Study on flax and ramie fibers reinforced functionalized polypropylene hybrid composites: Processing, properties, and sustainability assessment

Flax Fibers (FF) and Ramie Fibers (RF), with equal holo-cellulose contents (approx. 87%), have been used in equal proportions as reinforcements to develop their Chemically Functionalized Polypropylene (CF-PP) hybrid composites: [5/5]/90, [10/10]/80 and [15/15]/70 [FF/RF]/CF-PP hybrid composites. These hybrid composites, developed by extrusion followed by injection molding, exhibit good adhesion of FF and RF with CF-PP, as evident in their FE-SEM micrographs. FTIR establishes this adhesion originating from ester bonds and hydrogen bonds, formed between the reinforcements and the matrix by Palsule process. These [FF/RF]/CF-PP hybrid composites display higher tensile, flexural and impact properties than their matrix, and the property values increase proportionally with the total reinforcement content in the hybrid composites. Of all the hybrid composites, the [15/15]/70 [FF/RF]/CF-PP composite exhibits the highest mechanical properties, likely due to the highest total reinforcement content. Water absorption by the composites increases with the reinforcement content, and the [15/15]/70 composition shows the highest water uptake. Relative to the synthetic and inorganic fiber based composites, these [FF/RF]/CF-PP hybrid composites offer relatively better life cycle assessment parameters and higher sustainability with potential for reduced adverse impacts of environmental and energy during their manufacturing and applications.