Thermoplastic polypropylene (PP) composites containing 10, 20, 30, and 40% wt% of calotropis gigantea fiber (CGF) were created in the current study using compression molding in the presence of alkaline pretreated CGF (ACGF), which was modified with aminopropyltrimethoxy silane (ACGF/AS) and tetramethoxyorthosilicate (ACGF/TS) as a silane coupling agent. The composites' CGF content has been tuned, and a 40-weight percent CGF content exhibited the optimum mechanical performance. In comparison to virgin PP, composites containing 40% CGF increased their impact strength and tensile strength by 225.4% and 54.2%, respectively, but only 39% when using 30% CGF. After alkali pretreatment, silane is added to CGF/PP composites to improve the mechanical properties, which in turn causes the composites to absorb water. The increase in CGF content has made this tendency more obvious. When compared to CGF/PP composites, which demonstrated 18% tensile modulus and 59% impact strength, ACGF/TS/PP composites showed maximal mechanical characteristics at 40 wt% CGF content, while CGF/PP composites only managed 20% tensile strength at 30% CGF content. To find out more about fiber-matrix adhesion, SEM revealed enhanced adhesion between CGF and PP following silane modification. The horizontal combustion rate was dramatically lowered by adding Mg(OH)2 to ACGF/AS/PP and ACGF/TS/PP. According to DSC data, adding AS and TS to CGF increased the crystallinity, melting, and crystallization of the composites. Compared to ACGF/AS/PP and ACGF/PP composite, ACGF/TS/PP composite had superior thermal stability.
