| Research Abstract |
Cellulose diacetate (CDA) was intended to convert into thermoplastics by ring-opening graft-co-polymerization of cyclic esters as well as by blending with biodegradable thermoplastics. For the former, fundamental properties of the products including grafted amounts, grafted branch chain lengths, constructed structures of the grafted chains, crystallinity, as well as the micro phase separation characteristics were investigated in detail through polarized microscopic observations, DSC and melt-viscoelastic measurements and so forth. As the results, (1) various types of plastics, ranging from glassy state polymers to elastomers at room temperature, could be easily obtained by the ring-opening graft-co-polymerization, depending on the species of cyclic esters used and the introduced chain length, (2) self-assembly among the introduced grafted branch chains was developed, which was strengthened with an increase in the chain length resulting in their crystallization, (3) when the introduced
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chain length enlarged more than certain limited amounts, their assembly effect exceeded the thermoplasticization effect, resulting in the strength increases revealed at room temperature, (4) this crystallization among the introduced graft-chains was repressed by their binding to the grafting sites of CDA, (5) these phenomena became unrecognizable when the chemical structure of the introduced branch chains turned to be irregular as the result of mixed graft-co-polymerization of different cyclic esters, and effective plasticization and decrystallization could be obtained These interaction among the branch-chains as well as their strength properties as coagulates are considered to correspond very well to the fact, being known to acylated cellulose, that the thermal-flow temperature and the strength are first decrease, passing through minimum points, and then increase with the increase in the carbon number of the acyl group. In the case of the latter, blends of synthetic polymers and cellulose derivatives, centering on acetylated propionylated cellulose, have widely carried out, and the corresponding findings for their blending states in molecular level could be obtained, among which even compatible blends could be found. As a functionality development of the products, the fiber forming property was studied. For this case, while a useful and important analyzing methodology for this evaluation was obtained, the fiber forming property for the plasticized CDAs is not so good and not comparable to polymers having crystalline main chains. Less
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