CELLULOSE ESTER ALIPHATIC POLYESTER BLENDS - THE INFLUENCE OF DIOL LENGTH ON BLEND MISCIBILITY

A series of aliphatic polyesters consisting of a C5 dicarboxylic acid (glutaric acid) and C2 to C8 straight-chain diols were blended with ce llulose acetate propionate (CAP) at different composition levels. Char acterization by dynamic mechanical thermal analysis revealed that, whe n blended with CAP, the polyesters prepared from C2 to C6 diols formed transparent, stable, amorphous glasses which exhibited a single compo sition-dependent T(g). Upon reaching a C8 diol, the blend became parti ally miscible. Within the miscible blends, analysis of their DMTA spec tra indicates that the polyester prepared from the C4 diol had the hig hest level of miscibility with CAP while the polyesters prepared from C5 and -CH2CH2OCH2CH2- diols gave the lowest degree of miscibility. Su b-T(g) mobilization processes, centered in the range -60 to -50-degree s-C, were observed for the blends prepared from polyesters which conta ined C2, -CH2CH2OCH2CH2-, and C6 diols. The activation energy for the sub-T(g) relaxation process (210 kJ mol-1) for the 40% poly(diethylene glutarate)-CAP blend suggests cooperative, localized motion of a CAP- polyester complex. However, no relationship was found between low temp erature relaxation processes and blend miscibility.