THERMOMECHANICAL PROPERTIES OF BLENDS OF PECTIN AND POLY(VINYL ALCOHOL)

Blends of citrus pectin and several types of poly(vinyl alcohol) were investigated to determine the effects of compositional variables and p olymer type on Aim properties. Some films were also plasticized with g lycerol. Films were cast from water onto Lexan(TM) plates, dried, and removed. Thermomechanical properties were obtained using a dynamic mec hanical analyzer, and thermodynamic transitions were also obtained usi ng a differential scanning calorimeter. Increasing the amount of poly( vinyl alcohol) in the blends reduced the storage and loss modulus of t he films above the glass transition temperature (T-g). The T-g values observed decreased as the amount of PVOH in the blend increased. Addit ion of glycerol depressed the PVOH T-g and merged it into the T-g of t he pectin/glycerol blend. Changes in the molecular weight and degree o f ester hydrolysis of poly(vinyl alcohol) exerted a rather small effec t on the blends. (C) 1996 John Wiley & Sons, Inc.(dagger)