Mechanical Properties of Hybrid Composites Based on Polypropylene Modified with Natural Fillers

Abstract

Hybrid composites based on a polymer matrix and a natural (renewable) filler can be one of the alternatives to widely used polymers. It is well known that natural fillers have poor adhesion to hydrophobic polymer matrices. In order to improve the interaction between hydrophilic fillers and hydrophobic matrix, fillers are usually pretreated with activators. Composites made by injection molding based on polypropylene and Kraft-lignin, microcellulose from hemp waste with filling from 9 to 27 wt % were investigated in work. In order to enhance the adhesion between the filler and the polymer, a special chemical treatment of the components was used with the addition of talc as a compatibilizing agent. Tensile and bending tests of the composites were carried out, as well as studies on the determination of microstructure features and evaluation of the influence of reinforcement and homogenization of mixtures using SEM. It was established that, compared to primary polypropylene, the flexural strength of composites with microcellulose practically did not change, Young’s modulus (E) increased to 12% depending on the degree of filling, and the flexural strength of composites with lignin increased to 42.3 MPa (32%), E up to 1570 MPa (22%). The tensile strength is practically unchanged for the cellulose filler and slightly increased to 10% for lignin, and Young’s modulus, depending on the type of filler and degree of filling, increased from 10 to 32%. Structure studies indicate a good interphase interaction of components in composites.