A research team has discovered a new method of producing polybenzoxazole (PBO), which is commercially known as Zylon and used in body armor. This new production method may be able to make PBO products less apt to degrade, an issue that has continued to adversely affect PBO-based materials.
Shouheng Sun, a Brown University chemistry professor and co-author of a paper on the research said, “By employing a nanoparticle catalyst, PBO can be produced without the chemical that causes the degradation and in more eco-friendly conditions.” He added, “We believe this path will lead to stronger PBO materials.”
Up to now, nanoparticle composite catalysts have mostly been used to make small organic molecules. Whether or not a composite catalyst like gold particles and palladium alloys, which have been used in this case, could be affective in catalyzing the controlled expansion of polymer chains, has been unknown.
“The question the research was trying to answer was if there was a way to control the reactions in order to obtain control over the degree of polymerization,” he said. “In the end we showed that this could be done by fine tuning the size and composition of the alloy nanoparticles being catalyzed.”
An alloy composed of 60% palladium and 40% gold was shown to be highly effective for controlling the reaction speed necessary to make PBO. Particles of about 8-nanometers created a reaction speed that optimized the PBO polymer’s molecular weight.
To determine whether the PBO could resist degradation, the researchers teamed up with researchers at the School of Engineering at Brown University to conduct mechanical testing. That testing proved that PBO polymers produced with the nanoparticle catalyst were indeed much less prone to degradation than Zylon, even when they were boiled in acid and water for days.
The researchers will now work towards generating even heavier PBO polymers. The ones generated for this particular study were much lighter than the PBO polymers in commercial products, which limits their mechanical strength. Even so, the work that has been done by this research team strongly shows proof-of-concept for the theory that by using composite nanoparticles you can produce PBOs that resist degradation.
Another study co-author, Jerome Robinson who is an assistant chemistry professor at Brown mentioned that the widely diverse expertise of the research team at Brown was vital to the success of the project.
“It was extremely important for us to collaborate on this with engineers and other top-notch researchers,” Robinson said. “Just being able to cross the street and bring on the School of Engineering to conduct the mechanical testing was a huge advantage, and we now have the perfect team to carry on with this research.”