Wednesday, February 29, 2012

"Future" Problems of Theoretical Rheology

I ran across an article in the Journal of Rheology with just such a title (subscription require), but since it was written 80 years ago in 1932, the "future" is now the present (or maybe even the past). When this article was written, the term rheology had only been around for dozen years, so the subject was quite new. The article has aged quite as most of it is now incorporated in textbooks, but a couple of passages caught my eye and are worth a comment or two. The first was this: "In practice, the results can be applied to ordinary inhomogeneous materials, if their structure is sufficiently fine grained so that the structural units are small compared to the dimensions of the narrowest passages through which flow of any kind takes place." I say this is eye catching as it is a concept that many people today still fail to grasp. I've lost track of all the papers that have modeled fluid mechanics on such small scales that the whole idea of fluid continuum breaks down, and yet the researchers continue to use it. 80 years on and too many people fail to understand this basic concept.

As for specific "future" problems, the author proposed a dozen of which a few are interesting: "(5) Consider the effect of the temperature rise due to dissipation of energy in shearing a plastic material. There were not many plastics around in 1932, so I was surprised to see that extruders back then were so well equipped that they could detect the heat from shearing.

This next one shows that we've had a change in perspective over time: "(6) Investigate mathematically the change of consistency with working, as well as thixotropic and other irreversible effects" So thixotropy was considered irreversible back then? That is not in alignment with current definitions which in fact require that the effect be instead reversible.

And this last one shows how some thing never change: "(10) Rationalization of the pour-point: correlate if possible the customary ASTM observations on pour-point, penetration, and other consistency phenomena with the intrinsic rheological constants of the material." People have been developing endless additional ad hoc tests since and still want them correlated to the fundamental underlying principles. Melt Flow Index, Ring and Ball Softening Point, Probe Tack (and Loop Tack and Rolling Ball Tack and __________ Tack) - the list goes on and on. Problem #10 here is still a "future" problem of theoretical rheology.

Tuesday, February 28, 2012

How Sweet It Is

At the beginning of this month, I discussed the rich number of monomers that can be used to create polyurethanes. I just ran across a new research article ($, a free review is is available) describing one such monomer that I surprisingly hadn't run across before: sugar. It makes perfect sense - sugars (after ring opening) have hydroxyl groups exposed, making them a polyol, and a partially green polymer.

Friday, February 24, 2012

Unusual Job Seeking Advice

A poster over on the engineering reddit needed some unusual job seeking advice, something that is right up my alley. I've always gone with unconventional options if needed. Years ago when I was finishing school, if I couldn't get on an on-campus recruiter's formal schedule, I'd show up at the end of the day and try and talk with them then, in some cases even driving them to the airport if time was short. My car of course was parked outside the building all ready to go - it was even clean! - yes, I was that dedicated to the effort. Since that reddit is not widely read, I'm reposting my advice here:

"Your mission, should you choose to accept it, is to get past the HR firewall. Bring your best cyberstalking skills and your sense of adventure. Buckle up, this is going to be a rough ride.
  1. First thing you need are names of individuals in the company. Search LinkedIn for employees of the company. Find recent patent applications from the company, and look at the inventors names. Google the company's name for news articles, PR releases,...all of which may have more names.
  2. Be on a constant lookout for what style the company's email address are, such as Once you know the style, combine that with the names you have and you can mail anybody you want in the company. Sometimes they use initials, such as one place I worked it was jaspevacek@..., (john is my first name, a is the middle initial, spevacek is a tongue twister). Don't know the persons middle initial? I bet you can find out in 26 or less guesses. Sometimes there will also be a number after the name for common names, such as jasmith1@...
  3. Back on LinkedIn, ask to make a connection (it's like asking someone on Facebook to be their friend). If they ignore you, so what?
  4. Use your phone for that one app that it's never used for: making phone calls. Call the central switchboard for the company and ask to be transferred to the people who's names you have. Tell them your story. If you knowingly call someone in the wrong department, tell them (lie) that the switchboard operator sent you there by mistake and ask if they could they tell you who you should talk to or transfer you to them.
  5. When you find the ideal person to talk to or even someone close, tell them that you are just trying to get past the HR firewall (they all understand that as all of them have had to deal with that themselves) and that you are taking a creative approach that you think will reflect on the creativity that you will bring to the job (unless it is a QA department for life-critical medical devices, in which case creativity is the last thing they want from an employee).

Now go out there, start knocking heads and taking names. Be loaded for bear and always leave a round in the chamber. And let us know how you did."

I'm sure those are not the limits on creative approaches to avoiding a firewall. Anybody else with good suggestions?

Thursday, February 23, 2012

An Edible Drink Bottle - No Thanks, I've Lost My Appetite

Plenty of people take issue with the existence of single-use water bottles and the related disposal issues, so the recent announcement of an "edible drink bottle" being developed by a Harvard professor may seem like a real winner. There is nothing to dispose of - you can just eat the bottle when you are done. No waste, no garbage, no nothing to end up in the environment.

But before we all go out and invest in this technology, we need to review everything that a drink bottle does:.
  • It needs to seal the water in and all other contaminants out.
  • It needs to be made from materials that will not leach unsafe levels of chemicals into the water, or react with the water.
  • It needs to not have any structural failure:
    • during shipment from the bottles' manufacturer (who is often someone different than the company filling the bottle) to the filling plant
    • while it is in the filling equipment
    • while the bottle is put into
      • the secondary packaging (often shrinkwrap)
      • into the tertiary packaging (a cardboard box)
      • additional packaging (such as to secure it to a pallet)
    • or during shipment via (multiple) trucks or boats
    • while on the shelf or rack, particularly when multiple layers of filled bottles are stacked on top of it
    • during the "normal" lifespan that the consumer has it
    • Keep in mind that during shipment and in the hands of the consumer, the bottle can see temperature extremes from below freezing temperatures to 140 oF or more, as well as UV light which can degrade polymers. If there is structural failure, the water will leak from the bottle, requiring that at the very least, that bottle be thrown away or recycled. Keep in mind that that bottle's contents are then also wasted. Depending on the extent and location of the leaker, the cardboard packaging may be weakened so that handling the other bottles or even the pallet with a forklift may be a problem, and therefore many more bottles may end up being trashed.
  • The bottle needs to cost as little as possible.

  • The water can only diffuse very slowly through the bottle's walls. Once too much water has evaporated, the bottle no longer holds the volume stated on the label, say 500 ml. Now it's mislabeled, and cannot be sold, so into the wastestream it goes.
I think this list is a pretty daunting challenge for the new material. Nothing was mentioned about the strength of the new material nor the diffusivity of water and other liquids through it, but considering that it is described as a "membrane", it probably leaks like a sieve. I've done enough product development to know better than to expect detailed costs estimates at this point, but this new material will be expensive if for no other reason than it will have to be treated as a food item and that means a whole boatload of regulations need to be followed in the production of it that a simple PET bottle is exempt from. But the real limitation will be this: if the bottle is to be edible, then it will have to be kept clean and sanitary, just like all food is, and the only way to do that is to have additional packaging around the bottle and that pretty much defeats the whole purpose of the bottle, doesn't it? Unless a PET bottle is filthy, people give little regard to where it's been or who/what has touched it, but if you are going to be eating that bottle, then everything contacting it will be a concern. A coworker handing you a bottle would be just like that coworker handing you a donut - not the box of donuts, but a donut directly with their hands. Anybody still hungry for these bottles?

Wednesday, February 22, 2012

To Develop Biofuels or Not?

One aspect of photosynthesis that has always struck me as odd is the poor efficiency of that reaction: about 1%. This inefficiency is embarrassing enough, but when you consider that it is the result of 3.5 billion years of evolution, it becomes abominable. While research is being done to try and increase it, I think that the eons that nature has had to work on the problem pretty much guarantees us failure. For whatever reason, plants started out with an inherently poor reaction and have optimized it about as much as they can. Evolution can only build on what was there before. It is constantly working with legacy systems, and can never completely escape what was there before. What is really needed is a quantum leaps - the development on an entirely new photosynthetic mechanism, but that is far beyond our current capabilities and will be for the foreseeable future.

As a result, any efforts that we put into the development of biofuels will be limited by those same inefficiencies. Nobel Prize winner Hartmut Michel has a short editorial entitled "The Nonsense of Biofuels"(open access) which details the inefficiencies that I just described. He is not completely against the idea of only harvesting food from plants, but instead proposes that "[t]he best use of the biomass lies in its conversion into valuable building blocks
for chemical syntheses."
This is the same idea that is indirectly echoed in another recent editorial entitled "Alternative feedstocks: a continuing trend in the polymer industry?" (open access). I say indirectly as this latter editorial advocates strongly that refineries for biofuels will be developed on a size and scale comparable to existing petroleum refineries, all the while recognizing that in the refineries, "[b]iomass...loses all of the chemical complexity that is inherent in bio-derived molecules."

I may have a biased perspective, but this does seem to be by-and-large the options that are being explored by industry. News of biobased chemical developments and investments in the corresponding plants seems to be dominating that of biobased fuels, so it seems that at least for now, we are moving in the right direction.

Tuesday, February 21, 2012

Recycling Wine Bottles

Today's post is inspired by the comment left by an anonymous poster on a different website. The website mentioned that Amcor is now supplying both natural and synthetic corks for their PET wine bottle. The anonymous poster had a one-line comment:"At the end of the day, I would rather recycle the glass".

While this is a nice thought, the reality is that wine glass bottles are difficult to recycle. They are green and the largest user of green glass is the wine industry, with imported beers following after that. Unfortunately, the wine industry is located in very small regions of the country, so while you can place a wine bottle into a recycling bin, the recycler who then takes that bottle will have a difficult time working with it. Shipping it to California is not a viable option for most of the country, as is re-exporting the beer bottle glass.

On the other hand, the marketplace across the country for recycled PET has never been better, and since a case of wine shipped in PET bottles is lighter the glass alternative, less fuel is needed to transport it in the first place, making it a much more green option overall.

Monday, February 20, 2012

A Green Polyethylene - Is It Worth the Effort?

Plastemart is reporting that "[a] method of converting plant matter into ethylene and propylene using a nanotechnology process that offers an alternative to oil-based production, has been developed by a team from Utrecht University and Dow Chemical Co, as per Reuters. This also means they will not be biodegradable [*], although they will be made from renewable resources."

This strikes me as odd - not that it can't be done - but that anyone would try to undertake this. Polyethylene (PE) is the largest volume plastic in the world. It has been in that number one position for as long as I can recall and I don't see anything displacing it in the near future and possibly forever. Similarly, polypropylene (PP) is the second largest volume polymer produced in the world and again similarly, nothing is going to displace it anytime soon.

Given these large volumes of plastic, it may seem like making more would be a good idea since the demand is already so high. The problem with making more of these plastics however, is that the existing margins for these materials are very thin. They are made in highly specialized, extremely large (200,000 metrics tons or more) and expensive factories ($200 million or more), all in an effort to squeeze out costs. If you wanted to get into the polymer business, PE and PP are not the way to do it. This is not a "make a little, sell a little" business that you gradually scale up. You go all in or you go home. If you want to start small and grow, start with more exotic polymers that you can make and sell in very small quantities - medical grade plastics such as used in coatings are a terrific example. As the demand for your product slowly grows, you can slowly increase capacity. Plus you can sell them for a lot and make large margins.

But as we've discussed here many times, Dow works exclusively on a big scale. They have no interest in low volume polymers - the bigger the better, and so the idea of having a green source for polyethylene and polypropylene are going to catch their eye. While I think that this is potentially interesting to source these polymers from plants and not petroleum byproducts, unless the economics of this option are significantly different than existing option, I can't see this technology getting off the ground. It works in the lab, fine. It will be cheap enough to build a small pilot line, and see how the scale-up goes, although even that will be fraught with problems. The pilot plant will make such small amount of materials that no one other than a small-time operator would be able to use these novels materials, and Dow will be far more interested in the opinion of large consumers (Berry Plastics, or Bemis or Trex) and not 'Bubba John's Blow Molding, Insurance & Appliance Repair Shop'.
It the classic chicken-and-the-egg scenario: Dow needs to make a large quantity of material to decide if they want to make a large quantity of material.

I am far more optimistic about other bio-sourced polymers. Sources for various diols, diacids, etc. are begining to emerge for making polyamides, polyesters, etc. and all of these will have the potential to make gradual introductions into the marketplace since the volumes needed to make the decisions about the viability of the new materials are not so high. The investment needed is lower and so you don't need a massive bank statement to get into the game.

[*] I would hope that anyone regularly reading this blog would know that just because something - plastic or otherwise - is made from renewable resources, it is not necessarily biodegradable.

Friday, February 17, 2012

Reusing Old CD's - but for Artists Only

Like most people, I've plenty of old CD's that get pitched (microwaving them has lost all it's excitement), but if I were more skilled as an artist, something like this sculpture would be an incredible reuse for them:
This sculpture, and all the additional ones made by Sean Avery are tiny fragments of a CD. I have neither the patience, creativity or imagination to create something like this.

Hat tip to the ThisIsColossal webpage for the lead. A fascinating blog featuring visually impressive art from around the world. I highly recommend it.

Thursday, February 16, 2012

Data Doesn't Lie

An editorial in the current issue of Nature magazine ($) is so poorly written and twisted in its logic that I am shocked a respected journal such as Nature would publish it. The editorial is about methane emissions from fracking operations. Methane is widely recognized as a greenhouse gas - even by climate change deniers. But all of this is beside the point. I'm not discussing fracking, greenhouse gases or climate change today. Instead I'm focusing on two aspects that every scientist and engineer deals with daily: data, and making conclusions from data. Here's how not to do it:

"How clean is natural gas? Although it is often lumped in with coal and oil, many in the energy industry are at pains to point out that burning gas to generate electricity produces fewer greenhouse-gas emissions than does burning other fossil fuels. Certainly, countries claim reductions in carbon emissions when they switch from coal to gas, as Britain did on a large scale in the 1990s...Industry maintains that the problem has been exaggerated, and many scientists agree. Sorting fact from fiction has been difficult, however, because nobody had any independent data — until now.

As discussed on page 139, a study led by scientists from the US National Oceanic and Atmospheric Administration (NOAA), headquartered in Washington DC, and the University of Colorado in Boulder looked at methane and other emissions from a natural-gas field north of Denver, where fracking methods are used to open up sand formations. They estimated cumulative emissions from the field using not industry reports or conceptual models, but concentrations of pollutants in air samples. This is important because the atmosphere does not misrepresent data or make mistakes; nor does it bend to ideology or political will.

The data suggest that methane emissions from natural-gas operations could be substantially higher — and so be worse for global warming — than was thought. At works in the Denver-Julesburg Basin, methane emissions were roughly double the official estimate.

This will by no means settle the debate. The NOAA scientists had to make assumptions to convert atmospheric data to cumulative emissions from a vast energy complex. They readily acknowledge substantial uncertainty in their calculations, and estimate that between 2% and 8% of the methane produced from wells in the Denver-Julesburg Basin is lost to the atmosphere, with a best guess of 4%."
(emphasis added)

Wasn't that a perfect setup? "This is important because the atmosphere does not misrepresent data or make mistakes; nor does it bend to ideology or political will." So then how come "this will by no means settle the debate"? We have ideologically/politically neutral data? What's the problem?

This is a perfect example of the Achilles Heel of science: making a conclusion from data. It is such a fragile endeavor because it involves human beings and their thoughts and their biases. That is when assumptions are made and logic is applied. Worse yet, there is no guarantee that any conclusion reached is correct. This is why we have climate change deniers - not because of data, but because of the conclusions made from it.

How can Nature publish an editorial like this that is so removed from an understanding of how science works?

Tuesday, February 14, 2012

ISO 17025

Aspen Research is now officially ISO 17025 certified. The certificates finally arrived in the mail yesterday. A lot of people here spent a large amount of time for those sheets of paper that are so precious - or are they? The certificates are 4 sheets of paper obtained with less than a years worth of work. Everybody reading this blog has spent (or is spending) 4 years just for a single piece of paper. [*]

I was not actively involved in the effort, but from the outside looking in, I would explain ISO 17025 vs. ISO 9001 this way. In ISO 9001, you wrote down what you did, you did it and then you write down what you did. The quality of what you did did not matter at all. You could make the same rotten stuff day after day and still be ISO 9001 certified - and there are plenty of companies that operate that way. With ISO 17025, you now have to show how well you do something. It still may be awful, but now it is known to your clients that it is awful.

Note to self: do not ever again work for a company that simultaneously pursues ISO 17025 certification and relocates to a new building.

[*] Some of us were so excited about that arrangement that we repeated that effort! And guess what? We are too. GLP registration is the next target.

Monday, February 13, 2012

Eating Plastic

As you might imagine, I love plastics and other polymeric materials. They intrigue my mind and they have allowed me to make a living using that knowledge. At the same time, I realize that they have their limits. There are times that metals will solve a problem better, or maybe ceramics or sometimes, maybe nothing at all is the best solution - I'm thinking of the Vuvuzela as a good example of something that should not be made at all -regardless of the material used.

To be clear - there are times that plastics are the wrong choice. Such as in the case of this young women who eats plastic. Yes, eats plastic. And not just in small doses, but large quantities - 60,000 items - including
"I have eaten 12 remotes, over 5,000 beads, over 1,000 cocktail swords, 100 forks, about ten water bottles, two pacifiers, three CD cases, about 50 hangers, about 25 plastic lids on to-go cups..."
I hope that she gets some help, as eating all that plastics cannot be good for anyone. I'm not thinking about anything leaching from the plastic, but just the large bolus of indigestible items that could lead to blockages, punctures and all sorts of physical issues. As I said, plastics are often the wrong choicee and that is clearly the case here - proper food would be so much better.

Stokes Flow

Anyone working with polymers is intimately aware of laminar flow. The viscosity of polymer is so high that achieving turbulent flow is pretty much impossible, at least for molten polymers. Solutions, and all the different ilks of dispersions are low enough in viscosity that turbulence can be reached, but for a typical molten polymer, turbulence isn't happening. Looking at the Reynolds number
Re = ρ v D / μ
(ρ is the density, v is the velocity, D is the diameter and μ is the viscosity) for different conditions can help show this. For circular pipes, turbulence can occur if Re gets above about 2100, so for a typical molten polymer with viscosity of say, 107 Pa s viscosity and a density of 1 kg/m3 in a 1 m pipe, the velocity would need to be over 21 x 106 m/s for turbulence to occur (that is 7% the speed of light)! Up the pipe diameter to 1000 m (the size of a nice river), and the velocity would still need to exceed a supersonic speed of 21,000 m/s.

Molten polymers actually under flow are at the opposite extreme: the Reynolds number is much less than one, a condition known as Stokes flow or creeping flow. When this happens, the inertial forces become negligible and the viscous forces dominate. The Navier-Stokes equations become very simple and in fact any time dependency in the equations disappear. This then means mathematically that the reverse flow is identical to the forward flow. While people can see this from the equations and are with it in an intellectual sense, seeing a reversible flow in real world situations is often quite shocking. Look at this video for a clear example:
That the initial conditions are not perfectly matched at the end of the video is due to a small amount of diffusion (Brownian motion) that is always present - just as if the initial colors would eventually spread out and mix over time in the absence of any flow field. Nonetheless, this would be a cool demo to put together. The colors are eye catching and while people may question the validity of it on video ("oh, they just ran the tape backwards"), this is one case where seeing would be believing.

Friday, February 10, 2012

A Sign Your Oven Might Not Be Working Properly

When it's set to 75 oC and the paper label is charring...
...your oven might no be working properly.

Birds and Gels and Arsenic

The last time I mentioned gels was over their use as the matrix for a cockroach repellent. I recently ran across another example of gels being used to repel undesired fauna - as a bird repellent. Apparently if you apply the gel to bird roosting areas, the birds dislike the sticky feeling on their feet and take flight. Speaking strictly from a rheological viewpoint, "tackiness" is largely independent of the thickness of an material, but only after reaching a certain critical thickness. Excessively thin layers will have lower levels of tack - something that the British city of Market Rasen recently discovered. They were testing a gel such is this on bridges, but applied it too thin. The material for 1 bridge was spread out over 3, so the gel was too thin and the tack was no where near where it should have been.

Another option for repelling birds, although in this case, it appears to be limited to bronze statues, is to have some arsenic incorporated in the alloy. The mechanism by which this repels birds is unexplained at present. The only problem with this approach is that a new report ($) which looked at 6 elements of the "geologic copper family" (Cu, As, Se, Ag, Te, and Au) [*], concludes that the supply risk for arsenic is critical at a global level. As such, making it available for use in semiconductors is in my mind more important than for keeping statues clean of bird droppings.

[*] Although these elements are scattered across the periodic table, they are a "geologic family" as they commonly occur together in copper ore deposits. Hopefully Th' Gaussling (a chemist with an intent interest in geology) can explain sometime how this occurs.

Wednesday, February 08, 2012

Biologists Messing with Polymer Nomenclature

As has been well established, polymer nomenclature is often very confusing, for those interested, you can see my past entries 1, 2, 3, 4. Today's target: polyhydroxyalkanoates, aka PHA's, the bio-based biodegradable polymer that can't seem to catch the break it needs to hit the big time [*]. To be clear, I have not problem at all with the term polyhydroxyalkanoate - it's a perfectly acceptable description of the polymer:
These area ll polymers based on hydroxyalkanoates - alkanes of all sorts with both acid groups and hydroxy groups. The problem I have is that in the picture above, n = 0 should also be an option. If it is and R = hydrogen methyl, then you have another biodegradable polymer, polylactic acid aka PLA.

So why isn't PLA considered a PHA? Blame it on the biologists. Practically all background discussions on PHA's mentions how these polymers are derived from bacteria, usually as the little bugs are put under stress. PLA isn't made that way and so apparently that is enough of a distinction to cut it out from the group. It's a pretty strange way to slice it if you ask me.

Update: Corrected the value for R to correspond to PLA, not PGA - see the comments from Barney below.

[*] ADM and Metabolix recently announced that their joint venture to make and sell PHA is ending immediately. Not a good sign for the commercial success of this polymer.

Monday, February 06, 2012

Polyurethanes - A Love/Hate Relationship

I both love and hate "polyurethanes".

Polyurethanes (PU) are a condensation polymer [1], usually formed [2] by reacting a diiscocyante and a diol:
The reaction can then continue from either end, leading to a polymer. The problem with this polymer is that the urethane linkage is actually the least important aspect of the polymer - the R1 and the R2 are where the action is. It's R1 and R2 that determine whether you have a bowling ball, a car bumper, a kitchen sponge [3], a pressure-sensitive adhesive, a chair cushion [3], a floor coating or any of thousands of other products. Polyurethanes are without a doubt the most versatile class of polymers that we have, and that is why I love them.

But their name, "polyurehtane" causes significant confusion because it is a generic name that is generic only at the molecular level. While all condensation polymers, such as polyesters, polyureas, polyamides... have the same issue where their generic name focuses on the functional group that forms between them and not what is actually between the named functional group, this seems to be especially prevalent with polyurethanes, probably because they are so common. I've lost track of all the times clients and colleagues have told me that "they tried polyurethanes and they didn't work". If they had told me they had tried polyethylenes or polypropylene or polystyrenes or polycarbonates and they didn't work, I would be inclined to eliminate them from further consideration because the properties of a single grade of those polymers is not too terribly different from the properties of any other grade. But it is impossible to eliminate polyurethanes from consideration just because a few examples didn't work. As a result of this confusion, I usually have to explain what I explained in the paragraph above in order to get the clients/colleagues approval to still consider polyurethanes for their situation, and that is why I hate them.

One last thought: I've mentioned before that when someone tries to play "stump the polymer guy" by asking what a particular piece of plastic is made of, polyurethane is always an excellent answer. It may not be correct, but because of the versatility noted above, it is very likely not a stupid answer. And sometimes, appearing to be "not stupid" is just enough.

[1] Depending on your definition of "condensation", you could argue that PU's aren't a condensation polymer since there is no by-product formed.
[2] I say "usually", as there are plenty of isocyanate-free urethanes, but most of them have not made too much of an inroad into the marketplace. I suspect price to be a huge factor.
[3] This is actually a foamed polyurethane which typically is prepared by adding a small amount of water to the mix. I won't go into the details here.