A group of scientists from Brown University (Brown University) studied the problem, which for a long time remained without a solution. So, at one time, an extremely durable polymer PBO (polybenzoxazole) was proposed for bulletproof vests. On the basis of polybenzoxazole, serial bulletproof vests were produced for the US Army, but after some time they were withdrawn. It turned out that this material of bulletproof vests is subject to unpredictable destruction under the influence of moisture. This does not prevent the production and sale of bulletproof vests from various PBO modifications under the Zylon trademark, but the reliability of the materials still leaves much to be desired.
The problem with PBO's reliability is that it uses highly corrosive polyphosphoric acid (PPA) to degrade the polymer chains during the manufacturing process. The acid works both as a solvent and as a catalyst. The acid molecules remaining in the polymer molecules subsequently make themselves felt during the operation of bulletproof vests by unexpected destruction of the material. If you replace PPA with something harmless, then the performance of PBO polymers can be dramatically improved, but with what?
Scientists from Brown University as a catalyst for building PBO molecular chains an alloy of gold (Au) and palladium (Pd) nanoparticles. During the experiment, the optimal ratio of one and the other was revealed - 40% gold and 60% palladium - which accelerated the production of the polymer as much as possible. At the same time, formic acid, an environmentally friendly and renewable raw material, acted as a solvent. In general, the new technological process turned out to be less energy intensive and not as expensive as using polyphosphoric acid.
After making sufficient volumes of PBO polymer in a new way, it was tested during several days of boiling in water and acid. The material has not undergone degradation, which gives hope for a significant increase in the performance of bulletproof vests with its use. An article on this study was published in the journal .
Source: 3dnews.ru