Properties of Untreated and Chemically Treated Cissus Quadrangularis Natural Fibers and Their Composites With Polyester as the Matrix

The main aim of this work was to study the effects of chemical treatments on veldt grape fibers (VGFs) and their composites with unsaturated polyester (UP) as the matrix. Alkalis such as sodium hydroxide (NaOH) and calcium hydroxide [Ca(OH) 2 ] and silane coupling agent (NaOH + silane) were used to modify the surface of optimally selected 40mm long fibers. The chemical treatments were carried with different concentrations of 5%, 10%, and 15% of chemical agents for 1 h. The chemically treated single fibers were subjected to tensile testing. The chemical analysis, crystallinity and functional group identification of both untreated and surface modified VGFs were carried out. The untreated and chemically treated 40 mm fiber length VGFs/UP composites were prepared with a loading of 40 wt% for studying the mechanical properties. The enhanced tensile strength of VGFs was found at the optimized concentration of 10% (NaOH), 15% [Ca(OH) 2 ] and 10% (NaOH + silane) for various chemical treatments. The thermal stability of treated VGFs was higher when compared to untreated ones. Among all, the Ca(OH) 2 treated VGF/UP composites possessed better mechanical properties. Scanning Electron Microscopic (SEM) analysis was performed to identify the failure mechanism for the impact fractured samples. POLYM. COMPOS., 39:876–886, 2018.