Comparison of the toughening behavior of nylon 6 versus an amorphous polyamide using various maleated elastomers

Abstract

The toughening effect of two types of elastomers based on ethylene/α-olefin copolymers, viz, an ethylene/propylene copolymer (EPR) with its maleated version, EPR- g-MA, and an ethylene/1-octene copolymer (EOR) with its maleated versions, EOR- g-MA- X% ( X=0.35, 1.6, 2.5), for two classes of polyamides: semi-crystalline nylon 6 versus an amorphous polyamide (Zytel 330 from DuPont), designated as a-PA, was explored. The results are compared with those reported earlier based on a styrenic triblock copolymer having a hydrogenated midblock, SEBS, and its maleated version, SEBS- g-MA, elastomer system. Izod impact strength was examined as a function of rubber content, rubber particle size and temperature. All three factors influence the impact behavior considerably for the two polyamide matrices. The a-PA is found to require a somewhat lower content of rubber for toughening than nylon 6. Very similar optimum ranges of rubber particle sizes were observed for ternary blends of EOR- g-MA/EOR with each of the two polyamides while blends based on mixtures of EPR- g-MA/EPR and SEBS- g-MA/SEBS (where the total rubber content is 20% by weight) show only an upper limit for a-PA but an optimum range of particle sizes for nylon 6 for effective toughening. Higher EPR- g-MA contents lead to lower ductile–brittle transition temperatures ( T db) as expected; however, a-PA binary blends with EPR- g-MA have a much lower T db than do nylon 6 blends when the content of the maleated elastomer is not high. A minimum in plots of ductile–brittle transition temperature versus particle size appears for ternary blends of each of the matrices with EOR- g-MA/EOR; blends based on SEBS- g-MA/SEBS, in most cases, show higher ductile–brittle transition temperatures, regardless of the matrix. However, blends with EPR- g-MA/EPR show comparable T db with those based on EOR- g-MA/EOR for the amorphous polyamide but show the lowest ductile–brittle transition temperatures for nylon 6 within the range of particle sizes examined. For the blends with a bimodal size distribution, the global weight average rubber particle size is inappropriate for correlating the Izod impact strength and ductile–brittle transition temperature. In general, trends for this amorphous polyamide are rather similar to those of semi-crystalline nylon 6.