THE RELATIONSHIP BETWEEN BLEND MISCIBILITY AND BIODEGRADATION OF CELLULOSE-ACETATE AND POLY(ETHYLENE SUCCINATE) BLENDS

The miscibility of cellulose acetate (CA; degree of substitution = 2.5 ) and poly(ethylene succinate) (PES) has been investigated using a var iety of thermal techniques and by solid-state carbon-13 NMR spectrosco py. The blends containing greater than ca. 70% CA were found to be mis cible. In the case of blends containing less than ca. 70% CA, a combin ation of thermal and NMR analyses suggests that these blends are not f ully miscible on a 2.5- to 5-nm scale. On the scale which can be probe d by dynamic mechanical thermal analysis (15 nm), the low-percentage C A blends exhibit ''significant local concentration fluctuations''. Inv estigation of the biodegradation of the blend components and of the bl ends revealed that PES degraded relatively rapidly and that CA degrade d slowly. The blends degraded at a rate essentially identical to that of CA. Miscibility (75% CA blend) or crystallization of PES (30% CA bl end) had no significant effect. These data suggest that a significant mode of degradation of PES during composting involves chemical hydroly sis of the polymer followed by biological assimilation of monomers. De gradation of the blends is initiated in the amorphous phase. Because C A is a significant component of the amorphous phase, a small amount of CA significantly impacts the biodegradation rates of the blends.