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In this study, the effects of alkali and silane coupling agents and coir fiber (CF) loading on the fundamental properties of the CF-filled polypropylene (PP) composites were investigated. Mechanical properties of the PP/CF composites, such as tensile strength, tensile modulus, impact strength, and water absorption were increased by the increase of the CF loading. The inclusion of 3-aminopropyl trimethoxy silane (ATS) and tetramethoxy orthosilicate (TOS) after the alkali pretreatment for the CF increased all the mechanical properties and water desorption of the resulting composites. This trend was more evident with the increase in CF loading. The best results were obtained for PP/TOS composites as compared to other composites. SEM images of fractured samples show improved adhesion between CF and PP matrix after treatment with ATS and TOS. The horizontal rate of combustion is significantly reduced with the inclusion of Mg(OH)2 in PP/ATS and PP/TOS composites. DSC results show improved crystallization temperature, melting temperature, and melting enthalpy as compared with virgin PP. The addition of ATS and TOS after the alkali pretreatment improved the thermal stability of the resultant composites. TOS-modified CF composites showed better resistance than ATS-modified CF composites in water medium. [ABSTRACT FROM AUTHOR]

Snake grass fibers (SGFs)-reinforced polypropylene (PP)-based longitudinal bio-composites (40 wt% by fiber) were successfully manufactured by compression molding and tested for their physicomechanical, hardness, and thermal properties. SGFs were modified with non-ionizing radiation at different intensities and then bio-composites were fabricated. The mechanical properties of irradiated-SGF/PP bio-composites were significantly improved compared to untreated parts. Irradiated SGFs were grafted with 2-hydroxyethyl methacrylate (HEMA) monomers by photocuring under UV light. The number of UV passes and therefore the HEMA concentration were optimized with the extent of grafting of HEMA, tensile, and impact properties. Bio-composites reinforced with 10% HEMA and the 50th UV pass of SGF show maximum mechanical properties. Again, the irradiated SGFs were modified with alkali (NaOH) solutions of different concentrations at different temperatures. Optimized alkali-treated SGFs were then grafted with optimized HEMA by photocured with the same UV-pass and their composite samples rendered the best mechanical properties like tensile strength, tensile modulus, impact strength, and hardness. Optimized alkali-treated SGF with optimized HEMA grafted composite samples had higher thermal stability than other samples. Scanning electron microscopy, water absorption, and weather tests of composites were also investigated. [ABSTRACT FROM AUTHOR]

Nonwoven unidirectional matted banana empty fruit bunch fiber (BBF)-reinforced polypropylene (PP) composites were successfully fabricated by compression molding method. The effect of fiber composition, mercerization of fiber as well as incorporation of acetylation as coupling agent on the properties of PP/BBF composites was studied. The results indicated that the BBFs acted as reinforcing fillers, increasing the mechanical properties (e.g. tensile strength, tensile modulus, and Charpy impact strength) of the composites. PP/BBF composites with acetylation after the alkali pretreatment showed better interfacial shear strength and mechanical properties compared to the alkali-treated and untreated fiber composites. Scanning electron microscopy studies carried out on fractured specimens indicated poor dispersion in the untreated fiber composites and improved adhesion and uniform dispersion in the treated composites. Thermogravimetric analysis/derivative thermogravimetric thermograms revealed an increase in the stability of acetylation-incorporated systems and differential scanning calorimetry results exhibited improved thermal stability as compared with neat PP. The heat deflection temperature and flammability also displayed improved thermal stability as compared with neat PP. The moisture absorption test showed that acetylation-treated banana matted composites exhibited less water absorption than both alkali-treated and untreated composites. [ABSTRACT FROM AUTHOR]