Segmented block copolymers based on dimerized fatty acids and poly(butylene terephthalate)

Segmented block copolymers based on dimerized fatty acids and poly(butylene terephthalate) (PBT) have been synthesized in the melt. Branched C36, C44 and C70 dimerized fatty acids with a low degree of unsaturation were used. The fraction of PBT was varied from 50 to 100 wt%. The resulting polymers were analysed with d.s.c, and d.m.a. The glass transition temperature (T~) increased with increasing weight fraction of PBT. T~ decreased with increasing molecular mass of the dimerized fatty acid. The melting temperature increased with increasing weight fraction of PBT and increasing molecular mass of the dimerized fatty acid. The range of service temperatures of the thermoplastic elastomers can therefore be enlarged by using dimerized fatty acid with a high molecular mass. With increasing molecular mass of the dimerized fatty acid the storage modulus and the melting and crystallization enthalpy did not change significantly. The storage modulus can be described as a function of the volume fraction of crystalline PBT, but is not a function of the type of dimerized fatty acid.