Polypropylene/glass fiber/ethylene propylene diene ternary composites with improved thermoforming properties for orthotic aids

In the present work, Polypropylene/Glass fiber/ethylene propylene diene rubber (PP/GF/EPDM) ternary composites were developed for orthotic applications. A series of PP/GF and PP/GF/EPDM composites with varied amount of GF and EPDM were fabricated through melt-blending process in a twin screw extruder. Maleic anhydride grafted PP (PP-g-MAH) was used as compatibilizer. The composites were characterized for its morphology through scanning electron microscopy (SEM). Mechanical properties of the composites were investigated as per ASTM standards and were compared with the costly commercial orthotic materials available in the market. The drawback of using GF as reinforcement fibers is the significant loss of impact and thermoforming properties of the composites. Incorporation of EPDM as elastomer is a promising approach to improve both impact and elongation of PP/GF composites. However, EPDM results in simultaneous decrease in the tensile strength and modulus properties. Thus, the proportion of GFs and EPDM were optimized in the composites to obtain an orthotic material with appropriate tensile and flexural properties for longer durability, high impact for its resistance to fracture and a limiting elongation at break for easy processing through thermoforming. The developed PP/GF/EPDM composites with balanced tensile and impact properties shows potential application as low cost orthotic material.