BLENDS OF CELLULOSIC ESTERS WITH POLY(CAPROLACTONE) - CHARACTERIZATION BY DSC, DMA, AND WAXS

Binary blends of poly(caprolactone) (PCL) with cellulosic esters [cellulose diacetate (CDA), cellulose acetate-butyrate (CAB), and cellulose triacetate (CTA)] were studied by using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and wide-angle X-ray scattering (WAXS) techniques, and qualitative comparison was made with the results obtained by polarizing optical microscopy. The PCL-CAB system was proved to be partially miscible, whereas PCL-CDA and PCL-CTA appeared to be immiscible. A double-melting behavior was showed for PCL-CAB and PCL-CTA blends. As these peaks did not shift by varying the heating rate of DSC runs, this behavior can be due to melting of two populations of crystals of PCL, which may be different in size. On the other hand, blends of PCL containing a low amount of CAB or CDA seem to develop more crystallinity for the PCL than this polymer alone. The solvent seems to have a certain influence on the thermal and morphological behaviors of the as-cast blends of these three systems, affecting the extent of crystallinity of PCL, as well as its T-m and Delta H-f. This finding is discussed in the light of WAXS and polarizing optical microscopy results. (C) 1994 John Wiley and Sons, Inc.