Wednesday, June 25, 2014

Upcycling PET Bottles - Roof Applications

While the ubiquitous PET bottles used for water or pop often get a bad rap, the used bottles are being upcycled in poorer parts of the world as part of roofs. I have two recent examples which are very different. The first uses the bottles as an internal light source. The bottles are filled with water (a touch of bleach to prevent microbial growth) and then placed in a hole cut into the metal roofing material. After being sealed into place, sunlight is collected by the upper part of the bottle and diffracted throughout the living quarters below providing the same light as a 40- to 60-watt incandescent bulb.
This ingenious invention reduces or eliminates the need for electric lighting during the day, with just short of a million such lights installed in numerous countries.

A more recent invention also upcycling PET bottles involves cutting the bottles into strips and ultrasonically wleding them to create a thatch roof alternative.
While lacking the simplicity of the previous innovation, it still is an improvement over the current materials being used - grass thatch and corregated tin roofs in that it allows plenty of light in while keeping rainwater out. This project is just starting up so the number of installations is much smaller, but I hope the project is successful. It certainly looks promising.

Previous Years
June 25, 2013 - Polymetallocenes. Not Metallocene Polymers, but Polymetallocenes.

June 25, 2012 - Researchers who found Estrogenic Activity in Nearly All Plastics Being Sued for False Claims

June 25, 2010 - Pushing a model too far

June 25, 2009 - Formulations, insomnia and career paths

June 25, 2009 - Melendez-Dias v. Massachusetts is overturned

June 25, 2008 - Now that we have that out of the way

Tuesday, June 24, 2014

Why are polymers more complex to recycle?

In principle, recycling polymers is no more difficult than recycling metals or glass. Heat them up until they melt and then reshape them into whatever form you desire. But in reality, it's actually not that simple. There are 3 major reasons for this:
  1. Part of the complexity arises from consumers having access to so many different polymers. You've got the Big 6 for starters, polyethylene (both high- and low-density - HDPE and LDPE respectively), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS) and polyethylene terephthalate (PET). And then there is nylon, acrylonitrile-butadiene-styrene (ABS), polycarbonate, maybe some polylactic acid (PLA) and others in just about every household. All these plastics need to be kept separate. Besides differences in melting temperatures that can sometimes be quite large, thermodynamics prevents these materials from being compatible with it other (although there are a few exceptions). You cannot melt PET and PP together and get a product of any value.

    Compare this with recycling metals. While metals need to be kept separate as well, consumers have access to large amounts of steel and aluminum and that's about it. And the steel and aluminum can easily be sorted with electromagnets rather than by hand. The same is true with glass and paper. There just isn't much sorting that can be done or needs to be done.
  2. Other issues arise from crosslinked polymers. Crosslinked materials, whether rubbers or not, cannot be recycled because they do not melt. This doesn't mean that nothing can be done with them, as there are a number of options to degrade them to other materials that can then be processed, but that isn't really recycling. And so we have massive piles of used tires around the countryside.
  3. Lastly, the range of physical shapes that polymers can be formed into adds to the complexity. Unless the plastic is already in small pieces, the plastic needs to be resized prior to being reprocessed. While all plastics can be resized, the initial form plays a huge role in deciding what equipment needs to be used. Sometimes grinders are used, sometimes choppers are used, sometimes shredders are use. This isn't really an issue that consumer is directly involved with, but it does explain why plastics films are so seldom recycled. They can be recycled quite easily, but they also can jam equipment that isn't designed to handle films. That leads to many municipalities not accepting them for recycling and then the perception that they can't be recycled.
So the complexity in recycling polymers arises from the large number of polymers available and all the uses we put them to. If we lived in a world that only had polyethylene and polystyrene available, recycling polymers would involve nothing more than separating the cloudy plastic from the clear plastic.

Previous Years
June 24, 2011 - Art - from Ocean Beach Junk

June 24, 2010 - Environmental Stress Cracking

Friday, June 20, 2014

Will we finally see less packaging when ordering lab chemicals?

In the past 2 months, shipping companies FedEx and UPS both announced that their shipping charges will reflect not only the weight of the package (as has been historically done) but also the size of the package. Does this mean that we will now see our lab chemicals arrive in boxes that are slightly more appropriate in size and slightly less. Maybe we can avoid scenes like this:
Or this:
Or this:
Anyone who has ever received lab chemicals could add to this with tales of bags inside metals can packed with vermiculite inside bags inside boxes...The bottle inside the Russian Doll-like packaging is called the primary package. The next layer out is the secondary packaging, the third layer out is the tertiary packaging. Here's your English language trivia tip of the day: there are words to describe the 4th, 5th, 6th, 7th, 8th, 9th, 10th, and 12th layers, but not the 11th.

Ironically, bulk chemicals are shipped with far less packaging, often in something as simple a plastic tote (maybe in a steel cage), or a double-walled tanker. Thank goodness for that. I can't imagine how many expanded polystyrene peanuts Aldrich could use to protect these larger quantities.

Ensuring that a chemical arrives in undamaged condition is very important, but since there has historically been little need to keep the final box small, then the result is as seen above. Hopefully this will now change with the new charges.

Previous Years
June 20, 2013 - Polylactic Acid - from Methane?

June 20, 2012 - A Vinyl Window with a Great R-Value

June 20, 2011 - Viscosity

Tuesday, June 17, 2014

Where did the polymer's chemistry disappear to? Here it is!

So yesterday I posed the question of when exactly does the "chemistry" disappear in a polymerization, referring to the idea that 99% of the polymers are used on their basis as a physical material rather than as a reagent for further chemistry.

So now let me invert that idea completely: there is still chemistry occurring in high polymers, if you want to refer to a lack of chemistry as chemistry. With polymers, their inertness and lack of reactivity is a large part of their appeal. In many cases, that inertness comes naturally, while in other cases, it must be implanted in the polymer through the use of additives such as antioxidants, UV absorbers, hindered-amine light stabilizers, etc. In still other cases, the choice of the monomers can help create a lack of reactivity in the final product, such as choosing monomers that create hydrolysis-resistant polyamides and polyurethanes. But in all cases, the end result is (hopefully) the same - a lack of further reactions.

All of this then means that polymer chemists can spend as much time get a reaction to NOT occur as they can getting one to occur. Producing a non-reaction will seldom result in the screaming and shouting that often accompanies a successful reaction (waiting 6 months for accelerated-aging results will slowly kill the excitement of even the most enthusiastic chemist) but it is just as important. And even though it may be viewed as "anti-chemistry", it is still chemistry.

Previous Years
June 17, 2013 - Dow Chemical Hit With Triple Damages for Price Fixing Case

June 17, 2011 - BPA Absorption from Receipts? I Don't Think So

June 17, 2009 - At least here the Editor loses his job

Monday, June 16, 2014

When does the "chemistry" disappear in a polymerization?

Polymer chemistry is unique amongst all synthetic fields in that the final product is seldom considered a "chemical".

Anyone attempting to argue with this statement is not going to get too far. Consider the Big 6 polymers - the polyethylenes (both high and low density), polypropylene, polyester, vinyl, and polystyrene. These make up 76% of all polymer production, and yet not a single one is used as a chemical reagent. And most other polymers beyond the Big 6 also fit this description, such as ABS, nylon, PEEK, polycarbonate...They are all produced from chemicals and yet the end product is desired entirely on the basis of physical properties.

Polymerization chemists have long recognized this, and every textbook on the matter has sections describing how different chemical structures within the monomer affect the final mechanical properties. For instance, ethylene oxide in the backbone adds flexibility. And alkyl side chains lower the glass transition temperature as the side chain increases - but only to about C8, afterwhich the side chains start to crystallize. And so on.

And while some may praise chemists such as George Whitesides for challenging chemists to "move beyond the molecule", polymer chemists have been doing this since polymer chemistry began some 3500 years ago.

This is not to say that "polymers-as-reagents" don't exist. They do and are commonly known as reactive polymers, but they are such a tiny fraction of commercial polymers as to be a mere outlier rather than a serious contender for "polymers-as-chemicals".

So when does the "chemistry" disappear?

P.S., I have some more thoughts about this subject, some that will completely invert the subject, but they have to wait until tomorrow.

Previous Years
June 16, 2011 - UV Abosrption and Sun Protection Factors

June 16, 2009 - A sign of economic turnaround?

Tuesday, June 10, 2014

Hillary woos the plastics industry

Hillary Clinton has "unofficially" begun campaigning for the US Presidency and is already trying to gather support from the plastics industry. She recently visited Intertech Plastics, a molding shop in Denver. She didn't take any questions from reporters but I'm sure she was able to help the production floor overcome issues with their new hot runner equipment.
While being knowledgeable about plastics may seem unimportant to most voters, a number of former national leaders have in fact been savvy about the plastics. Margaret Thatcher was a polymer chemist. The Supreme Leader, Kim Jong Il would often tour plastics manufacturing plants in his country and provide helpful insights. And even Saddam Hussein at one time thought to be was quite skilled with a plastics shredder (something I'm sure Hillary thought about using on Bill when he getting a little randy).

Previous Years
June 10, 2013 - The Future of Sustainable Polymers: Bio-based Monomers or Polymers?

June 10, 2011 - Have You Considered a Career in Plastics?

June 10, 2011 - The Supreme Court Decides On Freebase Cocaine

June 10, 2010 - Pull Up a Chair

June 10, 2009 - Another Journal Scandal

Wednesday, June 04, 2014

Water Everywhere

This has been one of the most frustrating weeks in my career. It's not that 5+ inches of rain fell Sunday morning, but that the relative humidity in the lab crept up to 70% over the weekend. And all that water was absorbed by components going into a polyurethane formulation.

Water and polyurethanes, and even more specifically isocyanates, do not get along.
The water reacts with the isocyanate to form a carbamic acid which is unstable and gives off CO2. And that means your urethane is going to get foamy. It's great if you want to make a polyurethane foam, but I don't. At least not for this project.

Worse yet, the isocyanate has now been reduced to an amine which then reacts with the isocyanate to make a polyurea. And since we know from Newton's Third Law of Isocyanate Chemistry that "For every urethane reaction, there is an equal but faster urea reaction", the isocyanate is now foamy and partially polymerized.

Our isocyanate and polyols were in sealed bottles and were fine, but the additives to the coating seem to have absorbed far more moisture than we ever thought possible. So we're firing up the vacuum oven to dry everything out. But just like how your clothing can get wet in a downpour in just a few seconds but need the better part of an hour to dry out in a dryer, so it is with drying our materials. There is no indicator that they are dry enough. We go for a while and run a test sample. Go for a while longer and run another test sample. Go for a while longer...

Previous Years
June 4, 2013 - Heads are starting to roll in Kuwait

June 4, 2012 - PPE for the Fashionable Industrial Polymer Chemist

June 4, 2010 - Plastic People of the Universe

June 4, 2010 - Clients and Secrecy

June 4, 2009 - The Queen is Dead. Long Live the Queen