INTERACTIONS AT THE PA-6/PA-66 INTERFACE

Refrigerant tubing used in some mobile air conditioning systems has a nylon core, often consisting of nylon 6, nylon 66, or a copolymer thereof. A blend of the homopolymers would be more economical than the copolymer. This article deals with the structural stability of such blends during processing. The crystallization and melting behavior of laminates and solution cast blends of nylon 6 and 66 were examined. Although they do not cocrystallize readily, their at least partial miscibility in the melt and possible coincorporation as crystal defects cause reductions of the melting points and heats of crystallization and fusion of both polymers. The crystallization temperature of the nylon 6, however, increases with increasing nylon 66 content, up to ca. 60% nylon 66, a feature attributed to nucleation of the 6 by the 66.