Preparation and characterization of polypropylene–wheat straw–clay composites

Preparation of polypropylene hybrid composite consisting of wheat straw and clay as reinforcement materials was investigated. The composite samples were prepared through melt blending method using a co-rotating twin-screw extruder. The composition of constituents of hybrid composite such as percentages of wheat straw, clay and maleic anhydride grafted polypropylene as a coupling agent was varied in order to investigate their influence on water absorption and flexural properties. The XRD analysis of composite samples containing clay showed shift in d001 peak to lower 2θ indicating slight intercalation of polymer in clay sheets. The results of the study indicate that the increase in wheat straw and clay content in a composite increases the flexural modulus and reduces the resistance for water absorption. The increase in PP-MA coupling agent also increases the flexural modulus and resistance for water absorption. The morphological study by scanning electron microscope reveals that the addition of coupling agent increases the interfacial adhesion between the fibers and polymer matrix which is evidenced further from increased flexural modulus. Further, the particle size of wheat straw was analyzed before and after extrusion in order to investigate the effect of extrusion on wheat straw dimensions. The addition of clay as additional filler had no significant role on water absorption and flexural properties of the composite.