Tuesday, July 31, 2012

Accelerated Aging, Flash Photography and Museums

I've written many times (1, 2, 3, and 4) of the challenges of accelerated aging and how, when improperly performed, it leads to incorrect results. Last week [*] a new example came to "light" when it was announced that the standard policy in museums of banning flash photography is without factual basis.

The standard explanation for the policies has been that the accumulated exposure of the art to the light would result in fading/decomposition of the paint/pigments/...and as you may have expected, there was some research to support the conclusions. But like so many accelerated exposure tests, this one was flawed, although I've not ever seen a study flawed in quite this manner:
"The flashguns were fired at the pigments every 7 seconds, and the total light quantity measured. At the end of a trial lasting many months it was found that these flashes had produced some change in the pigments. After more than 1 million of these test flashes, totalling 200,000 lux hours of exposure, about half the pigments showed changes just visible to the eye. The remaining pigments showed changes too small to detect with the eye, but measurable by photometry. In the vast majority of pigments there was no more change from UV-filtered xenon flash than from the same quantity of gallery lighting." (Emphasis added)
That's right, the flashes did nothing to degrade the art, and yet this research led to flash pictures being banned. Pretty scientific, huh?

Martin Evans has some further thoughts to sum up the logic:
"Is it worth getting steamed up about such a tiny extra quantity of light, as far as pigment fading is concerned? Several photographers have already suggested that any trifling damage done by a few hundred of these little flashes in a day could be fully offset by closing the gallery and turning off the lights a few minutes early."
But does anyone seriously expect this to change any museum policies?

[*] Last week? If you chase the references back far enough (Amusing News Aliquots --> Gizmodo --> Imaging-Resource --> Martin Evans, Ph. D.) , you see that some of this work goes back a few years.

Friday, July 27, 2012

The Most Overlooked Analytic Technique in Polymers - DSC

The most overlooked analytical technique in polymer science is DSC - differential scanning calorimetry.

The technique is pretty simple. Two small "pans", 1 containing the sample, the other empty, are heated (or cooled) at a constant rate and the difference in the amount of energy going to the two pans is monitored. (Hence the term "differential" in the technique's name.)

The most common use for the instrument is to study melting/crystallization behavior of materials. Melting/crystallization temperatures can be determined (look at the location of the peak) as well as the associated heat of fusion/crystallization (the area under the peak). If you know the value for a "perfect" crystal, you can then determine the % of crystallization in your sample.

But even beyond that, you can determine the glass transition temperature (it will appear as an offset in the curve, not a peak), you can determine if an sample is entirely cured (look for a small exotherm as you increase the temperature), and you can also use it to learn about antioxidants in a polymer. (Bring the sample to a constant temperature under N2, then switch over to O2. The longer it takes for the oxidation exotherm to show itself, the more antioxidants are present - a technique known as OIT, oxidation initiation time.) The list of other analyses that people have created with this instrument can go on for pages. All this from just a few milligrams of sample.

So why do I say the technique is so overlooked? It is one of the workhorse instruments here at Aspen Research (you should see the panic when the instrument is temporarily down) and I think most industrial polymer scientists and engineers would agree. I say the technique is overlooked as I've yet to see it discussed in any university classes, or even given proper treatment in a textbook (Billmeyer has less than a page of text on it, and Skoog mentions limited polymer application in passing.) I never learned of the technique in the classroom either as an undergraduate or graduate student, the two interns I had these last few years have not been taught about it either, nor have any of the recent hires. Dynamic mechanical analysis (DMA), gel permeation chromatography (GPC) and the Mark-Houwink equation (capillary viscometry) all get proper coverage, but not this versatile thermal technique.

I'm sure that there are some schools somewhere that teach it, but based on my experience, they are the exception and not the rule. Why is that?

Wednesday, July 25, 2012

Ocean Trash - It's Not What You Think

The Ocean Conservancy assembled nearly 600,000 volunteers recently to pick up trash from coastlines around the world. Considering that we are pelted nearly daily with "reports" about how much plastic packaging there is in the various garbage patches around the world, I was quite surprised by this graphic of the most commonly found items:
Cigarettes? The number one item by far was cigarettes, outnumbering plastic caps by almost a 2-1 ratio. I certainly didn't expect that.

The filters of most butts are made of cellulose di-/tri-acetate which has a specific gravity of about 1.3, which suggests that the butts sink rather than float and hence have a difficult time making their way to the great garbage patches.

The efforts to fight pollution are mostly based on visibility of the pollution. "Out of sight, out of mind" is never more true. The butts sink and it's tough to get people fired up about them, even though they are the most common type of ocean trash. But plastic packaging floats and is visible, and it will remain visible even if it is biodegradable. And that's why I don't believe biodegradable plastics will do anything to change public perception about plastic waste. As long as people can see the plastic waste on the coastline, the biodegradability will do nothing to change their perception of it.

Since plastic pollution is leading to cities banning bags and bottles, the same logic would lead us to also be considering a ban on cigarettes. Somehow I don't see that happening, as the tobacco industry is far more powerful than the plastics industry in lobbying against such bans.

Tuesday, July 24, 2012

Self Cleaning Plastics

You've probably seen over the years numerous examples of "self-cleaning" ______________, whether it be windows, sculptures or as was mentioned yesterday in the Polymer Solutions Blog, plastic outdoor furniture. While a variety of mechanisms exist for obtaining these surfaces, the most common route is to take advantage of the photocatalytic nature of the anatase [*] phase of titanium dioxide. If organic matter contacts the surface, and the surface is exposed to UV light, the organic material will oxidize, possibly going as far as becoming CO2 and water, leaving the surface pristine again. Hence the name "self-cleaning".

But there is one little glitch in the whole system that prevents the widespread adoption of these coatings. They only work on reduced (non-oxidized) materials. When inorganic materials, such as various clays based on SiO2 contact the surface, nothing happens. You have to then clean your "self-cleaning" surface.

So when the Polymer Solutions Blog says: "Manufacturers of cleaning supplies: Be afraid. Be very afraid.", you don't need to be selling your Chlorox or S.C. Johnson stock anytime soon. Maybe "semi-self-cleaning" would be a better descriptor.

[*] The rutile phase is used as a white pigment. We once had a client that accidentally used the anatase phase as a colorant...and had some major liability issues, but that's another story for another day).

Monday, July 23, 2012

Wrap-Up on the Nylon-12 Shortage

So the Great Nylon-12 Shortage of '12 (previously discussed here, here, here) appears to be fading.

While everybody was really concerned about the nylon-12 supply, to call it a nylon-12 shortage is to miss a important lesson. The Evonik plant that had the blow-up didn't make nylon-12, but instead my cyclododecatriene (CDT), a precursor to nylon-12. Evonik is a large supplier of nylon-12, but is even a larger supplier of CDT. That's why there was a problem - people thought that they didn't need to worry about nylon-12 suppliers since there were so many, but it really was the CDT supply that they needed to keep their eyes on (a point that the article linked to above fails to see - the table at the bottom of the page is about nylon-12 volume, not CDT volumes).

Think of a consumer product that you can buy from a number of different stores, such as a 2-liter bottle of Dr. Pepper. We all know that the product is coming from the same factory - that the different grocery stores all have the same supplier at some point back up the supply chain far enough, but that was not the case with nylon-12 and automotive suppliers. They didn't look up the supply chain far enough.

It certainly can be easy to blame the purchasers for this lack of insight, but at the same time, I imagine that it would be hard for Toyota or GM to really get much useful information about CDT. After all, it's not like car manufacturers or any of their suppliers are buying CDT. They could try questioning a nylon-12 supplier about their CDT suppliers, but that's not going too productive. The best way to avoid a repeat of this is to accomplish what Ford did - pre-identify alternatives to nylon-12 entirely. I can still imagine scenarios in which the supply lines for both a primary material and a secondary material could be taken down together, but that is pretty unlikely.

Wednesday, July 18, 2012

The 7 Worst Things Made From Plastics - Ever!

Things that never should have been made. A whole lot polymers died in vain over this stuff. These are items that are clearly and forever awful with no redeeming qualities at all. There are easily more horrible products made from plastics out there - Britney Spears CDs for instance - but I made a judgment call that the pox those CD's induced on humanity was probably offset by all the wonderful music also recorded on CDs, leaving CDs as an over positive product. The following 7 items however, do not have any such redeeming qualities and are pure evil:

7) The Leisure Suit. The Horror! The Horror! For the younger readers, back in the dark ages (the 1970s) men actually wore these to bars looking to pick up women.
6) The Dipr, a plastic tool for dipping sandwich cookies in milk. If your fingers work well enough to put the cookie on the Dipr, they work well enough for you to not need it.
5) The orginal PLA-based bag for Sun Chips. When you have a Facebook page devoted to hating your product's packaging, you're in trouble.
4) Clamshell packaging. When packaging leads to a new social condition - "Wrap Rage" - you're in trouble.
3) The Happy Hot Dog Man. Can't you just do this with a knife? Even a plastic knife would work.
2) Expanded polystyrene (aka Styrofoam) peanuts. Maybe a nice dose of an antistatic coating would help make them more tolerable, but even that is doubtful.
1) The Vuvuzela.

Tuesday, July 17, 2012

Gel Rheology (and How to lose a Stage in the Tour de France)

While most of the coverage of Sunday's stage in the Tour de France was about the "tack attack", the outcome of that day's race was ultimately decided by rheology. Gel rheology in particular. The gel is barely covered by the cycling media, so let's get to that first:

While the main pack of riders was dealing with the tacks, a smaller group was well up the road, and one of the riders in that group was the feared Slovakian Peter Sagan. Sagan has already one three stages of the race this year and looked to be on the way to his fourth since nobody in the breakaway group could outsprint him unless Sagan stopped in the sprint to tie his shoes, and even that might not be enough of a hindrance. He is that fast.

But Sagan made one mistake with only 11.5 kilometers to go in the day's race, a mistake that was the equivalent of stopping to tie his shows: He was hungry and did something about it. He reached in his back pocket and pulled out an energy gel [*]. At that point, another one of the riders in the group, Leon Sanchez, attacked and rode as hard as he could. He was able to open up a gap and keep it all the way to the finish. Sagan ended up coming in second.

So what does rheology have to do with this? Well, Sagan had three options to address his hunger - drink something, eat something or go for a gel. Had he gone for his water bottle (assuming that it contained some kind of energy in it and wasn't just water), he would have been able to respond to Sanchez's attack. Eating something was not an option as chewing solid food is normally only done in slow portions of the race. You Mom always told you to not talk with food in your mouth and the same rule holds for bicycling racing - it's impossible to ride hard with a mouth full of food. So that left the gel as the only option. The fact that the gel is soft enough that it can be quickly swallowed, but still stiff enough that you need a good hand grip to extrude it is what caused Sagan to choose that option, and thereby lose the race.

Years ago before these gels existed, Sagan would not have had the gel option and most likely would have won the race, assuming he didn't "bonk" (hit the wall/run out of energy), but that sweet gel with that easy to swallow rheology tempted him and he paid the price.

Don't feel too bad for Sagan. He's only 22 and just starting his career. There will be many more wins to come, but hopefully his coach will speak to him about different rheological options for refueling. (If not, I'd be willing to be hired on as a rheology consultant!)

[*] These gels are carbohydrate-based, with various sugars, electrolytes... You tear off the top of the package and squeeze the gel out into your mouth.

Monday, July 16, 2012

Rheology, Theology and Deborah

If you ever studied even a little rheology, you've probably been exposed to the Deborah number, a dimensionless number that is the ratio of relaxation time of a polymer (or other non-Newtonian material) and the observation time. Or if you haven't been taught the actual number, you've no doubt been taught about the ideas it represents. If the relaxation time of a material is very long and your observation time is short, then the material will appear to be solid. But the timescales are inverted and the relaxation time is short while the observation time is long, then the material will appear to be liquid. That means that a material can appear to be either a liquid or a solid - all depending on the relaxation time and your observation time.

This idea is intimately tied to the name Deborah, far more than any other name is associated with any other dimensionless number such as the Reynolds number, the Prandtl number, or the 2nd Domköhler number, all of which are named after researchers. Instead with the Deborah number, it is named after a person that is long deceased for over 3000 years and obviously not a rheologist. The Book of Judges in the Bible has the victory song that the prophetess Deborah wrote after she gave the Canaans a good a**whooping on the battlefield. One line of that song is "The mountains flow before the Lord", which a prominent rheologist (Marcus Reiner) thought captured this concept perfectly. On the observation scale of God, mountains could appear to flow like a liquid, while for people and their short observation times, the mountains appear very solid. And so the name of this dimensionless number is "Deborah".

Reiner described this line of thought in an article (open access) published in 1964, in which he also further describes the relationship between "rheology" and "theology". Since that time, the relationship has been further blurred by spellcheckers. The first time someone tries spelling "rheology", the spellchecker doesn't recognize the word and instead suggests "theology" as a correct word. (Not that bad a choice, as the "r" and the "t" are adjacent on the QWERTY keyboard.)

Steve Carrington of Malvern Instruments however, has proposed yet the latest connection between the two subject this last week:
"How many times have you looked at some rheological data....and hoped for some divine intervention to help you understand it?!?"

More times than I ever imagined. More times...

Friday, July 13, 2012

Open Access Polymer Journals and Other Links

The posts this week have (unexpectedly) been entirely about open access, so I might as well finish it up that same way.

A reader of this blog, Dr. Maria Bellantone, who is a senior editor at Springer of a number of European Physical Journals (EPJ) and other journals, pointed out to me that her publisher has a monthly highlighted EPJ article which is free to read for that month. The "E" edition (Soft Matter and Biological Physics) would be of the greatest interests to readers of this blog. This link has a summary of those articles as well as the links to the articles. (Shhh! It seems like some of the older links still work. Hurry before anyone notices and shuts them down.)

I've promised in the past to try and keep readers up to date about articles that are free to read for limited time periods, but I've not done a good job. Here's to trying to improve on that effort.

I've also located a number of open access journals that are entirely or partially devoted to polymer science. I've given the links below, but will also add them to the "Free Access..." page too.


Express Polymer Letters

International Journal of Polymer Science

The Open Macromolecules Journal

Polymeri: Plastics and Rubber Journal


These journals were located via the Directory of Open Access Journals

Thursday, July 12, 2012

What if...?

What if we did suddenly have open access to all technical literature? And by this, I mean that the publishers can still keep publishing just as many journals and articles as before and the quality is the same as before and...and...and...Basically the world is the same as before, except that you will never again see those disheartening words that "Your current credentials do not allow retrieval of the full text" or any of a number of equivalent messages.

I see plenty of people that want open access, and plenty of publishers that want to avoid it, but very little thought as to what would happen if universal open access did occur. Here are my thoughts:

The most significant change would be that people like me and hundreds of thousands like me in medium and smaller industrial settings around the world would have access to information that we did not have before. Importantly, this is information that we can use. We are capable of reading it, understanding it and using it. To use the words of one publisher, we are "qualified readers" (even as he argues that we aren't) [*].

With that sudden influx of information, does anyone not think that there would be a sudden increase in innovation? More innovative products like we've never seen before? And what would be the economic impact of that? More jobs?

I'm not saying that people in smaller companies are more creative than in large companies, it's just that we are not burdened by the slow pace that the large companies move at. We can run circles around them in getting things done. That's why when we get great ideas and develop them, we are snatched up by the big companies.

We already face many restrictions at a small company - lack of capital, equipment, manpower...and to propose a fantasy world where these restrictions would be magically removed is really too much to even imagine. But removing limitations on access to the latest scientific information is not that large of stretch, and would have tremendous benefits to the country and the world.

When I am speaking of innovations, I am not just thinking of disposable consumer products that the world can probably be just fine without. Here in the Twin Cities we have probably the largest number of medical device startup companies in the world. How many new live saving devices could this information generate? How much could efforts towards sustainable chemistry be advanced? Or new energy alternatives? Or improvements in food, or clean water or...

I am not and have never argued "Death to Publishers!". They provide an great service that should be compensated. But can that happen in alternative manners that allow for open access? And would that world be a better world than what we currently have? I would argue that that vision should be used to guide our way forward, not simply "Open Access? Yes or No?"

[*] The irony is that many of us in industrial settings provide the peer review for journals that we do not have access to. If we are qualified enough to review the paper, we are qualified enough to use it.

Wednesday, July 11, 2012

"What is Journal Access Like in an Industrial Setting?"

A semi-anonymous individual left a comment in yesterday's post "I was wondering how subscriptions to journals work in an industrial setting. Do you have at least some journal subscriptions available?"

Having worked for a range of companies, some that have spanned the globe while others have barely spanned the spread of my arms, I've seen lots of different approaches to journal subscriptions in an industrial setting. The confounding aspect in all of this is the time factor - approaches that companies took in the past have undoubtedly changed to at least some degree.

My first job was at Hercules, a company that no longer exists. This was a reasonably good-sized company (multibillion in sales). I was not located at the main research center but at a remote site, so if we needed articles, we could call the company library to have them mailed to us. I also recall that some of the consistently popular journals were put out on a routing list. The biggest issue back then was not getting the articles as the company was willing to pay for them, but instead finding out what articles were even available.

I next went to 3M, which had multiple libraries scattered across most of the buildings on their campus. Pretty much anything you wanted was available or easily accessible. By the time I left there in 2002, internet access to the journals from your desktop was well established.

Since that time I've worked for smaller and ever smaller companies, none of which have had subscriptions to any journals at all. If you've ever looked at the list prices for a few journals, you'll know why. I'm not attempting to pick on any particular publisher, but look at the subscription prices for these key journals in polymer science:

Journal of Polymer Science, Part A or Part B - $20,000.

Polymer - $9,301.

Soft Matter - $2,438.

Polymer Bulletin - $3541.

These are institutional rates, which is what would apply to us here [1]. For a company with only $10 million in sales, we just can't afford that overhead, especially when you consider that we work with more than just polymers. We have metallurgists, analytical chemists, physicists, mechanical engineers...

I do have a personal subscription [2] to the Journal of Rheology ($80) and I couldn't pass up a special price on Nature this past year ($36, but that will increase to $79 this coming year and I'm not sure if I will renew it or not).

The point of this is NOT to rant about high prices, open access or anything else in that arena - simply to state that at a small company, access to the literature is very limited.

So we get creative instead.

It's not very visible [3], but I do have a separate page in this blog where I've listed some of my tricks for accessing the literature for free. These efforts are helpful, but they do require far more work than just being able to click on a link and get an article.

I do see the situation improving over time. The US and the UK are starting efforts to ensure that publicly funded research is freely available, and the editor of Nature magazine just recently stated that open access is "inevitable".

So that's the view from an industrial setting. It all depends greatly on where you work, with the larger companies have the better access, and the smaller companies have little or no access.

I have some additional thoughts on this matter, but I'll post them in a day or two.

[1] From what I read, it is possible to negotiate lower prices, but that would only be an option for large institutions that are looking at multiple journal subscriptions. There is no reason for any publisher to lower the price for a single journal.

[2] Being the only rheologist at this company, it is truly a personal subscription. As soon I start mentioning "storage modulus", my colleagues eye glaze over and... I get the same reaction when I try and tell them about my glory days as an amateur bicycle racer in downstate Illinois, like the time that I chased down breakaway by myself and...

[3] If anyone knows what HTML I need to improve the visibility, I'm all ears.

Tuesday, July 10, 2012

Swelling Rubber to Measure Toluene Content in Gasoline

Materials View, a weekly product from Wiley which highlights an article in a Wiley journal [1] this week points to an article from the Journal of Applied Polymer Science regarding the swelling of rubber after immersion in gasoline. The swelling of rubber in a solvent is nothing new. Flory laid out some the theoretical details behind it back in the 1950's. It's a technique that I often use - usually to determine the amount of non-crosslinked material [2] and/or the relative degree of crosslinking in similar materials [3] as it is very easy to set up and run. A balance and/or a ruler, some beakers and lots of solvent is all you need. Oh one more thing - time. It typically takes 24 hours for the rubber to swell completely, although if the rubber sample is very large, it can take longer. This is usually not a problem as I can be doing other things while the samples are soaking. Heating the solvent baths can decrease the time to equilibration, but has to be used cautiously as many of the solvents that swell rubber are rather flammable.

In this particular article, the authors claim that the swelling can be used to determine the amount of toluene there is in gasoline. The researchers state in the title that toluene is an adulterant, although there is certainly evidence that toluene in fuel can be beneficial in many cases. The researchers had to rely on quite a bit of statistical analysis in order to get the results, which doesn't surprise me at all. I wonder how sensitive the test is to other nonaliphatic additives that can be added to gasoline too, such as ethanol.

I've not read the article [4] so I'm to going to be able to make extremely definitive statements about the motivations of this research, but there already is an ASTM standard (D3606) for determining the amount of toluene (and benzene too) in gasoline, this being done by GC. While I've never thought of GC as being a particularly difficult or expensive test, there might be cases were access to a GC is difficult, but I am having a hard time imagining when and where that would be. If you are in a place in the world where you care about toluene as an adulterant in gasoline, then you are not in some remote location, but instead are in a spot where electricity and the carrier gases and the money for a GC are available. Besides, this swelling test takes at least a day to run, and more importantly, is heavily reliant on the rubber test specimens being of a constant composition and crosslinking over time.

While this is a new test, it seems to me like a big step backwards in time.

[1] How come these articles are never free to read? Other publishers that have similar schemes to draw attention to certain articles have them free-to-read for at least a short period of time.
[2] The non-crosslinked material will diffuse into the excess solvent. Massing the initial sample and the what is in the bath will give you the percentage of uncrosslinked material.
[3] The larger the dimensional change in the part, the lower the degree of crosslinking.
[4] My employer doesn't have a paid subscription to the journal and I would have a very hard time telling them with a straight face to pop $35 for an article about swelling rubber in gasoline.