Monday, March 31, 2014

The Sources of Beach Waste

Plastics News reported late last week on new research regarding beach trash. It turns out that at least for the locale studied, the biggest source of the trash was from beach users themselves.
"Litter dropped or left by members of the public accounted for 39.4 percent of litter recorded over the weekend of Sept. 20-23 the MCS {Marine Conservation Society] said. This was followed by ‘non-sourced’ (38.1 percent), described by the MCS as “all the bits and bobs that we can’t really identify,” then fishing debris at 12.6 percent; shipping-related waste (4.5 percent); sewage-related debris (4.3 percent); fly-tipped material (0.9 percent), and medical (0.2 percent)."
This study is important since beach trash is the only type of "ocean trash" that most of the public ever sees, and so understanding it and its sources is critical. It also is hard to eliminate waste if you don't the know the source of it. That beach users were the immediate source suggests that more garbage bins might be needed as well as some signs or other educational/reminder type materials. If the beacher users assume that beach trash is only stuff tossed up by the ocean, then they might feel less obligation to clean up after themselves.

While it might be tempting to use this study to conclude that beach trash is then the largest source of ocean trash, but that would be premature, and likely inaccurate. Just as no two beaches are the same, the findings for different beaches will likely differ as well. But this study still reinforces the importance of cleaning up after ones own self. Failure to do so results in an immediate problem. And as always, waste, plastic or otherwise, has no business being in the ocean or on the beach

Previous Years
March 31, 2011 - Recycling Symbol Confusion

March 31, 2010 - More on DNA Patentability

March 31, 2010 - The Dreamliner did O.K.

Friday, March 28, 2014

Yet Another Round of Edible Water Bottles

It's often said that history repeats itself (although I tend to agree with Mark Twain that it rhymes), but I wouldn't expect it to occur on a 2 year interval. Yet that is what has happened. is reporting on another attempt to make edible containers for water. Just 2 years ago, a Harvard professor came up with such an item (more on that in a minute). The new invention uses calcium alginate to create soft spheres of water that can (messily) be used and then eaten.
Ooho - A blob of water (calcium alginate)

As much as people like to malign PET water bottles for being "single use" and disposable, that bottle has to meet an incredible array of requirements:
  • It needs to seal the water in and all other contaminants out.
  • It needs to be made from materials that will not leach unsafe levels of chemicals into the water, or react with the water.
  • It needs to not have any structural failure:
    • during shipment from the bottles' manufacturer (who is often someone different than the company filling the bottle) to the filling plant
    • while it is in the filling equipment
    • while the bottle is put into
      • the secondary packaging (often shrinkwrap)
      • into the tertiary packaging (a cardboard box)
      • additional packaging (such as to secure it to a pallet)
    • or during shipment via (multiple) trucks or boats
    • while on the shelf or rack, particularly when multiple layers of filled bottles are stacked on top of it
    • during the "normal" lifespan that the consumer has it
    • Keep in mind that during shipment and in the hands of the consumer, the bottle can see temperature extremes from below freezing temperatures to 140 oF or more, as well as UV light which can degrade polymers. If there is structural failure, the water will leak from the bottle, requiring that at the very least, that bottle be thrown away or recycled. Keep in mind that that bottle's contents are then also wasted. Depending on the extent and location of the leaker, the cardboard packaging may be weakened so that handling the other bottles or even the pallet with a forklift may be a problem, and therefore many more bottles may end up being trashed.
  • The bottle needs to cost as little as possible.
  • The water can only diffuse very slowly through the bottle's walls. Once too much water has evaporated, the bottle no longer holds the volume stated on the label, say 500 ml. Now it's mislabeled, and cannot be sold, so into the wastestream it goes.
  • It needs to be made of material that will not biodegrade or be edible to rats, mice, etc.

Does anyone seriously think that this new invention can handle all these requirements? People get so focussed on just the act of consumption and waste disposal that they completely overlook all the additional requirements. Just the last requirement alone on this list means that this new idea is dead on arrival.

Earlier I mentioned that Harvard professor's similar invention. He has actually gotten a small business going around the concept, calling them WikiPearls, but instead of encapsulating water, they are encapsulating various food items such as ice cream, yoghurt and cheese. Right now, they are being sold at only four Whole Food Stores in the Boston area. Since "The Rheothing's " corporate jet is in the shop, I can't fly out to to Boston to check these out. (Too bad, as they look delicious.) If someone out there has access to Wikipearls, I'd be curious to know about what no one is telling us about - the packaging that is part of this "package-free" food. The WikiPearls must be packaged in something in order to be shipped to the store, even if they are just thrown in a cardboard box, and they have to have some primary packaging which would include the FDA-mandated nutritional information, ingredients list, etc. and that would protect them from premature consumption by animals. So what's the real story about the packaging?

Previous Years March 28, 2012 - The Treasure of Plastic Waste
March 28, 2011 - Thank You, Chubby Checker
March 28, 2011 - Shocking, But Not Really

Thursday, March 27, 2014

One Beautiful Salt Mine

I've not had the chance to get into a salt mine yet, having to be content with gold and copper/nickel mines. A colleague used to work at one and they differ quite a bit from hard rock mines or coal mines. Typically they are under lakes. While that may make you more hesitant to go into such a mine (what if the lake leaks into the mine), it actually should comfort you quite a bit. In the US, salt mines are typically over 1000 feet underground, while even 100 feet of water makes for a pretty deep lake. And the weight of all that water actually puts less pressure on the roof of the mine that rock does. The other advantage of being under a lake is that the state owns the land/mineral rights, and it is more willing to negotiate them away than many private individuals are. Since explosives are used to loosen up the salt and reduce it to manageable size, the salt from underground mines is not fit for human consumption. Due to our beloved polar vortices this winter, the underground salt mines in the US got a workout.

I'm about to show a couple of pictures from a really striking salt mine in Russia that is mostly abandoned, but I do want to re-emphasize that exploring abandoned mines is not a good idea. Falling rocks and cave-ins are the least of your concerns. Exposure to gases, explosives, degraded construction and more are only some of the concerns. A modern, working mine has ventilation, safety inspections, warning signs and more to protect the people, and even with all that, mining is still one of the most dangerous industries to work in. From what I've learned in the last year or so of this job, there is no way I'm ever going into an abandoned mine.

And now, some pictures from a really incredible salt mine, courtesy of the Daily Mail
Russian Salt Mine

Russian Salt Mine

Previous Years
March 27, 2012 - Is "Plastics-to-Oil" recycling?

Wednesday, March 26, 2014

Plastic Coins

The US is behind much of the world in having plastic currency. Ours is still printed on a cotton/linen blend. They only way we can pay with "plastic" in the US is by using a credit card (or charge card or debit card) and that doesn't appear to be changing anytime soon. Speaking just for myself, I really don't care either way whether our currency is printed on plastic or not - it's just not something that I feel strongly about.

A new proposal in India is now taking the idea of plastic currency further however and looking at replacing metal coins with plastic ones. This strikes me as odd for a number of reasons. While polymer currency id more durable than paper currency, metal coins are already quite durable, lasting in some cases hundreds and thousands of years. Plastic coins just aren't going to match that. And since do-it-yourself injection molding already exists, plastic coins could be cheaply counterfeited. While counterfeiting metal coins can also be done, there is little incentive as the margins would be pretty limited. Plastic coins will weigh less than the metals ones they replace, which can be viewed positively for anyone that has to transport a large amount of them, but all the vending machines would have to be retrofitted to compensate for their radically different electronic signature. But perhaps most importantly, metals coins have some romantic aspects to them that plastic won't match. The sound that they make clinking together is strongly associated with wealth. Imagine the 100th anniversary remake of Pink Floyd's "Money" using plastic coins in the intro instead of metal.
Three Coins in the Fountain
And since plastic coins aren't going to be dense and could, depending on the polymer used, even float on water, then far fewer wishes and love affairs would ever occur. There would be nothing romantic about throwing coins in Trevi Fountain only to have them float. The density could be increased by adding metal fillers, but that would just defeat the whole purpose of going to plastic in the first place.

This is a great example where plastics shouldn't replace metal.

Previous Years
March 26, 2012 - Plastic Recycling Conference 2012 - The Fight (Literally) over Biodegradability

March 26, 2009 - The Ongoing Saga of Open Access

March 26, 2009 - Misc.

Tuesday, March 25, 2014

More Exaggerations about Ocean Trash

Plastic waste has no place being in the ocean. Environmentalists are upset about the problem of that trash, but they have a problem of their own: the trash, and in particular the famed "Gyres" aren't readily visible to the human eye (or even satellites, but more about that in a minute).

Ocean Plastic, as it truly is
A photo such as this one on the right, taken by Scripps Institute researchers, shows what plastic in a gyre looks like. There aren't large items in the gyres, just mostly tiny specks of plastic and that's just not going to get most people worked up about the problem. Calling it a thin soup of plastic is accurate but not inflammatory.

Ocean plastic - NOT!
So instead, other pictures and even image-evoking words are used to describe the problem. Instead of "gyres", terms such as "garbage patch" or "islands" are used, and somehow this photo (taken in Manila Bay, not a gyre) is commonly used. Looking at this heap of trash gets people way more upset about the problem even if it isn't a true representation.

And then there are the environmentalists that are opportunistic and take advantage of working their issue into the news of the day, in this particular case, the missing Malaysian airliner. CNN had a headline last week, "Plane search hampered by ocean garbage problem". By the third short paragraph, the article is already quoting environmentalists:"'It isn't like looking for a needle in a haystack,' Conservation International senior scientist M. Sanjayan said of the difficulty in finding the Boeing 777 aircraft. 'It's like looking for a needle in a needle factory. It is one piece of debris among billions floating in the ocean.'" Somehow I think the difference in size between billions of specks of plastic and debris from a crash size can be easily discerned, especially since the latter can potentially be seen in satellite imagery and the former can't.

Sadly, this is not the first time that environmentalists have used a plane crash to advance their cause. In 2009 when an Air France jet disappeared on a flight over the Atlantic, environmentalists were again pushing their cause."...Brazilian officials said what they had found was nothing more than run-of-the-mill ocean trash. This highlights a little-seen environmental problem: Scientists say the world's oceans are increasingly filled with junk -- everything from large items like refrigerators and abandoned yachts to small stuff like plastic bottles."

While I find it fairly appalling that the disappearance of a jet over the ocean is being used to leverage one's political position insteading of recognizing the human tragedy that it is, I accept that many people do not. But the inaccuracy of these articles continues to propagate the false imagery that the oceans are filled with large pieces of plastic waste. And that is just not true.

Previous Years

March 25, 2010 - What Are The Odds?

Friday, March 21, 2014

A Friday Morning Fight

While Sir Elton John may think that Saturday Night is Alright for Fighting, I think Friday morning is fine too. And what better topic than the always controversial glass transition? ACS Macro Letters just published "When Doe a Glass Transition Temperature Not Signify a Glass Transition", so you can see that this battle is ready to go from the bell.

Over in one corner we have the defending champion of the world, dilatometric techniques. Pull out your old PChem book (or just take my word on it) and you'll see that in a second-order phase transition such as the glass transition, the slope of a volume vs. temperature plot has a discontinuity at Tg, the glass transition temperature. This then is the basis for dilatometric techniques. With polymers, kinetics always plays a role so reaching equilibrium at temperatures near Tg takes extremely long times. Consequently, reported Tg values are all over the place depending on the equipment used and the rate of cooling. Since the temperature gradients within thin samples of material will be much less, variability can be reduced by working with thin samples.

Except it isn't. That is where problems arise and we meet the challengers sitting in the other corner. While thin films do have smaller thermal gradients, the generated data doesn't give us a better picture of the world.
Glass transition for thin polystyrene films
Consider this plot of Tg as a function of film thickness for polystyrene. That is a 50 oC change in the Tg! For better or worse, the researchers have found that this can be explained away as being due to the kinetics of a very thin layer of material at the surface of the sample. This surface material is responsible for the apparent depression of the Tg and hence the title of the paper. The large dropoff seen in the plot above is not representative of the bulk polystyrene and other glass forming polymers and so the measured Tg's are not really Tg's.

While this is a great result, it doesn't make life easier for people making the measurements. Either they need to run thicker samples or correct for this phenomenon.

Tg's are also measured with differential scanning calorimetry (DSC), which looks for an offset in the heat capacity of the sample vs. temperature. While I can see that these results could in principle also apply to DSC measurements, in reality they probably won't. Most DSC's need a pretty good sized sample (a few mg) which inherently forces you to work with samples thicker than 20 nm.

Previous Years
March 21, 2013 - Ink in Water

March 21, 2012 - Rock Star Jobs for Polymers?

Wednesday, March 19, 2014

"Openness in Science"

A few months back, the Royal Society of Chemistry held a writing competition on "Openness in Science"held a writing competition on "Openness in Science". Having to spend the day at home prepping for a medical exam the next day (that kind that start becoming routine once your age can be rounded up to 100), I wrote up an entry and submitted it. I didn't win or even get on the shortlist, so I am seeking revenge by posting here so that my readers can be subjected to it. I admit it is an unusual take on "openness", and the first paragraph may make you blush, but you'll get past it. Just like I did with my exam.

Openness in Science
The researcher stood at the podium. He had presented his new, revolutionary idea with data to support it, and yet he could still tell that the audience was skeptical. And so he did the only thing he could do to further convey his results – he pulled down his pants.

Openness in science usually refers to the sharing of data and critical samples, the public publishing of results, or the open discussions that occur at conferences. But openness can also refer to the concept that is most closely related to the historical meaning of the word open: that of public exposure and the almost nakedness associated with it.

In my own field of polymer chemistry for instance, consider the difficulties faced by Hermann Staudinger. In the 1920’s, scientists were beginning to measure the molecular weights of naturally occurring macromolecules such as natural rubber, starches and proteins. The results of the measurements were unbelievable at first, suggesting molecular weights so much greater than anything previously known. Such eminent chemists such as Emil Fischer and Heinrich Wieland (both Nobel Prize winners) scoffed at the idea of such large molecules being made up of covalent bonds and instead proposed that the observed results were arising from colloidal associations between large numbers of smaller molecules. Staudinger was convinced otherwise, that covalent bonding to such a large degree was not only possible, but was in fact occurring and was responsible for these molecules of such large molecular weight.

The mockery of his idea wasn’t just from Fischer and Wieland, but from whole groups of chemists, climaxing at the 1925 meeting of the Zurich Chemical Society. Here is where Staudinger, facing a heckling crowd, famously quoted Martin Luther “Hier stehe ich, ich kann nicht anders” (Here I stand, I cannot do otherwise).

It takes a tremendous amount of courage to open oneself up like this, especially to well-respected colleagues. How intimidating it must have been to be standing at a podium with fellow chemists so motivated to object to your talk that they break the expected rules of decorum to do so. Unlike the researcher referred to earlier, Staudinger did not undress on the stage, but nonetheless he hardly would have been more exposed if he had.

Why is openness such as this so important to science? Because it allows for the rapid study of novel ideas. While many ideas are complete flops, other succeed and more importantly, many of these ideas are revolutionary, upsetting existing paradigms, suggesting whole new fields of research or otherwise changing the history of science. But when an idea is kept to only one individual or even a small group, no one else can contribute to advance (or denigrate) it.

Wallace Carothers, a young chemistry professor who had just started at Harvard University became intrigued with Staudinger’s ideas and started devloping polymerization reactions, ultimately leading a research team at DuPont that created for the first time the neoprenes, nylons and polyesters that are still being made by DuPont today. 10 years would pass before the needed scientific measurements came about to convince the general body of chemists that molecules of such high molecular could indeed exist, and yet the idea was already being explored, developed and put to practical use before such data existed.

As for the researcher who actually did undress on stage, that was Sir Giles Brindley who was speaking about pharmaceutical treatments for erectile dysfunction. The talk was given back in 1983, well before Viagra or similar medications were available, and at a time when the concept of pharmaceutical treatments was not even thought possible. Dr. Brindley’s research had involved injecting various agents into his own penis and recording the results. The skepticism from the audience was enough that at the end of his talk he dropped his pants to prove his point, having previous injected himself before the lecture had started.

As with Staudinger, such openness allowed others to advance on it. Pharmaceutical companies quickly took notice of the research, developing the many erectile dysfunction drugs that we have today.
Both Staudinger and Brindley could have kept quiet and not spoke up. They could have slowly continued to collect the necessary data until the proof was definitive. They could have waited until their older opponents had passed on or retired and a younger, more receptive set of chemists came along. But they didn’t. They opened their ideas up to the scientific community and in doing so, exposed themselves to derision and potential embarrassment and their reputation to possible ruin.

Such openness is risky, very risky. I’m not sure that I would have the wherewithal to ever take such a stand, but I am elated that there are some who will when such openness is warranted.

Previous Years

March 19, 2012 - Plastics Recycling Conference

March 19, 2010 - Another Use for FTIR in the Medical Lab

March 19, 2009 - Nitrogen Enriched Gasoline???

Monday, March 17, 2014

A Most Unusual Case of Stolen Plastic - It's In the Bag

Just a couple of weeks ago, I wrote of thieves in England stealing plastics for personal gain. In that particular case, the plastics bread baskets were being ground down for recycling. But that time of crime is getting to be rather normal. For an unusual case, look at what Plastics News is reporting.

In this incident from Runcorn, England, the thieves made off with $1 million of virgin resin pellets, high density polyethylene (HDPE) about 500 metric tons (and in fact Marlex grades 5502BN, 50100 and TR131 were even called out by Plastics News). The crooks, who have already been arrested, were not opportunistic but in fact looking for the plastic from the get go.
"According to Frank Keddle, of claims assessor Wendt & Company, the gang that carried out the robbery clearly had knowledge of the plastics market. 'They cleared away salt, which was being stored in the warehouse, to get the plastic, so they were looking for it specifically,' he explained."

But that is not what makes this case so unusual in my mind. Instead, it was the fact that the resin was in 25 kilogram bags! 500 metric tons of HDPE in 25 kilogram bags is 20,000 bags. What company has that many bags of any resin?

For those not familiar with large-scale polymer processing, bags are good for pilot plants where you might go through one every 15 minutes or so. 25 kg is about the limit of what a worker is expected to lift on a repeated basis.
Makes a Swell Playhouse
A Gaylord Container
If you are in production running hundreds or thousands of kilograms and hour, you need better options, ones that won't require so many workers and generate so many waste bags. Gaylords for starters (such as the box shown on the right which hold about 1100 lbs - I believe that the name was given to a standard container first popularized by the Gaylord Container Company) with a suction tube. But the really big operations use hoppers with pneumatic lines to move stuff around and even bring it in by railcar (each car holding about 50,000 kilograms). Which is another way to look at it: 500 metric tons is about 10 train cars full of plastic pellets.

But it was all in bags! That's weird. So weird that it almost makes me suspicious of why they had so much bagged resin in the first place. I can't imagine a nefarious angle to all these bags, but maybe a reader can.

Previous Years
March 17, 2010 - Why I Hate PVC

Wednesday, March 12, 2014

If It Ain't Broke, Don't Fix It

Long time readers know how much I adore the thiol-ene reaction for making polymeric coatings (see for instance, these posts 1, 2, 3 or this 2- part video). It's fast, really fast (I've made coatings that go from pure monomer to cured coating in 0.1 seconds), it doesn't suffer from oxygen inhibition, it's solvent free and works well with endless varieties of terminal enes. So when I see a new report in Angewandte Chemie entitled "Repairing the Thiol-Ene Coupling Reaction", my first thought was don't fix what ain't broke. Unless you can eliminate the smell of the thiols. Then by all means, feel free to do so. My wife will be endlessly thankful as will my labmates.

But it does turn out that my beloved reaction has a technical flaw. It doesn't work well with allyl ethers, such a R-O-CH2-CH=CH2, giving either poor yields after tremendous increases in thiol (oh, great!), or multiple reaction products.
As shown on the right, the hydrogens of the CH2 between the ene and the ether are reasonably labile and will react with the thiyl radical leaving you with a carbon-centered radical rather than the thiol-addition product that you wanted across the double bond. Hence the need for more thiol - it will react with the radical to become a thiyl radical, but that has now taken you 2 equivalents of thiol to do what should be done in one - assuming that the second thiyl radical radical reacts properly. If it doesn't, then add more thiol.

But it turns out that the addition of catechol is able to overcome this. (The authors used 4-tert-butylcatechol since it was more soluble in the reactants, but it's the catechol that is doing all the work.) The proposed mechanism is this:
While I like what the authors have accomplished here, there is just one teeny fly in the ointment that you can see when you look at the reaction in detail: they are using triethyl borane (Et3B) as the initiator. Et3B is pyrophoric, meaning it will go up in flames upon contact with air. While that may make for an exciting coating operation, this seems to confine this improvement to closed reactors with inert atmospheres, quite different than the open air conditions that I normally coat and cure in.

So can this reaction be done with my standard UV absorbing photoinitiators? I have my doubts, since the triethyl borane and the catechol directly react via an undescribed mechanism. But it would be fun to try someday. Maybe the next time that my wife is out of town - for a week or more so that I have plenty of time to do the laundry. However, if you look at the videos linked to earlier, you will see me discuss results of thiol-ene polymerization using allyl ethers. I never knew of the problem back then so I just plugged along, but a more thorough analysis of the product would be needed now. So maybe...

P.S., This article had a structure that I've never encountered before:
What is ragus? After some serious thought, I realized that it was "sugar" spelled backwards, much like a "normal" methyl group, -CH3 is often inverted on the left hand side of a drawn molecule to H3C-. Having never worked with functionalized sugars, is this usage common? More importantly, is it really necessary? It's not as if "sugar" implies a certain orientation, unlike what CH3 does.

Previous Years
March 12, 2012 - PLA as a replacement of PC? or HDPE? or PP? Are you Nuts?

march 12, 2012 - Open Problems in Non-Newtonian Fluids

Tuesday, March 11, 2014

Be Gone, Heater Bands!

Processing molten plastics (such as in extrusion or injection molding) is not for the impatient. If you want to do something fast with polymers, look into UV curing or solvent coating or something else where you aren't working with just a bulk, molten polymer. High polymers possess both a high heat capacity and low heat conductivity so that getting the pellets to melt in the first place and then reach a (more or less) uniform temperature throughout the equipment takes a lot of time. Working with (relatively) large machinery doesn't help either, as even though metal has a low heat capacity and high conductivity, melt processing equipment is still made from large pieces of metal that take time to initially heat up. The end result is this: anytime I've ever had to work with the production extruders, it was always a great time to make a huge dent on that stack of papers I've been wanting to read and never had the chance.

Most people do not have such a stack so for them, anything that can be done to speed along heating can be a tremendous boon. Plastemart is reporting that Nordson XALOY has developed a new heating system that is appears to be a faster and more effective alternative to the band heaters traditionally used.
"The ... system consists of two layers of plasma-sprayed metallized ceramic with a nichrome wire wrap sandwiched in between, plus a thermal insulation cover. Because the heat from the wires is conducted throughout the ceramic material, the system raises the temperature of a machine component to target levels more quickly than with band heaters, maintains it more uniformly, and uses less energy. The tightly strapped thermal insulation wrap over the ceramic coating virtually eliminates heat losses to the workplace, saving on air conditioning costs and reducing the risk of operator injury."
While this is limited to barrels and pipes (you're still on your own with dies), any gain in efficiency will be helpful. You just need to recognize that when this heater fails, you are looking at a replacing the whole part (only after disassembling much of the equipment to access the piece) rather than just slapping on another external heating band. But given all the bad experiences I've had with heater bands conking out at the worst possible moment (Thank you, Mr. Murphy!), I'd be seriously interested in seeing how this heating system performs.

Previous Years
March 11, 2013 - What's Wrong with this Picture?

March 11, 2010 - Qualitative Science

March 11, 2009 - The "Most Admired" Chemical Company

Wednesday, March 05, 2014

Mother Jones Tries to Raise the Dead with a "New" Expose of an Old Issue

Mother Jones this week published an article, "The Scary New Evidence on BPA-Free Plastics". I'm not sure what dictionary MJ uses as a reference, but to me, evidence that is 3 years old hardly qualifies as "new".

This is a topic that I've followed closely over the years, so I'm not sure what reason MJ has to try and resurrect the issue now. I've strongly criticized the research in the past (I'll give a quick synopsis of that in a minute), and the researchers were sued (and lost) last year by Eastman. And that was it. Nothing more has happened since then, so I am very confused as to why this is resurfacing, especially under the guise of being new. Sadly, MJ knows how the PR game works and the story has been picked up and repeated by numerous sites (1, 2, 3), all of which unquestioningly use the "new" adjective.

Of course, this is just window dressing as none of the "evidence" qualifies as evidence. The original research that started all of this was deeply flawed. The researchers took a number of different plastic samples, exposed them to abusive conditions and then ran tests to determine if the abused plastics exhibited estrogenic activity (EA). While there have been numerous researchers arguing about the validity of the EA test, I was far more concerned about the abuse that the samples underwent. For instance the UV exposure was to a 254 nm lamp. Such a lamp is highly energetic, capable of inducing countless free-radical reactions in any organic material including plastics. Quite simply put, the plastic sample after this exposure was not the same as the plastic sample prior to the exposure. It had new chemicals in it. Unfortunately, the chemicals that exhibited EA were never clearly identified via analysis, so it is impossible to say that the EA came from what was in the original plastic or what the plastic had been morphed into after the UV exposure.

Similarly, the researchers used an autoclave (water at 134 C) to simulate a dishwasher. Again, a very abusive test, but one they had to run since dishwashers aren't available in the Austin, Texas area.

I've spent a number of years working on accelerated aging of plastics, including making a presentation at a technical conference on how easy it is to completely botch the testing. Without prior experience, people assume that you can just crank on the sample with the worst jungle test you can imagine, such as exposing the sample to 254 nm light rather than the the 340 - 400 nm light that dominates the UV light on the earth's surface. Such abusive testing will give you the wrong answer. There are many subtleties that researchers have found over the years that are surprising, such as the case with polyolefins, where shutting the light source off every once in a while actually ages your sample faster than having it on continually.

The fact that one of the largest chemical companies in the world screwed up their accelerated aging testing [*] shows how easy it easy to do it wrong. That these neurobiologists would make similar mistakes is hardly surprising, but it is time that their errors be fully noted. Rerun the tests, rerun them properly and then you will have my support.

[*] I know because I was professionally involved in helping a client company successfully sue them...

Previous Years
March 5, 2012 - Here Come the Patent Trolls

March 5, 2010 - Reducio ad Absurdum

March 5, 2009 - Some Hints on the Rheology of Ketchup

March 5, 2007 - Information Just Wants to be Free