Interpenetrating blends of rigid aromatic fractal polyamides and nylon‐6

Abstract

AbstractBlends of nylon‐6 and up to 20% rigid aromatic fractal polyamides (FPs) were prepared by precipitation from a mutual solvent and by two melt‐processing procedures. In general, no grafting of the flexible linear nylon chains onto the rigid FPs took place, but in several instances of melt‐blending of nylon with FPs whose amine end‐groups were exposed, a low level of grafting occurred.The glass transition temperature and the tensile modulus and yield strength of the blends were greatly elevated as function of the FP concentration in the blends. This was demonstrated to be caused by the openness and rigidity of the FPs, and the connectivity of the FP segments through rigid branchpoints. The great porosity of the FPs allows the chains of the amorphous fraction of the nylon to interpenetrate and pass through the FPs, and the stiff segments of the FPs to suppress the chain motions of the nylon, which accounts for the enhanced glass transition temperature (Tg) and tensile properties. When non‐porous amorphous silica particles or stiff linear or essentially unbranched zigzag polyamides were blended with the nylon, the Tg of the nylon either did not change at all or changed only very little. Several analytical procedures were used to verify that the nylon chains occupied most of the free space in the pervaded volumes of the FPs in the as‐prepared blends and filled this space completely when these blends were compression‐molded. The point where the FPs filled all the volume of the amorphous fraction of the nylon‐6 was reached between 5 and 7.5% FP concentration. Below this, traces of the original nylon‐6 Tg could be occasionally detected. Above it, only the high Tg of the nylon chains interpenetrated in the FPs was detected.