Mechanical properties of glass fiber reinforced, rubber toughened nylon 6
MetadataShow full item record
The mechanical properties of glass fiber reinforced, rubber toughened nylon 6 are presented with attention given to the tradeoff between stiffness/strength and toughness. Proper addition of maleated ethylene-propylene rubber (EPR-g-MA) or maleated styrene-hydrogenated butadiene-styrene triblock copolymers (SEBS-g-MA) to nylon 6 produces “super-tough” polymer blends; however, tensile modulus and yield strength are decreased. The addition of glass fibers can compensate for the loss of stiffness and strength. By adding 15 wt% or more glass fibers to a material that contains 20 wt% rubber, materials can be made that have a higher modulus, yield strength, and fracture energy than neat nylon 6. Although the toughness of these materials is lower than super-tough nylon 6 blends, a high level of toughness can be retained such that the materials have balanced mechanical properties. Fracture analysis according to a modified essential work of fracture model, indicates that the presence of glass fibers in nylon 6/EPR-g-MA or nylon 6/SEBS-g vi MA increases the limiting specific fracture energy, associated with fracture processes that occur near the fracture surface. At the same time, the dissipative energy density, ud, associated with energy absorbing processes that occur in an outer zone away from the fracture surface, decreased. Transmission electron microscope 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, where 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-gMA materials did not exhibit this deformation process. In general, smaller rubber particles led to higher fracture energies. Using an anhydride functional surface treatment on the glass fibers produces materials with higher fracture energies than an amine functional silane. This result was attributed to the fact that the amine treated glass did not bond well to the rubbertoughened polyamide matrix. As a result, amine functional silanes, which are commonly used surface treatments for reinforced nylon 6, may not be suitable when a rubber toughened polyamide is the matrix material.