Biodegradable plastics from cellulose

Brief history of the attempts trying to develop biodegradable plastics from cellulose acetates were reviewed in the first part. Then, two kinds of authors' trials were introduced. One of them is a plasticization trial for cellulose acetates (CAs) that is based on the reaction with dibasic acid anhydrides and monoepoxides during melt processing under practical process conditions. This reactive melt-processing method allowed the preparation of biodegradable cellulosic plastics with enough thermoplasticity and moldability. The biggest problem was the occurrence of external plasticizer's bleeding, which was found to be prevented by effective yield of grafting. Higher biodegradabilities have been found for the grafted CAs compared to the unmodified CAs. From the above trial, the amounts of grafting and the graft efficiency were intended to increase. As one of its extensions, a plasticization method for CA based on selective grafting of epsilon -caprolactone (CL) and lactide (LACD) has been developed. The selective-grafted products could be prepared by ring-opening polymerization in the melt state. By using adequate reaction conditions, the grafting reaction proceeded and completed rapidly (within 10-30 min). Transparent amorphous molding were obtainable. The fact that the formed graft side-chains contain a large amount of randomly polymerized parts explains the high thermoplasicity and amorphous nature of the grafted products.