Miscibility of Aliphatic Polyester/Cellulose Acetate Blends

Miscibility characterization were performed on binary blends of aliphatic polyester with cellulose acetate (CA). Poly(ethylene succinate) (PES) and poly(butylene adipate) (PBA) were selected as aliphatic polyester components. Three samples of CA having different degrees of substitution (DS = 2.45, 2.70, 2.95) were used. Blend films of aliphatic polyester with CA were prepared from mixed polymer solutions by solvent evaporation. The estimation of the blend miscibility was carried out by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). From thermal data obtained by DSC analysis, it was found that PES was miscible with CA (DS = 2.45) and CA(DS = 2.70). However, it was immiscible with CA(DS = 2.95) and PBA was immiscible with all CAs. The isothermal crystallization behavior of PBA/cellulose ester blends was followed by POM. For blend samples of PES with CA(DS = 2.45), the radial growth rates of PES spherulites were depressed remarkably by increasing the amount of CA in the blends. Such depression of the crystal growth rate may be attributed to the diluent effect of CA, supporting the good miscibility of these blends. When the blend samples were prepared by using PES and CA(DS = 2.95) or PBA and CA(DS = 2.45), the radial growth rates of spherulites were almost constant regardless of the amount of CA in the blends, showing the immiscibility of these blends. From these results, it was assumed that good miscibility of PES/CA blends would be derived from the structural affinity of repeating unit of PES and acetyl side groups of CA.