MECHANICAL-BEHAVIOR AND MORPHOLOGY OF TOUGHENED ALIPHATIC POLYAMIDES

The mechanical properties of a series of polyamide materials (nylon 6,12, nylon 11, nylon 12 and nylon 12,12) were investigated using triblock copolymers of the type styrene-(ethylene-co-butene)-styrene (SEBS) and a maleic anhydride (MA) functionalized version (SEBS-g-MA). The results have been compared with the behaviour reported for nylon 6 and nylon 6,6 in our previous work. A much lower concentration of the maleated elastomer (SEBS-g-MA) was required for effective toughening of these polyamides with higher CH2/NHCO ratios. This is believed to be a consequence of the inherently more ductile polyamide matrix as the methylene content of the nylon material increases. Further evidence of this was given by the trends in the ductile-brittle transition temperature of the various binary blends of these polyamides with SEBS-g-MA. Transmission electron microscopy techniques used for investigating the morphology generated in these blends showed that ternary blends of nylon x (monofunctional) materials (nylon 11 and nylon 12) yielded regular, spherical rubber particles with a continuously varying particle size as the proportion of SEBS and SEBS-g-MA in the rubber phase was changed, while ternary blends of nylon x,y (difunctional) materials (nylon 6,12 and nylon 12,12) yielded rubber particles with varying levels of complexity and size depending on the SEBS-g-MA/SEBS ratio. Such differences in the blend morphology between nylon x and nylon x,y materials have been attributed to differences in the basic chemical structure of these polyamides. The existence of critical limits on the rubber particle size for toughening these blends was also explored.