Processing conditions and properties of semicrystalline polymers, I: Effect of mechanical properties of a chlorinated polyether

Abstract

AbstractControlled changes in crystallization conditions and shear history prior to and following both extrusion and compression molding were shown to drastically alter the mechanical properties of the polymer studied. This material, Poly[3,3‐(bischloromethyl) oxacyclobutane], is an essentially linear polymer with a number average molecular weight of 300,000. The effect of heat transfer, as limited by experimental conditions, had a primary influence upon the crystallization phenomenon and therefore also upon the morphology and the resultant mechanical properties.By proper selection of processing conditions it was possible to alter the mechanical properties of this polymer from brittle behavior to the ability to form a neck and draw to high degrees of elongation. Using conditions that imparted the ability to neck and draw, it was shown that this process is sensitive to both strain rate during testing and extrusion rate during processing. The underlying cause of the effects upon mechanical properties appear to be the dramatic changes occurring in morphology as a result of the selected processing conditions.A chemical etching agent was used on these samples prior to replication, and observation in the electron microscope. Using this technique the internal morphology was studied and compared to the surface morphology. There was not a gradient of morphology in these samples. Furthermore, the use of this etching agent that attacked non‐crystalline regions preferentially, suggested that the lamellar fine structure of spherulites is composed of smaller units.