Interview: Dr. John Spevacek, "It's the Rheo Thing"

John Spevacek is the writer of the rheology and polymer blog It's the Rheo Thing and a valued Chemjobber commenter. Not knowing much about either the rheology and polymer fields, I asked him for an interview. What follows is an e-mail interview that has been lightly edited and checked with Dr. Spevacek for accuracy.

CJ: Can you tell us a little about your background and your experiences?

JS: My degrees (Bachelor’s, Masters and Doctorate) are all in chemical engineering (Minnesota and Illinois–Urbana). There are very few schools where you can get a formal degree in polymer science or engineering. Most commonly, professors who study polymers are in a university’s chemistry, chem-eng, mech-eng or material science departments. This difference is not a concern, as the quality of the education can be excellent in both settings.

I’ve worked for a number of companies over the past 20 years (Hercules, 3M, Conwed Plastics, Envoy Medical and now Aspen Research). I didn’t get to do any polymer chemistry in school but have been able to do so while working. With each passing job, I have become more and more involved in polymer chemistry and loving it. Having been educated more on the physical side, it is fun to be able to manipulate the chemical end as well. I now have twice the levers to play with.

CJ: What is rheology? How is it different from polymer chemistry, as understood by organic chemists?

JS: Rheology is the study of the flow and deformation of materials. It is purely a physical study and shows that the line dividing liquids and solids is not a clear as most people think. It also can be used to understand some of the underlying chemistry.

Whenever a stress is applied to any material, the molecules will try and move past each other so that they end up in a lower stress – rheologists speak of this as relaxation. For small molecules that form the basis organic chemistry, this can happen quite quickly, but for very long molecules, it takes quite some time – seconds, minutes, days or even years in some cases. The issue then becomes a matter of comparing the relaxation rate to the rate at which a stress is applied.

The iconic example is Silly Putty. When you first take the Silly Putty out of its container, it has the shape of the egg-shaped container. Gravity has stressed the Silly Putty, and over a long period of time, the molecules have been able to move past each other and the Silly Putty has flowed like a liquid. However, if you then take the Silly Putty and roll it into a ball, it will bounce like a solid. In this case, the stress is applied very quickly, quicker than it can be relaxed and so the material appears as a solid. So Silly Putty has both liquid and solid characteristics. Which one you see depends on how fast you stress it.

I used Silly Putty as an example because it is something everyone is familiar with and the relaxation time is in a convenient range, but all polymers, both hard and soft, show similar behavior. The physical properties depend on the rate at which you stress the material. Unfortunately, the physical properties also depend on temperature, the extent of the stress, and even the stress history. In short, things can get very complicated very quickly. Much of the mathematics used to describe this is the same that was used by Einstein to develop the Theory of Relativity!

CJ: What does a typical polymer chemist/rheologist do all day?

JS: Polymer chemists are fortunate in that their reactions have to run quickly since the same reaction is repeated hundreds or thousands of time to form each molecule. In addition, they are usually not multi-step, and have fairly simple separation and purification steps. So that means that a typical position would involve preparation of polymers. In some cases, it could be creating a new polymer that has never existed before, maybe from new monomers or combinations of monomer, or it could be creating replacement polymers that are lower cost than current formulations such as by going from a solvent-based polymer to a water based one,. or it could be developing new catalysts for existing polymers so that customers can process them easier.


In a typical rheology position, there would be quite a bit of testing, but that is only the beginning. Because modern instrumentation measures a number of properties simultaneously, the data analysis can be quite involved and take just as much time as the testing. And you also will spend a lot of time trying to explain the concepts of rheology to someone who is only familiar with viscosity. You never see this last step in any job description, but every rheologist knows it’s part of the job.
CJ: What is the economic outlook for the polymer industry? Has it been affected by outsourcing as much as other chemistry specialties?

JS: Everybody is probably aware of that scene from the movie “The Graduate” so I won’t repeat it here. It still is good advice, but not the killer advice it was in the 60’s. The industry has matured some so the across-the-board growth opportunities with everybody getting wildly rich are not there. Plenty of great opportunities still exist, but they are more specialized and in the smaller companies.

Outsourcing (to Mexico, China and elsewhere) is occurring, but mostly with finished or semi-finished products – the steps at which the resin is been molded or otherwise processed. This affects engineers more than chemists. Shipping unfinished pellets around the world is just not profitable in most cases as the raw materials (petroleum byproducts) are available around the world, the amount of labor/unit involved is less, and the plants to polymerize the monomers are being built worldwide.

CJ: What excites you about your science? Where do you think it is going?

JS: I am excited about the constant changes. The demand for polymers is constantly increasing. More and more metals in cars and airplanes are being replaced with plastics in order to reduce weight and increase mileage. All the efforts in renewable energy require plastics such as in wind turbine blades.

A large challenge in the future will be handling the changes in feedstock from petroleum byproducts to bio-based feedstocks. I make no predictions about when this will occur, but I would not put money on the short term.

One coarse manner to look at the situation is that petroleum industry is largely interested in refining crude oil into saturated hydrocarbons for use in fuels. Unsaturated hydrocarbons are not desirable as they will oxidize in the fuels and cause problems so refiners try to remove as many as economically viable. This is great for polymer chemists as all those double bonds are polymerizable and we take advantage of the situation. This has two implications: 1) as long as oil is being refined, the byproducts will be used for making polymers, and 2) while many people think of polymers as being a cause for our dependency on oil, it actually is not. Only about 5% of all petroleum production is used to make polymers (the same percentage as is used for supplying the rest of the chemical industry). If polymers were completely eliminated or sourced from bio-feedstocks, the world would still be drilling for oil in deep water and other sensitive environments. (They’d also be looking for something to do with all those double bonds.)

At the same time however, there is extensive and interesting work going on in developing alternate feedstocks. Polylactic acid is the most visible example today with the lactic acid being derived from fermentation of corn sugar. I can’t say I’m crazy about using food as a source of plastics however. Other promising work is focusing on the use of algae as bioreactors for making monomers and some of it is getting commercialized. I’m anxious to see how this trend shapes up, as I anticipate getting to play with some new monomers.

CJ: Is there anything you'd like to tell the Chemjobber readership?

JS: Two things:

Chemistry is needed to make polymers, but they are bought and sold almost exclusively because of physical properties, so to be successful you need to understand something about the physical properties and how chemistry affects them.

And lastly, here is my universal tip to make everyone appear smarter about polymers: When in doubt, say “polyurethane”. The term polyurethane simply means that the monomers (typically a diol and a diisocyanate) reacted and formed the polymer by creating urethane linkages. The name says absolutely nothing about what the chemistry is between the urethane groups, so your readers should be able to quickly see that pretty much anything is possible. And it really is. Polyurethanes are used to make bowling balls, sponges, pressure-sensitive adhesives and everything in between. If you can imagine it, you can probably make it with a polyurethane. Conversely, if someone has a piece of plastic or rubber and asks you what it is, “polyurethane” is never a bad answer. It may not be correct, but you won’t look foolish either - always a good thing!

CJ here again. Thanks to Dr. Spevacek for a wonderfully informative interview!