Reactive Processing of Cellulose Acetate/Corn Starch Biodegradable Composite Materials and their Characterization
Mariko YOSHIOKA, Seiji MIZOHATA and Nobuo SHIRAISHI
Abstract:Simultaneous grafting of poly(ε-caprolactone) (PCL) onto cornstarch as well as cellulose diacetate (CDA) and their composite machining were tried and succeeded by reactive processing using a twin screw extruder to result in plasticization of CDA, and at the same time, to obtain water-resistant and highly biomass-containing biodegradable composite materials. The properties of the composites obtained were examined through solvent fractionation, FT-IR, 1H NMR, tensile test, thermal flow test, SEM observation, water absorption test and biodegradability test. It was demonstrated that the composite materials containing maximum 60 % cornstarch and maximum 70 % biomass could be produced by the reactive processing method and they have good tensile property, processability, water resistance, and biodegradability. Especially the materials of which matrix polymer, PCL grafted CDA (PCL-g-CDA) in the degree of molar substitution range, 1.72－1.84 showed desirable biodegradability, having a certain induction period before rapid degradation, being attributable to the strong interaction between cornstarch and PCL-g-CDA, which is caused by somewhat long PCL chains grafted on both starch granules and CDA molecules. Furthermore, it was found that starch could accelerate the biodegradation rate of the matrix polymer, associating with starch degradation because of increase in surface area for microbial attack and its naturalization. Key Words:Reactive processing, Twin screw extruder, Cellulose acetate, Corn starch, Molding processability, Biodegradability, Composite material, Poly(ε-caprolactone), Grafting copolymerization, Water resistance