Monday, April 29, 2013

Sometimes the Best Reactions are Those that don't Run

As chemists we pride ourselves on our abilities to get reactions to run. Reactions that don't run are failures - or are they?

I have spent considerable time working on preventing reactions from occurring in plastics. Oxidation is very seldom desirable, and so I'll add antioxidants to prevent an oxidation reaction. The same is true for ozonation (which is different than oxidation), in which case I'll antiozonants, and UV degradation, in which case I'll add a UV absorbers (plus hindered amines plus...). And while I can seldom prevent a plastic from burning, adding flame retardants can slow the fire or extinguish it once an external flame source is removed. In the same vein, there are numerous additives that can be used to prevent microbial/fungal attack to a polymer as well (although this is bordering on biochemistry!).

A more extreme example of preventing a reaction is seen in 2-part polymers, such as silicones, urethanes, which physical separation is used to prevent a reaction from occurring. And then there are the "1-part" silicones, urethanes, acrylates... that are actually 2-parts systems. I'm talking about the materials where the other part is atmospheric moisture. The packaging is design to prevent moisture diffusion into the base polymer.

Last week during #RealTimeChem week on Twitter, many people were all excited about the success they had in getting their reactions to run. But I can often come home just as excited about reactions that I have prevented from running.

Wednesday, April 24, 2013

Hurricanes, Earthquakes and the Rheology of Water

Almost imperceptibly weak, the hydrogen bonds in water make their presence known by occurring in numbers so vast that their presence cannot be ignored. As chemists, we all know that they are responsible for the relatively high boiling point of water, for holding trees up and countless other examples. But here is a new one: they allow hurricanes occurring on one end of the continent to be detected on the other end through seismological measurements.

Skeptical? I was too at first when I read this news release: Superstorm Sandy shook the Earth" (open access).
"When Superstorm Sandy struck the United States on 30 October, it didn't just devastate the Eastern Seaboard, it shook the ground as far away as the West Coast, producing tiny vibrations in Earth's crust that were picked up by seismometers there."
At first I thought that the signals were being formed from the crashing waves on the shoreline, but that is only part of the signal that the researchers were detecting.
"While some of the motions were produced by surf pounding beaches, a larger fraction came from large storm waves far offshore that smashed into each other."
So how is it that possible in a viscous fluid like water? Recall that the effects of surface waves are practically imperceptible more than a few meters beneath the surface due to viscous dissipation. The critical clue to the answer is provided in this sentence: "The ground motions generated by strong storms over the sea typically cycle at low frequency...". Low frequency. That's important.

Late last summer I blogged about a research paper that made measurements of the viscoelastic properties of water. This plot from that paper shows the frequency dependence of the storage and loss moduli. As with most viscoelastic materials, at low strain rates, the material is more like a solid than like a liquid (G' is greater than G"). That all arises from the hydrogen bonding that exists in water. Without it, the viscous elements would dominate and the storm signal would be quickly lost. Sadly, this same phenomenon also allows for the occurrence of tsunamis, waves that also occur at low frequencies.

Incredible as it may seem, hurricanes can induce earth movement across a continent, all due to hydrogen bonding in water.

Monday, April 22, 2013

Polymers, both Trademarked and Generic

Somewhat surprisingly, polymer trademarks have often gone generic. Maybe not "generic" in the legal sense where anyone is free to use the word, but certainly generic enough that the public is unclear about what is and isn't trademarked. Consider the following examples:
  • Styrofoam. This is probably the best example of a polymeric product that has lost most of its original meaning. Dow owns this trademark for their expanded polystyrene boards used as insulation (and some crafts applications). And that's it. It has nothing to do with coffee cups, takeout food containers, packaging peanuts, beer coolers, ceiling tiles or anything else. This is an case where the public is taking the original product name and expanding it [GRIN] to other products.
  • Mylar. Mylar is Dupont's tradename for PET film. This is a strange example as it is one of the few cases where the public has a more limited understanding of is trademarked. It is generally believed that it only applies to aluminum-coated PET films, such as are used to make helium ballons and not all PET films, even clear ones.
  • Saran (not to be confused with Sarin, the nerve gas). This is one that leaves me confused as you will see. In fact, the public really hasn't genericized the term at all - the trademark owner has. Let me explain. Saran was originally a Dow trademark for PVDC - polyvinylidene chloride. When I worked in the food packaging arena, engineers would speak of Saran as the equivalent of PVDC, regardless of who made it. Some years ago, Dow sold the product line to S.C. Johnson who still makes it. No, wait, they don't make it. Well, they make Saran, but it isn't Saran. Or at least it isn't PVDC. S.C.Johnson, concerned about chlorine in their products ending up in the environment, now sells only polyethylene film under the Saran trademark. This is the only case that I am aware of where the trademark now protects an entirely different product that what it originally did.
  • Nylon. Another Dupont trademark, and seeing this one going generic has twice the sting for them. Nylon is Dupont's trademark for aliphatic polyamides. Dupont makes them by copolymerizing diamines with diacids. For a product like Nylon 6,10, the 6 indicates the number of carbons in the diamine and the 10 indicates the number of carbons in the diacid. Dupont patented this process and thought they had it nailed up tight, only to find out that BASF could get around it. BASF developed a process for the ring-opening polymerization of lactams - a molecule where the acid and the amine are in the same monomer. Seeing a competitor work around a patent always hurts, but this must have really caused some coronaries in Wilmington: BASF used the same name and numbering scheme for their new product. A lactam ring with 6 carbons polymerizes to form Nylon 6. Ouch. Double ouch.

Friday, April 19, 2013

Chemistry Movie Carnival - "Duplicity"

Chemistry blogger SeeArrOh is organizing a Chemistry Movie Carnival this week to celebrate chemistry in movies. I thought I'd talk about the chemistry in the movie "Duplicity". Not just because a silicone polymer played a key role in the movie, but because it the only movie that I can think of where being a chemist added an extra level of enjoyment to the movie. Or in this particular case, an extra level of duplicity.

The movie has more twists than than a α-polypropylene (3/1) single crystal, but the overall gist is that 2 CEO's of rival companies hate each other with the intensity of 2 wolves in the desert fighting over the only rabbit in the county. One has just secretly discovered a revolutionary hair-growing gel, and the other CEO wants to steal it. Enter 2 corporate security professionals, Clive Owen (fabulous as always) and Julia Roberts (so-so as always). These 2 decide to take advantage of their positions to steal the secret for themselves and sell it for bookoo bucks.

After a number of plot twists with people duping and reduping each other to get access to the formula, we finally get to see the secret molecule. I admit that I was greatly disappointed when they showed the structure. It was just a cyclic polysiloxane, something incapable of growing hair. But guess what? I was duped. The fact that the molecule wasn't a hair-growing gel was recognized by the first company. The first CEO had created a whole fakery about it in an effort to draw out his competitor, and it worked beautifully. When the second CEO is informed that his company has successfully stolen the formula, he holds a major press conference to announce the discovery, not knowing that it is fake. One can only imagine the volume of egg on his face that will have to be removed at a later date, and how much that is going to drop the price of shares for his company.

My enjoyment of the movie however, would be less were I not a chemist. The general public didn't get that extra level of unintended duplicity. Here was a movie where Hollywood got the chemistry right, even though my first thought (correctly) was that they got it wrong. I've never seen that before or since, and that make this movie extra special in my mind.

Wednesday, April 17, 2013

Polymers from Elemental Sulfur

I written a fair bit in the past about my interest in thiol-ene polymers, but that is as far as my love affair with sulfur-based polymers has gone. Until now. A new paper in Nature Chemistry (pay-per-view) shows the copolymerization of elemental sulfur with a vinyl monomer. While this has been done in the past, this is the first time that it was done solvent-free - a divinyl monomer was dissolved in molten sulfur and copolymerized.

Sulfur is a large waste product of petroleum refining. While it only is present in a very small amount - just a few percent or less - its presence is a huge headache for refiners and the public in general. For the refiners, the sulfur quickly poisons the various catalysts used in the refinery. And since 90% of petroleum products are intended to go straight in some form of combustion reaction (both heating and transportation), sulfur in those fuels is oxidized to SOx, which eventually ends up as sulfuric acid in the atmosphere. And so the sulfur is quickly removed for the good of one and all.

An obvious way to reduce the amount of sulfur removed is to simply buy crude oil with less sulfur in it. Petroleum with less than 0.5% sulfur is referred to as "sweet" crude and commands a higher price because of the greater demand. But even given these options, refineries still end up producing way to much sulfur and there is only so much demand for sulfuric acid. So being able to use a cheap feedstock like sulfur is a good option even if the comonomer (diisopropenyl benzene) is a little bit offbeat. The fact that this polymer is crosslinked by the organic compound and not the sulfur compound is the inverse of a normal vulcanized rubber and so the authors call this "inverse vulcanization". This is neat concept that bears further exploration.

Tuesday, April 16, 2013

Are Gene Patentable? How the Supreme Court Decision Will Affect the Polymer Industry

The Supreme Court heard arguments yesterday about whether or not single genes are patentable. While at first glance, the only relationship this may appear to have to polymers is that genes are made of DNA which is a (bio)polymer, I would argue that these issues over patentability can and will affect the commodity plastics industry in the near future.

Before getting to how this will affect our industry, let me give some background on the issues of patenting DNA and genes. The suggestion of patenting genes hits a lot of people personally, as we all know that we have our own genes and that raises the argument "how can someone patents my genes"? Furthermore, patent law declares that "natural products" are also unpatentable and since DNA and genes are natural products, they should be unpatentable. But that is where that line of argument stops.

The longstanding recognition of the patent office and courts both high and low is that any "natural product" that has been modified, purified, altered, isolated, or otherwise processed to any form that is not found in nature is patent eligible. Your genes when they are part of your DNA and in their natural environment are not patentable, but withdrawn from you and isolated, they are potentially patentable. You may not like that line of reasoning, but that is the law of the land and it has been for 30 years. Personally, I am fine with it. It give a fairly bright line as to what is and isn't potentially patentable, and bright line tests in patent law, despite their great desirability in making issues black and white, are few and far between.

Back to our favorite subject of polymers. Algae and other single cell animals create in large quantities (up to 25 wt%!) a polymers called PHA - polyhydroxyalkanoates. These are polymers that are used as a form of energy storage. We humans store our excess energy as fat, while algae store theirs as PHA. There are extensive efforts to commercialize it as it is a biodegradable plastic. I personally think it could have great potential as a thermoplastic, much greater than that of another biodegradable plastic, PLA (polylactic acid), in that the algae can be farmed on non-arable lands. Unlike PLA, you are not taking foodstuffs (corn, sugar cane...) and using farmland to create single-use plastic. Instead, you are using waste materials and non-cropland to make the plastics. The economics are not there at present, but people are trying to change that and should eventually succeed.

But keep in mind that just like the genes in the algae, the PHA is a natural product. The algae create it biochemically as part of their natural life cycle just like they create their own DNA.

So now you should be able to see my concerns about the court ruling that genes are unpatentable. To be completely honest, this example is not perfect as we have known of the existence of PHA in algae for decades, so it is non-patentable for lack of novelty, but imagine if it had only just been discovered. If the Supreme Court rules that genes are not patentable, PHA could also become nonpatentable and that would greatly disincentivize efforts to commercialize it. But also considered researchers who genetically modify the algae to produce more or higher quality PHA. Shouldn't that product also be patentable? Or back away from the whole polymer issue and consider microbes or algae that produce a unique monomer, one that can create a (co)polymer with wonderful properties. Again, shouldn't that also be patentable?

With the bright line gone, we would unquestionably be on a undefined, slippery slope. It is an irony of the current age that civilization has spent the last millenia moving away from nature and now we are relying more and more on biobased technologies to create the materials of the future. That further highlights the importance of this future decision. Without a bright line test on patent eligibility, we will have more and more arguments and cloudiness over patents. Such chaos is the opposite of why the patent system exists - " promote the Progress of Science and useful Arts..." (citing the US Constitution).

While yesterday's arguments were about genes, to think that the outcome won't have an impact on the polymer industry is to not see the future.

Monday, April 15, 2013

A Novel Flame Retardant Coating for PU Foams

A persistent black-eye and challenge for polymers used in durable settings is their lack of fire resistance. Being made of mostly carbon and hydrogen (although other elements are used too), they tend to catch fire. That fire then spreads to the rest of the plastics and often to surrounding surfaces as the burning plastic melts and falls away. Foams are particularly prone to this behavior as they are already pre-filled with oxygen inside the foam and are structurally weak.

Flame retardants can be added to polymers to increase their flame resistance. While they can work quite nicely, they bring plenty of baggage with them. The most effective (on a weight basis) are based on brominated compounds, but there are plenty of health and environmental concerns about their usage, especially in regions of the world that seem to be worried about chemicals in general (Europe, California...). If you are trying to sell your products widely, you can't overlook those concerns. Inorganic materials such as aluminum trihydride can be used, but in that case, you are filling up your polymer with small rocks. This not only makes it heavier, but it also hurts many of the mechanical properties. These are fillers after all. Functional fillers, but fillers nonetheless.

The biggest disadvantage of these flame retardants is that they are added throughout the polymer even thought they are really only needed at the surface. That's why I'm excited about a new paper in Macro Letters (open access for just a few days) which describes a process for creating an electrodeposited coating that is flame retardant. Being a coating, it's only appears where it is needed, but what is more exciting yet is that it's based on sulfur, and that's a first as far as I know. It's a short report, but in it, the researchers showed that when applied to polyurethane foam, the foam not only did not propagate the flame, but it also did not slough off molten material.

As with any academic research, lots of effort will be needed to turn this into a viable option, as apply 10 layers of the coating (as was done in this case) is not going to be a viable option for most applications, but as is so often the case, once the initial prototype is shown, the floodgates will open and this (or something similar) will become part of our lives.

Thursday, April 11, 2013

Cleaning Up the 5 Gyres

You may have seen in the past week or so reports of a 19-year old Dutch student who claims to have invented/designed/imagined a device that would clean up all the plastic floating in the 5 Gyres, also known as the Great Garbage Patches. While I thought maybe I would comment on the non-viability of the device, I'm glad I didn't as I ran across a pretty good takedown of it yesterday. What made the takedown all the more pleasant to read was that it was written by Stiv Wilson of the 5 Gyres Institute.

Long-time readers of this blog know that Stiv and I have...well...not been able to agree on much of anything in the past. That's not entirely true, as we both hate the existence of the Garbage Patches. There is no reason for garbage to be in the oceans at all. But Stiv has always gone out of his way to exaggerate the extent of the problem, way beyond what the evidence shows.

He does do some exaggeration in his latest critique (more on the exaggeration in a minute) but overall he thinks the proposed garbage collector is flawed because 1) the oceans are far more vast in size than most people realize [*] 2) the ocean environment, especially the corrosivity and intense storms with no place for shelter, are very harsh on equipment 3) the economics are poor 4) the inability of the design to not also catch zooplankton and algae, and 5) the device would not ensnare plastics that are below the surface, which is a fairly large portion of the pollution. I think the reasons he gives are all excellent.

Stiv can throw a good zinger too such as this one:
"The public, for their part, loves the thought of a quick fix and wants to believe that a ‘boy genius’ can come along and solve a problem that all the old crusty PHDs can’t. It’s a great story, but it’s just a story. I find debating with gyre cleanup advocates akin to trying to reason with someone who will argue with a signpost and take the wrong way home. Gyre cleanup is a false prophet hailing from La-La land that won’t work – and it’s dangerous and counter productive to a movement trying in earnest stop the flow of plastic into the oceans. Gyre cleanup plays into the hand of industry, but worse, it diverts attention and resources from viable, but unsexy, multi-pronged and critically vetted solutions."
Notice the obligatory assault on the plastics industry. (Hey Stiv, I would love to see this plastic-free fleet of boats you take to the Gyres. No nylon ropes or sails? No rubber tubing for fuel and water lines? No gel coats and paints on the surfaces? No electronics with internal PVC-coated wiring?)

As I mentioned, there are a couple of comments from Stiv that I disagree with, such as this one about recycling plastics:
"Most plastics are very difficult to recycle not because we lack infrastructure, but because they’re not worth enough in a commodities market to incentivize [sic] venture capitalists to invest in more infrastructure to process them."
That is something that I have covered many times - the economics for recycling plastics are there - the prices make the resins attractive and demand for them keeps growing every year. And you certainly don't need venture capitalists to make these investments.

And of course Stiv then pulls out this old chestnut about "downcycling":
"But even when plastics do get recycled, in the vast majority of cases, recycling only kicks the can down the road one generation by creating a product that can’t or won’t (because of economic constraints) be recycled again."
which I debunked just two days ago.

Realize that I am only criticizing these statements since they speak to recycling plastics in general. Speaking specifically about the plastic in the Gyres, any effort to recover plastics from the them will be extremely uneconomical, even if these devices could be build for free and worked like a dream. As Stiv says, "Hiring people to climb trees in New York City to gather all the plastic bags in their branches would be more efficient and cheaper than ocean harvesting."

So will Stiv and I ever get along and become BFF's? I'm not sure that either of us will live long enough for that to happen, but I am happy that maybe we are seeing more eye-to-eye. I see things this way: a problem this big in both space and time will require a multitude of efforts over extended periods of time from the most of the people of the world to achieve any degree of success. Picking on one industry in one country is as simplistic an approach as any proposed ideas for cleaning up the Gyres. Changing human behavior (regarding waste disposal as much as buying habits) will ultimately determine the success and failure of these efforts.

[*] I drove from Chicago to LA and back last summer - 2100 miles each way. Yet 2100 miles is pretty much the width of the Atlantic Ocean at its narrowest (St Johns, Newfoundland to Clifden Ireland). To build a device that is even a tiny fraction the size of this distance can be done (look at the roads, railroads and pipeline that span those distance), but only with a tremendous amount of manpower and materials. Remember, for every square mile of land you see, there are 2 square miles of ocean that you don't.

Wednesday, April 10, 2013

A Hodgepodge of Rheology and Polymer Matters

  • Watching the Pitch Drop Demonstration can be likened to watching grass grow. But thanks to time-lapse photography, we can enjoy a nearly a year's worth of time in just 10 seconds. Even with that level of time compression, the movement is still almost imperceptible. Be sure to click on the link and check out the video.
  • Why is there a ketchup bottle near the end of this slide deck? I sure hope the author isn't making that dreadful comparison of thixotropy and/or shear-thinning in ketchup to the crude oil he was studying. As I discussed in the not-too-distant past, neither of those non-Newtonian characteristics dominates the rheology of ketchup.
  • It is widely known that the recently-deceased, former Prime Minister of England, Maggie Thatcher was a chemist by training. Nicknamed "The Iron Lady", I would have thought she was an inorganic chemist, but I found out yesterday that she was in fact a polymer chemist who worked on developing "an adhesive to stick PVC to wood and metal". She only "stuck" (GRIN) to the task for a few years before going to law school and then entering politics.
  • I added The Polymer Innovation Blog to the blog roll. Written by Jeff Gotro, he has authoritative articles on a wide range of polymeric subjects, with new articles appearing every Monday. I also deleted from the list any blogs that hadn't been updated in a year.

Tuesday, April 09, 2013

Can We All Just Get Along?

Plastics News reported last week that both the states of North Carolina and Alabama has proposed laws that would require that biodegradable or compostable plastics be clearly label as "not recyclable".

This could get ugly.

The public in general already has a hard enough time understanding that most plastic is recyclable (see for instance this classic example I once personally witnessed). Even fewer people know and that it can and should be recycled. But these news proposals would take a quality that is generally seen as being desirable - compostability/degradability - and making it stand in opposition of recycling. I don't see how anyone can think that this will help the public in the least.

I understand the technical issues here. Taking the ubiquitous PET (polyethylene terephthalate) bottle as an example, PET is not by itself considered compostable/degradable. However, there are additives available that do increase the degradability of the PET. Additionally, other similar plastics such as PLA (polylactic acid) are similar enough in appearance that they can inadvertently get mixed in the recycled PET stream. Either of these options could play a significant role in reducing the durability of the recycled PET. The suppliers of the additive and makers of PLA will argue otherwise, but no one has yet studied if there are any additive or symbiotic effects if more than one impurity/contaminant is present. So yes, there are very real concerns that the degradable materials will harm the durability of recycled plastics, and these need to be addressed. But this law is a really lousy idea.

This could get ugly. This law is going to divide the industry and force parties that should be united together to face off against one another. The plastics industry as a whole has enough of a bad reputation. The makers of compostable/degradable materials will continue to get their name dragged through the mud along with everyone else and covered with the same broad brush. More and more people are ganging up against consumable plastics regardless of source and final resting place, so we all need to be in this together.

I've said in the past that I don't support the idea of compostability/degradability in general as it is a long-term treatment to an immediate need, and I still feel this way. Much like the doctor would take immediate reaction to remove an ugly wart from your nose rather than apply a cream that will work in 90-180 days, bags and bottle and packaging materials polluting a roadside need to become invisible immediately, not in 90-180 days after then have photodegraded. But those issues are beside the point in this discussion.

My proposal would be that any material that has a compostability/degradability additive not be marked with the corresponding SPI (Society of the Plastics Industry) recycling codes 1-6, but instead either become a 7 ("Other") or not be marked at all. To mark it otherwise is to contaminate valuable waste streams.

I thought that the previous proposals by the SPI to expand the number of recycling codes was a bad idea, but marking materials as "not recyclable" is even worse. The public will be confused and the plastics industry will be internally divided. Increasing the effectiveness of the nation's plastics recycling industry is already challenging enough without these additional issues.

Thursday, April 04, 2013

Plastics Company finding a lack of math skills in job applicants

A news article from a few days ago highlighted the lack of math skills in applicants to a plastics manufacturing company. Apparently on 10% of the people pass the test even though it is aimed at high school level graduates. You can read the original article here (Portland Press Herald) or here (Physorg) or any of a number of other places (the article is always the same). What I find far more interesting is the reaction of a small set of people to the news.

The author of a Mother Jones commentary is very critical of the employer not paying enough and therefore not getting suitable applicants. There are no data to support his wild speculation. I know this is Mother Jones so I'm not overly surprised that most of the commenters to the article echo those thoughts but this much is clear about the original author: he has not been involved in hiring anybody lately as he would know all too well that ALL positions get a huge number of over qualified candidates, regardless of pay.

My personal opinion is that if they can fill their employment positions with only 10% of the candidates passing the test, what is the problem? Since a copy of the test is not available for public perusal, we have to blindly assume that the test is actually at high school level. Maybe it is, maybe it isn't. Until we know, we really can't comment. (But that is using logic taught at a college level.)

Venn Diagrams for Rheologists

I love a good meme as much as the next person does, so inspired by both BRSM and Chemjobber, here are my contributions:

Wednesday, April 03, 2013

Misperceptions of Plastic Recycling

The general public has many misperceptions of the plastics industry. A great example is this set of recent comments made in a reddit group:
"The main problems in the US for plastics is that we do not actually recycle very much of it. It is still cheaper to make new plastic than it is to recycle and all plastic is currently being "down-cycled"--a water bottle will never be a water bottle will be plastic lumber or some other low risk item...plastic water bottles are always brand new plastic."
Let's look at these comments one at a time.
"The main problems in the US for plastics is that we do not actually recycle very much of it."
This is actually a worldwide problem. Recycling rates for plastics overall are about 8% although some specific materials have higher rates. Water bottles are at 40%. These rates are lower than for say, aluminum, but even aluminum cans only have a 45% recycling rate and that has been steady for decades. Plastic recycling rates are increasing as the public becomes more and more aware that plastic can be recycled. Keep in mind that it took a long time for aluminum cans to reach that 45% recycling rate. People were patient while the recycling industry became established, and they should be equally patient for the plastics recycling industry.
"It is still cheaper to make new plastic than it is to recycle..."
This is where the writer goes off the cliff. Recycled plastic is cheaper than virgin resin. Proof can be found via a quick look at the resin pricing data available at Plastics News. PET resin for instance, the plastic used to make water bottles run between 102 and 107 cents a lb. for virgin (depending on the volume) while recycled PET is between 44 and 80 cents a lb. depending on color and how much processing has occurred. Other resins will show similar trends, but in all cases, recycled resin are cheaper than virigin.
"...all plastic is currently being "down-cycled"--a water bottle will never be a water bottle will be plastic lumber or some other low risk item..."
I do not understand this comment at all. While "down-cycled" is a very popular term, there is no consistent definition of what it actually means. What determines whether a process is up-cycling or down-cycling? One of the most common knocks against PET water bottles is that they are disposable, but then if this disposable product is turned into something durable such as clothing (not lumber - there is no PET-based lumber), this is suddenly considered going "down" and a bad thing? And lets look at the idea of risk. If a lumber board on a deck fails, the manufacturer is at risk for replacement of the board (or possibly the whole deck), as well as the health of the person who was standing on the board when it collapsed. That is a far greater risk than a water bottle manufacturer will ever face.

And lastly, there was this ignorant statement:
"...plastic water bottles are always brand new plastic"
That is hardly the case. Arrowhead Water and Evian both have water bottles made from 50% recycled materials and others are on the way.

Is the plastics recycling industry as effective as it could be? Or should be? No, but recycling of too many other non-plastic materials are far less than 100%. Effective recycling requires that consumers participate by keeping materials from the general trash, that businesses or governments are able to collect the recyclables, that recycling businesses exist that can processes the materials and that there are markets for the recycled materials. All four of these components exist to some extent, but there is still plenty of growth required to reach the target of 100% recycling.

We'll get there. I'm old enough to remember when aluminum cans first came out, so there obviously was no recycling of them initially. The same is true with plastics. We'll get there, we'll get there.

Tuesday, April 02, 2013

Improving Control over Polymerizations

In the world of organic chemistry, polymer chemists running polymerizations are like the baggage handlers on your last flight– we shove all the monomers in there with little regards for how they arrange themselves during the polymerization. For instance, if I were to copolymerize acrylic acid (monomer A) and butyl acrylate (monomer B), I would end up with a statistical copolymer, meaning that the odds of an A being next to a B and not another A is statistically determined. Those statistics are a function of the amount of A and B in the reactor, the temperature, the solvents (if any), etc. [1] I can do a little better with making a polyamide for instance, since it’s not free radical chemistry, but only if I have just 1 diamine and 1 diacid. If I introduce a third or fourth monomer, then it’s back to the statistics. It’s a mess and we just can’t control it. Toss the luggage in and as long as it stays in the plane and gets to Wichita Falls, everything is fine. Toss the comonomers in the flask and as long as they don’t exotherm out of the reactor, everything is fine.

Compare this to the people doing multistep organic syntheses – they are the watchmakers exerting precise control over how all the pieces fit together and in which order they are installed. Polymer chemists will complain that the size of the monomers is so small that they can’t be handled with that degree of precision, but the irony is that final product of many polymeric materials is wholly macroscopic (something discussed here in the past).

Things are slowly getting better with each passing year decade [2], but we still have a long ways to go before we can exert anything like the control that cells have in synthesizing proteins from 20 different comonomers. While we can’t duplicate that, the fact that it can be done can still inspire us to do better.

A number of people have attempted using the existing DNA replication methods provided by cells to produce polymers, and they have had success – as long as the monomers are pretty close to being DNA bases themselves. Look at this row of monomers and tell me how many people want polymers of them:Those phosphate groups will wilt at the first sign of some serious heat.

But there now a new hope that can being to bring polymer chemistry in line with the detailed synthesis of a drug designer. Nature Chemistry (pay-per-view) has a recent article from the Liu group at Harvard that shows that using DNA can aid in the synthesis of polymers of that are completely distinct from DNA. As you will see, there are a lot of steps involved (the Supplementary Information is 86 pages! Glad I wasn’t reviewing this one!), but I find the overall procedure clever enough that it’s worth thinking about further. Below is a simple picture of what each monomer looks like (I redrew the picture from the article as I thought the pictures in the article were pretty confusing until I figured out what was going on). Each monomer is a ring that has 6 parts to it.

There is a segment with 5 DNA bases attached, 2 cleavable segments, 2 linking sections and the polymer segment of interest. (Making those monomers themselves would be a large chore.) Each monomer has a different DNA sequence on it. The DNA segments mate with corresponding DNA segments on a substrate (according to the usual A-T and C-G mating rules). Once the mating is done, all the monomers are geometrically close to each other in the desired sequence and orientation. The linking sections are then linked to create a ladder polymer. This is also why the monomers start as rings – it helps to keep the linking sections close to each other. Finally, the cleavable sections are cut, leaving you with a polymer of desired composition detached from the substrate.

Obviously not all polymers can be prepared in this manner. You’re stuck with those possibly undesirable linking segments, the monomers have to be largely water-soluble and be able to withstand the linking and cleaving reactions, but still, this is a big breakthrough in that the resulting polymer doesn’t look like DNA at all. It’s a very clever use of geometry and sequential reactions that ultimately produces a unique product. And it’s quite a bit different from the approach used by luggage handlers. Remember that next time you’re in Tampa and your clothes are in Cheyenne.

[1] With free radical polymerizations, the emphasis is on the free and the radical is never too far away.

[2] I just don’t think I will live long enough to see the control that I can dream of. Progress is woefully slow in this field. And what am I doing to speed it along, you ask? Nothing. Absolutely nothing. So no, don't think that I am be overly critical. This is a very challenging problem and I know it.

Monday, April 01, 2013

An Open Letter to Justin Bieber

April 1, 2013

My dearest Justin,

It is time that you and I came out our about relationship. Yes, it’s time that the world knew. Many have suspected it for a long time. It’s now your turn to do the right thing and speak openly about what you have longed dream about and desired to have come true one day : to give up music and become a rheologist.

The stress of keeping it secret any longer is tearing you apart. Look at how everything is falling apart for you on your European tour. The paparazzi know about secret love of rheology and that’s what led to that scuffle with them in London.

I didn’t need to listen to the audio to know that they provoked you by telling you that the shear rate in a melt flow indexer CAN be calculated. You know better. Now I see that you spit on your neighbor because he told you “the glass-transition is not a ‘real’ phase transition”. This will only get worse. Next time it will be a customs official telling you that “physical aging doesn’t occur” or maybe it will be a Bieberhater saying that you don't know the difference between the Deborah and Weissenberg numbers.

You can make this stop by telling the truth about your great longing to be a rheologist.

When you first came to me, you were so young and innocent. You asked about the rheology of hair gels and other personal care products. I could see then that you were driven by a deep desire that would have to be fulfilled. And so I’ve been your mentor, your teacher and your sensei. And I am so proud of all the progress you have made so quickly, more than I ever imagined possible. Our relationship has blossomed and we are both better for it. I can give you the support you will need to give up music.

Giving it up won’t be easy. I know that personally. My family name, Spevacek, is Czech for “little singer”, so when I became a rheologist, I turned away from my heritage. I will never forget the silent scorn and hate in my parents eyes when I told them that I was going to be a rheologist. I tried to explain that it was something I had long suspected, and had tried to deny to myself, but I couldn’t handle the lies. I asked them for their support and love, and assured them that I would still be able to find someone special to love and create a family and have children, but they refused to listen and tossed me out of the house without even a Brookfield viscometer.

I know you will have more support than that. To be sure, TMZ will give you a hard time for about as long as three Harlem Shake videos, but it will pass. Many of your fans will leave, but in that way you will learn who your real fans are – the ones that stay with you. And sadly, your Klout score of a perfect 100 will also drop to almost nothing as it must for all rheologists, but think of the joy in your heart every time a new edition of the Journal of Rheology arrives in your mailbox. Or when you make your first master curve. Or being able to explain the difference between thixotropy and rheopexy.

So Justin, do the right thing and cancel the rest of your tour. Come home and follow your true calling. Become a rheologist. Together with me at your side, we can rule the rheological universe.

Oh, and one last thing? Could you put me in contact with Lindsay Lohan? I hear she has some messed-up ideas about reactive extrusion of urethanes in twin-screw extruders. That girl needs some serious help.


To my readers, while it is true that Spevacek is Czech for little singer, nothing else in that paragraph (or the rest of the letter for that matter) is truthful in the least. My parents have always been supportive of whatever I’ve wanted to do, and Simon Cowell would be at a complete loss for words to describe how truly awful my singing voice is. "Giving up my heritage"? Hardly. Being a rheologist is proof that singing ability is not genetic.