| Research Abstract |
It has been found that cellulose diacetate (CDA) was effectively plasticized by using epsilon-caprolactone (epsilon-CL)/lactic acid (LA) or glycolic acid (GA)/LA as graft-co-monomers. The degree of plasticization of CDA was influenced by the sequence of co-monomers within the graft chain, which was controlled by the fact that reactivity of epsilon-CL was greater than that of LA.The more epsilon-CL was introduced in graft side chains, the more elastic the grafted CA became. When GA/LA co-monomers were grafted, the amount of grafting side chains increased with increasing in the ratio of GA to LA, and consequently the physical properties of the products were improved. From the results of measurement with differential scanning calorimetry, it was made clear that glass transition temperature due to CDA shifted to lower temperature, that is, increase in the thermoplasticization of CDA, with increasing in the ratio of GA to LA.In the other trial, these grafted CDAs, were successfully blended with biodegradable polycarbonate, resulting biodegradable composites with high mechanical properties, being biodegradable, was tried to get satisfactory results. In order to confirm the biodegradability of the products, composing test was adopted. By this testing, weight decrease of more than 60% and large decrease of the products' molecular weight were found. From the analysis of the composed materials, it became apparent that there occurred not only the scission of grafted side chain but also that of acetyl group from CDA during the degradation treatment. Thermoplasticization of corn starch was also attempted. In this case, starch was first acetylated by transesterification using vinyl acetate as the acetylating agent, followed by the ring opening graft-co-polymerization with epsilon-CL and L-lactide. The obtained grafted acetylated starch revealed preferable thermoplasticity with retaining the high molecular weight.
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