Recent interest in lignocellulosic fibres was devoted to improve the mechanical properties of polymers. But one of their main limitation is the poor compatibility and adhesion between these polar/hydrophilic fibres with most commercial resins being non-polar and hydrophobic. This problem has been partially solved using physical and chemical surface treatments, and/or the addition of a coupling agent (phase compatibilization). So better interfacial adhesion was found to further improve the rigidity and strength of polymers. But several applications may need more elongation/elasticity/impact strength where a compromise must be made. This is where hybrid composites come into play: by a careful selection of two or more different types of "additives", a good balance between stiffness and strength is possible. But for industrial processes, another important issue is the cost. This is why a quality/cost ratio is proposed to account for the complex relations between all the parameters where "quality" must be defined based on the final application.
In this work, it i is proposed to use hemp fibers (reinforcement) as a residues from the textile industry and ground tire rubber (impact modifier) as a post-consumer residue. To improve interfacial bonding, maleic anhydride grafted polyethylene was selected and high density polyethylene as a commercially available matrix. For each mechanical property (tension, flexion and impact), a non-linear regression model was obtained and the results were combined with the raw material costs to optimize the quality over cost ratio. Although the numerical values obtained are a function of the materials and processing conditions used, this methodology can be applied to any system to optimize formulations while simultaneously taking into account the economics and performances of the materials.
Reference: Yousefian H. (2017). Optimization of Hemp, Ground Tire Rubber, High Density Polyethylene Composites Based on a Quality Over Cost Ratio, Curr Applied Polymer Science., DOI: 10.2174/2452271601666161213164904