Dynamic mechanical properties and characterization of chemically treated sisal fiber-reinforced polypropylene biocomposites

Abstract

The incorporation of sisal fiber as reinforcement materials for polymers will be advantageous if it is synthesized and manufactured perfectly. In this study, surface modification using polymeric diphenylmethane di-isocyanate and gamma-aminopropyltriethoxysilane was applied for further amelioration of polypropylene–sisal bonding. Surface morphology, thermomechanical properties, thermal stability, and chemical bonding were investigated using scanning electron microscopy, dynamic mechanical analysis, thermogravimetric analysis, and Fourier transform infrared spectroscopy, respectively. A number of mathematical models were studied for predicting the effect of untreated and modified sisal fiber loadings on the mechanical properties of biocomposites. Polymeric diphenylmethane di-isocyanate showed a significant improvement on the thermal and mechanical properties of polypropylene biocomposites. Fourier transform infrared spectroscopy analysis of polypropylene–sisal biocomposite showed the formation of urethane group at 3333 cm−1 in the presence of polymeric diphenylmethane di-isocyanate. Glass transition temperature of polypropylene–sisal was slightly increased to 6.8°C by chemical modification with polymeric diphenylmethane di-isocyanate. Yield strength of polypropylene–sisal (30 wt%) was enhanced by more than 50% with polymeric diphenylmethane di-isocyanate chemical treatment. Halpin–Tsai and Nielsen theoretical mathematical models showed a good agreement with experimental results of polypropylene–untreated sisal and polypropylene–treated sisal, respectively.