Cyclic oligomers of butylene terephthalate (CBT®) represent a new chemical route to semi-crystalline thermoplastic polybutylene terephthalate (PBT). The oligomers of interest melt completely at about 150℃ to produce a low viscosity fluid that is ideal for wetting and dispersing fibrous fillers and reinforcements thereby enabling the development of composites that were previously not possible when working with high viscosity commercial PBT. Introduction of catalyst to undiluted molten cyclic oligomer leads to rapid ring opening polymerization and the formation of high molecular weight thermoplastic PBT without the generation of volatile organic compounds. The polymer resulting from this polymerization will be hereby referred to as pCBT. Treatment of cyclic oligomers in this fashion results in pCBT thermoplastic resin with a high melting point (230℃) and physical performance similar to that of other commercially available PBT resins. The low viscosity oligomers enables the selection of processing technologies that are typically reserved for thermosetting systems that work in conjunction with easy flowing monomers or pre-polymers. The combination of excellent mechanical performance and the ability utilize processing techniques typically reserved for thermosets enables broad uses for these oligomers in a range of applications including; interior, exterior and structural automotive components. Additionally, the thermoplastic nature of pCBT holds promise to provide a low capital route to a new family of pCBT based recyclable materials made using a range of plastic processing technologies.
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