Preparation and Evaluation of Plant-Based Coir Fiber-Reinforced Polypropylene Composites

Abstract

In the present article, unidirectional coir fiber (CF) and alkali-treated CF (ACF) were incorporated in polypropylene (PP) with and without 3-aminopropyl trimethoxy silane (AS) and tetramethoxy orthosilicate (TS) to produce composites by a compression molding technique. The basic properties of PP/CF composites (e.g. tensile strength, tensile modulus, impact strength, and water absorption) have enhanced with increasing CF content. The incorporation of AS and TS after alkali pretreatment for CF composites enhance all the mechanical properties and consequently the water absorption of the composites. This trend was even more pronounced with the increase in CF content. The best mechanical properties of PP/ACF/TS composites have been achieved in 40 wt% fiber content in this article, which showed an 18% increase in tensile modulus and 70% impact strength compared to PP/CF composite but achieved 23% at 30% CF content in tensile strength. To learn more about fiber-matrix adhesion, scanning electron micrograph (SEM) of the tensile fractured sample showed enhanced interfacial adhesion between CF and PP matrix in reinforced composites with AS and TS. The addition of Mg(OH)₂ in PP/ACF/AS and PP/ACF/TS composites significantly reduced the horizontal flaming rate. Differential scanning calorimetry (DSC) outcomes showed that incorporation of AS and TS into CF resulted in higher crystallization and melting peak temperature and fusion heat than virgin PP. The percentage of crystallinity increased with the addition of TS to the PP/ACF/TS composite. The thermal stability of PP/ACF/TS composite was higher than PP/ACF/AS and higher than PP/ACF composite. The physical tests revealed that PP/CF composites showed maximum water absorption although the quality of water absorption decreased after treatment. Therefore, AS and TS are deliberated to be effective silanes for PP/CF composite systems.