Design and optimization of biopolyester bagasse fiber composites

Bagasse fiber, a by-product of the sugar making process, maintains a coherent xylem structure and can offer mechanical reinforcement to composite materials. Biopolyester bagasse composites were prepared with biodegradable matrices polyhydroxylbutyrato (PHB) and its copolymer containing poiyhydroxyvalerate (PHBV). Both biopolymers were reinforced with treated and untreated bagasse fibers, as well as fiber volume fractions involving two fiber lengths. Optimized properties were achieved with PHB-bagasse composite surpassing the PHB flexural strength by 50% and achieving higher strength and modulus than the standard thermoplastics. The bagasse fibers were cleaned with boiling water and acetone soxhlet extraction to avoid using adhesive chemicals and, therefore, comply with biosafety standards in the packaging industry. A significant improvement in the interfacial stress transfer between the fiber and the matrix was achieved with the fibers subjected to both washing and acetone treatment. While the crystallization of PHBV was shown to be controllable by processing conditions, it was concluded that no transcrystalline region was formed with this particular resin in any of the composites. Bagasse was shown to be an effective filler for PHBV; although the results varied somewhat due to the surface treatment of the bagasse fibers. On average, long fiber bagasse composites displayed flexural moduli 33% higher than those of PHBV. Overall, the results demonstrated the positive potential of bagasse to reinforce both biopolyester matrices.