First, at the time the bracket was designed, there was a global shortage of PA6/6 owing to shortages in adiponitrile (ADN), the key raw material used to produce hexamethylene diamine, one of two monomers used in the production of PA6/6. (During the same period, raw material costs for aluminum also spiked owing to trade tariffs imposed on imported metals.) Switching to a copolymer system involving both polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) meant that the resulting polymer blend has two glass-transition temperature (Tg) values instead of just one, which expands the temperature range where peak loss factor — a measure of NVH damping — occurs. Depending on fiber orientation, chemistry, and temperature, thermoplastics such as polyamide and polyesters typically exhibit 10-20 times higher loss factors than aluminum. Using the PET/PBT blend improved NVH across the full operating temperature range of the vehicle, with peak damping between 55 to 80°C. Furthermore, this particular composite provides very high (>20 gigapascals) modulus thanks to high glass loading plus excellent dimensional stability regardless of humidity level (since PBT and PET are far less hygroscopic than PA grades).