Thursday, December 30, 2010

Adieu 2010...

..and the whole rest of the first decade of this millennium [*]. It has been an extremely challenging 10 years for myself and others close to me, so please 2010 and your ten predecessors, go gentle into that long night and never return. I used to joke that the year I spent in Terre Haute was the worst decade of my life. Not any more!

As for the rest of you readers, I look forward to continuing this blog in 2011. The blog readership has grown tremendously over this year (I am ever so grateful), a trend I hope will continue.

Aspen Research is closed both tomorrow and Monday, so this is the last post of the year. Until then!

[*] Remember, the millennium didn't start until January 1, 2001.

Can You Design the Next Great Symbol?

Winning $25,000 would be a great way to start the new year, wouldn't it?

Cereplast is launching a contest this coming Monday (January 3) for the creation of a symbol that they hope would become the standard symbol for bioplastics.

I've got some ideas, and with my son's graphic abilities, this contest might be all over before it starts :) [*] Complete details won't be available until Monday, so I can't even tell yet when the contest closes, but it would be pretty cool to see a polymer guy win the contest, not a graphic designer or such.

[*] Or then again, looking at the weird corporate logo of my employer, I might just increase everyone elses chances. By the way, I had absolutely NOTHING to do with our corporate logo. NOTHING!

Tuesday, December 28, 2010

Would You Want to Process This Recycle Steam?

Chevrolet is getting some green kudos for taking 100 miles of oil-soaked booms from the Deepwater Horizon cleanup and using them in the new Volt. I'm all in favor of anybody that wanting to use the booms for any other purpose than landfilling them or burning them, but think about this from the viewpoint of a plastic processor: would you really want to put that stuff into one of your extruders?

Keep in mind that this has never been done before on this scale, so there is real risk involved from just that, and yet at the same time, the amount of materials involved (100,000 lbs) is too small to really stake a claim for the future.

I understand that the booms are being "cleaned" prior to this, but still, there will be some oil left, crude oil at that, that will be rather compatible with the polymer in the boom. (If it wasn't compatible, the boom would never have been able to absorb it.) And all that means that the "cleaning" operation will not be 100% efficient, so now you have crude oil in your polymer feedstock. Would you really want to run that? Particularly for something as mission critical as an automobile part? Making widgets for souvenirs is entirely different. Explaining to your customers that the air deflector broke prematurely because it was made from oil contaminated recycle might not go over so well in a few years.

Update on that Epoxy Art Puzzler

As I threatened, I contacted Momoko Sudo about that puzzling drop of epoxy that she posted on her blog and she was happy to reply. She has posted a few comments on my original posting - the long and short of it is that the "wrinkles" are not wrinkles but are the arise from color variations in the resin.

She also added a new entry to her blog about the whole matter. I really recommend you read her posting as she has some new insights not only about her role as an artist, but also about how puzzling the drop can appear to her too if you look at it anew. Her own words say it best, so check them out.

Monday, December 27, 2010


My wife discovered this unusual lineup of icicles hanging off the back of our house:Unusual, in that they form a peak [*] suggesting a Gaussian distribution.

Icicle formation is actually a non-trivial subject. An article available from the Physics Arxiv shows new research from earlier this year on the subject, not just a theoretical model, but also their efforts to create an icicle growing apparatus under controlled (and adjustable conditions). The challenge in the modelling is that the boundary of the icicle is not defined in advance, but is actually the output of the exercise. Combine that with the nonlinearities of flow, heat transfer, external air currents,... and uniquely for icicles, water purity and you have quite a set of equations to work on simultaneously.

This is quite similar to the problems in modeling polymerization fronts - cases where polymerization in a pool of monomers starts on one side and advances through the liquid, also a nasty little problem to solve despite its simplicity to describe and understand.

[*] Let's just pretend that we are all electrical engineers for a moment, shall we, since they are the ones that always have "peaks" upside down from the rest of the world.

Tuesday, December 21, 2010

Uncertainty in Polymer Molecular Weights to Arrive in 2011

Not content to let 2011 arrive in peace and serenity, IUPAC is at it again, in this case changing the atomic weights of atoms from single values to ranges. The current single values are averages of the known natural distributions (Cl being probably the most famous, with the current single value of 35.453 being an average of 35Cl and 37Cl, the former isotope being about 3x more common than the latter.)
"According to Michael Berglund, a member of Iupac's Commission on Isotopic Abundances and Atomic Weights, which proposed the change, it is purely because more reliable and precise measurement data are now available. He points out that in its previous form, the standard atomic weight for an element like lithium was just an average value. 'It would actually be very difficult to find a material with this exact atomic weight,' he says"
Certainly a valid point.

I see potentially two issues down the road: 1) this is going to be extremely difficult for students (how can they calculate the MW of a molecule when the atomic values have a range? [*]), and 2) for our little world of polymers, the changes could be quite large simply because our molecules don't have a single digit quantities of any one atoms, but have immense amounts of them. As a somewhat extreme example, consider ultrahigh molecular weight PE. If I recall correctly, the molecular weight is about 4 million, meaning that there are about 290,000 carbon atoms and over half a million hydrogen atoms per molecule (4,000,000/14, the molecular weight of the methylene repeat unit). Changing the atomic mass value of either C or H by even as little as 1% will still result in a noticeable change in the molecular weight. End group analysis is going to be a lot more challenging.

And to really delight us, the changes are coming quickly:
The first ten elements for which atomic weights will be stated as intervals in the Table of Standard Atomic Weights are: hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium.
i.e., Let's try this out on the organikers first!

[*] And of course, we should always rearrange chemistry to please the students, right? But seriously, I'm just not sure how high school teachers will handle this.

Monday, December 20, 2010

Art & Rheology (Again) but no Puzzles This Time

Last week I posted about a rheological mystery that was presented as art. This week, I also found an artist, Jesse Higman, using resins but in this case, the carefully designed flow of the uncured materials is integral to creation of the art. The website of the artist is full of picture, but short on technical details, but the page devoted to the "Spiral" image shows how the canvas is meticulously distorted from a plane so that the resins flow in the desired shape. It's worth taking a little time to check out the page. Given the disability of the artist, the devotion to the picture (3 years work) is all the more exciting.

A second picture is labeled with "Rheology" on the page header, although I do not explicitly see the connection.

Friday, December 17, 2010

Thoughts on Transport Phenomenon

The article "Thermal Facts and Fairy Tales" [*] starts with a bang: "...a fixed temperature boundary condition in a thermal simulation represents an infinite heat sink." Fair enough. I always understood this, but have never seen it represented so succinctly. Having been educated as a chemical engineer, my thoughts immediately went back to my days hovered over a copy of BSL, aka Bird, Stewart and Lightfoot, aka the little red book "Transport Phenomena", which for decades was pretty much the only textbook on the subject used in undergraduate ChemE programs across the country. (Can anyone name a similar book in any subject that was so canonized?) A central tenet of the book was the similarity of heat, mass and momentum transfer.

So taking the opening statement and applying the basic concept in transport phenomenon to it, you can make the sentences "...a fixed concentration boundary condition...represents an infinite flux sink/source" and "...a fixed momentum boundary condition...represents an infinite stress sink/source", both of which I think are far more obvious than the original sentence.

[*] What am I doing reading "Electronics Cooling"? Well, I have done work for clients with heat transfer problems. The clients are mostly electrical engineering companies. I don't know if EE's are taught heat transfer at all (I suspect not) or they just don't pay attention in the class because they want to focus on circuits, antennas, IC's,... all the things that they went into electrical engineering to study - not heat transfer. You can infer the lack of understanding from the sentence quoted from the article. It only refers to a heat sink, even though the boundary could also be a heat source.

Thursday, December 16, 2010

PLA that acts like ABS

That's what Purac is claiming for a new PLA (polylactic acid). The trick to acheiving this performance leap is not the result of any additive or modification of the monomer by the addition of various moieties, but instead occurs at a more fundamental level: the polymer is a block copolymer of both the D- and L- stereoisomers. There is no mention of the level of blockiness in these polymers (are they di-block, tri-block,...?), but I imagine that the blocks are not able to co-crystallize and will instead phase separate and crystallize separately. I'm also not able to find anything suggesting that the D- monomer will also not be as biodegradable as the L- monomer is, but that should certainly be confirmed.
It's pleasing to see a simple change in monomers that can produce such a large change in a polymer. (And what about those people who thought that chemists couldn't do anything new with C, H, O and N? Heck, this didn't even need the N!)

Tuesday, December 14, 2010

Epoxy Resin Drop as Art - and Rheology Puzzler

Momoko Sudo is an artist who works in a variety of media, including colored epoxy resins. She has a blog that's a good starting point to explore her work. It's all abstract, so it may not be everyone's choice for art, although I certainly enjoy it. And maybe in the same way in which art and science are at opposite ends of a continuum, she calls the epoxy resin by the term "resin" while we would call them "epoxy".

The picture above captivated me, not only because of the colors, but also the wrinkles in the drop. (No idea what size the drop is.) I've seen piles of polymers before with similar surfaces, usually sitting at the end of an extruder that is undergoing a purge or such, where a steady stream of hot material is piled onto a cooling base. But this is supposed to be just epoxy, or more correctly, curing epoxy. How would it have gotten such wrinkles? Given the small drop size, I imagine any adiabatic build up of heat would be limited, so that the drop should be more or less isothermal, and so should the cure (there should be no oxygen inhibition in an epoxy either).

Any ideas? Not knowing any more than what I see in the picture, I'm baffled. It appears that this drop has flowed, but how could it have?

Will the Supreme Court become Probabilistic?

If this case gets acccepted by the US Supreme Court, it is going to be awful, just awful. A Guaitanamo detainee is appealing his case on the basis that the previous rule was wrongfully made using arguments of conditional probabilities. Keep in mind that this is the very same Supreme Court (well, Kagen is new, but the other 8 are the same) that previously stated 2 + 2 = 5, so how are they going to understand probabilities, their proper use and potential for abuse?

Monday, December 13, 2010

Career Advice

A reader of this blog, a student graduating soon, recently asked me for some career advice. Given the active discussion this week in neighboring blogs on the job situation for chemists, I decided to repost the email, slightly modified so as to protect the privacy of the individual and also fixing spelling/grammatical errors. The tackifier footnote isn't technically correct in all the details, but is fine given the context of the present situation.

My career advice is based on three principles: 1) focusing on the fundamental science in any situation 2) keep learning everything you can about ALL AREAS of science (the divisions of physics, chemistry, biology, metallurgy... are all man made and nature ignores them), and 3) be flexible – as was said by Robert Heinlein: "A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects."

I’ve moved around throughout my entire career. In brief: 1 year @ Hercules (BOPP film), 11 years @ 3M (broken down as 5 years in pressure-sensitive adhesives, 2 years in EKG electrodes, 4 years in microbiology products), 1 year @ Conwed Plastics (PP netting), 1 year at Envoy Medical (implantable hearing aids) and 6 years @ Aspen Research (everything under the sun). There is a polymer thread throughout it all, and I was able to make it work by focusing on the fundamentals of polymers in all cases and not worrying about the jargon of any particular industry. For example, if you understand how a tackifier changes the rheology of an adhesive, then you won’t be confused when you discover that adding too much tackifier actually decreases the tack of an adhesive, despite it being called a “tackifier” [*]. I’ve seen people just baffled by that concept because they keep thinking that it’s a tackifier and it should keep making things tacky.

I’d say start in a big company if possible, as they will have resources (equipment, libraries and experts) that you cannot find anywhere else. Also, a big company will allow you to move around internally without major disruptions. Going to a small company is a whole different world as they lack equipment, libraries and experts. This can be overcome, as you can outsource testing and manufacturing, libraries are online and experts (old colleagues) are just a phone call away. Oops, make that a text away (I’m showing my age). Since you already know what can be done by large companies, you are not limited in what you can do at a small company. It just is a little more complicated. Also, instead of being say 1 of 10,000 employees, you are now 1 of 50. When you do well, everybody sees and knows it. (Conversely, when you screw up, everybody sees and knows it.)

Going into management is not something I can give any advice on, other than be aware that it is a 1-way street. If you leave the bench, you can’t go back. There will always be some newly laid-off employee who was working at the bench just last week – how can you expect to compete with that?

[*] In case you are not familiar with tackifiers and rheology, tackifiers are low MW materials with a fairly high Tg. They lower the plateau modulus of the adhesive, thus making it tackier, but at the same time of course, raise the Tg. Since most adhesive bases have such low Tg’s, you can raise the Tg some and there are no problems. But too much tackifier raises the Tg too close to RT and then you start losing the tack.

Slip-Sliding Away

While you may first think that this will be an entry about the massive snow storm that struck town on Saturday (even when it is light and fluffy, 17.1 official inches of snow is a lot of snow - the fifth largest snowfall on record and enough to collapse the roof of the Metrodome (video) [*]), this is actually about wall slip occurring at the solid boundaries of flow fields.

Richard Buscall has a letter to the editor published in the latest Journal of Rheology (subscription required or pay-per-view) that made a salient point or two regarding slip. My favorite quote was regarding the use of roughened or serrated tools in rheometers.
The author once heard somebody accused of neglecting slip say 'Yes, I am aware of the possibility of slip but did not want to compromise the accuracy with which the gap was set and quantified.' Now, one can be sure that that person did not actually mean 'I was prepared to risk the possibility of an error of unknown and therefore arbitrarily large magnitude in order to avoid the uncertainty in the gap setting of, perhaps, 1%'. Except that is what their assertion amounted to."
I always love the way the British are able to insult in such an incisive manner.

[*] Even though we all know that it was Brett Farve who did it just because he wanted another day to recover from his injuries.

Friday, December 10, 2010

The Impact of Biology on Polymers

I'm very excited about what new polymers we will be able to make in the not too distant future. Not because chemists are devising new monomers, but because biologists are. I wrote yesterday about isosorbide and how a new polycarbonate can be made with it. Today's post is about a new polyester.

The basis for these materials are a genetically modified strain of yeast (Candida tropicalis) which is able to take normal fatty acid and pin a hydroxy group on the end of the saturated chain. The picture below is from the articles abstract where all the "X"'s in the diagram are existing biochemical reactions that needed to be stopped in order to have the desired output, and the only way to stop them was by genetic modification, no small feat I'm sure. You can certainly read the article (paid subscription) if you want, but the rest of my post is on what I see happening with the newly created w-hydroxy fatty acid.

The easiest reaction I can imagine would be for the material to create a self-condensing polyester - a head-to-tail combination that much like normal PET production produces water. What sets this reaction about is that normal PET is made from two monomers - ethylene glycol and terephthalic acid, while this could be made from just the single monomer. Depending on the length of the saturated carbons, you could imagine crystallinity developing to a certain extent. It could also be worthwhile to investigate the biodegradability of the new materials, as a shorter version of these, polyhydroxybutyrates are known to have this property. You also could also try reacting it with one or more additional diols to create a random copolyester.

I have no idea as to the economics of scaling up production of the these monomers - I certainly have some doubts just because it is new, but still, this post and yesterday's post should have you convinced that polymer chemistry will be undergoing a revolution at some point in the not-too-distant future. New materials with new properties, courtesy of some microbial life modified to meet our needs.

Thursday, December 09, 2010

Isosorbide as a BPA replacement

One of the big corn processors from here in the Midwest is suggesting that isosorbide could be used as a replacement for bisphenol A (BPA) monomer in polycarbonates and epoxies and anything else that uses this versatile chemical. While it certainly can be used in place of the monomer-that-has-fallen-into-political-incorrectness, it will not be a drop-in replacement. This can be seen by simple inspection of the chemical structures.

BPA:Isosorbide:There are a couple of key structural differences. First, the overall length between the two hydroxy groups is much larger in BPA than in isosorbide (keeping in mind that the drawings above from Wikipedia are not on the same scale). That means that the comonomers are going to be much closer than in a BPA based system, and will make up a larger volume than before. Second, the stiffness of the central structure is greatly different, in that the phenyl rings in the BPA have some ability to rotate around the central carbon, while the center part of the isosorbide is going to be pretty much as still as a snowboard. Tg will undoubtedly be affected. Also note that isosorbide has more oxygens available for hydrogen bonding, another potential influence on Tg.

Let me be clear on what I am saying: the two monomers will produce different polymers. Not that different is inherently bad. The new polycarbonates produced with isosorbide can and will have very useful properties, but they will be different than those of standard polycarbonate.

If I was looking to replace BPA with another monomer, I'd keep in simple and look at the rest of the bisphenol family. Bisphenol E

and bisphenol F
would be a good starting point to cause the least disruption to existing polymers. You can see that the methyl groups on the central carbon are replaced by one or two hydrogens. The overall length of the molecule remains the same. I'm not sure that enough is known about the exact mechanism of endocrine disruption to dissuade the use of either replacement monomer.

Wednesday, December 08, 2010

Bone Cements

Reports are starting to appear of a new bone cement. The reports are all complimentary in that the material is an injectable fluid that quickly sets. However, these reports overlook one key issue and that is the thermodynamics of the reaction, specifically is there an exotherm and how large is it?

I worked briefly with bone cements while with my last employer (Envoy Medical), where we were using the cements to attach the implanted device to the various bones in the middle ear. We looked at a wide range of chemistries, and had several that, like this new material, were liquids and set very quickly but they provided excessive amounts of heat - not a good thing to have against living tissue. While this new chemistry looks exciting, I am curious about the exotherm that it generates. Any reaction that occurs quickly will generate all its heat quickly which is never appropriate for implantation.

Tuesday, December 07, 2010

Which is more Dangerous? Plastics or Tobacco

Apparently, the Indian Supreme Court believes plastics are. They have outlawed the use of plastic pouches to package gutkha, a type of tobacco clearly associated with various oral cancers.

The cynical side of me notes that gutkha is taxed, but as far as I can tell, plastic pouches are not.

Monday, December 06, 2010

A Very Minor Milestone

Sometime over the weekend, visitor # 10,000 [*] came by. As you can see from the log, it was someone (or something?) from MIT.
10,000 visitors in a little over a year. What's the next big mark, 100,000? Depending on whether the numbers take a linear or exponential growth, that could take 1 - 5 years. Or it may never happen. A linear growth pattern would reflect the continued poor quality of the writing and that the blog is merely taking up more space, while the exponential writing would also indicate that the writing is no better, only that more people are finding it and passing it along to others as "here's what you don't want to do".

[*] This number isn't very accurate as I started the counter only last October and the blog goes back a number of years before that, albeit with much less vim and vigor. It is also totally blind to anyone using a reader to follow this blog and those people would certainly be the most regular readers of the blog. So there are no "lucky customer" prized for being #10,000.

Only in California...

...would officials burn a house filled with explosives. I'm not going to go into the details, The Chem Blog covers them quite well. I would strongly suggest reading that entry. The short story is that police found a house with an unknown quantity of explosives and other chemicals in it. Rather than remove them, they plan to torch the place. Seriously.

They are taking precautionary steps like oh, say, evacuating 200 homes, shutting down the nearby freeway, installing firewalls... but still, doesn't this strike you as a wee bit insane? They have no idea what all is in the house, so why does burning it seem like such a great idea? They have no idea what they will be burning and releasing into the environment.

I can guarentee that the media circus of California will be watching the whole episode from helicopters, planes and the ground, and video will certianly be widely circulated when the day of the bonfire comes. And others will be monitoring the air for whatever is released, sure to incite hysteria. This will be fun to watch, but I'm glad I'm almost 2000 miles away.

Friday, December 03, 2010

Reviewing a Paper - Round 2

I review a fair number of papers [*] for the Royal Society of Chemistry, but this last week something new happened: I had a paper returned to me for a second review. I originally had been critical of the paper, somewhat for what was done, and somewhat for the way it was presented (quite sloppily with mistakes you would expect from an undergrad taking a lab class). I've been critical of papers before when reviewing them and never have really followed up on what happened to them (I've been meaning to, but it's not a top priority). I figure either the editor ignored my feedback or the authors went elsewhere with it.

So you can see that I was pretty amazed to get a paper back with an attachment showing the comments that I had originally made and their responses to them. They agreed with all them and made the appropriate changes. I figured this was the way it was suppose to work, but I've not seen it yet. So now I'm excited because I can see that I actually made a difference. How cool is that?

[*] What's a "fair number"? I probably average about 1 a month, although that actual event - "1 a month" never occurs. They always come in groups of 2 or 3 followed by longer periods of inactivity. I have no idea how 12/year compares to other reviewers. I suspect some do more, some do less.

Bridgestone Cutting Rubber Usage

Just this headline is eyecatching: Bridgestone to Halve Rubber Use by 2020. Overlooking the obvious solution of cutting sales in half, Bridgestone clearly has developed a significant new technology here and plan to take full advantage of it. The article does not hint at what it is; I'd be quite curious to know.

Thursday, December 02, 2010

Think It's Obvious? Prove It.

As promised back in October, the US Patent Office now is opening select patents applications up to the general public to comment on. And lucky us in the polymer community, the first one in organic chemistry is from IBM and it is for monomers that can be used to make polycarbonates, polyureas, polyurethanes...

How many times have you read a patent is said "that is so obvious" or "that is already being" done? (Please don't reply. If everyone did, it would crash the servor for weeks.) So here's your chance to change that. Register on the site and serve up some existing documentation to shoot this thing down - if you can. I haven't really looked at it in enough detail to make a decision about it for myself yet.

Wednesday, December 01, 2010

My Personal Kryptonite

I feel fortunate that the various aromas, fragrances and odors that are given off by chemicals never seem to bother me much. Whether its mercaptans,pretty much anything with a nitrogen in it...whatever, there is very little causes problems. But I was reminded yesterday of one solvent that will quickly have me leaving an area if I get even a small with - ether. That's right, diethyl ether.

A bunch of us were playing around with some nitrocellulose that was dispersed in ether. Out of the 6 of us, 1 was the only one that got light-headed and bolted. I wasn't even the closest person to the sample. And I also had a very strong emotion come rushing in from long ago and far away.

When I was 5, I was hospitalized with pneumonia for 10 days. That may seem like a horrible case, but keep in mind that at that time, women routinely stayed in the hospital for a full week (or more) after giving birth, quite a bit different from the 2 days maximum that insurance companies currently cover. Regardless, that whiff of ether immediately brought me back to those days in the hospital. I don't know why, as I wasn't operated on - maybe a nurse used some to get an antsy 5-year old to fall asleep.

It been said that the sense of smell is the most emotional of the senses, and this certainly provides evidence of that. I very seldom think about that time in the hospital, but that shot of ether brought it all back and with some other emotions that are hard to describe.

I'm fortunate that I never have had to do an ether extraction. That would be something for me to hand off to someone else, or find another extracting agent. But if you ever want to either 1) get me out of the lab or 2) just quickly know me out, a faint fume of ether will do.

Tuesday, November 30, 2010

Black Hole Entropy, Loop Gravity, and Polymer Physics

I didn't invent that title, I am only reprinting it. And no, I do not understand it. Black holes I understand (or I think I understand them as much as a non-physicist can), but I have no idea what loop gravity is - the best I would guess would be the force you feel in centrifugal acceleration on the Rotor ride at an amusement park.

Somehow the author of the paper is able to establish an equivalency between the counting of the microstates in a black hole and the statistical mechanics of a polymer chain, and even another relationship between a rotating black hole and an elongated polymer. Please feel free to read the paper yourself. I certainly recognize the statistical mechanic equations from polymer science, but nothing of the black holes or loop gravity formulae.

Every once in a while [here and here] I've posted on weird connections between polymers, rheology and modern physics. This is probably one of the more practical applications -- if you consider black hole entropy to be a practical problem!

Monday, November 29, 2010

Time to Update the Weathering Mechanism?

There's an interesting new research article out that is getting some buzz in the popular press. It is an open access article if you register (for free) with the Royal Society of Chemistry. I'm withholding judgement at present, but it does seem to merit further investigation.

The article looks at the autooxidation mechanism that is commonly used to describe the (photo)oxidation of polymers and why they breakdown when weathered. It's a free-radical propagation scheme not too unlike a polymerization reaction.

I certainly had no idea that the mechanism was first proposed 65 years, and on that basis alone, it probably would be a good idea to re-examine it. I also was unaware that the mechanism had been used to describing degradation of materials that a chemically distant from olefins (the materials that I am most familiar with in a degradation setting), to even include acrylates. [1]

Using computer modeling [2], the researchers found that the existing mechanism is thermodynamically unfavorable in most cases, and "in most cases" here covers an impressively wide range of chemistries. They also found that temperature doesn't change influence at all. Instead, the authors look at defects that occur in polymerization and found that the defective sites are sites where the thermodynamics are favorable for hydrogen abstraction. They then suggest that examining materials made with non-conventional and more constrained polymerization mechanisms may avoid these problems.

As I started with, I find this a very intriguing paper and one that needs more research. There is a tremendous amount of existing research in degradation that was not mentioned here, and it would be invaluable to look at it anew to see if the new mechanisms are supported by it.

I am greatly concerned that the influence of temperature was minimal. Whole books, journals and companies exist because of accelerated weathering, and temperature always plays a key role in it. (If reaction (1) above is the result of a photoinitiation, then that step is pretty much temperature independent, but all the remaining steps certainly have a temperature dependency.) Nonetheless, I still found the whole article worthwhile to read and hope that it leads to new insights quickly. I'd be curious if it leads to the development of new antioxidant chemistries to fight these "new" reactions.

[1] I'm glad that the researchers had the same thought I did in reading that: the proposed scheme won't work because it is well known that oxygen inhibits acrylate polymerization. The peroxy radical in step 4 can't abstract a hydrogen. So either the mechanism above is correct, or our understanding of oxygen inhibition is correct, but they both can't be correct.

[2] Gas phase, and some liquid phase. Ever seen a gaseous polymer? Think it might behave just a little differently in a solid? Unfortunately, even with supercomputers, modeling is still challenging and gas phase analysis is just easier to perform.

The Shortcomings of Business Management Books

My last post on corporate cultures got me thinking a little more about businesses. Years ago I use to read at least major parts of business management books, the ones that are always feature the hot trend of the year, usually published by some prof a the Harvard Business School. The ones where they look at a company or a bunch of companies and then generate data of some sort to prove their idea of why the companies succeeded or failed. The last conclusion then is that everyone should be doing what was discovered.

Completing ignoring all the issues associated with a lack of a control study, the big problem is that they never play their results forward. If they really believe that X is the secret to unlocking value in a company, then find some company and install X in it and see what happens. It's no different that what we do in science and engineering: if you think you have the answer, then run some experiments to check it.

Personally, I think that running a business is about the most complicated human undertaking ever attempted. As such, you can always find data to support anything you want to believe. For comparison, consider the 210 reasons for the Fall of the Roman Empire", all of which are supported by data. The real test is when you have to work with your results.

People always complain that weather forecasters have such an easy job since they can be wrong over half the time and still keep working. I'd say business profs have it easier yet since they never even try to see if they are right or wrong. They just need to keep cranking out new books.

Wednesday, November 24, 2010

That's all for this week

I alluded to Thanksgiving earlier this week. Given that most of the US will be stuffing themselves on turkey tomorrow and then doing all we can to stimulate the sluggish economy on Friday, this will be the last post of the week. That's no loss however, as I strongly expect readership to drop since about 60% of it is here in the US.

Happy Thanksgiving to all.

Corporate Cultures

There has been quite a bit of discussion this week in other blogs (In the Pipeline, The Chemjobber) about the new "Lab of the Future" as designed by Novartis. Obviously there is a strong angle in the discussions towards pharma, but all R & D organizations face the same challenges: how do you get people to work together effectively.

Working at Aspen Research, I've been fortunate to gain access to dozens of different companies, all with different floor plans and building architectures and meeting rooms and... I have not seen that the physical structures matter at all.

As much as I hate starting up buzzword bingo, to me the stronger signs of success are corporate culture. Within about an hour, you can tell which companies are going to succeed and which aren't. And that usually carries over into the project that we are working on. I've had clients where I know that the work I'm doing will just be lost or poorly implemented and others were I knew it was going to be a great success.

I would be rich, extremely rich if I could tell you why the differences exist and what to change. (If it was easy, some business prof would have done it already.) However, some of the common threads I see in good businesses are:
  • Intelligent people. This can be broken into two subsets:
    • They have areas of expertise and know what they are
    • They also know what areas are not their expertise, they recognize this and publicly acknowledge this
  • Management that may or may not be present, but certainly show restraint in their involvement
  • Clear definition of both what the problem is, and what a successful resolution would be (Scope creep in a project a great warning sign)
  • Open communication:
    • Bad news can be spoken about
    • Politics are very limited below the management levels
That's what's there off the top of my head. Again, no revolutionary ideas here.

Just so that I don't fall into the trap that I just accused others of, note that this is descriptive, not prescriptive. The real question is if a company doesn't have this culture, can it be made to have one? And how can it be done? I have no idea.

Tuesday, November 23, 2010

Why I Hate 1-Part Silicones (and Urethanes and...)

Personally, I really don't have much against the 1-part systems, it's just that I've seen other people use them willy-nilly because they don't like mixing, and then they get in trouble. Properly used, a 1-part, be it sealant, adhesive or whatever, can be great.

But one problem that I've seen repeatedly across countless industries [1] is people thinking that because these are moisture-cured products, as long as they have high humidity in the assembly area, everything will be fine. Seriously, I've heard people say "We're in East Texas where it is more humid than all-get-out. There must be something wrong with the adhesive since it isn't curing. Ship it back!"

The problem with this line of thought is that yes, moisture is needed to aid the cure [2], but there is that other end of the reaction to worry about called the products, or in this case, the byproducts. The water displaces some other molecule, often acetic acid or ethanol, but no matter what it is, that byproduct has to get out and disappear. And if you are putting the silicone into an enclosure of some sort, or even a partial enclosure, all that acetic acid may not be able to find its way out and that causes problems. If instead it is used in thin layers, everything should be fine.

Trapped inside, it can form hollow pockets or end up at the surface where they cause adhesion problems. And thick sections like this also can take a long time to cure just because of the diffusivity issues. [3] I've seen all this too many times. Please, next time you reach for a 1-part, make sure that you've thought it all through.

[1] Medical devices, construction and telecommunication to name a few. Your industry is certainly on the list, I just haven't seen it yet.

[2] So you see, a 1-part silicone is actually a 2-part silicone; it's just that the other part is present in the atmosphere.

[3] Remember that with Fickian diffusion, time scales with the thickness squared.

Monday, November 22, 2010

Bicycle Helmet meets Air Bag

The London Evening Standard has a short story about a new bicycling helmet. It basically worn around the head like a collar, and it inflates (courtesy of stored compress gas) when electronic sensors detect an appropriate situation, probably via some accelerometers. There is embedded video in the article which shows the helmet inflating when a crash-test dummy is rear-ended by a car.

It certainly is an interesting concept, but the whole approach seems to be one of vanity: You don't have to put up with helmet hair anymore! Feel the wind in your hair! No more funny tan lines on your face from helmet straps!

Being rear-ended is not what I would consider the most appropriate demo - hitting a large hole and doing a end-over would be better, or so would sliding out in a corner.

I'm also curious about the material of construction and how it interacts with pavement. When bicycling helmets first became popular [*], they had a hard plastic shell and foam liner. Lighter weight helmets quickly evolved, in part by removing the hard plastic. This was not without issues however, as rumors quickly spread that the foam would stick to the pavement and twist the riders neck in the process, so the hard shells began to reappear. (The hard shells were rumored to bounce you head - is that really any better?) So what happens when this helmet meets the pavement?

[*] i.e., after the various bicycle racing organizations ourlawed the leather hairnets (yes, I am really old enough to remember hairnets! Nailed on cleats, too!)

Turkeys & Netting

For those of us in the US, this is a short work week. Thanksgiving is this Thursday, and Friday is a widespread holiday [*] for most businesses - anything except retail stores. The traditional meal for Thanksgiving is a turkey, and this where we can begin to tie plastics in to the topic.

While I've certainly had turkeys that tasted like plastic, this is a more direct approach. A processed turkey can be difficult to handle. They are heavy, coated in a fairly slippery plastic that might be wet from condensation, and also fairly well rounded with few good areas to grip them. In order to allow for easier handling, they are most often put in plastic netting, something that I look at with a little more intimacy than the average person, as for a very brief period, for you see, I worked very briefly for a company that made plastic netting, some of which was used on turkeys.

There are a wide range of options for making netting, although they all have movable extrusion dies. The netting discussed above, also used for bagging onions and other food items, is made by extruding multiple strands through two coaxial circular dies that are rotating in opposite directions. The strands are oriented at an angle to the machine direction some too, which gives the net the characteristic diamond pattern. Where ever the strands meet, they stick and the netting is formed.

Another option is to use an annular die, similar to what is used to make tubing or blown film. The difference is that the movable part of the die has slots cut into it and this part then moves back and forth against the rest of the die. When the movable part is against the die, the polymer can only flow through the slots, thereby creating the downweb strands. When the movable part retracts, the polymer flows through the entire annulus, creating the crossweb strands. Needless to say, this is quite a noisy operation, what with the die opening and closing with high frequency. This netting can be oriented with a tenter just like biaxial films are.

Yet another option is to just make a circular film and poke holes in it while it is still soft. Seen orange snow fence? Now you know how that is made.

[*] Strangely, the Friday after Thanksgiving is called "Black Friday". Normally a descriptor used for some tragic occasion, this is actually considered a good name as so much shopping is done on this day that retailers are finally able to change financially from being in the red for the year to being in the black - or least that is the urban myth. Regardless of the veracity of the name, everyone knows that it is the busiest shopping day of the year.

Thursday, November 18, 2010

Why the Cox-Merz Rule?

There are some aspects of blogging and Google searches that I do not understand (and not trying to be disrespectful of the intelligence of my audience who I don't think will understand it either), there are certain search terms that attract people to this blog. The biggest ones: "cox-merz" and "cox-merz rule". Why? I have written about the rule just a little bit, but never would expect it to be such a hit - always somewhere in the top five or so depending on the details of the search.

But then try "rheology blog" and the top result is for the Zimbio blog which hasn't had a contribution in over 4 years. "The Rheol World" is near the top, but I can't find this blog anywhere.

Wednesday, November 17, 2010

ANTEC Craziness

Posting is getting to be pretty spotty this week, as most of my writing efforts are directed to papers that we (Aspen Research) are submitting to ANTEC. The deadline is Friday and I have my not only my own paper to finish writing up, but am also helping out on 2 others. They are a good set of papers, but you always wonder about the payoff for this work since 1) they might not be accepted, and 2) much of it is done after hours as we can't let our regular work slide.

Tuesday, November 16, 2010

On Stirring Polymer Solutions

One other thought I had following up on yesterday's post about mixing up the PAm/water concentrate was that I knew I had a good batch when I saw the Weissenberg effect. That's the unusual situation that occurs when stirring a polymer solution and instead of seeing the normal vortex that occurs in the center of the swirling, the surface rises up and starts climbing the stirring rod.

Thank goodness we don't use polymer solutions in toilet tanks.

Monday, November 15, 2010

A Polymer Contradiction

Over the weekend I remembered an unusual proposal for polymers that seems to have fallen by the wayside and I don't know why.

Polymers of course have a very high viscosity and their solvents have very low viscosities. Yet there are a few circumstances when mixing them results in an even lower viscosity (or least, an "apparent" viscosity). The specific example I am thinking of high molecular weight polyethylene oxide (PEO) in water. At dilute concentrations, the polymer can stifle the formation of turbulent flow, and thereby allow more liquid to be pumped at a given pressure.

The application that was most discussed was to use this system in fire fighting - more fluid for a given would be a good thing, or (semi) equivalently, being able to spray the water further also be helpful.

For reasons that I heard, this application never caught on. Anyone know why?

Polyacrylamide (PAm) of high molecular weight can also pull off this trick. When I was a TA at the University of Illinois for the undergrad ChemE unit ops lab, one of the experiments involved a large water tank that drained through a horizontal pipe at the bottom into a drain trench in the flow [1]. The tank was first filled with water and the vertical distance that the water shot was recorded as a function of the head. The tank was refilled and some PAm was added [2] and dispersed, and amazingly the water shot out quite a bit further.

[1] Yes, the polymer went right down the drain. This was not a problem, as PAm is used in water treatment plant to help flocculate and settle particulates - we were simply helping out the water treatment plant.

[2] One of the responsibilities of the TA was to prepare a 5 wt% solution of the PAm in water. This could take a while to prepare - the guide from the profs was 4 hours - the PAm had a tendency to clump together as is common with many water soluble polymers so if you tried to rush it, you ended up with a snotty mess and not a really thick, viscous liquid. Since I was studying polymers, I knew of a shortcut - use ice water, not tap water. The cold water limits the rate at which the polymer dissolves and prevents clumping. After everything is dispersed, you heat it up and your done. The other TA's always wondered how I could mix the concentrate up in 30 minutes. (Shhh, a magician never tells his secrets!)

Friday, November 12, 2010

Jensen's Inequality

Jensen's inequality is a simple math relationship that everyone should know. Like most mathematical relationships, it can be written with enough symbols to make it impossible to understand, but the qualitative idea is very simple: if you have a nonlinear relationship between an input and an output, and if you look at the output from those two inputs, the average of the outputs is not equal to what you would find for the output from the average of the inputs. Too wordy, I know. Let me give you an example.

This picture below is a good graphic of the situation.The two inputs are Z1 and Z2, and you can also see the corresponding values f(Z1) and f(Z2) which unfortunately are not labeled. Halfway between Z1 and Z2 is their average, < Z > and halfway between f(Z1) and f(Z2) is < f(Z) >, which you can see is greater than f(< Z >). So this then is Jensen's inequality:
< f(Z) > ≥ f(< Z >)
In this case (and in the example above), the nonlinear relationship is concave up, so the "average" output is greater than the output of the average input. Certainly concave down relationships can happen, and the outcome will be the opposite.

Chemical reactions have a non-linear relationship with temperature (i.e., the Arrhenius equation). So if you first run a reaction for a certain amount of time at one temperature, T1, and then change the temperature to T2 and run it for the same amount of time, the extent of the reaction will be greater than if you had run it at the average temperature, (T1 + T2)/2. Why? Given the non-linear nature of the reaction to temperature, the reaction runs quite a bit faster at the higher temperature compared to how much the colder temperature slows it down.

I've used this relationship in the past quite a bit when I was working with perishable food items. The food was never stored at a constant temperature - even properly working refrigerators cycle around a set point, so we used data loggers to record the temperature at regular intervals. The software that came with the data loggers actually would calculate the "average" temperature, a value that you can see is meaningless. Instead we would calculate a "mean kinetic temperature". Using the Arrhenius equation, we would determine the extent of degradation during each time interval, sum up the total extent of the reaction, and then back calculate the temperature that would have given us that reaction extent. (This is trivial to set up in a spreadsheet - import the data, hit F9 and you're done.) The mean kinetic temperature was always higher, and the higher the activation for the food, the greater the deviation.[*]

I was directly reminded of the inequality today when I came across a paper that looked at the implications of Jensen's inequality as applied to Ca2+ oscillations in cells. Surprisingly, the cells do much better than when the output is steady, and this was shown to be a direct result of the inequality.

[*] This is what I was getting at a few weeks ago after the power went out and we had to triage the food in the fridge. I tossed all the food with high activation energies since Jensen's inequality greatly disfavored them after temperature abuse.

Thursday, November 11, 2010

Olefin Metathesis

The blog All Things Metathesis has a nice entry about a large scale metathesis reaction, and how the changing economy has impacted it.

Metathesis can be (over)simply stated as moving double bonds around. The reaction is actually a combination of breaking and reforming the double bonds, but from looking strictly at the inputs and outputs, it looks like the double bonds are moving around. This is obviously important to the polymer industry as the double bonds can be used in polymerization schemes.

What I never knew was that metathesis is an equilibrium process, so that it can be run backwards - an important part of the post. Read the entry and see why.

Wednesday, November 10, 2010

Flow-Induced Crystallization #4

A new development in the area of flow-induced crystallization is the discovery of "dormant" nuclei.

Back when I was last in the field, the thought was that the development of a stable crystallization nuclei was a balancing act between the surface energy of the crystal and the Gibbs energy released during crystallization. As a nuclei first forms, the surface area is relatively large and so the surface energy required to grow it initially works against the effort, even though Gibbs energy favored crystallization. After reaching a certain size however, the energetics for growth became more favorable and it proceeded without further problems. The figure below shows this with the solid curve. Initially the slope of the thermodynamics (DDG/size) is against growth until the nucleus reaches the size rc, after which the slope become favorable. Unhindered growth only occurs after the curve drops below DG = 0.

You can also see on the figure the new understanding which follows the dashed line. In the past, surface energy was taken as a constant and so the solid line was the result. Surface energy is now understood to be somewhat variable, thereby creating the situation shown with the dashed line. Very, very small nuclei of size r1 are actually stable. These form quickly and easily underflow and stay there until the thermodynamics are favorable to grow, i.e., they are dormant.

Despite all these theoretical machinations, you can probably see that this phenomenon can impact real world problems. Just about all industrial polymer processes have some sort of shear and/or extensional flow and so all this unusual crystallization is out there lurking. Since the end product is crystallized, it's not like things will look different, but the potential still exists particularly if your temperatures are not very hot.

So with that, I'm going to wrap of this series of posts. There certainly is more information in the article, but I'll leave that for another time if it is relevant. My point here is that even in a relatively staid field like polymer science, (minor) revolutions in theoretical understanding can easily occur - especially when you disappear from the field (ala Rip van Winkle) for 20 years.

Tuesday, November 09, 2010

Can’t Touch This

Everybody is aware of the exploding red dye packs that banks throw into bags of stolen money; upon exploding, the money is permanently dyed and unusable. Now a new alternative solution has been invented, one that uses polymers, specifically polyurethanes. Apparently a quick reacting foam is created which envelopes and encases the money into an unmanageable blob. An interesting idea.

This was first reported in South Africa, which is a good thing. Here in the US, I can certainly imagine the scenario where the criminal gets some of the isocyanate on their skin, have a cardiopulmonary seizure and then they (or their survivors) then sue the bank (and their owners), the foam manufacturer (and their owners and their suppliers and the owners of the suppliers), the city, the state, and the Federal Reserve for 685 million dollars.

Tip of the hat to the Urethane Blog for the heads up.

Flow-Induced Crystallization #3

So the big question about flow-induced crystallization is "WHY?". Why does it occur. And this is where what I use to know and what is now known begin to diverge.

Any flow field takes the random coil that a polymer is in and begins to orient it to some degree. Extensional flow fields (a zone that necks down) is better than a shear flow, but both will do fine. Given this, the old explanation was that the partially oriented polymer had a lower entropy, and so the entropy change upon crystallization would be less than before. At a phase change (such as crystallization), T = DH/DS, where DH is the heat of crystallization and DS is the entropy change upon crystallization. Since DS is now less and DH is constant, the temperature at which crystallization occurs is increased.

Nice idea, but this now appears to be totally wrong - note that the orientation does occur, and the formula given is also correct - it's just that it's now been shown that the entropy change induced by the flow is too small to give a meaningful change in the crystallization temperature.

And so an old idea goes down in flames. But we're just getting started. A bigger blow will come tomorrow in the next post of this series.

Monday, November 08, 2010

Flow-Induced Crystallization #2

As promised, here is the first of a set of entries on different aspects of flow-induced crystallization.

The picture below shows the tremendous impact that flow can have on crystallization rates. It's a little confusing, but it will become clear shortly. This plot is for polypropylene, but you will find similar results for HDPE and others. Look first at the left-hand side. This shows the number of crystal nuclei formed (Nc on a log scale) under non-flow conditions and at different temperatures. The cooler the temperature, the more crystals there are - pretty standard stuff. Any higher than 130 oC and the number of crystals is too small to measure (or at least wait around for them to form!).Now look at the right-hand side. This data is all taken at 140 or 150 oC, higher than all the data on the left-hand-side and look at what is going on - the number of crystal nuclei is in the same range as under the quiescent conditions, but the temperatures are 50 degrees or more higher.

Considering that most polymer processes have some form of flow occurring in them, the applications for this can be extremely profound across a wide range of products and processes.

As I mentioned before, things have changed in this area of research in the last 20 years, but data such as this has not. In the next post, I'll start talking about the explanations for why this behavior occurs - what we use to think and what is the current thinking.

If All You Have is a Hammer...

The ChemJobber had an entry today about interviewing at a small company. I posted some comments there, but realized that I could have said more.

As CJ notes, small companies do not have complete analytical labs and instead use analytical labs to fill in the gaps. Even analytical labs don't have everything - we certainly don't, but I don't see that as a bad thing. It's great having the equipment on site as you can play with it on your own to solve a question that is nagging you and you don't have to worry about whose paying for it, but at the same time, the fact that you do have the equipment can limit you.

An example might be best. We don't have any NMR equipment. However, when we do need, NMR, we have the whole world to choose from for the testing. Sometimes a simple setup is all we need, sometimes we need cutting edge equipment - it's our choice as to who to work with.

Compare that with any instruments that we have onsite. They are all good instruments, but as a result of a) easy access, b) laziness, c) financial incentives [*] and d) the "If all you have is a hammer, everything looks like a nail" syndrome, we can often use them when sending a sample out could be better choice.

That said, sending samples out can still be a hassle. Some companies have good turnaround, some don't. Some will give you great analysis, some will tell you "we conclude that the sample was 12% carbon" which you already know from looking at the data tabulated in the report. It takes a while to develop a good network, so I certainly ask colleagues for recommendations before sending anything.

[*] If we use our instrument, we can charge the client for the instrument time and keep all that money. If we use outside equipment, we only pass those charges through. The bill to the client is the same, but the amount we keep is different.

Friday, November 05, 2010

Flow-Induced Crystallization

My graduate research was in the title topic. It actually a very interesting topic to study as it is a very unusual phenomenon. In a nut shell, crystallizable polymers (such as PE, PP,...) can crystallize extremely quickly at high temperatures when flowing, temperatures that are so high that the crystallization is non-existent in the absence of the the flow. This happens in both the melt as well as in solutions.

After school, I left the topic alone. My work had been in ultra-dilute solutions, (0.01 wt%) so the practical applications of that specific approach were negligible. However, I just ran across a review paper that just came out back in September (open access until the end of November) and was shocked by how much the field had progressed. Basically, all the rationalizations that we used to have 20 years ago to explain why things were happening as they did have been proven wrong and replaced with better explanations. Wow. From my dissertation, you could basically take the background discussion and many of the calculation results based on that and just put a big X through it.

I'm a little short on time today to discuss this much further, but I will get into it more next week. For polymer melts, the ramifications of flow-induced crystallization can be quite severe, so it is not just an esoteric topic. 'Til then.

Thursday, November 04, 2010

Plastics in the "Economist"

It's always nice to see a main stream publication discussing a more technical aspect of polymers, especially for a respected one such as the Economist. Last week they discussed the new results (Biomacromolecules - subscription/pay-per-view required)from the Schiraldi group at Case Western, making a casein based polymer reinforced by nanoclay. The hype here is that it is biodegradable as it is protein based.

The summary in the Economist has a few laughable details - such as describing some of the processing conditions as "freezing it at 80°C below zero" and just to be sure that this was not just a on-time error, they repeat is again later: "It was then cured for 24 hours in an oven at 80°C above zero." (-80°C and 80°C are sufficient). And somehow they are not concerned that it takes 4+ days to make a batch of this new material, obviously ignorant of how short a time period is involved in modern polymerization schemes.

The biodegradablilty of the material is (as expected) only measured in compost conditions, where 20% of the material was degraded in 18 days. The lack of widespread composting conditions was also overlooked by the Economist, which is especially poignant since they call the compost conditions as a "dump-like environment".

You will recall that the Wall Street Journal made an attempt not too long ago to explain the glass transition temperature, an effort that came off a little better than this one.

Tuesday, November 02, 2010

Funding "Meaningless" Research

Again, staying on the scientific sides of politics, it is very common for politicians of a certain persuasion to rant and rave about wasteful research supported by the federal government. Giving chickens Perrier water [*] is my favorite example; you'll have your own.

What never gets mentioned are is what is really happening behind the research, no matter how silly it may seem or even how inane it really is. In every case of research, a student is getting educated and a higher degree - either a master's or a Ph.D. The only way those degrees come about (in the sciences and engineering at least) is from government support of research.

At least when I was in grad school, the payback to the government and society was pretty clear. At my first job, I was paying in taxes what I used to receive as my stipend; I am now a better educated engineer, able to contribute to my employer and our clients in ways far beyond what I could without the advanced degree. The actual work that I produced has had little practical value, but that is beside the point. It was only a vehicle for an advanced education, not an end in itself.

So the next time you hear a politician rail on money going to study the birth defect in earthworms or some other silliness, think of the students behind the work bettering themselves. That is always a success even if the research is a failure.

[*] I remember this one well. Illinois has a very big ag department. One of the researchers discovered that chickens laid poorer quality eggs in the summer because the eggshells had less CaCO3 in them, a result of the chickens expiring CO2 in an effort to stay cool. (Like dogs, chickens don't sweat and cool themselves through increase respiration rates.) So one thought was to increase the CO2intake in the chicken by giving them carbonated water. The local press actually called it "Perrier Water", apparently taking it as a generic term. While this approach did work, it was found to be more cost effective to run cool water through the chicken's perches.

Election Day

This blog is not about politics. Today's post will briefly look at predictions for today's elections across the US, but only because there is one site that takes a scientific look at the polling data and uses it to make projections. That site is FiveThirtyEight.

The details of the methodology used are somewhat unclear (certainly for porprietary reasons) but the blogger, Nate Silver, a baseball statistician, uses a Monte Carlo method to run simulations using published polling data. This election cycle is actually his second time out - the first time was 2 years ago and covered just the presidential election, and in that case, his model was pretty accurate in predicting the electoral college results (hence the title of his blog). This time, he's looking at the governor races, senate race and the representatives too. I think this will be much more challenging as the number of polls for many of these races are quite a bit smaller.

Regardless, the outcome of the 100,000 simulations is a distribution with an average and a range of what we can expect, all of which is more meaningful to us scientifically inclined individuals than what is reported by the talking heads. If you've read his stuff in the past, you know he personally has a leftward bend in his politics, but to me, he really tries to be as accurate as possible with these predictions. He is very up front that for 10 races that he is 90% certain of the winner, he had better be wrong (or near wrong - that's just the way statistics works) in one of them, or else his model is wrong.

I will be quite curious to see tomorrow how well the predictions come off. As of this moment in time, he has the Democrats as 93% favorites to control the Senate, but only a 16% of controlling the House. He has odds for all the individual races as well, so check out your local ones for yourself.

Monday, November 01, 2010

2012 ANTEC back to Orlando - but with NPE

Courtesy of the "In the Hopper" blog, the Society of Plastics Engineers has announced that the 2012 ANTEC show will be in Orlando, but in a big change, it will be at the same time (April 1 - 5) and place as the NPE show.

ANTEC was just held in Orlando last year although it was in early May. I personally found the weather to be pretty uncomfortable, so I am looking forward to an April show instead. Plus I've never been to the NPE, so if I can just get a paper worked up and accepted, it could be a great trip.

Of course, I still have to work on this years paper - something I am taking a break from to write this. Remember, the deadline for abstracts AND the complete paper are November 19th this year - considerably earlier than in the past.

Dynamic Mechanical Analysis of Polymers

I was running some PLA this last week and just fell in love with the stuff - it's basically as well behaved as acrylates are. The time-temperature superposition is very easy to run with both G' and G" coming together beautifully. I also get a good amount of horizontal shifting too, so that the master curve really takes in a wide range of frequencies. Basically, I look like a genius because the data is so good.

The other extreme that I have to face on a very regular basis is a PVC-wood flour composite made by our parent corporation. It's just a nightmare - got to move fast and can't go too high in temperature before it starts burning and degrading (both the PVC and the wood!). I end up with lots of scatter, a limited output range and data that is only maginally helpful to reach any conclusions.

I hate working with silicones as well because they are so insensitive to temperature that you really have to make large changes before you get anything to change.

So what are your dream and nightmare materials to test?

Friday, October 29, 2010

Good Advice

The Curious Wavefunction has a review of a biography of the Indian chemist Chintamani Nagesa Ramachandra Rao (known as C N R Rao). This quote pretty much speaks for itself, so I will present it unadorned without further comment:
"So how does one do high-quality research in a resources and cash-strapped developing country? Rao’s approach is worth noting. He knew that the accuracy of measurements he could do with the relatively primitive equipment in India could never compete with sophisticated measurements in Europe or the US. So instead of aiming for accuracy, Rao aimed at interesting problems. He would pick a novel problem or system where even crude measurements would reveal something new. Others may then perform more accurate measurements on the system, but his work would stand as the pioneering work in the area. This approach is worth emulating and should be especially emphasized by young scientists starting out in their careers: be problem-oriented rather than technique-oriented."

Garbage Patch Vacuum Cleaners

Back in June I wrote about Electrolux plans to retrieve plastic from the various Garbage Patches in the oceans and turn them into vacuum cleaners. Somehow I was under the impression that the plastics was going to retrieved and then thermoprocessed into the parts needed for the vacuum cleaners (a task with a very challenging set of issues as I noted earlier). However, that doesn't appear to be the case - the plastics appear to be merely surface decoration on an existing cleaner.Each vac is made up of pieces collected from each ocean. Nonetheless, the vacs are attractive, but certainly an immense amount of energy went into collecting this relatively miniscule amount of plastic, all for a cute PR plug.

Thursday, October 28, 2010

Is this safe to eat?

Due to the massive storm that hit the Midwest earlier this week, we lost power at our house for 18 hours. After it came back on, we did the usual - reset the clocks, purge the air in the water lines (we have a private well - no electricity means no water means the system loses pressure and lets in air) and then the nasty task of triage in the fridge: what do we keep and what do we toss.

In a previous employment situation, I worked on developing a time-temperature indicator. Perishable foods are sensitive to both time and temperature - you can't keep food safe forever even if the storage temperature is ideal - the degradation kinetics still keep clicking, albeit slower at lower temperatures. As with any chemical reaction, the kinetics are governed by the Arrhenius equation:r = A exp (-Ea/RT), although it is usually plotted on a semilog plot where the slope is -Ea and the intercept is ln(A). The higher Ea is, the more sensitive it is to temperature variations.

So given this, we looked in the fridge. We had cups of yogurt (expiration date in about 1 week) and cups of pre-made pudding (expiration date sometime next year). You may be shocked, but I pitched the puddings.

Why? Keep in mind that these are all perishable food items that need to be refrigerated at all times - that means that at room temperature, they have a short shelf life. But since the puddings have such a long shelf life at proper storage temperatures, that means they have a very high activation energy, and that they suffered far more from the fridge warming up (it was 55 oF when the electricity came back on.)

Similarly, in the freezer we had some ground beef that is stored in a modified atmosphere package, a package which also elevates the activation energy for the degradation. We ate it last night, or else I would have pitched it.

Modern food preservation techniques are all prone to this problem: they increase the shelf life at proper temperatures but do little to help at abusive storage conditions. People see the long shelf life dates and feel reassured.

A Foreign Body

About once a year there is a medical image published in the New England Journal of Medicine that is memorable. Today's image is just that - one that you don't need to be much of physician to diagnose: The first line of the caption: "A 35-year-old man presented to the emergency department with profuse rectal bleeding, abdominal pain, and an altered mental status..."


Wednesday, October 27, 2010

How to Get Around FDA Regulations - Legally!

It can be done and now that the Supreme Court has given its stamp of approval. The Supreme Court has now stated that it is o.k. to import drugs from a non-approved source foreign source and use them for their intended application. I never thought I'd see the day, but it has happened.

Oh, before I go, I forgot to mention the one little restriction: this only applies if the drug are intended for a court-ordered execution!

Apparently being concerned about the purity of the chemicals, their storage, etc. is just not an issue if you are being sentenced to death. If you've worked in an FDA regulated environment, the reasoning in the Court's Order is going to get you like fingernails on a chalkboard:
"There is no evidence in the record to suggest that the drug obtained from a foreign source is unsafe."
Try telling that to the FDA inspector next time they audit your facility and watch them die laughing. Sorry, if you are making a regulated drug/device, the burden of proof is on you to show that it is safe - the presumption is that it is not safe, even as the Supreme Court here attempts to reverse that.

Obviously this won't change anything except for the suppliers in this ultrasmall niche market. And it certainly was a creative attempt by the lawyer to delay the execution, but I imagine that more than a few people at the FDA heard about this and were aghast as it really was a complete reversal of their regulations.

The Coolest Thing You Can Do With a Polymer - Set Yourself Ablaze

Of course, all that heat is not very cool.

The Gray Matter feature over at Popular Science has a brief description of the art and skill of setting stunt people on fire for movies. Not to be outdone, the author sets himself on fire. Video included.

The combustable material is a sodium polyacrylate gel, which is a novel use of this polymer that I normally think of as being used for a more wasteful purpose. Being that this trick will be tempting to plenty of people who think immolation is neat or are otherwise attracted because of pyromaniac desires, I'm not going to go further details about the polymer or where to obtain it. Just watch the video, say "Kewl" and move on.

Tuesday, October 26, 2010

Shuffling up the PET Business

Buying and selling chemicals companies and divisions continues. The latest announcement is that Eastman is getting out the PET arena entirely and selling their plants to DAK.

It appears that DAK intends to keep operating the plants, so this is not a "jobs going to a foreign country" story, just a division going to foreign ownership story. The report from C & E News had a sentence that I am questioning.
"Eastman is the last publicly traded U.S. company to be involved in the PET business."
First, it is an odd distinction to make, as why does public/private matter? But I also recall that when I was working at 3M, they made a lot of their own PET for captive use in their tenter lines, largely to support the mag-media business [*]. 3M shut much of that down in 1995, so they may have cut back or eliminated the internal PET production as well. The PET also was use for backings on adhesives tapes and other 3M products but they certainly didn't have the volume of the mag-madia. If any knows if 3M still makes PET internally and feels like stating so, I'd be curious.

[*] For you young 'uns, before digital storage existed, data was storage in an analog form in magnetic materials that were coated on polyester film. Sometimes it was in the form of a circular disk (kinda like a DVD) and sometimes it was in the form of a long ribbon that was wound from one spool to another. I promise to say just one more bad thing and then I will stop scaring you - the spooled ribbons did not have random access!

A Tale of Two Tenters

It was the best of times, it was the worst of times...Let me stop right there before Charles Dickens' ghost comes back and starts haunting me this weekend.

I ran across this old relic (an umbrella)
and it reminded me of my choice between two tenters [1] that I once made. I was finishing school and had begun interviewing. One of the positions was in Hopewell, Virginia at the ICI PET film plant. I was given the umbrella at the end of the day when the rain that had been threatening all day finally let loose. My host gave me the umbrella to keep my suit dry, although the rain was bouncing off the parking lot surface so hard that it did little good. Regardless, I still got a nice keepsake that only now is starting to fail. (Also, a million manhours without an OSHA reportable injury? That is impressive.) ICI is no longer which I still find shocking since at that time it was the 4th largest chemical company in the world. I think the PET plant is still operational, now being run by DuPont.

The other position was at the Hercules PP film plant in Terre Haute, Indiana. Hercules is also no longer in existence, but the plant still is. In this case, Applied Extrusion Technologies bought it, and looking at the satellite pictures, seems to have expanded it considerably. For a number of reasons, this is the job that I took.

I always wonder how life would have turned out if I had taken the other job. It is truly impossible to say. I left Hercules after 10 months. Some of the reasons for that may not have existed if I took the ICI job.

A coworker is of the opinion that life is made up of only about 5 serious choices (Which college? Which career? Which spouse? Which job? Kids, yes or no, and then how many?) and the rest is fluff. Certainly those choices are the big one and few people appreciate the simplicity of his viewpoint, but when I remember the tiny little twist one day [2] that allowed me to meet my wife, I can't help but feel that the butterfly effect is still mighty significant.

[1] Plastic films are made either by the blowing a large bubble and slitting it, or by the tenter process. In the latter, the film is stretched first in the machine direction by using rollers that a running faster at the output that at the input. This film is then fed continuously in the tenter (the second "t" is silent), the piece of machinery that stretches film in the cross-direction by grabbing it on the edges with clamps that are on a ever widening track.

[2] My advisor was out of the country and a secretary in the department office was typing up a paper for him (yes, on a typewriter!). She couldn't be sure what one of the handwritten words was, so she called me. I went down to the office, deciphered the word, and turned to leave. At the same moment that I opened the office door, she was walking down the hall right past the office...

Monday, October 25, 2010

Maybe Artificial Human Skin Does Exist

A little over a month ago I wrote about the difficulty of testing medical adhesives. The challenge is that human skin is difficult to mimic, not only because of it's low surface energy, but also because it is elastic - most adhesives adhere well enough to deform it and that work of deformation is always included in the measurement.

So here's to me embarrassing myself by finding a couple of papers that claim to have developed a suitable substrate for testing medical adhesives. One is in the Journal of Adhesion Science and Technology (2007, Vol. 21, No. 15, 1497-1512) and the other is in The International Journal of Pharmaceutics (2009, Vol. 368, No 1-2, 83-88).

It seems pretty simple, cook up some gelatin in water and NaOH, add some glycerol, some fatty components and then finally crosslink the whole mess with some formaldehyde. I've got to try some of this soon, as it will great to (verify and) know about before we get another medical adhesive project.

And best of all, my back will thank me. (See the earlier post if you don't get this reference.)

Chain Folded Polymer Crystal Picture

This is the first time I've seen a color version of a picture of a chain-folded polymer crystal. I like it a lot. It sure beats the black and white drawings that I put in my dissertation. Source

Except in exceptional circumstances, polymers do not crystallize in an extended-chain conformation (spaghetti in a box) but instead are repeatedly folded along the chain and re-enter the crystal. You can see this in the blue and green chains above - the red ones appear to be too short to fold over and re-enter. The length of the chain folds depends on the temperature and can be changed by annealing - another topic for another day.

This is from a simulation effort, but it still is better than the idealized hand drawings like this: