Abstract
The polyester-polyester block copolymers were prepared by the reaction of poly (1, 4-butylene terephtalate) (PBT) with ε-caprolactone (ε-CL). The effects of molar ratio of PBT to ε-CL on molecular weight and on the character of block copolymer were studied. At the higher molar ratio of hard segment, the reduced viscosity ηsp/c of block copolymer tended to be higher. Good correlation between the numberaverage molecular weight _??_n and the intrinsic viscosity was well confirmed. The sequence lengths of the hard and soft segments depended both on the feed ratio of hard-PBT and soft-ε-CL, and on the rate of transesterification. Average sequence length of hard segments (m) became shorter with increasing the amount of ε-CL in feed, whereas that of soft segments (n) became longer. DCS curves of the copolymer having soft segment content lower than 60wt% showed no soft crystal melting. However, melting could be observed when soft segment contents of copolymers were higher than 75wt%. The hardness and modulus of block copolymer decreased with increasing the weight ratio of soft segment up to 60wt%, while they became higher when soft segment content was over 75wt%.
