Synthesis and characterization of polyether ester elastomer based on poly(ethylene glycol terephthalate) and poly (butylene terephthalate) with different soft segment length

A series of polyether ester thermoplastic elastomers based on poly(ethylene glycol terephthalate) (PEGT) and poly(butylene terephthalate) (PBT) have been synthesized and characterized by means of NMR, FTIR, DSC and mechanical testing. The influence of different soft segment length on the copolymer properties was investigated with invariable hard segment length. It was observed that, firstly, there coexist four phases corresponding to the amorphous and the crystalline phase of soft and hard segments in some compositions; secondly, the glass transition temperature (T_g) of the soft segment PEGT decreased, and its molten point (T_m) as well as the degree of crystallinity increased with the increase of its number-averaged molecular mass, at the same time, T_g and T_m of the hard segment changed slightly in the vicinity of 326 K and 459 K, respectively, while the degree of crystallinity of the hard segment decreased; thirdly, the drop in the inherent viscosity after molten moulding showed that the copolymer was prone to thermooxidative degradation. All the copolymers were distinguished by a high elastic and plastic deformation and were broken at very high relative deformations. The increase of PEG molecular weight in the composition shifted the stress-strain curves from the one with neck-formation characteristics to the one with typical high elastic state. Thus the elastic modulus, tensile strength and yield stress as well as the relative elongation at break were seen to have changed accordingly.