Effects of fiber surface modification on mechanical properties of short pineapple leaf fiber-carbon black reinforced natural rubber hybrid composites

Abstract

At present, the world is focusing on the circular economy by turning waste into production resources again, reducing waste generation, and making it circulate in the system. This research focuses on using agricultural waste, which is pineapple leaves abundant in Thailand, to be processed into pineapple leaf fibers (PALF) and used to reinforce natural rubber. PALF has relatively high strength when compared to other natural fibers. On the other hand, the challenge of using PALF to reinforce natural rubber is the difference in the polarity of the fibers and rubber matrix. Thus, surface modification of PALF was studied to enhance the adhesion between the fiber surface and the matrix. Four systems were compared, i.e., untreated PALF, alkaline-treated, silane69-treated, and aminosilane-treated PALF. A unidirectional fiber-reinforced natural rubber composites were prepared with fixed fiber and carbon black contents of 10 and 30 phr, respectively. Mechanical properties of the composites were determined by tensile test and morphology was observed by scanning electron microscope (SEM). It was found that silane69-treated and aminosilane-treated PALF could reinforce the rubber matrix over the entire strain. However, silane69-treated and aminosilane-treated PALF had lesser reinforcement effect than alkaline-treated PALF at low strains. Despite a clear change in mechanical behavior, SEM could not tell the difference or changes that occur at the interface. Fiber surface modifications with silane69 and aminosilane have the potential to be further developed to improve properties of natural rubber composites and will, hopefully, increase the value of rubber products for Thailand industry.