronouncing "Thixotropy"

O.k., I get it. People love to use the word "thixotropy" whenever they can. It's a very unusual word and can sound rather impressive. It's pretty much impossible to figure out the meaning just from the word itself and even from the context in most cases. If you use it incorrectly, I will track you down and correct it, but what I cannot do is make sure that at every watercooler conversation around the world the term is pronounced correctly. So let me do what I can to help. Merriam-Webster has the proper pronunciation while Forvo does not

That's right, just like "kilometer" is not "kilo-meter" but "ki-lom-meter", "thixotrpy" is not "thixo-tropy" but "thix-ot-tropy". You've been warned.

Thursday, October 25, 2012

Chem Coach Carnival Entry

SeeArrOh is organizing a Chem Coach Carnival this week through his "Just Like Cooking" Blog. Here's my rundown on his questions

Your current job
The company that I work for is quite small, so short and sweet, I'm the polymer guy. Polymer chemist, polymer physicist, polymer engineer and rheologist. I get to do it all. Even if I'm not formally assigned to a project, I can still be brought in as a consultant to other projects.

What you do in a standard "work day"
While it is quite common for people to say that there no standard work day where they are employed, this place, with its emphasis on contract R & D guarantees that no day is like any other. Over the years I've worked for clients in flooring, construction, telecommunications, automotive, sports and leisure, oil production, medical devices, aerospace, food, packaging and biotechnology. There aren't too many industries that I haven't done something in. With that variety of clients, there is an equivalent variety in my work days. Sometimes I'm running rheology tests, sometimes I'm formulating polymers, sometimes I'm prepping to be an expert witness, sometimes I'm reading papers or patents...

What kind of schooling / training / experience helped you get there?
Finally an easy question with a formulaic answer. All my education (B.S, M.S. and Ph. D.) was in chemical engineering, but I also took as much chemistry as I could fit in too. As my colleagues would say, I am a "Big C" chemical engineer, while most of them are "Big E" chemical engineers. What I find most interesting is that, while there certainly are times when my graduate education is needed, the variety of problems I face forces me to rely my undergraduate education far more often than I ever imagined. In any new situation, I always reduce the problem to the fundamental science principles and not get hung up on the views and jargon of the industry. Those principles were learned as an undergrad.

How does chemistry inform your work?
Even when I am working on the physical side of a polymer problem, I am always thinking of the chemical side. For instance, the chemistry of pendant groups hanging off the polymer backbone greatly impacts the properties of it such as
  • the glass transition temperature
  • how the polymer interacts with fillers and other additives
  • how temperature, UV light, solvents and other environmental conditions will affect the polymer
Also, being able to work intelligently with reactive polymers such as urethanes, epoxies or thermosets requires knowledge of the chemistry that is occurring. (I love it when clients say they tried a urethane, it didn't work and so we shouldn't waste our time trying a urethane.)

Finally, a unique, interesting, or funny anecdote about your career
For my first job, I worked in the R & D section of a large company. The company wanted their R & D people to have some practical experience so a group of us were located at a polypropylene film plant in Terre Haute, Indiana. I had just gotten my Ph.D., and my supervisor was also a Ph.D., but no one else at the plant was.

The plant had a number of large ovens that heated the film so it could be stretch thin. These ovens also had access points where you could go in the oven. One day, I went into the oven to show my supervisor something and the door shut behind us. I kicked and kicked and could't get the door open. After a few seconds, one of the smart-aleck engineers opened the door from the outside and loudly yelled so everyone else could hear, "How many Ph.D.'s does it take to lock themselves in the oven???"

Wednesday, October 24, 2012

Different Chemistries for a Different World

With each passing day, more and more progress is being made in bio-sourcing polymers that have been traditionally based on petroleum products. While the end polymer will have the same generic name (polyethylene, polypropylene,...) the chemistry involved in getting to the starting monomer will be completely foreign to a traditionally trained chemist or chemical engineer. Currently, ethylene, propylene, butadiene,... are made from hydrocarbon feedstocks that are "cracked', dehydrogenated or otherwise processed to form the desired product. It's simply a matter of selectively removing a few hydrogen atoms from each molecule.

Preparing these same monomers from bio-based feedstocks however, is an entirely different matter. For starters, the feedstocks are not just C & H hydrocarbons, but instead have oxygen in them, which one way or another has to be removed. This illustration shows the differences in the two approaches:
Source: Hydrocarbon Processing, February 2012, p. 19

Ethylene for instance, is made by the dehydration of ethanol, while PX (para-xylene, which ends up becoming p-terephthalic acid, a monomer used to make PET) starts out from isobutanol, which like ethanol, is dehydrated to become isobutylene, but then is dimerized to become isooctene and then cyclinized (?) to become PX. That's quite a bit different than the standard route of physically separating the PX from the BTX (benzene-toluene-xylene) mix. Or who would think that propylene would be made from plant oils? The fatty acids are removed to leave glycerin, which is then reduced to the monomer.

Once the monomers are made, they can be polymerized as before. This is significant as it means not only that the capital investments already made in polymerization plants will endure, but also that the final products will be virtually indistinguishable from their petroleum-base equivalents. While long-time readers know that I loathe calling anything a drop-in replacement, this might be one of the few exceptions I would consider using the term with. The only difference would be that the bio-based polymers would have a few extra neutrons - biobased feedstocks have a small but measurable amount of carbon-14, whereas petroleum based feedstocks have long ago lost all traces of this radioactive component. This difference ensures that it will be difficult for someone to greenwash a petroleum-based polymer and sell it as bio-based.

This is the future of commodity chemistry. It is very different from that which our forefathers had and it will replace the knowledge that they passed on to us.

Monday, October 22, 2012

White Isn't Always White

Today's post isn't about polymers per se but about additives for polymers. With the exceptions of pigments and dyes, the manufacturers of most additives strive for a lack of color in the their products, with Nirvana being "water white". This has always struck me as a strange term, and newcomers to the industry need to have it explained to them the first time they hear it, but "water white" does not refer in any way, shape or form to "white", but rather to the "water" aspect - they are as clear as water.

The term is most commonly used for petroleum-based products, and often the "water" is dropped so that we are left with such liquids as "white oils", "white mineral oils" and "white gas". There are many hydrocarbon-based resins (polymerized olefinic materials of low molecular weight, often used as tackifiers) that are sold as "water white", but the term is even used to sell modified rosin compounds that are nearly colorless when molten.

I'm not having any luck finding the origin of the term, but given that it came from the petroleum industry that is used to working with liquids that are as black as anything you can find, I can imagine that liquids that are purified as much as possible could be "white". Any other ideas?

Friday, October 19, 2012

Linear and Non-Linear Rheology - Doing it Wrong and Right

Today's post features original rheology data. I can't really call it origianl research, as it is something that is not surprising in the least, but at the same time too, it is something that I have never seen formally documented. It's been nagging at me for a while, so I thought I would give it a run on some polystyrene sitting around the lab and see what happens.

Whenever I get a new sample in for rheological characterization, the first screen that I run is a strain sweep, such as you see here.
At low strains, the storage modulus, G', stays constant, but at higher strains, G' begins to drop. (Need a primer on G'? You can get it right here.) The flat section is the linear deformation region and is very important to many rheological measurements. Typically, once a sample is put into the rheometer, you expose it to multiple measurements (various strains or strain rates and all at one or more temperatures). But at the same time, polymers have a "memory" of how they have been previously deformed. They do not relax instantaneously, but can need seconds, minutes, hours or even in extreme cases, days and years to relax. So how can we resolve this dilemma of a polymer that remembers with multiple measurements on the same sample? By working in the linear region. In the linear region, the deformations are small enough that what happens in one measurement will not influence what occurs in the next. So by looking at the plot above, you can see that for this particular polymer, a strain of about 50% or less will still be in the linear region.

Rheometers, like pretty much any analytical equipment these days, are computer controlled. The plot above was made using the strain sweep program which starts at the lowest strain measurements and increases the strain over time automatically. A sweep like this is done in about 2 minutes depending on how much the strain is increased between measurements.

The problem with the output above is that it is wrong. Or at least, the nonlinear region is wrong. Why? For the reasons I gave above. Once the strains are high enough to result in nonlinear deformations, then the sample still has memory of that deformation while the next measurement is being started.

The plot below shows the same data as before, but also shows additional data in the nonlinear region.
Each of those samples was taken by putting a new sample into the rheometer for each measurement. (A big hassle, let me tell you.) As expected, there is a difference. With the continuous sweep, the deformed polymer is already shear-thinning does not recover from that state before the next measurement begins. Hence the next measurements show more shear-thinning than actually is present.

One last plot. This is the same as before, but has a third set of data that is a combination of the two measurement options.
It was made with a single sample, but each measurement was made 60 seconds after the previous one. At the lower strains, G' tracks what happened with the individual samples, but at the highest strains, it begins to drop below that curve, just as the continuous sweep data does. This says to me that the 60 second interval is enough time for the polymer to relax from small nonlinear deformations, but not the large ones.

All in all, this is what I expected to see, but as I said initially, I've never seen these actual plots - just an admonition to work in the linear region. If you ever wanted proof for that guidance, now you have it. That said, LAOS (Large Amplitude Oscillatory Spectroscopy) is a very active research area that is in fact making measurements in the nonlinear region. From what I've read of it, I'm not even sure that the single point measurements that I made are that correct either.

Thursday, October 18, 2012

3 Views on 3-D Printing

  1. The cover story for the October 2012 issue of Design News is "3D Printing Takes Off".
  2. Plastic News is reporting that the future of 3D printing "is not so rosy."
  3. Coincidentally, print versions of both items 1 and 2 were in my mailbox this morning.
  4. So which is it? Probably somewhere in the middle. 3D-printing will continue to grow and impact us in new ways (good and bad), but it's not as if my mom is going to have a printer anytime soon.

Wednesday, October 17, 2012

Overlooking the Obvious: Self-Healing PVOH Hydrogels

While polymer research is typically done with ever more advanced technology, every once in a while I run across something amazingly simple that makes me wonder how many other what other simplicities are so readily available.

This new research (free access for a very short time period) is about a rather mundane subject - polyvinyl alcohol (PVOH) [1] hydrogels. I say mundane as PVOH hydrogels are more commonly known to school children as "slime" - the result of mixing white glue with borax. The borax crosslinks the chains using their pendant alcohol groups.

The researchers took a slightly different approach to making their gels, one that did not require the addition of any crosslinking agent. They made a very concentrated (35 wt%) PVOH hydrogel by first dispersing it in 95 oC water [2], froze it for an hour, and then warmed it to room temperature, a process that is well-known for forming crystallites that serve as crosslinks for the gel. What is surprising is that these very stiff gels could self-heal upon being cut, but only under certain circumstances. The plot below shows the stress-strain curves for the original material and also how the repaired gels improve their properties over time.
If you've ever played with slime, you are probably wondering what all the fuss is about. Slime will self-repair very quickly as it is not only very soft, but also crosslinks are rather fluid and prone to breaking and reforming. Those are not characteristics of these gels however, as not only are they stiffer, but the crystallites are pretty well frozen into place. What is surprising about these gels is that in fact, higher concentrations of PVOH are necessary for the self-repair features to be present as this figure shows.
What is not as surprising is that the separation time affects the ability to self-repair. The results above were for gels that were rejoined after 5 seconds of separation, but as the plot below shows, leaving the parts separated for an hour reduces the gel's strength by about 20%, and leaving them apart for a day pretty much eliminates all the self-repair characteristics.
This strongly suggests that the surface of the gels is rearranging itself over time, a rearrangement that then prevents the necessary interdiffusion of the PVOH chains. A similar trend, also not surprising is seen as the number of freeze/thaw cycles increases, steps that are well known for increasing the crystallinity of the hydrogels.
Gels with increase crystallinity will also have a harder time interdiffusing their chains after being cut.

Being that these gels are made only from PVOH and water - no crosslinking agents are needed or used - these materials and their simple chemical makeup have an appeal for biomedical applications. But that such unexpected behavior can be found in such simple formulations and processes is what is intriguing. Making these gels is no more complicate than making slime and could be done by college students (or high schoolers if they can handle the long cooling/freezing times and the boiling water.) How many other simple systems with such surprising properties are out there?

[1] I prefer to use PVOH as the abbreviation for this polymer rather than PVA, as PVA could stand for either polyvinyl alcohol or polyvinyl acetate. And it's all the more confusing as polyvinyl alcohol is made from polyvinyl acetate. You can't polymerize vinyl alcohol as vinyl alcohol doesn't exist. Even if you could make it, it would undergo a keto-enol rearrangement to form acetaldehyde. So instead, polyvinyl acetate is hydrolyzed to form PVOH. If you've ever look into ordering PVOH, you will find that the various grades are not only the result of differences in molecular weight, but also differences in degrees of hydrolysis.

[2] PVOH readily dissolve in water at room temperature - too readily - so much so that making a solution with more than a percent or two is a really problem. If you aren't adding the powder very slowly and with large amounts of mixing, you will end up with lumpy snots of undissolved material. Two options to avoid this are to 1) cool the water (adding ice directly is best), or 2) use extremely hot water as the researchers did here. The former option works because it slows down the dissolution rate so that you can evenly disperse the powder and then dissolution occurs as the water slowly heats up, while the second option works because PVOH is insoluble in the extremely hot water, so that again, it can be dispersed first and then slowly dissolved as the water cools. The ice option can work for solutions of about 10 wt% max. I have no idea what the maximum concentration is for the second option. The researchers here were able to make 40 wt% solutions.

Friday, October 12, 2012

Biobased Polypropylene

In the past, most if not all commercial polymers were based on petroleum. That is changing as bio-based polymers are becoming more common. Polylactic acid (PLA) is clearly the leading commercial polymer with a volume of probably about 500 millions lbs. annually. Other polymers are available, polyhydroxy alkanoates (PHA's) for one, but these polymers have yet to achieve the volumes to be deemed a commercial success.

Further up the development pipeline are other biobased polymers that are, at least from a chemical structure viewpoint, drop-in replacements. [*] Dow/Braskem are working on biobased polyethylene, and Coke has a supplier for biobased PET. Now comes an announcement that a biobased polypropylene is being worked on. Making propylene monomer without petroleum feedstocks is pretty challenging:
"Since there are no known natural pathways leading to propylene in microorganisms, creating a process for the direct bio-production of propylene required the design of an artificial metabolic pathway based on previously unknown enzymatic reactions and on novel metabolic intermediates."
As I said yesterday, we are beginning to see the future of chemistry and chemical engineering and it will not be anything like the organic reactions that we all learned as sophomores. We can either embrace these changes or let them run us over.

[*] I've discussed a time or two or three in the past that "drop-in" replacements are never that. Ask any engineer who has been on the job for more than 2-years and they will agree.

Thursday, October 11, 2012

Yes, This Year's Nobel Prize Chemistry Prize was given for Chemistry

The 2012 Nobel Prize in Chemistry was announced yesterday and the reaction from many chemists in the various social media outlets was of outrage that the prize was again awarded for work in biochemistry and not "true" chemistry.

I am not sympathetic to the arguments in the least.
  1. I've yet to see anyone in social media complaining who actually stood a chance to win the prize. The uproar is all caused by bystanders who are never ever going to be considered for the prize. As such, this no different than sports fan complaining about a call in the big match that went against their team. And the end result is the same in both cases. The sun will rise tomorrow and life goes on and years from now no one except the complainers themselves will remember their complaints and their bitterness.
  2. Look at what is being published in leading journals that qualifies as "chemistry". Here's what the most recent issue of Nature Chemistry has for research articles:
    • Use of the interior cavity of the P22 capsid for site-specific initiation of atom-transfer radical polymerization with high-density cargo loading
    • Selective transformations of complex molecules are enabled by aptameric protective groups
    • Electrode-assisted catalytic water oxidation by a flavin derivative
    • Rapid point-of-care detection of the tuberculosis pathogen using a BlaC-specific fluorogenic probe
    • Ab initio carbon capture in open-site metal–organic frameworks
    • Thiourea-catalysed ring opening of episulfonium ions with indole derivatives by means of stabilizing non-covalent interactions
    • Visualization of hierarchically structured zeolite bodies from macro to nano length scales
    • Submicrometre geometrically encoded fluorescent barcodes self-assembled from DNA
    • The energy barrier in singlet fission can be overcome through coherent coupling and entropic gain
    • Label-free measuring and mapping of binding kinetics of membrane proteins in single living cells
    • Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions
    That's pretty heavy on the bio side of things, isn't it? Well, how about another major chemistry journal such as The Journal of the American Chemical Society?(I bolded the articles that are clearly bio-oriented, and I arguably could have bolded even more)
    • Direct Stereospecific Amination of Alkyl and Aryl Pinacol Boronates
    • Photoinduced Dynamics of Oxyluciferin Analogues: Unusual Enol “Super”photoacidity and Evidence for Keto–Enol Isomerization
    • Tuning the Thermoelectric Properties of Conducting Polymers in an Electrochemical Transistor
    • Femtosecond Conical Intersection Dynamics of Tryptophan in Proteins and Validation of Slowdown of Hydration Layer Dynamics
    • Porphyrin Shell Microbubbles with Intrinsic Ultrasound and Photoacoustic Properties
    • Ruthenium-Catalyzed Aldehyde Functionality Reshuffle: Selective Synthesis of E-2-Arylcinnamaldehydes from E-β-Bromostyrenes and Aryl Aldehydes
    • Photodriven Charge Separation Dynamics in CdSe/ZnS Core/Shell Quantum Dot/Cobaloxime Hybrid for Efficient Hydrogen Production
    • Pt5Gd as a Highly Active and Stable Catalyst for Oxygen Electroreduction<
    • Light-Inducible Spatiotemporal Control of Gene Activation by Customizable Zinc Finger Transcription Factors
    • Coherent Picosecond Exciton Dynamics in a Photosynthetic Reaction Center
    • Antibody-Linked Spherical Nucleic Acids for Cellular Targeting
    • Efficient Medium Ring Size Bromolactonization Using a Sulfur-Based Zwitterionic Organocatalyst
    • Catalyst-Controlled Regioselectivity in the Synthesis of Branched Conjugated Dienes via Aerobic Oxidative Heck Reactions
    • Direct-Write Patterning of Bacterial Cells by Dip-Pen Nanolithography
    • Bulk Superconductivity in Bismuth Oxysulfide Bi4O4S3
    • Tryptophan Switch for a Photoactivated Platinum Anticancer Complex
    • Predictions for Cholesterol Interaction Sites on the A2A Adenosine Receptor
    • Transition-Metal-Free Oxyarylation of Alkenes with Aryl Diazonium Salts and TEMPONa
    • Ba1–xNaxTi2Sb2O (0.0 ≤ x ≤ 0.33): A Layered Titanium-Based Pnictide Oxide Superconductor
    • Facile “Modular Assembly” for Fast Construction of a Highly Oriented Crystalline MOF Nanofilm
    • Nanofluidic Ion Transport through Reconstructed Layered Materials
    • Diketopyrrolopyrrole–Diketopyrrolopyrrole-Based Conjugated Copolymer for High-Mobility Organic Field-Effect Transistors
    • Glycine Rescue of β-Sheets from cis-Proline
    • Synthesis of Thieno-Bridged Porphyrins: Changing the Antiaromatic Contribution by the Direction of the Thiophene Ring
    • Chain-Walking Strategy for Organic Synthesis: Catalytic Cycloisomerization of 1,n-Dienes
    • Low-Voltage Organic Field Effect Transistors with a 2-Tridecyl[1]benzothieno[3,2-b][1]benzothiophene Semiconductor Layer
    • Cyclization Cascades Initiated by 1,6-Conjugate Addition
    • Neuron-Targeted Copolymers with Sheddable Shielding Blocks Synthesized Using a Reducible, RAFT-ATRP Double-Head Agent
    • Near Infrared Light Triggered Release of Biomacromolecules from Hydrogels Loaded with Upconversion Nanoparticles
    • Modulation of a Pre-existing Conformational Equilibrium Tunes Adenylate Kinase Activity
    • Catalysis through Temporary Intramolecularity: Mechanistic Investigations on Aldehyde-Catalyzed Cope-type Hydroamination Lead to the Discovery of a More Efficient Tethering Catalyst
    • Multiprotein Heme Shuttle Pathway in Staphylococcus aureus: Iron-Regulated Surface Determinant Cog-Wheel Kinetics
    • Kinetic Stability of the Streptavidin–Biotin Interaction Enhanced in the Gas Phase
    • Solar Cell Efficiency, Self-Assembly, and Dipole–Dipole Interactions of Isomorphic Narrow-Band-Gap Molecules
    • Identification of an Aggregation-Prone Structure of Tau
    • Macromolecular Crowding and Protein Stability
    • Detection of the Water-Binding Sites of the Oxygen-Evolving Complex of Photosystem II Using W-Band 17O Electron–Electron Double Resonance-Detected NMR Spectroscopy
    • Multiple-Site Concerted Proton–Electron Transfer Reactions of Hydrogen-Bonded Phenols Are Nonadiabatic and Well Described by Semiclassical Marcus Theory
    • A New Direction in Dye-Sensitized Solar Cells Redox Mediator Development: In Situ Fine-Tuning of the Cobalt(II)/(III) Redox Potential through Lewis Base Interactions
    • Fe/N/C Composite in Li–O2 Battery: Studies of Catalytic Structure and Activity toward Oxygen Evolution Reaction
    • From Aggregation-Induced Emission of Au(I)–Thiolate Complexes to Ultrabright Au(0)@Au(I)–Thiolate Core–Shell Nanoclusters
    • Ruthenium Stilbenyl and Diruthenium Distyrylethene Complexes: Aspects of Electron Delocalization and Electrocatalyzed Isomerization of the Z-Isomer
    • Photoelectrochemical and Impedance Spectroscopic Investigation of Water Oxidation with “Co–Pi”-Coated Hematite Electrodes
    • Spectroscopic and DFT Studies of Second-Sphere Variants of the Type 1 Copper Site in Azurin: Covalent and Nonlocal Electrostatic Contributions to Reduction Potentials
    • General Acid–Base Catalysis Mediated by Nucleobases in the Hairpin Ribozyme
    • Nanoscale Graphene Oxide (nGO) as Artificial Receptors: Implications for Biomolecular Interactions and Sensing
    • Mechanistic Studies on Histone Catalyzed Cleavage of Apyrimidinic/Apurinic Sites in Experimental Verification of the Homoaromaticity of 1,3,5-Cycloheptatriene and Evaluation of the Aromaticity of Tropone and the Tropylium Cation by Use of the Dimethyldihydropyrene Probe
    • Exploiting the π-Acceptor Properties of Carbene-Stabilized Phosphorus Centered Trications [L3P] 3+: Applications in Pt(II) Catalysis
    • Self-Assembly and Photopolymerization of Sub-2 nm One-Dimensional Organic Nanostructures on Graphene
    • Total Syntheses of HMP-Y1, Hibarimicinone, and HMP-P1
    • Superoxide Reaction with Tyrosyl Radicals Generates para-Hydroperoxy and para-Hydroxy Derivatives of Tyrosine
    • Identification and Characterization of the Echinocandin B Biosynthetic Gene Cluster from Emericella rugulosa NRRL 11440
    • Lateral Distribution of Charged Species along a Polyelectrolyte Probed with a Fluorescence Blob Model
    • Crystal Structure of a Preacylation Complex of the β-Lactamase Inhibitor Sulbactam Bound to a Sulfenamide Bond-Containing Thiol-β-lactamase
    • Mechanism of Metal-Free Hydrogen Transfer between Amine–Boranes and Aminoboranes
    • Single-Molecule Electrochemical Gating in Ionic Liquids
    • Tailoring Bimetallic Alloy Surface Properties by Kinetic Control of Self-Diffusion Processes at the Nanoscale
    • Populated Intermediates in the Thermal Unfolding of the Human Telomeric Quadruplex
    • Dynamics of Catalytic Resolution of 2-Lithio-N-Boc-piperidine by Ligand Exchange
    • Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates
    • Mechanism of Amination of β-Keto Esters by Azadicarboxylates Catalyzed by an Axially Chiral Guanidine: Acyclic Keto Esters React through an E Enolate
    • Reactivity of U–E–U (E = S, Se) Toward CO2, CS2, and COS: New Mixed-Carbonate Complexes of the Types U–CO2E–U (E = S, Se), U–CS2E–U (E = O, Se), and U–COSSe–U
    • Theoretical Investigation into the Mechanism of Au(I)-Catalyzed Reaction of Alcohols with 1,5 Enynes
    • Site-Selective Chemistry and the Attachment of Peptides to the Surface of a Microelectrode Array
    • Dynamic Nuclear Polarization NMR Spectroscopy of Microcrystalline Solids
    • Are MXenes Promising Anode Materials for Li Ion Batteries? Computational Studies on Electronic Properties and Li Storage Capability of Ti3C2 and Ti3C2X2 (X = F, OH) Monolayer
    While not as bio-bent as Nature Chemistry, there still are a lot of those awful biochemical names that end in -ase and all those protein code names... It's just horrible to think that someone would let that soil the pages of a pure chemistry journal like JACS. I could go one with other journals, but you get the point. Chemistry journals long ago decided that chemistry could have a strong bio-base orientation and still qualify as chemistry.
  3. The underlying foundation for much of chemistry is changing from its traditional petroleum-basis to a biological basis. This is most apparent in the areas of polymers and fuels, but it will soon spread to the rest of organic chemistry and beyond. But more to the point, the reactions that are creating these materials ARE NOT in many cases, the classic reactions that we all learned as sophomores, but are different and will require that synthetic chemists of the future become familiar with these bio-based reaction options as well.
  4. What I find most laughable about this whole situation is that I'm the guy that is on the backside of my career and yet I'm the one that is both applauding this new breadth of "chemistry" and having to tell younger people to adjust to the new paradigm. Shouldn't I be the old curmudgeon who grinds my teeth and complains about those upstart bio people who are coming on my yard ("Get off my grass or I'll get my shotgun...")? I don't get it.
While I'm not going to predict specific individuals who are going to the Nobel Prize in the future, I will say that an ever increasing number of the awards are going to go to "bio" chemistry in all it's many forms. That's the way research and industry are heading. If you don't like it, that's too bad. You can do no more to change this than you can stop the tide from coming in.

Update: Stuart Cantrill, the Chief Editor of Nature Chemistry pointed out that the articles I originally had posted were incorrect. And that I still wasn't right when I corrected it.