RUBBER TOUGHENING OF POLYAMIDES WITH FUNCTIONALIZED BLOCK COPOLYMERS .2. NYLON-6,6

The toughening of nylon-6,6 using triblock copolymers of the type styrene-(ethylene-co-butylene)-styrene (SEBS) and a maleic anhydride (MA) functionalized version (SEBS-g-MA) is examined and compared with the behaviour reported for nylon-6 in the accompanying paper. Nylon-6,6 can be made super-tough by blending with SEBS-g-MA, and addition of SEBS merely reduced toughness. For nylon-6 super-toughness was achieved only with certain combinations of SEBS and SEBS-g-MA since with just the latter the rubber particles (approximately 0.05-mu-m) generated were too small for effective toughening. The SEBS served to raise particle size to within the optimal range. In contrast, blends of nylon-6,6 with SEBS-g-MA give rubber particles that are within the optimal size range (just less than 1-mu-m); however, these particles have a very complex structure. For blends containing both SEBS and SEBS-g-MA, there seem to be two distributions of shapes but not size. Evidence is shown that the extent of grafting to nylon-6,6 is less than that in nylon-6 for similar conditions. It is proposed that the large difference in morphology found for nylon-6,6 versus that for nylon-6 stems from basic chemical differences between the two polyamides rather than rheological or processing factors. Nylon-6 is monofunctional while nylon-6,6 is difunctional in their reactions with anhydride. The possible consequences of this are discussed.