The thermal stability of a poly(ester amide) copolymer (PBTA) based on poly(butylene terephthalate) (PBT) and nylon-4,T with the diamide of butanediamine and dimethyl terephthalate (N,N'-bis(p-carbomethoxybenzoyl)butanediamine) and homopolymer PBT was studied. The development of inherent viscosity and endgroup concentration was determined during prolonged condensation reactions at 255-275°C. Analysis of the kinetics lead to degradation rate constants for PBT and PBTA with 20 mol% amide (PBTA20). The degradation rate of PBTA20 was comparable to that of PBT, thus fl-elimination of the ester groups is the main degradation mechanism in PBTA. At high temperatures ester-amide interchange reactions also take place in PBTA. The change in the melting temperature of PBTA has been related to the decreasing uniformity of the amide segment length. The decomposition was further studied by thermogravimetry and mass spectrometry.

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The synthesis of poly(ester amide) copolymers (PBTA) based on poly(butylene terephthalate) (PBT) and nylon-4,T with the diamide of butanediamine and dimethyl terephthelate (N,NLbis(p-carbomethoxybenzoyl)butanediamine) has been carried out. Different melt and solid state condensation reactors were used. The polycondensation of PBT and PBTA with 20-25 mol% of amide units (PBTA20/PBTA25) was carried out in the melt at 255-265°C under high vacuum. The inherent viscosity ~Tinh, the amino and carboxylic acid endgroup concentrations and the melting temperature (Tin) were determined. The influence of diamide purity and concentration of Ti catalyst (0.02 0.28 mol%) was studied. The concentration of Ti catalyst had little effect. The purity of the diamide had an effect on r]inh but also on T m. Postcondensation in the solid phase, 20°-30°C below T m, was most effective after short melt polymerization times.

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