Studies on biodegradable and non-biodegradable polymer composites with chemically modified betel nut micro to nano fiber

Abstract

This thesis is composed with the aim of use of resources and management of waste betel nut husk fiber (BNHF) in a more sustainable way. In this research work betel nut (Areca catechu) husk fiber reinforced thermoplastics were prepared by compression moulding technique.BNHF were extracted from betel nut fruit and the chemical composition of BNHF was analyzed. To improve the properties of BNHF reinforced thermoplastic composites different types of chemical treatment with BNHF were carried out. The effects of this treatment on physico- mechanical and thermal properties of the composites were studied. Different types of non-biodegradable polymer such as low density polyethylene (LDPE), high density polyethylene (HDPE), Polypropylene (PP) and polystyrene (PS) were used as matrix materials. BNHF were treated with sodium hydroxide to improve their adhesion to LDPE matrix.The changein the functional group of treated BNHF was studied by FT-IR spectroscopic analyses. Compression molded BNHF-LDPE composites were prepared using different weight percent of treated and untreated BNHF with compositions 5, 15, 20, 25 and 30 wt% in LDPE. BNHF were used as reinforcing materials to prepare HDPE matrix based composites. Extracted BNHF were chemically treated with sodium meta-periodate to enhance its compatibility with the HDPE matrix in treated BNHF-HDPE composites.Another chemical treatment of BNHF with hydrogen peroxide was done to achieve mild oxidation by converting cellulose in BNHF to dialdehyde cellulose in BNHF.These chemically treated fibers and untreated fibers were used as reinforcing material to prepare PP-BNHF composites. The reinforcing effect of BNHFin polystyrene (PS) matrix was also studied. BNH fibers were chemically modified with sodium hypochlorite. The sodium hypochlorite treated and untreated BNHF were used for composite fabrication as reinforcing material with polystyrene in different weight fraction of fiber loading. An improved new extraction procedure of cellulose has been developed and the nano-cellulose was successfully isolated by chemical and mechanical treatment. The reinforcing effects of these cellulose and nano cellulose with biodegradable polymer polyvinyl alcohol and poly-acrylic acid have been studied. The composites were characterized by FT-IR and SEM analysis and their physico-mechanical and thermal properties were analyzed by tensile test, TGA and DSC analysis. According to the FTIR spectroscopic results the positive chemical treatment removed an amount of lignin and other impurities and produced dialdehyde cellulose in BNHF. Mechanical properties such as tensile strength, elongation at break, impact strength were measured. Improved mechanical properties were obtained for all the treated fiber reinforced composites over untreated BNHF reinforced plastics composites. Morphological analyses showed the evidence of stronger interfacial adhesion between the fiber and matrix in the all treated BNHF-polymer composites than the untreated BNHF-polymer composites. Almost same thermal properties were obtained for all treated and untreated BNHF reinforced polymer composites. Water absorption test were carried out for all composite to investigate the effect of chemical treatment on the moisture absorption properties which have direct effect on dimensional stability of the composites. Water absorption tests and SEM observation results revealed that the composites with treated BNHF absorbed the less water and good uniformity between fiber and matrix than composites with untreated BNHF. It was found that 10 wt % treated fiber reinforced composites have higher tensile strength than all other composites. It was also found that nanocellulose fiber reinforced polymer nanocomposites have higher tensile strength than cellulose fiber reinforced polymer composites.