Tuesday, May 26, 2015

Polymers as a Art Media

"Plastics are forever" is a common catch phrase of the anti-plastic movement, but as with all catch phrases, it's simplicity misses much of the truth. Plastics ARE NOT forever, and museum curators will correctly tell you this. The Victoria and Albert Museum's problems were discussed yesterday in an article published by the Daily Mail.
"An inflatable chair from 1969 has gone rigid, while a PVC minidress is now so sticky that it must be kept behind glass...The problem is that plastic is not as stable as many thought, and is now decaying. 'It's something that museums all over the world are trying to find a solution to,' says head conservator Sandra Smith."
The real problem that I see is that the solutions are not very acceptable. You are pretty much stuck with keeping the items in a dark, oxygen- and moisture-free environment, all of which prevents anyone from viewing the objects.

These objects were born staring at a premature death. They were made from resins that were inadequately stabilized for the long-term (meaning centuries). If a plastic chair or dress lasted for 10 years of use, that would have been considered acceptable in most situations, but art conservationists have a much longer viewpoint, and so artists need to adapt too. Just as there is artist grade paper, pencils, paints etc., artists need to start working with more highly stabilized plastics if they wish for their art to last.

While it is tempting to comment about how "natural materials" have been used in the past to create long-lasting art and that plastics should not be used to enduring creations, this view is a classic example of "Survivorship Bias". The paintings, sculptures and other objects that we have kept from over the centuries are ones that, probably more from luck then intelligent foresight, have survived. Early oil paintings for instance, are seldom found as no one knew initially how to make them durable. That knowledge has since been discovered and we now have oil paintings from the centuries ago. That same path will be repeated with plastics. As artists become aware that they need special materials (and possibly processing techniques) to make a truly durable creation, they will adapt rather than create objects from inherently weak materials.

Previous Years

May 26, 2010 - Redundancy in a Journal Title

May 26, 2010 - How to Not Plot Your Data

May 26, 2009 - Harry Gray

Wednesday, May 20, 2015

Are Shape Memory Polymers "Plastic"?

Just a quick, semi-serious question to ponder: The word "plastic" means that something is moldable, that it can undergo a permanent change in shape. (This applies not just to polymers, but to metals and other materials as well. Blacksmiths specialized in the plastic deformation of iron). So consider shape-memory polymers, polymers that can be shaped but then when heated (or otherwise given energy) recover their original shape. Is it proper to call shape-memory polymers "plastic"? (1, 2 and 3.)

Previous Years

May 20, 2013 - That Didn't Take Long

Monday, May 18, 2015

Fracking and the Stresses it Adds to Railroads

The current fracking boom in the US has had a positive impact on the plastics industry, reducing the cost of many resins and leading to the construction of new facilities for their manufacture. But it has also placed an immense strain on the railroads. Because the fracking is generating some much petroleum products in areas that are without pipelines, the extracted liquids are shipped by rail, and so demand for rail cars is at an all-time high. And this means that any little hiccup only makes the stress on the logistics that much worse. Train derailments, especially those that lead to conflagrations are sure to be on the national news.

But fracking is also also stressing the railroads in other, far more subtle ways that associated with pre-extraction activities, ways that never make the national news.

The key step in fracking, the step that makes fracking all worthwhile, is the placement of proppants in the underground formation. Fracking wells are trying to extract petroleum from "tight" formations, ones where the rocks have low porosity. The porosity can be increase by fracturing the rock (hence the term "fracking") with by pumping high pressure water into the formation, but once the water is removed, the porosity drops again. Enter the proppants. Proppants are small particles, typically fine sand that is placed into the formation and keep the rocks "propped" open after they are fractured so that the porosity remains high.

But just as there are no pipelines in areas where fracking is prevalent, there is seldom the correct sand in the fracking area and it needs to be brought in. For the Bakken formation in North Dakota for instance, te sand is brought in from Wisconsin. And it should come then as no surprise that the preferred mode for bringing the sand is railroads. Which is creating further demand for rail cars. Derailment of a train carrying sand is not something that will hit the national news, so all these sand shipments to support the fracking industry are seldom discussed.

But that shipping that sand can create an even bigger problem for the railroads. The preferred sand is pretty fine and can leak from the rail cars onto the rail bed bellow and when wet, the sand can play havoc on the stability of the rail bed.
"The big chunks of rock — crushed limestone or dolomite that engineers call ballast — that keep railroad tracks in place look like a solid footing even as freight cars rumble overhead...In Wisconsin, a booming industry mining sand used by oil and gas drillers in hydraulic fracturing has presented a new challenge: fine grains of sand can leak from rail cars, accumulate in rail bed ballast and, during a rainstorm, turn into mushy, track-loosening mud."
Fracking sand on a railroad bed
It's not just by accident that rail beds are always laid on a bed of crushed rock - it is very much be design. And adding fine sand to the mix is NOT part of the design.

The page linked to above discusses some work of University of Wisconsin professors to attempt to stabilize the bed by injecting a reactive polyurethane into the spaces between the crushed rock (Look! Another tie-in to polymers!). I wish them a lot of luck. While creating a system is pretty straightforward, getting it approved for use in something as big and important as a railroad will be a long and difficult battle. Not railroad engineer will ever get in trouble for doing things the way that they have always been done before, but if a section of track repaired with a new technique fails and leads to a derailment, fire, possibly evacuations, injuries and maybe even deaths, that engineer, even if they are still in their 20's, would do well to consider an early retirement since it would place on them regardless.

Previous Years

May 18, 2012 - The Impact of the Nylon-12 Shortage Grows

May 18, 2011 - I think we've beat biobasing to death, haven't we?

May 18, 2011 - Goodbye, Harmon Killebrew

Tuesday, May 12, 2015

Sir Sam Edwards, RIP

The field of polymer science lost one of its giants last week with the passing of Sir Sam Edwards. [*]

Edwards most lasting contribution will likely be the Doi-Edwards theory which describes the reptation of polymers. Small molecules in a liquid can easily slip past each other just like people in a crowded party can move around. But polymer chains do not have it so easy. Continuing the crowded party analogy, a polymer chain would be like a conga line. The big difference is that individual people can move in pretty much any direction, but the conga line can only follow where the head of the line goes. This snake-like motion is what is referred to as "reptation" (coming from the same Latin root as the word "reptile", meaning to crawl).

If there is only one conga line (analogous to a dilute polymer solution), the line can move around easily. But for a liquid made up exclusively of polymer molecules, you have a whole room of conga lines. The only way anyone of them is going to move is to get some cooperation from neighbors, and that will take some time. That is why polymers have such a high viscosity.

The Doi-Edwards theory was able to model this reptation motion and found that the viscosity of a polymer melt increases with the molecular weight to the third power. As in the number 3. As in 3.0, or 3.00 or 3.000 etc.

Polymer viscosity to the 3.4 power of molecular weight
Why the big deal on 3? Well, the theory is close to the data, but not not quite. The data, for numerous systems, shows that the exponent should be 3.4, not 3.0. And everybody knows this. Everybody has seen this famous plot on the right, showing the same slope for all those polymers. That was a big gap to try and close.

Shortly after the Doi-Edwards theory was published, I was fortunate enough to attend a lecture of Sir Edwards where he tried to soft-shoe and hand-wave over the difference. (I don't think he did too well.) Regardless, reptation has been clearly document via experimentation, and Doi-Edwards is still widely used as the basis for modelling polymer dynamics, so it all to the good. Whoever does find the missing 0.4 (if it hasn't been found already) will not receive the same recognition. That's how it goes.

[*] Dame Athene Donald seems to be the only one to have noticed this passing. There is a post in her blog and an article in the Guardian, but Google comes up empty when I search for an obituary. Strange indeed for such a large figure of science.

Previous Years

May 12, 2014 - Dow Chemical's biggest critic has forgotten college mathematics

May 12, 2011 - Polypropylene Pricing

May 12, 2010 - The World's Smallest Rheologist?

Monday, May 11, 2015

How Cheap are Recycled Plastics Nowadays?

"Prices for recycled plastic are so low now, it's not worth stealing anymore" according to Richard Stegner, president of Regency Recycling in Rosedale, Queens. Stegner is noticing a drop in theft that followed recent the large drop in oil and resin prices.

While the common perception of plastics is as cheap, junky material, crime statistics will tell you otherwise. I've been writing about plastic thievery around the world for the last 5 years ([1], [2], [3], [4] and [5]) so it is nothing new, but it also gives pause to those who think that plastic doesn't have much economic value. On a $/lb. basis compared to precious metals it doesn't, but that isn't always a good comparison. Stealing plastics is comparable to robbing the local liquor store, while stealing metals is comparable to robbing a bank. The former is extremely common, seldom reported in the news and doesn't net a whole lot of money, but the chances of getting caught are small. The latter is much less common, more newsworthy, but also much more difficult to pull off (successfully). People aren't going to be suspicious if you have a truckload of plastic; they will be extremely suspicious if you have a truckload of silver or gold.

As petroleum prices slowly increase, the price of everything made from it will increase too and so the crime rates for stealing those more valuable materials will once again increase. As will the stories of incompetent thieves (see links above).

Previous Years

May 11, 2012 - What a Crappy Project

May 11, 2011 - Bouncing Jello at 6,200 Frames/Second

May 11, 2010 - Flow-Induced Phase Separation

May 11, 2010 - "9 Shocking Things Made from Oil" - Not!

May 11, 2010 - 10 Things I Like about Polymer Chemistry

May 11, 2010 - Follow Up on "9 Shocking Things Made From Oil"

May 11, 2007 - A much better QC test

Thursday, May 07, 2015

Fast Times at Aspen Research

Looking back on all the job changes that I've made over the decades, I really don't regret any of them (regardless of whether I left the job or the job left me!). But a recent local news report made me "light up" when they mentioned a former employer - Aspen Research.

Before we get to them, you need to know that last year, Minnesota approved the use of medical marijuana. You can't grow you own, but have to get the stuff from certified dispensaries which are supplied by certified growers. And as a compromise needed to get the bill approved by the governor, the THC and CBD can only be in pill or oil form - no smoking allowed. And that means that someone needs to test the pills and oil for the content of the active pharmaceutical ingredient. And that's how Aspen Research entered the picture. They were one of two labs selected by the state to perform that analysis.

Oil? As in a liquid? As in there is some rheology that should be studied? Oooh! Let me help! It's probably going to take a lot of material to get a good protocol set and there will be lots of waste and nothing left over to return to my supervisor...

But seriously, I am happy for Aspen that they got this contract. They are ISO 17025 certified, and at least one of the people on staff has prior experience with testing wacky tobaccy, so it was a good choice for the state.

And no, this really doesn't change my thoughts about going back there. The reasons I left that job are still just as valid as they were before. Besides, I've never yet partaken of the stuff and I'm not about to start.

Previous Years

May 7, 2014 - Innovations in Polyurethanes Blog

May 7, 2013 - "Downcycling" of Plastics - It's Time to End the Destructive Namecalling

May 7, 2010 - 99 Plastic Bands on the Wall...

May 7, 2010 - Seeing the Spin

May 7, 2009 - I guess this is the week for "Peer Review"