Thermoplastic Copoly(Ester Imide)s Derived from PBT, Trimellitic Anhydride, and 1,4-Diaminobutane

Starting from 1,4-diaminobutane and trimellitic anhydride, alpha,omega-diaminobutanebis(trimellitimide) was synthesized and subsequently esterified with methanol. Thermal polycondensation with dimethyl terephthalate in mol ratios from 0 to 100% and 1,4-butanediol yielded the corresponding series of random copoly(ester imide)s based on poly(butylene terephthalate) (PET). Differential scanning calorimetry and wide-angle x-ray scattering showed that all poly(ester imide)s are semicrystalline with degrees of crystallinity up to 50% (depending on the comonomer content). Compared to pure PET, the rate of crystallization, however, is strongly decreased if the content of the comonomer is higher than 20%. Annealing is necessary to crystallize these materials. The melting temperatures (T(m)s) of the copoly(ester imide)s display the usual melting point depression of copolymers: by increasing the content of the comonomer, the melting temperatures initially decrease but increase when the content of the comonomer is increased further. The glass transition temperatures (T(g)s) increase linearly with increasing content of the comonomer. The maximum T-m(258 degrees C) and the maximum T-g(100 degrees C) were obtained for the homopoly(ester imide) derived from N,N'-butane-alpha,omega-diyl-bis(trimellitimide) and 1,4-butanediol. Some mechanical properties were determined on injection-molded testbars of three poly(ester imide)s containing various amounts of N,N'-butane,alpha,omega-diyl-bis(trimellitimide). They were compared to those of pure PET and poly(ethylene terephthalate).