Biodegradability and mechanical properties of silane treated microcrystalline cellulose / poly(lactic acid) composites

Abstract

Biodegradable plastic reinforced natural fiber composites are finding applications in many fields ranging from construction industry to food industry. The use of natural bio based fillers as reinforcements in composites has several advantages over inorganic fillers including lower density, renewability, low cost, lower CO₂ emissions, reduced abrasion, and thus machine wear during production processes, eco-friendliness, and biodegradability. In this research, polylactic acid (PLA)/ microcrystalline cellulose (MCC) composites were investigated as a means to reduce the material cost and enhance the material properties. The coir fiber was prepared by 3 steps process namely delignification, bleaching, and hydrolysis, respectively, to obtain MCC. The MCC was then surface treated by 5 wt.% of 3-aminopropyl triethoxy silane (APS). After that, PLA was mixed with MCC at various ratios by twin-screw extruder and fabricated into test specimens by compression molding. The Biomax® was used as the modification resin. The results shows that, the polylactic acid with 5 wt.% of microcrystalline cellulose and blend with 2 phr of Biomax® exhibited the best mechanical properties compared with all prepared composites. Thermal stability of PLA composites were decrease with increasing MCC content but it can be improved by treated the MCC by APS. The percentage of biodegradation of neat PLA and PLA-5MCC-Si-Bi and %biodegradation reached the values of 80.1% and 78.2%, respectively, at 40 days of test period according to ISO 14855-2. In aqueous medium, the percentage of biodegradation of neat PLA and PLA-5MCC-Si-Bi reached the value of 37.6% and 42.1 %, respectively, according to ISO 14852. The weight remaining of PLA composites buried in landfill was decreased with increasing MCC content and degradation time. Surprisingly, the PLA composites were not degraded under real seawater condition in 30 days.