The Rates of Crystallization of Copolyamides

Abstract

A group of polymers and copolymers based upon polyhexamethylene adipamide (66 nylon) have been prepared. The comonomer ingredients included 6-amino hexoic acid (for 6 nylon) , the salt of terephthalic acid with hexamethylene diamine (for 6T nylon) ,and a blend of trimesic acid with the diamine acting as a branching agent. The polymeric materials were characterised by solution viscometry. Apparatus for studying the rates of crystallization of polymers and the published information for polyamides and copolymers is reviewed. The construction of a hot stage attachment for a polarising microscope is described, and the results from this equipment of the crystallization rates and melting behaviour of the copolyamides are reported. The results can be grouped into three series; 1. copolymerisation of 66 nylon with 6 nylon resulted in a loss of crystallinity together with a reduction in the melting temperatures and the temperatures for observing crystallization behaviour; 2, copolymerisation with 6T nylon resulted in a moderate retention of crystallinity due to isomorphous crystallization; and 3, copolymerisation with a branching agent resulted in both a loss of crystallinity and deviation from the normal kinetic behaviour of polymer crystallization. Observations on the melting of materials showed that the microscopy technique is complementary with differential thermal analysis. Some of the theories of the melting of polymers and copolymers have been introduced in an attempt to explain the experimental data. Quantitative measurements of the heats of fusion and densities of the copolymers are reported.