Rheological properties and processability of chemically modified poly(ethylene terephthalate-co-ethylene isophthalate)

Rheological properties and extrusion processability have been evaluated for poly(ethylene terephthalate-co-ethylene isophthalate) (P(ET-EI)) modified by a styrene-acrylate-based copolymer with glycidyl functionality in an extruder. Adding a small amount of the modifier enhances melt elasticity to a great extent. Consequently, modified P(ET-EI) exhibits excellent processability without sagging, that is, downward deformation of extrudates by gravitational force. Considering that molecular weight and its distribution hardly change, which is confirmed by GPC measurements, generation of long-chain branches is responsible for the rheological properties and thus the processability. (c) 2007 Wiley Periodicals, Inc.