MECHANICAL AND DIELECTRIC-RELAXATION IN CELLULOSE ESTERS

The dynamic mechanical and dielectric relaxations of plasticized and un-plasticized cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate were characterized. Three relaxations common to all compositions were found (a, B, and 7), while a fourth (6) was observed only in cellulose acetate butyrate. Absorbed water had a strong effect on the dielectric loss but not on the mechanical loss. Plasticization occurs through a specific type of plasticizer-polymer interaction that lowers the temperature of the a relaxation, suppresses they relaxation, and gives rise to a new relaxation, B’The characteristics of the b’ peak depend on the nature and concentration of the plasticizer. If b’ occurs at a high enough temperature, a temperature region below TB’ exists in which the modulus of the plasticized polymer is higher than that of the unplasticized polymer. This apparent antiplasticization is merely an effect of the temperature of measurement relative to the features of the loss spectrum. A given diluent may thus appear to be a plasticizer at one temperature and an antiplasticizer at another. © 1979, Taylor & Francis Group, LLC. All rights reserved.