Dimethyl benzene-1,4-dicarboxylate; ethylene glycol; 2-(2-hydroxyethoxy)ethanol

synthetischeIt is prepared from 1,4-butanediol and terephthalic acid or dimethylterephthalate by processes which are essentially the same as those used for poly(ethylene terephthalate) and described in the preceding section. Due to the longer sequence of methylene groups, the polymer chains are more flexible and less polar than in poly(ethylene terephthalate). This results in a lower crystalline melting point (225°C) and glass-transition point (22-43°C). The low glass-transition temperature facilitates rapid crystallization in the mould and most poly(butylene terephthalate) is processed by injection moulding.