POLYETHER-POLYESTER THERMOPLASTIC ELASTOM ERS CONTAINING A-B-A OR B-A-B TYPE BLOCK COPOLYETHERS AS SOFT SEGMENTS

Polyether-polyester block copolymer is a thermoplastic elastomer prepa red by the polycondensation process; it is composed of polyether soft segments and polyester hard segments. Its outstanding elastic behavior is dependent on a favorable micro-heterophase separated structure. Ac cordingly, physical and mechanical properties of polyether polyester e lastomers are strongly governed by the extent of compatibility between the two segments. In molecular design, to properly build up a dispers ed micro-heterophase structure, the polyether soft segments should be noncrystallizable. The present report deals with the synthesis of A-B- A and B-A-B type block copolyethers, each composed of PEG (A part) and PTMG (B part) segments. It also presents physical and mechanical prop erties of elastomers which include block copolyethers as the soft segm ent and poly(ethylene terephthalate) [T] as the hard segment. As a res ult of the incorporation of the block copolyether which has a low crys tallizability into skeletal sequences of the block copolymer, a well m ixed phase of hard and soft segments was observed, due to the improvem ent of compatibility of the soft phase with the hard phase. A good ela stic fiber with high tensile strength and low Young's modulus could be prepared from a block copolymer.