MODIFICATION REACTIONS ON THERMOTROPIC LIQUID-CRYSTALLINE POLY(ETHYLENE TEREPHTHALATE-CO-OXYBENZOATE)S WITH BIVALENT AND TRIVALENT 2-OXAZOLINE COUPLERS

Carboxy-terminated liquid-crystalline poly(ethylene terephthalate-co-o xybenzoate)s with 60 and 75 mol-% oxybenzoate units were modified with phenyl-1,4-bis(2-oxazoline) and phenyl-1,3,5-tris(2-oxazoline) in pla sticorder and extruder. The modification gave rise to significant incr ease in molecular weights and also slight crosslinking and branching. The course of the reaction was followed by means of torque-vs.-time cu rves measured during the plasticorder modification. In spite of strong increase in melt viscosities the processability of the modified copol yesters was not worsened. Samples were injection-moulded and tested. M odifications improved the mechanical properties, distinctly. Especiall y, samples which were slightly crosslinked with phenyl-1,3,5-tris(2-ox azoline) demonstrated outstanding tensile and impact strengths. Signif icant differences in fracture behaviour could be evidenced by recordin g impact bending tests.