Path Dependent Microstructure Orientation During Strain Compression of Semicrystalline Block Copolymers

Published

June 1, 2001

Author(s)

P L. Drzal, J D. Barnes, P Kofinas

Abstract

The shear-induced morphologies produced by channel die processing of a semicrystalline ethylene/ethylene-propylene/ethylene (E/EP/E) triblock copolymer were investigated as a function of processing conditions. The microphase separation of the block constituents under the processing conditions used in this work leads to a lamellar stack morphology, referred to as the B population, whose dimensions are controlled by the block molecular weights. In addition the crystallizable part of the E polymer forms lamellar stacks which are referred to as the C population. The orientation textures of these two populations depend upon processing in a complex manner. Two dimensional small angle x-ray scattering (SAXS) was used to determine the domain spacing and orientation of the B and C populations relative to the process directions. The rate at which the channel die was cooled following compression was found to strongly affect the microstructure of the end product. Using a cooling rate of 0.27 C/s produces a B population oriented predominantly perpendicular to the direction of shear [Bp], while a cooling rate of 3.50 C/s yields a population [C_t] of C lamellae which are oriented predominantly transverse to the direction of shear. This C_t microstructure is novel for block copolymers and is attributed to deformation of preexisting crystallites. This study clearly demonstrated that dramatic morphological control of both B and C populations is possible through changes in melt processing of semicrystalline block copolymers.

Citation

Polymer

Volume

42

Issue

No. 13

Pub Type

Journals

Keywords

block copolymer, ethylene/ethylene-propylene/ethylene, morphology, plane strain deformation, polymer processing, SAXS, small-angle scattering

Citation

Drzal, P. , Barnes, J. and Kofinas, P. (2001), Path Dependent Microstructure Orientation During Strain Compression of Semicrystalline Block Copolymers, Polymer (Accessed May 9, 2025)