MIXED AGRO-WASTE FILLER AS REINFORCEMENT: IMPACT ON SOME PROPERTIES OF POLYPROPYLENE

This research studied the impact of mixed sawdust-cowpea agro-waste as filler on the properties of polypropylene (virgin and recycled). Sawdust and cowpea hull powders of mesh sizes 75µm were homogeneously mixed in a 1:1 ratio to form a hybrid filler. Different weight percentages (0, 5, 10, 15, 20) of the hybrid filler were mixed with the respective matrices to produce the composites using the injection moulding technique. The mechanical properties, tensile strength, compressive strength, shear modulus, and hardness test of the composites were studied according to the American Standard Testing and Measurement methods. The mechanical properties showed the greatest improvement in tensile strength compared to PP at 15 wt%, at 34%, and compared to rPP at 10 wt% to 15 wt%, at 38.5%. For all other tested parameters, the PP composite had the greatest improvement at 10wt%; shear strength 35%, compressive strength 10% and hardness 42%, while rPP composites observed 17% shear strength increase, a decrease followed by a steady increase in compressive strength and a decrease in hardness. The solvent imbibition after a seventy-two-hour test duration showed `zero water absorption and less than 0.5% toluene absorption for all composites. The degradation after the 180-day burial test period showed some weight loss, suggesting initiation of degradation. The micrographs of the composites obtained via Scanning Electron Microscope at 10,000 magnification showed that both PP and rPP composites have good interactions with the filler. Hence, agro-wastes such as sawdust and cowpea hulls could be used as fillers in the production of degradable plastics, where strength and a reduced absorption rate are of great importance.