Mechanical, Thermal and Rheological Properties of Polypropylene/Wheat Straw Composites and Study of the Effect of Nanoclay on Their Mechanical Properties

Polymer–wood fibre composites utilize wood fibres as reinforcing filler in the polymer matrix and are advantageous over the pure polymers in terms of the materials cost and some mechanical properties such as modulus and strength. The scope of the present paper is to study the prospects of using wheat straw fibres as a reinforcing filler in polypropylene (PP). Untreated and silane-treated fibres having a variety of fibre lengths were used at various fibre contents to reinforce PP. Composites were tested for their mechanical, thermal and rheological properties, and the assessment of the adhesion at the interface was made via observations by SEM microscopy. The results showed that for untreated fibres, an increase in fibre content up to 20% (wt) led to an increase in the tensile strength of the composite. However, beyond this amount, tensile strength decreased. On the other hand, the tensile modulus increased due to higher stiffness of the fibres. By using silane treated fibres, both tensile strength and modulus increased, but the viscosity was reduced because of better dispersion of the treated fibres. By the addition of nano-clay, the mechanical properties of the composites, compared to the pure polymer, increased up to a certain fibre content, and after that the trend was reversed.