Preparation of biocomposite films from cassava starch reinforced with crystalline cellulose

Abstract

An environmentally friendly biodegradable composite films between plasticized cassava starch and crystalline cellulose from agricultural wastes were successfully prepared. Two types of agricultural wastes, bagasse and banana stem, were made into crystalline cellulose by acid hydrolysis using HCl and H₂SO₄. The suitable condition for preparing crystalline cellulose from each agricultural waste was investigated. From the results, the suitable NaOH concentrations for delignification of bagasse and banana stem fiber were 0.5 M and 1 M, respectively. For bleaching, 6% H₂O₂ in alkali solution was the most appropriated condition for both pulps. HCl and H₂SO₄ at 2.5 N concentrations were used for hydrolysis at varied reaction time in order to obtain microcrystalline cellulose (MCC) with determined average particle size. The suitable reaction times for hydrolysis bagasse and banana stem were 60 and 30 min, respectively. The prepared crystalline cellulose as well as a commercial MCC were mixed, at 0-40 wt% (based on starch), with plasticized starch. The films containing MCC were less transparent than the one without MCC. The haze of biocomposite films readily increased with the increasing amount of MCC. The incorporation of MCC improved the tensile strength and Young’s modulus of plasticized starch. In general, the maximum tensile strength and Young’s modulus of the prepared film were as high as 10-15 MPa and 600-800 MPa, respectively. The biocomposite films showed higher degree of biodegradability comparing with the plasticized starch film. The biodegradability increased when the amount and the average particle size of MCC increased. These results are in agreement with the water absorption behavior of the films. Biocomposite film reinforcing with bagasse MCC prepared using HCl had better thermal stability, mechanical properties, and biodegradability than other prepared biocomposite and plasticized starch films.