Effect of rubber particle size and rubber type on the mechanical properties of glass fiber reinforced, rubber-toughened nylon 6

The effects of rubber type and particle size on the mechanical properties of glass fiber reinforced blends of nylon 6 and EPR/EPR-gMA or SEBS/SEBS-g-MA were investigated; rubber particle size in the two systems could be controlled by varying the ratio of EPR to EPR-g-MA or SEBS to SEBS-g-MA. Unreinforced materials with the highest levels of toughness did not necessarily lead to the highest fracture energy when reinforced with 15 wt% glass fibers. Materials toughened with SEBS/SEBS-gMA, which are tougher in the absence of glass fibers had lower fracture energies when 15 wt% glass fibers are present. In general, smaller rubber particles led to higher fracture energies. Fracture analysis according to a modified essential work of fracture analysis reveals that SEBS/SEBS-g-MA have high values of the dissipative energy density, u(d), in the absence of glass fibers. When 15 wt% glass fibers are added, u(d) is essentially zero for all the materials tested. The limiting specific fracture energy, n(0), on the other hand, was higher for both unreinforced and glass fiber reinforced EPR/EPR-g-MA toughened blends than for SEBS/SEBS-g-MA based materials. Transmission electron microscopy observations of fractured specimens indicate that glass fibers decrease the size of the damage zone of rubber toughened nylon 6. Shear yielding was seen in fractured specimens of reinforced nylon 6 blends containing either SEBS/SEBS-g-MA or EPR-g-MA, but the size of this shear yielded zone was larger for EPR/EPR-g-MA. In addition, EPR/EPR-g-MA based materials displayed craze-like deformations, while SEBS-g-MA materials did not exhibit this deformation process. (C) 2003 Elsevier Science Ltd. All rights reserved.