Dynamic Mechanical Analysis of PMMA-Cellulose Blends

Dynamic mechanical analysis (1-30Hz, 274-414K) is employed to study the inter- and intramolecular dynamics in a set of PMMA-CELL blends. Two relaxation processes are observed, the dynamic glass transition (-relaxation) being characterized by WLF law and secondary transition (-relaxation). The -relaxation is strongly influenced by the composition of the blends and shows a rapid slowing down with increasing cellulose (CELL) intake. Increasing the content of the latter reduces the strength of the -relaxation strongly and increases its activation energy by more than 60%. This proves that owing to the interactions between the cellulose hydroxyl group and PMMA ester group, the -relaxation no longer has a local character only. By fitting the Tg data for the blends to Tg-composition models proposed by Gordon and Taylor and by Jenckel and Heusch, it is shown that the strength of the interaction increases strongly beyond 72% of CELL intake.