This month Frank Bates, is here to answer your questions about the inventing new materials. Learn more about Frank Bates' work.
How did you get the idea to put little wormlike structures in a polymer to make it less brittle?
I was just wondering professor if long chain molecules used in synthetic motor oils are truly superior. Many are of the opinion that such lubricants are a waste of money. Are these in fact polymer related or away from your chosen field of endeavor? First of all, what is a long chain molecule, and why does it operate in the innards of an automobile engine in a manner which prevents or might prevent excess wear? Bearing in mind that there is no such creature as a perpetual motion machine, what role do lubricants posess toward the illusive goal of producing "the ultimate machine," that is, a machine which will last indefinitely and under a difficult operating environment. Thank you, professor for your generous time. we are very proud of your accomplishments.
My student and I did not really anticipate that these miniscule wormlike objects would work the way they do. We had experience creating similar structures in water and decided to see whether it was possible to duplicate them in a piece of cured epoxy. I suppose this is a classic example of an experiment that produced an unexpected but useful result.
Is Kevlar an acronym? And if so, what is it an acronym for?
Joe, I believe Kevlar is simply a tradename. The chemical name for this polymer is poly(p-phenylene terephtalamide). You can find out all sorts of interesting information regarding Kevlar, and other "aramid" polymers using a serach engine on the web.
I always read about materials scientists "assembling" polymers to have the qualities they're looking for. It's obviously not like building something out of Tinkertoys, so how DO you create a custom polymer?
Lisa: This phrase "assembling", and sometimes "self-assembling", is used to describe how specific parts of a molecule are attracted to and locate near certain portions of other molecules. A nice example of this process can be found in living cell membranes, which are formed from lipids. One end of the lipid molecule likes water while the other end hates water. When lipids are dispersed in aqueous solution they pair up with the heads and tails in close proximity. The result is a "self-assembled" bilayer membrane. Polymers can exhibit similar behavior. In order to make theses gigantic molecules assemble according to some game plan you need to use very specific synthetic chemistry tools that sequence the small (monomeric) building blocks correctly. The world of biology provides the most exquisite examples of such sequencing in the form of DNA, RNA, and proteins.
Sorry for such a long answer!
How come #1 and #2 plastics are recyclabe and others, like #5, are not?
In order to recycle a plastic it must be processed into a useful product. Certain types of polymers can be heated to a temperature where they begin to flow. Provided there is no chemical degradation they can be reshaped into a new form. Polystyrene is an example of such a polymer. Above about 100 degrees centigrade polystyrene becomes soft. Other polymers are formed by irreversible chemical bonding leading to a network like molecular structure that can not be broken down. Two examples in this category are epoxy resins and rubber tires. Neither of these can be recycled. You are probably familiar with the problems created by plastics and other materials that can not be used over. One way to avoid this problem is to create polymers that decompose when left in the environment. Polylactic acid is a nice example of such a biodegradeable plastic.
Is there anything new in materials science that will help air pollution?
I can think of several technologies that rely on materials to reduce air pollution. The first item would be filters, which can be made from many types of materials including polymers. Recent advances in processing methods permit the formation of polymer fibers that are as small as 100 nanometers in diameter. A thin layer of these fibers on top of a conventional course filter can improve the separation efficiency enormously. However, this technology is expensive and isn't found in common houshold filters like the ones used in a furnace to clean the air in your house. Filters are used in many other applications in addition to cleaning air. The oil in your car must be continuously filtered and the disk drive on your computer has a small but very high tech filter to keep all dirt (including bacteria) from getting between the high speed disk and the reading head.
What is your favorite part of your job?
I have many responsibilities in my job and fortunately I really like several of them. Teaching is one of the best aspects of being a professor and I very much enjoy working in the classroom. I also supervise a number of graduate students in their research projects and this also is a lot of fun. Working with creative people (students, faculty, industrial colleagues) on intellectually stimulating topics is probably the best part.
would we ever have coats that have heat producung materials in them? you would make a fortune here!
Coats already have a heat producing material - you! All kidding aside, you could make a heated coat using a variety of approaches. For example - and I am making this up - a microwavable vest, that could be inserted in the coat, would be rechargable. Or you could use packets of chemical heat, like the handwarmers that you start by squeezing on the package. However, replacing these could get expensive. In the end I would opt to improve the insulation in the jacket therby reducing the heat transfered and rely on good old fashioned and cheap body heat.
is it hard to be a scientist?
Claudia, I will offer two answers to this question. Firstly, is it hard to become a scientist? In general you need to study for about four years at a college or university focusing on one of several disciplines including physics, biology, chemistry, geology, and others. In some cases, students choose to continue with graduate studies leading to masters (about 2 more years) or doctoral (about 5 more years) degrees. All these degrees require hard work and dedication, but they lead to rewarding careers. Perhaps the trickiest part is choosing the subject that suits you best.
Secondly, once you have entered the workplace you will have an opportunity to make a real impact on society. Just think of the technical challenges that confront our nation and the world: a lack of adequate clean renewable energy; many health issues; emvironmental problems; and many more. Are these hard problems? You bet they are. But what a thrill to go to work each day and know you are doing something so positive.
What is the biggest challenge you have faced? could you ever get something not to work quite right?
I would have a difficult time picking one technical challenge that most stands out. Nevertheless, last year a team of five graduate students and I solved a difficult problem that we had worked on for about five years. We were trying to get a complicated typee of polymer, known as a block copolymer, to arrange into an elaborate structure in which three nanoscale pieces of the material each independently spanned all three dimensions. We finally figured out how to do this, which was very satisfying. The project has generated four Ph.D. thesis as well.
For your second question the answer is all the time! Most ideas don't work out the way you expect them to in science and engineering. However, usually something unexpected occurs and you just have to be able to adapt.
can you make fake human skin\r\nthat can be used in transplants\r\nmanipulating poly mers
Yes, there has been much progress in making artificial skin using various types of polymers. Perhaps the most important application is in burn victims. The artificial skin must combine the proper balance of water transpiration, oxygen diffusion, and of course provide a barrier to invasive organisms such as bacteria. Ultimately, these materials are temporary fixes that provide time for skin to regenerate.
How did you get involved in science?
I took an indirect route to my present career. In college I majored in mathematics, but took quite a bit of science as well. When I graduated I didn't have a concrete idea of what I really wanted to pursue. Although I knew little about it, chemical engineering sounded like something I would find interesting so I applied to graduate school (sort of like grades 17 to 22). After completing my classes I started studying polymers, and have been enamored with this class of materials ever since. My first job after graduate school was at AT&T Bell Laboratories, which at the time was one of the greatest research establishments in the world. After seven years at Bell Labs I joined the faculty at the University of Minnesota where I work today. Each of these different experiences has helped shape the way I think, teach, and solve problems.
Hello, and thank you for this opportunity. I'm wondering if you know how soon carbon nano-tubes will be put into commercial use...such as for bicycles.
Thako, that is a great question. Many people, including many scientists and business entrepreneurs, are anxious to take advantage of the remarkable properties of carbon nanotubes. Unfortunately, they are very expensive to make and difficult to mix with other materials. In order for a new material to be successful it must exhibit superior properties and be cost effective. Until scientists and engineers get the price down, and find ways to better mix nanotubes with plastics and other compounds, I'm afraid this form of carbon will remain a lab curiosity. Don't forget that carbon fibers already plays an important role in composites.
Why are some plastic containers microwaveable and others are not?
Microwave ovens work by exciting water molecules using electromagnetic radiation in the microwave energy range. The excited molecules vibrate and give off heat. Provided your container doesn't include chemical substances that absorb the specific type of radiation being emitted it will simply transmit the microwaves. (One exception is metal, which can cause problems for different reasons). Most polymers are essentially transparent to these microwaves. For example, polypropylene, a common plastic for food containers, is made up entirely of carbon and hydrogen, and is ideal for the microwave oven. Polyethylene also works. Packaging materials may also contain other additives that could leach out of the plastic if heated to elevated temperatures and get in your food. I suspect this is the reason some plastic materials are considered non-microwaveable. You wouldn't want to cook with these materials using your gas oven either.
How are MEMS actually built considering each gear/mechanism is as tiny as it is. Are they "grown" like crystals?
Wil, I must warn you that I am not an expert on this topic. In general, MEMS are fabricated using lithographic methods. A layer of polymer is cast onto the surface of the material you wish to pattern, let's assume this is silicon, and specific shapes are imaged in this polymer using light (sometimes electrons or x-rays). The places where the light hits the polymer react to solidify or sometimes decompose the film, leaving a two-dimensional pattern that exposes features on the underlying silicon. Then the exposed silicon is etched with reactive gases or a plasma transferring the pattern from the polymer film to the substrate. Repeating this process many times permits you to build up complex three-dimensional objects such as tiny gears and levers. My advice is to search on the web using the subject title "MEMS fabrication". I found lots of interesting sites this way.
I'm looking for a material to use for a roll cage, what is the lightest most durable material that is suitable for this?
Well I cannot provide a single answer to that question. Materials selection depends on many factors including the type and magnitude of stress applied and the cost. If you are considering a roll cage for a vehicle such as an automobile plastics will almost certainly be ruled out due to low strength. Ceramics are too brittle, which leaves metals. If cost is a consideration then you would probably select some type of steel, which combines excellent strength and toughness with low cost. There are many different grades of steel (this is determined by the added elements such as chromium, nickel, molybdenum, and many others). If you want corrosion resistance then stainless steel (lots of chromium) is the best choice. For a lighter and very durable metal you could go with a titanium alloy, but these are much more expensive. Aluminum is even lower in density (lighter) but does not have the mix of properties displayed by steel. Another issue may be the ability to weld pieces together. So, actually designing a roll cage requires balancing all these considerations. That's the sort job that a materials engineer would perform.
How do new plastics get invented?
I very much like this question. The answer is dependent on the price you are willing to pay for your new plastic. New cheap commodity plastics that cost about fifty cents to a dollar a pound are virtually impossible to find. Today about 80% of the polymer industry relies on just four polymers: polyethylene, polypropylene, polystyrene, and polyvinyl chloride. These materials are made from simple starting chemicals that can be efficiently coupled together into long "macromolecules". Since chemists have been searching for simple polymers for nearly a century it is highly unlikely they have overlooked one. However, it is always possible that a new one will emerge - you'd make lots of money if you made this discovery.
Most new polymers are what are known as specialty chemicals. They can be created by changing the molecular structure of the starting compounds, known as monomers. Chemists and materials scientists in both industrial and academic labs pursue these chemical modifications all the time. Often what is needed is a new type of chemical reaction facilitated by a catalyst, which coordinates the sequential addition of individual monomers into the long polymer chains. In most cases the scientist will be searching for specific set of material properties, like strength or permeability to a gas (for example oxygen) or perhaps electrical conductivity. Last December the Nobel Prize in chemistry was awarded to three chemists who had discovered just this type of catalytic polymerization reaction.
So, the answer to your question is that new polymers are discovered all the time, but usually for specialty applications. I should add that my colleagues and I synthesize polymers every day in our lab at the University of Minnesota. One of the most thrilling aspects of our work is to create a new type of molecule and witness its evolution into a tangible material with new and useful properties.
How can tires made out of recycled plastic be safe?
I don't believe you would want to buy such a tire! Tires are made from rubbery polymers such as natural rubber (extracted from trees) and synthetic rubber (usually containing polybutadiene). To convert the starting "gum" into a resilient tire the rubber must be compounded with chemicals that react with the monomers creating strong chemical bonds called crosslinks, which link the polymers together. (In practice making a tire involves many other steps including adding a significant amount of tiny carbon particles (that's why they are black) to adjust the stiffness and wear behavior). One way to envision the difference between the starting and crosslinked polymer is to compare "silly puddy" and silicon caulking that you might use to seal your bathtub or shower. The silly puddy flows over time because the polymer molecules are not linked to each other. The silicon caulking starts out as a liquid but then undergoes chemical reactions that lead to crosslinking and a rubbery solid.
Goodyear discovered this crosslinking process in 1839 when he added sulfur to natural rubber. This was one of the great discoveries of the century and spawned the rubber industry. So, now I can answer your question. In order to recycle a plastic you must be able to heat or dissolve them so that they can be reformed into a new product. Crosslinked rubber tires cannot be reprocessed because of the strong chemical bonds that fix together all the chains. Perhaps you are interested in other plastics that are not crosslinked, such as polystyrene or polyethylene. Well, these polymers don't have the appropriate rubbery behavior nor can they be easily crosslinked to achieve the necessary mechanical stability for tire applications. Your question deals with an important environmental problem. We generate millions of tires annually and most end up in waste dumps. If you could find an economically competitive way to recycle you would benefit society, get famous, and rich!
What are ferrofluids good for? I mean, they're cool, but what sort of practical application is there for them?
Are you also trying to invent ways to safely, quickly and economically breakdown plastics?
My daughter, Harlee, would like to know how scientists can figure out how to put the bone structures of dinosaurs together. Thank you.
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