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In this investigation, sisal fibres were treated with the combination of alkali and high intensity ultrasound (HIU) and their effects on the morphology, thermal properties of fibres and mechanical properties of their reinforced PP composites were studied. FTIR and FE-SEM results confirmed the removal of amorphous materials such as hemicellulose, lignin and other waxy materials after the combined treatments of alkali and ultrasound. X-ray diffraction analysis revealed an increase in the crystallinity of sisal fibres with an increase in the concentration of alkali. Thermogravimetric results revealed that the thermal stability of sisal fibres obtained with the combination of both alkali and ultrasound treatment was increased by 38.5°C as compared to the untreated fibres. Morphology of sisal fibre reinforced composites showed good interfacial interaction between fibres and matrix after the combined treatment. Tensile properties were increased for the combined treated sisal fibres reinforced PP composites as compared to the untreated and pure PP. Tensile modulus and strength increased by more than 50% and 10% respectively as compared to the untreated sisal fibre reinforced composite. It has been found that the combined treatment of alkali and ultrasound is effective and useful to remove the amorphous materials and hence to improve the mechanical and thermal properties.

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Mechanical, dynamic-mechanical and thermal performance of polypropylene (PP) composites which are composed of (3-Aminopropyl) triethoxysilane (APTES) functionalized Halloysite nanotubes (HNTs) were investigated. Functionalization of HNTs was confirmed by the presence of amine stretching peaks in the FTIR spectrum. A decrease in the agglomeration and high dispersion of APTES-HNTs across the PP matrix was confirmed by scanning electron micrographs (SEM). The mechanical properties of APTES-HNT-PP polymer composites were superior over their unmodified counterparts. Tensile properties such as maximum strength, Young’s modulus and impact strength were significantly enhanced by 28%, 45% and 60% respectively, with 6 wt% incorporation of surface-modified HNTs into PP matrix. A drastic improvement of stiffness and thermal stability of composites was noted with the incorporation of APTES modified HNTs into PP polymer. Differential scanning calorimetry (DSC) analysis showed a total increase of 22% in the crystallinity of clay polymer nanocomposite after filled with surface-modified HNTs. Overall, the outcome of this research confirms the modification of the surface of HNTs with a silane coupling agent, which enhances the mechanical and thermal performance of PP composites incorporated HNTs.

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Polypropylene (PP) composites were prepared by reinforcing with suitable hybrid fillers such as short sisal fibers treated with an alkali and high-intensity ultrasound (HIU) and halloysite nanotubes (HNTs) modified with 3-aminopropyltriethoxysilane. The synergistic effect of surface-treated short sisal fibers and silane-grafted HNTs were systematically evaluated through morphological, mechanical, dynamic mechanical, and thermal characterization. Alkali and HIU treatments of short sisal fibers drastically enhanced the interaction between sisal fibers and silane-grafted HNTs, which improved the interfacial adhesion between the filler system and the PP matrix. Scanning electron microscopic images indicated the continuity and smoothness of the hybrid composite surfaces. Dynamic mechanical analysis confirmed improved interactions between the hybrid filler system and the matrix, leading to significantly enhanced storage modulus in the hybrid composites. Therefore, the interfacial adhesion between the fillers and the matrix plays a significant role in improving the mechanical, dynamic mechanical, and thermal properties of polymer composites.

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