Brittle-tough transition in nylon-rubber blends: effect of rubber concentration and particle size

Blends of nylon-6 and EPDM-rubber were prepared with various rubber contents (0–20 wt%) and particle sizes (0.3–1.6 μm). The effects of rubber concentration and particle size on the tensile modulus, torsion modulus, yield stress and notched impact strength of the blends were studied. Blend structures and fracture surfaces were investigated by scanning electron microscopy. Rubber particles induce a sharp brittle-tough transition which is independent of the glass transition temperature of the nylon matrix. The brittle-tough transition temperature for notched Izod impact tests shifts to lower values when the rubber content is increased or the particle size is decreased. A correlation was found between the brittle-tough temperature and the interparticle distance. Two deformation modes were observed: voiding and shear yielding. Particle size and interfacial adhesion affect neither the yield stress nor the modulus of the blends.