Tuesday, September 30, 2014

A Mixing Demonstration using non-Newtonian Blue Maize Flour Suspension

The Journal of Chemical Education has an article on mixing in non-Newtonain suspsensions that is visually appealing. They use blue maize flour, a material whose color is pH sensitive (I didn't know that). It goes through the color sequence shown below.
Blue Maize Flour at different pH values
Being a flour suspension, the material is non-Newtonian with a viscosity that changes with shear rate. But even more intriguing is that the viscosity of flour/water suspensions is pH sensitive. So as you might expect, the demonstration/experiment is to observe how well a liquid of different pH gets mixed into the suspension over time. Or doesn't, in this case. Taking 13 minutes to incompletely mix ~ 1.5 liters is not time effective in my world.

The authors are appropriately emphatic about the differences in mixing between laminar and turbulent settings (a distinction that any chemical engineering student understands, but few chemists do). Without getting into defining the Reynolds number and other engineering concepts, I'll keep it simple and say that with low viscosity fluids and high mixing speeds, you have turbulent flow and effective mixing. Conversely, with high viscosity fluids and low speeds, you have laminar flow and poor mixing [1]. In turbulent flow, mixing is as easy as falling off a chair, but in laminar flow situations, effective mixing is only achieved with chaotic mechanisms [2].

Mixing blades
The disappoint part of the paper is that the mixing blade is never shown and there is no discussion about how different mixing blades could alter the outcome. Given the wide variety of mixing blades available, this would be easy to pull off and would help students learn that picking the correct mixing blade is almost more art than science. And then there is blade diameter as well, and side sweep arms and...

Nonetheless, this is a good demonstration, one that I would have found helpful back when I was first learning of these issues. As more and more of our materials are produced from multiphase suspensions and emulsions, this knowledge will become that much more important.

[1] From Mixing in Polymer Processing ed, C. Rauwendaal, 1991, p. 2 "A polymer flow would have to be the size of the Mississippi River and moving at hundreds of miles per hour to have [turbulent flow]."

[2] The chaotic mechanism that most people are familiar with is kneading bread. You have a very high viscosity material and (besides building up the gluten network) you want to mix the ingredients very thoroughly. So you stretch and fold and turn, and stretch and fold and turn, and...

Previous Years

September 30, 2011 - Now that we have the "Perfect Plastic", you don't need me

September 30, 2011 - The Research behind "The Perfect Polymer"

September 30, 2010 - Pyridine

Monday, September 29, 2014

Ocean Plastic - The Truth and More Hype

I ran across a couple of articles this weekend regarding ocean plastics that are worth a read. The first is from Grist.org, entitled 8 Things You Should Know About Plastic in the Ocean. The amazing aspect of the article is that it gets it right. Or at least the text is correct. The pictures tell another story. They are still of macroscopic objects on beaches or in the water. But the text is correct. In brief, there is a lot of plastic particles out there, but we don't know how much, we can't collect it and the problem starts back on land.

Of course the comments go right back off the deep end (ha!) such as this one by Jeff:
"The ONLY real solution is to stop making plastic. Cleanup on a massive scale like this is pure fantasy and delusion. On top of that, there's no way to clean up the small stuff and what's been eaten by wildlife. Humans lived their entire history without plastic until recently. Plastic is unnecessary and totally harmful and should be outlawed."
Hey Jeff, no plastics? No Internet and no Facebook!

And then there is beauty about the newest brainstorm from James Dyson's (that charming Brit behind the Dyson vacuum cleaners that were claimed to "never lose suction" [1]). He's now proposing to use his one trick pony of cyclonic separation [2] to attack river plastic. While grabbing plastics from rivers before they make it into the ocean makes sense, his idea is problematic. First, it only focuses on large pieces of plastic. Second, the plastic, once recovered, is shredded and then passes into a cyclonic separate where it is magically separated. I say magically because the difference between all the grades of polyethylene (High-density, low-density and linear, low-density) is pretty small, making their separation very challenging. And then there is polyproplyene too that would mixed in as well. Yet the separation needs to be very effective or else the recovered plastic is of very low value. And Dyson knows this since that is why he wants to separate the various plastics in the first place.
"The Recyclone barge has not yet been prototyped or tested, but Dyson said he is convinced it can work."
Well that's enough to convince me. How about you?

[1] Funny how they don't make that claim anymore. Is it because it isn't true?

[2] Cyclonic separation is the answer [3]. What's the question?

[3] Multicyclonic separation is the answer. What's the question?

Previous Years

September 29, 2011 - Presenting Rheology Data

September 29, 2011 - Cool video of the day

September 29, 2010 - ANTEC is accepting papers

September 29, 2010 - More Destuction from Windows Reflecting Sunlight

Monday, September 22, 2014

Back from Vacation

I just got back from a week's vacation so this will be pretty short as the email box is quite full as so is the calendar. But it is worth it. Consider the alternative, which is what I tried this past summer - taking Friday afternoons off. What a failure. While it did avoid the overstuffed email box and calendar, what it really did was shorten the workweek, but not anyone's expectations of what I would/could/should accomplish.

So no more of that approach. This week was different. Everyone knew I was gone so no one expected me to do anything (except for the calls when there were some critical issues that really needed my input). Today will be hectic, but a week of peace and quiet was worth it. I even got to see Jens Voigt break the hour record online without feeling guilty about it.
Jen Voight - Hour Record
Jen Voight - Photo Courtesy of VeloNews

The hour record is arguably cycling's most difficult accomplishment and also it's simplest. You ride and see how far you can go in an hour. Whether or not you break it, it breaks you. It takes months of specialized preparation and then some. The effort is as much psychological as physiological, and there are months of recovery afterward just so you can look at your bike again and not want to destroy it with a 10-pound sledge. Hence, it is usually the capstone effort of a career and Jens is just such an example. He has now retired from professional bicycle racing.

Previous Years

September 22, 2011 - Another Source of Ocean Plastics - Your Clothing

September 22, 2010 - Watch out all you Grandparents!

September 22, 2009 - Self-Healing Plastics

Friday, September 19, 2014

Bayer's MaterialScience Spinoff

Plastics Today is reporting that Bayer is spinning off their materials science business, which include polyurethanes and their monomers, and also polycarbonates. There had been rumors for awhile that Bayer was going along this path, but I always figured someone would buy the business rather than have it spun-off.

I've never been party to a spin-off, rather I've been on the "spinning" side. While there are certain advantages (the company has more independence and can seek capital from a multitude of sources rather than just its new owner), there also disadvantages too (the stock markets are very short sighted and want good, consistent results every quarter). But spin-offs can also be a dumping ground for all the junk that the spinning company wants to rid itself of without any of the legal or PR issues associated with it. Want to cut your labor force by x thousand and not have to worry about the negative PR? Put them in the spin-off and let them bloody their hands while your hands stay clean. When there is a contract between a buyer and a seller [*], it's a lot tougher to shovel some dirt under the rug.

I'm just speaking in general terms. I have no idea if that will happen here at all. Just wishing everyone on both sides of the future spin-off all the best.

[*] Or should I say between a Bayer and a seller? Ha ha ha. I crack myself up.

Previous Years

September 19, 2011 - Recycling Paper Around the World - Literally!

Wednesday, September 17, 2014

Guess I won't apply for this job

I am not looking for a job but that doesn't mean that I don't receive an endless stream of emails from recruiters on LinkedIn [*]. A recent one came with this beautiful snippet:
"An Edisonian approach of trial & error, will not work for this role... this opportunity requires the ability to use theoretical modeling skills, fundamental / first principles knowledge, and deep understanding of polymer chemistry, in order to provide innovative solutions."
This is scary. That an employer would have such the expectation that experimentation is not needed and that computation and theory can be used to predict the properties of a polymer means that they will only be disappointed in the job performance of whatever poor soul takes that job. While there are some successes in such types of efforts to date, they are always for a single polymer genus and a very limited range of properties, such as this research relating reactor conditions for LDPE to the rheology. Not the mechanical properties of the LDPE, just the molten rheology. And again, this research is limited to LDPE.

There is no way I would ever apply for such a position.

[*] Sometimes I think that LinkedIn was start by recruiters for recruiters. Hence my low visibility there.

Previous Years

September 18, 2013 - "Dear, Do These Jeans Make My Butt Look Photocatalytic?"

September 18, 2012 - Toughening Up Hydrogels

Tuesday, September 16, 2014

Au Revoir, Auf Wiedersehen, Adios..to The Real World Blog

Eric F. Brown, author of the blog The Rheol World" signed off for the last time yesterday. His blog will be missed as during it's heyday around 2010, it was pretty active, being both humorous and informative. Sadly the posting frequency has slacked off greatly as of late and yesterday the end was formally announced.

I'm hoping Eric can restart the blog sometime in the future, so I will await that day patiently. My RSS feeder will be sure to alert me.

Do stop by his blog once last time and be sure to notice his unique logo with the built-in pun.

Monday, September 15, 2014

Plastics Scorecard v1.0 - I can't wait for v2.0

Being that I've spent my whole career working with plastics, I've had more than my fill of anti-plastic nonsense. But most of it is "harmless" statements about how bad plastic is. Statements such as "every piece of plastic ever made is still in existence" or any of a number of inane statements about "floating island of plastic in the ocean" or statements made by people thinking they are living a plastic-free life. When such statements are made by unprofessional individuals, I seldom get worked up or even respond.

But last Friday I ran across a new level of plasti-phobia that is so devoid of any technical support and yet, because of the graphics and table screams of respectability. It's all from this new "Plastics Scorecard v1.0" prepared by BizNGO. For reasons that are completely unclear, they have scored various plastics solely on the chemicals that are used in their preparation, or maybe more correctly, the chemicals that they think are used in their preparation. While that is a fair concern [1], focusing on just one aspect of a system is never a good idea and that applies in this case as well. So the fundamental logic of this scorecard is already incorrect. But what is really maddening is that the statements used in preparing this scorecard exhibit a new level of ignorance regarding chemical safety that I've seldom seen. Here are just a few examples of this. You can read the report and find more.

For instance, polyethylene terephthalate (PET) gets knocked heavily for its use of acetic acid in the preparation of terephthalic acid. Acetic acid? Yes, because the authors consider it toxic, even though the oral LD50 is about 3 g/kg. They are similarly upset about the use of ethylene glycol, even though its LD50 is higher yet at 5 g/kg.

The authors of this report have a very strange understanding of polymer chemistry. For instance, they are concerned about bis-(2-hydroxyethyl) terephthalate as an intermediate to PET, which it technically is [2], but it is never isolated in the process. Stranger yet is their understanding of the preparation of polylactic acid (PLA). They list glucose as the starting material rather than corn and they completely overlook the acids or enzymes used to hydrolyze the starch into glucose. No one makes PLA by starting with glucose, but rather from corn or some other source of a hydrolysable starch.

All of this shows a large shortcoming of this approach to scoring polymers: the starting point for a polymer is not always clear, and yet they are relying on the starting point to make their judgments.

The summary report is filled with howlers, such as "It is clear that manufacturers can make significant progress towards producing polymers from inherently safer chemicals" No, that is not clear in the least. What would these people consider inherently safer chemicals? Water? And where are is the carbon for the backbone to come from? Carbon dioxide? Coal? And similarly for hydrogen, what would that source be? Hydrogen gas? Prepared from what toxic chemical? And even the oxygen that is needed for making many polymers toxic to human in its pure gaseous form. That the highest scoring polymer was PLA and it only managed 58 out of 100 points shows just how ridiculous the entire scheme is.

While it is easy to write this off as the effort of just a few powerless individuals, the authorities that they have lined up supporting it is frightening, including Ken Geiser, professor emeritus, University of Massachusetts - Lowell and Helen Holder, Material Strategist, at HP amongst others. I have to seriously wonder if these people really read the report before signing onto the effort. I plan to contact them and let them know my opinions and challenge them on theirs.

[1] I've always had the willies thinking about phosgene being used to make polycarbonate (even though everyone is much more concerned about it's comonomer BPA).

[2] The initial condensation reaction yields water which limits the molecular weight that can be obtained. Using this intermediate "monomer" allows the polymerization to proceed without producing water.

Previous Years
September 15, 2011 - Follow Up on Yesterday's Post

September 15, 2010 - Purging

September 15, 2010 - A Strange Connection (if it even exists)

September 15, 2009 - Tires for the moon (and beyond)

Wednesday, September 10, 2014

Poster Sessions - Hey, My Eyes Are Over Here

Today and tomorrow are my companies annual internal poster session, so lab work will be down to zero as I will be presenting for both days. It is quite an exhausting experience, especially for a natural introvert like myself. But if you see me at the show, you would never guess I'm like that.

My attitude towards poster sessions has changed over the decades. At first I was trying to put as much information and words and data and graphs as possible on the paper, although I did know enough to ensure that the visual appearance wasn't too horrible. But the overwhelming thought was that the whole project would be there for someone to read while I stood silently by the side. If they had questions, I would gladly answer them. And when the session was over, I would judge it as a success if I talked to no one.

Coincidentally, my Powerpoint slidedecks were set up the same way. All the information was there and I didn't need to be there, although I never, never not even once stood there and read off the slides directly. That is and always will be a waste of time for all parties.

That all changed at my previous job where we did contract R & D. In a job like that, you are always selling yourself and your company. That's a big part of the reason you are reading this blog. It started as an aid to establish the credibility of me and my (previous) employer. And so despite being an introvert, I learned to engage people. And a great way to do this is to tell stories. There is a great story in every research project, you just have to find it. There is something about storytelling that attracts people. As long as people have gathered around a fire, they have told stories. I'm just tapping into that powerful aspect of human nature

So after 8 years of learning to sell myself and tell stories, my posters sessions have come to reflect that. The posters are now greatly simplified and stand as an aid to what I am talking about, a prop and not a crutch. Furthermore, I'm like a used car salesman - don't make eye contact with me. If someone slows or glances at my poster, I literally wave them towards me and start into my story. And to further freak them out, I talk to them face-to-face about my research. When I come to a point in my talk where a visual would help tell the story, I point to a section of the poster that has what I need. And then it's back to making eye contact until I need another visual. At the end, I now know that the person got the story I want to tell. And in most cases, I can tell that they are thankful. They will leave the session knowing at least one research project to some level of detail instead of it being a blur of endless posters.

Similarly, my Powerpoint presentations have over time had less and less on the slides to the point that now when someone asks for a copy of my slidedeck, I am quite sure that they will get very little out of it. Without me and my story, there is little there.

Unfortunately, I can't always get away with approach as often my slidedecks have to be approved/reviewed by others prior to my presentation. You can easily guess the feedback I get.

Previous Years

September 10, 2013 - A Pitch Drop Contest

Tuesday, September 09, 2014

Plastics to Oil - Hype or Hope?

The Wall Street Journal had a video Q & A with Steve Russell, vice president of the American Chemistry Council regarding efforts to convert plastic waste and other elements of municipal wastestreams to oil. This process, know as Plastics-To-Oil (PTO), is done by anaerobic pyrolysis - heating the plastic up in an oxygen-free atmosphere to temperatures that degrade it to low molecular weight liquids. The technology is not all that new - I discussed it here over 2 years ago. If obviously works best with plain hydrocarbons - polyethylene, polypropylene, EPDM rubber, etc. Heteroatoms such as oxygen from PET, chlorine from PVC, nitrogen from nylons, etc. make it a little more difficult to produce the pure hydrocarbon output so desired by refiners. But in all cases, the lack of sulfur in most plastics ensures that the output is a very sweet crude oil.

The title of the article, "Plastic May Well Be the Next Big Energy Source", however really bothers me. Of all the petroleum that is taken from the ground, 5% of it ends up being plastic. This then means that at most we can reduce our consumption of oil by 5%. And that's assuming 100% efficiency at recovering all the plastic from all wastestreams, and further that this process can be performed without any additional energy inputs.

The current reality is that about 10% of all plastics are recycled. Even aluminum cans, the paragon of recycling efficiency, has a recovery rate of about 60 - 70%. So 100% recovery of plastics is a pipedream. Even 50% recovery is probably too much to ask for. And of course pyrolysis requires energy to heat the plastics to over 400 oC, so that further reduces the net amount of petroleum that can be gained.

So can a 2 - 2.5% reduction in petroleum consumption through PTO be considered the "Next Big Energy Source"? Considering that petroleum consumption fell all of that and more during the Great Recession, I won't call it that.

Hat tip to Chemjobber (Blog and Twitter) for bringing this to my attention.

Previous Years
"blue"September 9, 2014 - Where's the Cheap Plastic We Were Promised?

Thursday, September 04, 2014

Polymer Single Crystals - "Spaghetti in a Box" or something else?

Chemical and Engineering News is celebrating the International Year of Crystallography in part by taking submissions from readers of their favorite crystal structures. They have quite a list going and somewhere buried in there is mine:
This simple picture completely changed our understanding of polymer crystallization. These are single crystals of polyethylene, carefully crystallized from dilute solutions in xylene. It had long been assumed that polymers crystallize as fully-extended chains - "spaghetti in a box". But there was no proof until Andrew Keller came along.

X-ray diffraction showed that the polymer chains in these crystals were oriented perpendicular to the surface - they are coming out towards the viewer and and are not running along the viewing plane. But the bigger question here is how thick the crystals are. And that can be differed from the the size of the shadows on the photograph. In order to more clearly observe the crystals, they had been coated with a thin layer of metal coming from a source laterally offset from the crystals. Because of the geometric constraints, some portions of the samples were shadowed from the stream of metal atoms. The size of these shadows then allowed for a quick and easy calculation of what the crystals thicknesses were.

And that is where the whole world shifted. The thickness of the crystals was just a fraction of what it should have been if the polymers really had crystallized as "spaghetti in a box". Since the chains were oriented perpendicular to the surface, the only conclusion possible was that the chains were folded back and forth. "Spaghetti in a box" became "ramen in a bag" [*]
.From this approach, it was then possible to determine the effect of temperature on fold length and a myriad of other aspects of polymer crystallization. All because someone paid attention to the details, those tiny little shadows in the image.

[*] "Ramen in a bag"? I just came up with that. It's weird, but the more I think about it, the more I like it.

Previous Years
September 4, 2013 - Fraud in the Literature, Blogs and Witchhunts

Wednesday, September 03, 2014

Will I poison myself if I reuse this plastic water bottle?

This question was asked at Grist on Monday. You can read their answer if you want (or you can read this synopsis: "yes, you will poison yourself"). Let me offer a different perspective.

The question that was actually asked is a little more involved:
"Is it OK to reuse the bottles that bottled water comes in? Sometimes when I am at a conference the bottled water they have is in a really sturdy bottle, and it seems like such a waste for it to be single use. But is it safe to refill it from the tap? My primary concern is BPA leaching into the water, but what about sanitation?"
Let's overlook entirely the misinformation about BPA leaching from a PET water bottle [1]. In fact the Grist article does catch that, but only after launching into a full paragraph about the horrors of BPA and then citing that discredited article from Bittner about other endocrine disrupters being in plastics of all sorts. But I'm fine with that, because even if the bottle is leaching an Unknown Nasty Chemical Attempting To Kill Us (UNCATKU) into the water, I would strongly recommend that the bottle be reused.

Assuming that there is an UNCATKU in the plastic, the concentration in the plastic is highest when the bottle is first drank from. The amount of UNCATKU that leaches out of the plastic into the water depends on two factors: 1) the concentration of the UNCATKU in the plastic and 2)the time that the water is in contact with the plastic. The higher the concentration of the UNCATKU in the plastic, the faster it will leach into the water. The longer the water is in contact with the plastic, the more UNCATKU will be able to leach into it. Given modern logistics, it is likely that the water in the bottle has been there for not just hours or weeks, but months and possibly a year or more.

For those reasons, I would suggest that if you are really concerned about the UCATKU, open the bottle, pour the water down the drain and then refill it before drinking. And for those same reason, I would recommend that you then keep the bottle and reuse it.

As the UNCATKU leaches into the water, the concentration in the plastic is reduced. [2] Every time the bottle is refilled and more UNCATKU leaches into the water, the concentration in the plastic is further reduced. If the bottle is refilled enough, it is conceivable that the bottle could become free of the UNCATKU. Similarly, when the bottle is refilled by someone, they are going to be drinking from it in short order, not months from now. Both of these factors which led to the conclusion of dumping the bottle out in the first place are now supporting reusing the bottle.

To close the Grist article out, the author comes up with a contradictory argument. The author further cautions against reusing the bottles because being "...moist, enclosed, and getting a lot of full-body contact with your hands and lips", they are bacterial breeding grounds. His advice: carry a reusable metal drinking bottle. This overlooks the fact that the metal bottle would also be "...moist, enclosed, and getting a lot of full-body contact with your hands and lips", but that's ok I guess since he is an anti-plastic advocate.

Worry if you want about the UNCATKUs hiding in plastic water bottles, but don't let that stop you from reusing them.

[1] PET is BPA-free because it was born that way. It always has been BPA-free. And I can't see that ever changing in the future. Making PET from BPA would be pretty idiotic.

[2] It is a little more complicated than this, as the concentration of the UNCATKU would be a gradient such as Fick's Laws would predict, and not constant. Correcting for that will not alter the overall conclusions of what I'm stating here, just the rate at which these events occur.

Previous Years
September 3, 2013 - A Nonprofit Tries an Unusual Approach to Recycling Plastics