Thermoplastic polyesters are widely used in the automotive industry and are the material of choice for many types of electrical and electronic components due to their excellent balance of mechanical and electrical properties. Under certain conditions including elevated temperatures and the presence of high humidity, thermoplastic polyesters such as polybutylene terephthalate (PBT) have the potential to suffer hydrolytic attack. Recognizing the need for standardization, USCAR USCAR (The United States Council for Automotive Research) established component level testing guidelines specific to connectors. In response, many companies developed HR (hydrolysis resistant) PBT resins to help manufactures meet these requirements. As with many additive technologies in plastics, there are trade-offs. In this case, hydrolysis resistance was often improved at the expense of melt viscosity stability and high flow during the injection molding process.
In addition to improved hydrolysis resistance, there is an emerging need for PBT with improved electrical performance for use in automotive connectors for electric hybrid vehicles. Such connectors must have outstanding color retention with heat aging (125C/1000 hours, especially orange “High Voltage” and yellow “safety” connectors), along with maximum CTI (600+ V) performance per OEM requirements.
DuPont has developed a new PBT Hydrolysis resistance technology to offer outstanding melt stability during molding. The process flexibility of the new Crastin® HR HFS allows more stable manufacturing processes and improvements in quality versus the existing PBT HR grades on the market. This unique combination allows a wider processing window, including the use of hot-runners and regrind, without sacrificing the hydrolysis resistance.