Effect of fiber-surface modifications onto material properties of sponge-gourd fiber reinforced polylactic acid bio-composites

Abstract

This research work has been undertaken to fabricate environmentally friendly biocomposites for biomedical and household applications. Sponge-gourd natural fibers (SGF) obtained from Luffa cylindrica plant were separately subjected to chemical treatments such as alkalization, acetylation, and benzoylation by 5−15 wt% sodium hydroxide (NaOH), acetic anhydride ((CH3CO)2O), and benzoyl chloride (C6H5COCl) solutions, respectively, in order to improve adhesion between fiber and polymer matrix. SGF reinforced polylactic acid (PLA) composites were then fabricated using solution casting method. Both untreated and chemically treated SGF as well as composites were subsequently characterized by using field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectrometry, X-ray diffractometry, universal testing method, thermogravimetric analyses and agar diffusion method. Surface analysis by scanning electron microscopy shows that the alkali treatments promote better outer surface layer than other treatments of SGF with the exposition of inner fibrillar structure, thereby increasing roughness of the fiber surface. Structural analyses of SGF show that the alkali treatment improves the crystallinity of fibers by 81% and FTIR spectrometry exhibits new chemical bond formation in the SGF. The tensile strength () and Young’s modulus (Y) have been analyzed through two-parameter Weibull distribution model, where  value increases by 150% and Y value increases by 80% of benzoylated fibers. The thermal stability of the treated SGF is also found to increase, showing the highest on-set temperature of 307.7°C for 10 wt% benzoylated SGF. Structural analyses of composites show that the chemical treatment of fibers improves the crystallinity and exhibits new chemical bond formation in the composites. Surface morphology indicates that by treatment of fibers and by increasing of treated fibers content, the interfacial adhesion between PLA and fibers is improved. Compressive strength of the composites has increased by 10–35% with incorporation of treated fibers into the PLA matrix. The thermal stability temperature of the treated fiber reinforced composites is also found to increase by an amount of 15–30%. The degradation test under soil has confirmed that the composites are biodegradable. Benzoyl chloride treatment of fibers shows superior mechanical properties and enhances thermal stability among the composites. The composites investigated have shown no antibacterial activities and no cytotoxic effect on non-cancer cell line.