Tensile properties and morphology of PP/EPDM/glass bead ternary composites

The tensile properties of three types of injection molded glass bead (GB) filled polypropylene (PP)/ethylene-propylene-diene monomer (EPDM) ternary composites have been determined at room temperature by using an Instron materials testing machine. The effects of the filler surface treatment, the glass bead (GB1) pretreated with a silane coupling agent and the EPDM (EPDM-MA) modified with a maleic anhydride, and the filler content on the tensile mechanical properties of the ternary PP composites have been investigated. The Young's modulus (E_c) increases while the yield stress (σ_yc) and tensile fracture strength (σ_bc) of the composites decrease with increasing the volume fraction of glass beads (φ_g) when the volume fraction of EPDM is constant (φ_e = 10%). The E_c values of PP/EPDM/GB1 and σ_bc for PP/EPDM-MA/GB2 (no surface pretreated) systems are the highest at the same φ_g. The tensile fracture energy (E_bc) and tensile fracture strain (ε_bc) of PP/EPDM/GB1 and PP/EPDM/GB2 systems appear to peak at φ_g = 25%. However, the E_bc and ε_bc of PP/EPDM-MA/GB2 system show little changes with increasing φ_g. The fracture surfaces of ternary composites have been examined in a scanning electron microscope. The correlation between the tensile properties and morphologies of these materials have been discussed.