MORPHOLOGICAL ORIGIN OF TOUGHNESS IN POLYETHYLENE NYLON-6 BLENDS

The effect of compatibilizing polyethylene and nylon-6 on the morphology and mechanical properties of their blends is investigated. A maleic anhydride functionalized styrene-(ethylene-co-butylene)-styrene block copolymer (MA/SEBS) is added to the blends as the compatibilizer. The compatibilizer is found to play a dual interfacial function. On the one hand, it reduces the interfacial tension of the system, resulting in reduction of the particle size of the dispersed polyethylene phase. On the other hand, it enhances the interfacial adhesion through the formation of micro-bridges. The fine polyethylene phase thus coupled to the matrix in compatibilized blends can carry load and deform co-continuously along with the matrix. This causes extensive yielding of the blend prior to its failure and high ultimate elongations. Unexpectedly, at MA/SEBS contents higher than 10%, the ductility of the blends drops sharply. This is attributed to flow-induced discontinuities within a large core in the tensile specimens. The lines of instabilities act as large notches within the specimen, causing brittle failure of the otherwise ductile blend.