Wednesday, March 28, 2012

The Treasure of Plastic Waste

One dominant theme from the Plastics Recycling Conference last week was that the public perception of plastic, and plastic packaging in particular, needs to change. Currently it is viewed as (wasteful) trash of no value. And any disposable plastic item only adds to that perception. That attitude needs to change so that people recognize that used plastic is valuable and that companies want it back for reprocessing, conversion to oil or other uses that do not include landfilling it. The real challenge is engaging the consumers and end users.

The problem is all the more significant because demand for recycled plastics is again exceeding the supply now that the economy is out of the worst of the economic funk from the past few years. While more and more recycling systems are being set up and are taking ever more diverse plastic streams, the shortfall will still exist for some time. Just as the efficient aluminum and glass recycling systems that we have weren't established overnight, plastic recycling systems will get there in the future.

And if all this doesn't convince you that plastic waste is valuable, consider this: LA police recently arrested the operators of a recycling company for recycling stolen plastic. I guess you cold say they were running the ultimate "chop shop", since the incoming plastic parts were chopped up into pellets. While I am not condoning the practice, chopping up the plastic to small pellets is certainly going to destroy all or nearly all of the evidence of what the pellets came from, making them very easy to sell.

Tuesday, March 27, 2012

Is "Plastics-to-Oil" Recycling?

One session of the Plastics Recycling Conference was devoted to plastics-to-oil (PTO) technology. Prior to the session, my thoughts had been that the technology was of dubious value - why not just completely burn the plastic for energy? But after the session, I'm beginning to have second thoughts.

PTO is thermal pyrolysis of plastics. The materials are heated in a vacuum or inert atmosphere to about 800 oF (430 oC) and reduced in molecular weight to a liquid that is similar to crude petroleum. Similar, but in fact better, as it is very low in sulfur, thus making it a (very) sweet crude oil, the grade that can command the highest prices. The oil is sold to local refineries who then mix it with their regular petroleum feedstocks for conversion to gasoline/heating oils/... The speakers were all emphatic that building such an operation is fairly easy, as there are no air emissions so permitting is trivial (once you can convince the agencies that there really are no air emissions).

What changed my mind about the usefulness of this technology is that it works best as part of a business model rather than as a stand-alone business. For instance, plastic recyclers receiving a mixed stream of plastics will sort the mixture into various outputs, but will veritably be left with materials at the end that they cannot sort and sell. That material could then be converted into oil.

Another concern that I had had previously about the process was how polymers with heteroatoms were processed - PET or PVC for instance - where the oxygen and the chlorine need to be removed. Without the introduction of hydrogen, the resulting liquid would be unsaturated and unstable, but since the oil is quickly shipped to the refinery, that is not an issue.

One of the speakers also pointed out that this truly is recycling, since the waste plastic is now be brought back - all the way back - to the petroleum refiners, rather than part of the way back to the plastic processors. At the same time, it cannot be ignored that this is most likely a one-time trip, as the refined oil will most likely be burned rather than serve as a chemical/plastic output. Also, the conversion of plastic to oil does nothing to aid public perception of plastic as being a valuable material. Instead, it only reinforces the idea that it is cheap junk (ideas that I will expand on tomorrow).

So as I stated before, I am now convinced that PTO does have some usefulness in certain situations. It is not a universal solution to plastic waste, but should be considered a valuable addition to the other recycling technologies.

Monday, March 26, 2012

Plastic Recycling Conference 2012 - The Fight (Literally) over Biodegradability

I was at the Plastics Recycling Conference in Atlanta last week and will spend a good portion of this week discussing what I saw and learned there.

While I was a little be skeptical before the conference of what I would find, I was almost immediately delighted with the proceedings. It was a fairly large conference (1400 attendees from 32 countries) and it was well organized in a way that I've not seen before: each session had 3 speakers, all of whom were on stage the entire 1.5 hours. Each spoke for about 20 minutes and then after all three were done, questions were taken from the audience (via cards) and discussed by all the speakers as appropriate. This format thus led to sometimes lively discussions and in one case, well..., let me detail that one a little more.

One of the late morning concurrent sessions on Tuesday was about oxo-biodegradable materials. The first speakers [1] was CEO of a company that makes an additive that upon exposure to UV light and oxygen leads to degradation of the plastic. The purpose of this is to solve the litter problem. No matter how good we are at trying to prevent it, plastic litter will occur to some degree [2]. If the plastic will degrade, the litter will no longer be visible, which certainly is a desirable outcome. As a CEO, he was constantly stating that he was not the technical guy in the company, but that the product was wonderful and had no impact on recyclability and that it must be good because Walmart and a hundred-and-some-odd-dozen countries are buying it and... Sorry, I can't write anymore about what was said, as at that point my notes have a very large B.S. and I appeared to have stopped writing. Clearly, he was not a technical guy.

The next speaker [3] spent a great deal of time and effort going into the meticulous details behind a biodegradability protocol that his institute was working on. It was fabulous. He really understands all the nuances of accelerated aging. While I was disappointed that he had no results as of yet, this was totally understandable as obtaining these results is a slow process if they are to be achieved correctly. (Bad results are easy to get but worthless to all parties concerned.)

The third speaker spent his time talking about the use of compostable food bag liners, which even allow for the composting of adhering food scraps. It was a nice, informative talk but a complete sideshow to the action that followed in the discussion.

This is when the kid gloves came off and the tension quickly built between the first and second speakers. The second speaker immediately went on the attack, stating that while the first speaker may be correct about his additive, the real challenge is when his additive is mixed into a waste stream with other similar additives: will there be a synergistic effect? No one knows and yet that is a chance that is being forced on recyclers.

Just as the session was winding up, the moderator gave the second speaker a chance to freely speak about degradability additives, to which he clearly, succinctly stated that they do nothing for litter. "Litter is an immediate problem", meaning that as soon as a bag is let loose, people see it as litter and really don't know or care that it will disappear in 40 days, as it is 100% visible right now. As he was saying this, the first speaker, 20 feet across the stage was glaring at him. At this point, everyone was on pins-and-needles not sure if fisticuffs was going to break out, if chairs were going to be tossed or a formal duel with pistols was going to be proposed. The first speaker had one point interrupted the second speaker to ask for a chance to respond, a response that was more of his standard canned speech of "with so many customers, how can we be wrong".

Fortunately for the moderator, time was up and that was the end of the session. Time for lunch. I found the second speaker and passed on my thoughts, telling him that I don't think I would have showed as much restraint as he had.

I would never have expected such excitement at a conference on recycling plastics, but if they are all this good, I can't wait until next year.

[1] Tim Murtaugh of Symphony Environmental, if you have to know.
[2] Even if it is the tsunami litter swept out to see from Japan that Doug Loep is warning will soon reach the US coastline.
[3] Dave Cornell, of the Association of Postconsumer Plastic Recyclers

Thursday, March 22, 2012

"Teaching Away" in Patents

Not being a patent lawyer, but instead being what patent lawyers call a PHOSITA (person having ordinary skill in the art) [*], I always thought I was on safe ground if an existing publication (patent or technical literature) described certain inventions and suggested that certain trends would be observed by say, adding more of A or less of B. I've heard people refer to that as "teaching away", meaning "don't go in that direction". Of course, I've never been good at following directions and so I often would go in the "wrong direction" and then find that in fact there was something valuable there. Since the prior art had steered me away, I have always thought that my new invention was nonobvious.

Apparently that is not the case. The Court of Appeals of the Federal Circuit has decided otherwise (see paragraph 36).
"A reference is no less anticipatory if, after disclosing the invention, the reference then disparages it. Thus, the question whether a reference "teaches away" from the invention is inapplicable to an anticipation analysis."
("Anticipatory" is the legal term for being obvious based on the prior art). Worse yet, this dates back to 1998. I've been in the dark for a long time.

This is another example of how patents should be left to the lawyers. There is plenty of bad advice floating around from scientists and engineers, and obviousness is probably the biggest snakepit of all. Given that, my standard operating procedure has always been to assume that any invention is unobvious until someone with authority tells me otherwise.

Knowing this decision will not change how I approach a problem. When the suggestion is given to avoid a certain direction, I've found that quite often that advice is an opinion based on what the person thinks will happen, not something backed with evidence. I've seen it in my own "advice", where I say (with an appropriately boisterous voice) "Oh no, that'll never work". I've learned the hard way how much joy Mother Nature takes in showing my opinions about chemistry and engineering are wrong, so I'm glad to see she is an equal-opportunity destroyer-of-opinions and not just picking on me.

[*] What's with this "ordinary" description? In my mind, "extraordinary" would be better. (Ha ha!) Actually, the patent law talks about "obviousness" and other issues as being in the view of an ordinary practitioner, hence the term.

Wednesday, March 21, 2012

Ink in Water

Words certainly fail to describe the beauty here in these pictures of fluid flow. Ink in water. From Alberto Seveso

Tuesday, March 20, 2012

The Mixed Up World Views of Paracelsus

Paracelsus was a very strange scientist, having both well grounded and mystical beliefs at the same time. Living back in the early 1500's, he contributed much to science that still is used to this day. The maxim "it's the dose that make the poison" is his most well known contribution to modern science[1], but he was also responsible for giving zinc its name, attempted to use chemicals as medicines and firmly believed that disease was caused by external agents.

But the really goofy stuff is lacking from the Wikipedia page. Paracelsus believed in Sylphs, invisible creatures that lived in the air. [2] They had a human, feminine form and ...well, there is not point in going on. Thankfully the notion of Sylphs was never taken seriously except by poets and writers of fantasy.

[1] Sadly, this is still poorly understood by most people. Chemophobia is a result - the fear of chemicals regardless of the quantity. Even more surprisingly, microbiologists overlook the wisdom too. They will endlessly report on e. coli or stapholoccocus or listeria monocytogenes being present, but they never quantify if enough it present to cause illness.

[2] Then again, maybe he wasn't such a crackpot. 500 years later, we still have people that believe in Sylphs. Paracelsus was trying to establish a scientific world from a non-scientific world. Some people are trying to do the opposite.

Monday, March 19, 2012

Plastics Recycling Conference

It's going to be a light week for posting. I'm going to the Plastics Recycling Conference in Atlanta on Tuesday and Wednesday, and then taking some PTO the rest of the week. I will have a couple of pre-planned posts throughout the week, but the heavy lifting will be put off until next week. I am hoping for some good talks to post about, but I've never been into tweeting or blogging during a talk (I would find it pretty rude) or even afterwards (I go to conferences to network face-to-face with people, not computer-to-computer).

Atlanta in mid-March seemed liked a good chance to get a little bit of extra warm weather, but since the Twin Cities have broken busted, seriously busted, weather records 7 of the last 9 days, there will be jealousy from coworkers about the getaway.

Wednesday, March 14, 2012

Open Problems in Non-Newtonian Fluids - The Details

As promised yesterday, here's a more detailed look at some open problems in non-Newtonian fluids.

  1. The first involves a rather surprising result from a very simple set of experiments. For bubble of gas rising through a non-Newtonian fluid, a plot of terminal velocity vs. bubble size shows a large discontinuity:
    As the bubble size increases, the discontinuity is also associated with a change in the bubble shape and also the appearance of a negative wake behind the rising bubble. The free-form shape of the bubble adds to the challenge of modeling this. I was never aware of this behavior before reading the article, despite this behavior first being described back in 1965.
  2. The next problem is much more of a modelling issue in my mind than an intellectual curiosity. The picture below shows the behavior of a polyacrylamide solution flowing downward and leaving through a small opening.
    These images are a series of stills taken through a plane in the flow channel. The recirculation pattern on the left moves later to the right and then later yet is not seen at all - the recirculation zone is rotating around the cylinder over time.

    One small bone to pick in this section of the paper was the introductory sentence:"Contraction flows occur in many polymer manufacturing processes, as molten polymer is extruded to form (ideally) a smooth, uniform thread." (Emphasis added). I would say that contraction flows occur in ALL or MOST polymer manufacturing processes. Any process that initially requires melting the polymer and then shaping it, such as extrusion (sheet, film, fiber...), or molding (blow, injection,...) will have contraction flows and the associated extensional components. Rotomolding (filling a hollow mold with polymer pellets, then tumbling the mold so that the molten polymer uniformly coats the walls of the mold) would be the only process that is on the edge of this definition. You still are melting the polymer in order to shape it, but the shaping is done only by gravity, not by any externally supplied pressure, a very unique situation for polymer processing.
  3. Lastly, there is the asymmetric flow patterns that occur in cross-slot flows. In the diagram below, the fluid is pumped into the die in opposing directions (from the left and right in this case) and exit the die through the top and the bottom.
    In properly machined dies, the impinging flows should split and an equal amount should exit the die in each direction but that is clearly not the case. It is thought that this is occurring to minimize the energy in the experimental setup. Because of the non-Newtonian nature of the liquid, higher overall fluid flow is obtained by dividing each flow into a wide and a narrow channel rather than having two equally sized channels. The asymmetry only occurs at higher flow rates.

    This is not strictly an academic problem as cross-slot flows are used for extensional flow viscometry. Being able to better understand the origin of the breakdown in the flow field could lead to more robust instrumentation.
What all three of these problems have in common are elements of an extensional flow field, although that is almost a tautology as any flow problem beyond flow in a circular pipe (or between two parallel plates) has extensional flow characteristics. Just like spherical cows of uniform density in a vacuum, pure shear flow fields are the study of academics, not of the "real" world.

Tuesday, March 13, 2012

A Bad Question about Dangerous Chemicals

The "Safety Zone" blog has a open question: what's the most dangerous chemical you've handled?

I hate that question. Most dangerous?
  • They are all dangerous - all chemicals can kill you. As such, all chemicals need to be treated with respect.
  • "Danger" has many aspects - toxicity, explosiveness, reactivity with the general lab environment, ability to cause long-term health issues,... How can these aspects be ranked relative to one another? That makes for good debate over a couple of beers, but it's not a serious safety discussion.
  • The question is begging for bravado: "Yeah, well I worked with X and that's twice as bad as your Y". Again reinforcing the concept that only certain chemicals need concern us.
I'm choosing not to answer the question, and I'm surprised that I'm the first to mention this.

Open Problems in Non-Newtonian Fluids

I wrote a few weeks back about "future" problem in rheology, and so a nice follow up would be to discuss a recent paper on "Open Problems Regarding Non-Newtonian Fluids. I admit that I didn't get far into the paper yet - the first sentence was a wonderful start:
"The major open question regarding non-Newtonian fluids is very simple: what equations should I use to model this fluid?"
That pretty much sums it up nicely, doesn't it? Note the first word: "The". Not "A major open question...", but "The major open question..."

The answer of course would be the simplest model that captures the essential features that you are interested. Sometimes an empirical power law will do: η = m γn-1 (that γ should have a dot over it, but that is beyond my HTML skills) and sometimes you pull out the 8-Constant Oldroyd model (which is far beyond my HTML skills, so you can Google it if you are interested). Sometimes a non-objective equation [1] will be just fine, sometimes you don't care about normal stresses, and sometimes you have to bite the bullet and go all in.

This still doesn't answer the question of how do you know which model to use. I admit that I am dancing around the question as I don't have a good answer. There is no cheat-sheet that you can refer to. I've not done much modeling over the years, but the advice that I would give would be to look at what others have done with similar type problems and do the same. It may not be the best answer, but it will still be safe and acceptable.

I'll discuss the rest of the paper tomorrow, but just really liked that opening sentence [2] so much that I just had to expand on it.

[1] The term "objectivity principle" is now being replaced by the "principle of material-frame indifference". In either case, the point is that the properties of a material should be the same regardless of the reference frame of the observer. In many simple models (i.e., ones lacking tensors), this is not the case. The classic example of this is using the general linear viscoelastic model for the case of a steady flow on a rotating turntable. The model shows that the viscosity depends on the rotational frequency, a result that is clearly wrong. See "Dynamics of Polymeric Liquids" by Bird, Armstrong and Hassager for details (Chapter 6). This is similar to equations that are dimensionally inconsistent.

[2] It's not a literary classic like "Call me Ishmael" or "It was a dark and stormy night", but for scientific writing, it pretty much ranks right up there.

Monday, March 12, 2012

PLA as a replacement of PC? or HDPE? or PP? Are you Nuts?

The use of bio-based plastics continues to grow, which raises the question of whether or not they are created with less energy (or greenhouse gases or environmental damage or...) than petroleum-based plastics. These are all good questions to ask, and while answering them can be tricky, with countless further questions about the methodologies used, at the very least, it is critical that the comparisons be made on an apples-to-apples basis. A recently published study fails on this basis.

The nova-Institute GMBH released the results of a meta-study on March 5 (the original study is in German, but an English summary is also available). The study found that polyhydroxyalkanoate (PHA) and polylactic acid (PLA) used less petroleum resources than other petroleum-based plastics did, albeit, as you can see from the plot below, there is such scatter in the data that the results are not statistically sound, but lets overlook that completely today.
To me, the more embarrassing failure of the study is the other plastics which they compared the PHA and the PLA to, specifically the polypropylene, polyethylene, polystyrene and polycarbonate.

In my mind, only the PET comparison has any validity. If I was designing a product that could potentially use PET, PHA and PLA could possibly be acceptable alternatives, although the low glass transition temperature of PLA is always a concern. A large industrial application for PET is packaging materials, an arena that is also an early foothold for PLA, so comparing PET to PLA is justified. But if the product I was designing was more likely to be made from PP, PE, PS and especially PC, it would quite foolish to consider PHA and PLA as alternative materials. PP, PE and PS are far to cost effective to consider replacing them with a more expensive alternative, even if the mechanical properties would be there (and they aren't). PC has outstanding optical clarity and is used almost exclusively because of that property, as it is otherwise too expensive to be used for much else.

No. Despite the apparent good news here, the news is really not that good at all.

Thursday, March 08, 2012

Extreme Misstatements about Polymers

By now, we've all seen our share of statements about polymers that are wrong, such as BPA leaching from PET or that PVC constantly emits dioxin, I find these to be fairly minor. Just this last week however, I ran across a couple of examples that pass way beyond what I just cited:
  • How about this for a headline? Funeral Held for Bartlesville Man Credited with Discovery of Plastic. It's not just the headline that's wrong (headlines are often written by someone other than the reporter). No, in this case, the reporter makes the same mistake in the first line of the article: "The man responsible for inventing plastic died this week." Not A plastic, or multiple PLASTICS, but the all the plastic in the world. I mean no disrespect for the deceased as the man in question is John Paul Hogan, and certainly a remarkable inventor as he codiscovered a catalyst that allowed for the polymerization of crystalline (high-density) polyethylene (HDPE) and polypropylene (PP). Prior to that, these materials could not be polymerized in ways that gave usable materials. The discover allowed for the commercialization of the two largest volume plastics in the world. It's just that HDPE and PP are plastics, but they are not generic, all-encompassing "plastic" referred to in the article. Synthetic plastic materials existed for well over 100 year prior to the discovery of these catalysts, the discovery of which occurred 70 years ago.

    I'll be honest that I never understood how this work differed from that of the Nobel Prize-winning duo Ziegler and Natta - I view it as independent discovery but I certainly would like to learn if someone else knows more.

  • This next one is probably not safe for work, or at least, the linked page isn't. The site advertises a prophylactic device used as a form a male birth control. In it, it makes the outlandish claim their their product is made from a "revolutionary NEW Non-Latex material called “Polyisoprene”". Polyisoprene, in fact is not a revolutionary new material, as it - the synthetic version - has been around since WWII, and the natural version - natural rubber - has been around for millenia. On the positive side, and as a follow up to yesterday's post about rubber/solvent incompatibility, the manufacturer of this product shares the same concerns. The bottom of their ad states boldly in red letters "DO NOT USE OIL BASED LUBRICANTS WITH POLYISOPRENE AS THIS WILL DAMAGE THE [generic description of the product]." So not only will knowing about rubber/solvent incompatibility prevent damage to your hands, it may also prevent having an extra set of hands around the house.

    Hat tip to Stuart Cantrill for providing me the lead for this second item. He commented on Twitter yesterday about the ad's claim and had the good sense not describe the product nor to post a picture.

Wednesday, March 07, 2012

Rubber Gloves -They're Not All the Same

Most people (and by that I mean chemists, engineers and other with a technical background) are comfortable with the notion that plastics differ in their abilities to resist attack from solvents and chemicals. Polyethylene for instance, laughs off most acids, but keels over when exposed to hot alkanes and aromatics. Polymethyl methacrylate will sluff off oils, but crumble to alcohols of all sorts. And so.

So why is it then that so many people don't extend this thought pattern to rubber, specifically rubber gloves? Just as different polymers will dissolve in some solvents and not others,
Any given rubber glove will be attacked by some solvents and not others
Is that really that surprising?

One of the more maddening issues I've had to deal with in the lab throughout my entire career here as well as at other companies has been rubber glove selection. To paraphrase Henry Ford, "I can have any type I want as long as they are nitrile". Absolutely this is said jokingly, as I can order in whatever gloves I want, but it is something that I have to initiate - the standard stock glove is nitrile and only nitrile. And not to knock nitrile, as it is probably the closest to be a universal glove as their is, but it still has its weaknesses. For instance, here's what happens to a nitrile glove after soaking in toluene (a solvent that I commonly use for cleaning up rubber adhesives) for 5 minutes:
As you can see, the finger on the right is quite swollen compared to the non-exposed finger on the left. What you can't see is how much softer and weaker the swollen finger is.

More than other people at my current employment site, I work with a wide range of chemicals, so that means that that standard nitrile gloves are sometimes the wrong glove. Personally, I have my own stash of different gloves that I draw from as needed and that I keep myself so that others don't blindly raid it thinking that a glove is a glove is a glove.

So how do you know which glove to use for any given situation? Lacking extensive experience in glvoe selection, look at the charts that the glove manufacturers provide. You can certainly go to each manufacturer's webpage, but let me make it easy for you. At the bottom of this page are links to over a dozen glove manufacturer's solvent compatibility charts. How easy is that? Now there is no excuse for not working with the correct gloves. And if you are working with a chemical that isn't on their chart, call them and ask what glove to use. They're your hands, so protect them. No safety officer is going to question you about having the proper gloves. They will see that your hands are covered and think that they've done their job. And now that your hands are protected, do something useful and productive with them, like sending a note to someone telling them that you love them...

Monday, March 05, 2012

Here come the Patent Trolls

Plastics News is reporting that Multilayer Stretch Cling Film Holdings, Inc. has filed suit for patent infringement against 9 film manufacturers. They may well have been here before, but this is the first instance that I am aware of in the plastics industry where a non-practicing entity is using acquired patents to sue external operations for patent infringement. A company or person engaging in this practice is commonly known as a Patent Troll, not the kindest term of endearment. You can see the preliminary complaint online if you are so inclined.

Normally in patent infringement cases, the plaintiff is largely looking to prevent the defendant from making any more of the contested material, and maybe make a few bucks in the process. The reason that patent trolls are looked down upon is that they are suing only with the intent to get a settlement - shake down the opposition, if you will. They are most definitely not looking to prevent the defendant from continuing to make the product. Since the troll is not making the patented material themselves, they have nothing to gain by shutting down the defendants. Yet strangely, that is what is requested in their complaint, but since they are also asking for triple damages, all attorney fees, and a new condo in Hawaii, the Kool-aid must be pretty good at that law firm. (Just kidding about the condo.)

Plastics News' report states that some of the firms have already settled, so things are going to plan for the troll. Sadly, sometimes it is just cheaper to settle a lawsuit rather than fight it, and patent lawsuits are pretty risky ventures. Consider this: the invention was made by people with technical training, the patent application was written by lawyers with technical training and examined at the patent office by examiners with technical training, but the trial will be in front of a judge and jury with no or minimal technical training. That is a very risky situation. And the best that the defendants can hope for is that they can keep doing what they've been doing in the past. Being a winning defendant in a patent lawsuit gets you the grand sum aggregate total of $0.

Most of the patent trolls I've seen so far have been in the electronics and software arenas where there are some pretty large cashflows to tap into. While some of the defendants here are pretty large - AEP for instance, in their 2011 annual report had sales of nearly a billion dollars, but an income of only 12 million [*], they are making very little if any money on the allegedly infringing product. For patent trolls to be bothering with the plastics industry says to me that the trolls have run out of place to look for easy money, and they know they will encounter little resistance in the plastics industry.

[*] That's 1.2% profit margin! Need any more proof that the film industry is cutthrout?

Friday, March 02, 2012

Cancelling a Stink with another Stink?

I'm not expert on stinky chemicals, but two major classes that send people reeling are thiols and amines. I personally find the thiols to be less offensive to work with. Not that they smell better, but because of odor fatigue - it just seems that you get use to them as your nose saturates, such as what happens with the thiol that is added to natural gas. Unfortunately, I do not have odor fatigue with amines. They smell just as bad at the end of the day as the beginning.

I bring this up because of a new thiol compound that I ran across. I run a lot of thiol-ene reactions, so I'm always on the lookout for new thiols. A biochemistry research group from Wisconsin reported the synthesis ($) last month of a novel dithiol. Their interest in the molecule and the focus of the report was in solvating proteins, which they claim the new molecule does better than existing alternatives. But most importantly for me they claim that it is nearly odorless. And how did they accomplish that neat trick? Ironically by incorporating an amine to the molecule.

Understanding how the nose senses odors has always been a challenge, as sometimes even the tiniest change to a molecule can have a tremendous impact on its aroma. The classic examples is that of carvone, a compound with two stereoisomers, one which smells like caraway while the other smells like spearmint. But this new molecule is almost a case of two wrongs making a right. Or tongue-in-cheek, proof that thiols and amines are on opposite ends of the stink scale, and that amines are twice as stinky as thiols.

The only downside for me is that the material is not commercially available and it is a 6-step synthesis to make it from aspartic acid. 6-steps is a lot, but I have to stay at least three times that number of steps away from my wife after a day in the thiol lab, so I may just make try to crank some out someday.