Technologically, "nanocomposite" is not a new word. However, it is currently a very exciting word for many researchers. Just like genome research. The recent development of nano-porous, nano-composites by researchers at Ohio State University adds a new dimension to heat resistant plastics.
Let's take the high-tech aerospace industry as an example. This industry is always searching for materials that are lighter and more heat resistant. The reason is obvious. If a jet engine can use lightweight heat resistant plastics it can go faster and while conserving fuel. But problem with plastics rest elsewhere. Heat resistant plastics are not tough enough. That is revealed by tests involving heat resistant plastics reinforced with graphite fiber. As Dr. John Lannutti from Ohio State University explains - an impact from a flying bird onto an airplane wing made of fiber reinforced plastics can shatter the plastic leaving behind the exposed graphite fibers.
The discovery of tougher heat resistant plastics comes from a completely different direction. Several years ago, Dr. Lannutti and Dr. Robert Seghi at Ohio State University were working on nanoporous particle reinforcement of plastic dental fillings in an attempt to improve their wear resistance. Guess what? Not only did wear resistance improve but improvements in impact resistance were also observed. This triggered Dr. Lannutti and his associates to combine a high temperature PMR*-type polyimide resin (Superimide TM 800 from BFGoodrich) with nanoporous silica particles. Researchers prepared nanoporous silica particles by sol-gel process. Using different quantities of catalyst, they produced nanoporous nanoparticles having different pore contents. The result contains two different pore size ranges. These silica particles are 50 nanometers wide (roughly 1,000 times smaller than the width of a human hair) and are riddled with pores as small as 15 angstroms in diameter (10,000 times smaller than the width of that same human hair). Silica particles were then introduced into the polyimide matrix via in-situ polymerization. The only task remaining was hot pressing to full density. That's it. The resulting plastic matrix and nanoporous silica formed a highly interpenetrating network (IPN). In addition to retaining the heat resistant properties of the SuperImide 800, the nanoporous, nanocomposite became 4-5 times as tough as the original resin. According to Dr. Lannutti, nanoparticle toughening starts at the nanometer level. Further, highly nanoporous silica enhances multiple-scale synergistic toughening. That is why he terms it "Nanoporous-nanocomposites".
This development has already sparked industrial interest ranging from aerospace (BFGoodrich) to automotive (Ford). Such nanocomposites can be manufactured by reaction injection moulding (RIM) or resin transfer molding (RTM) processes.
[* PMR is a reaction approach based on polymerization of monomeric reactants. For instance, NASA's PMR-15 polyimide resin which is widely known for advanced composite applications. This is a resin system that provides excellent retention of mechanical properties in the 260 - 316 C temperature ranges. The number 15 refers to the combined molecular weight (1500) of 3 components.]