Thermomechanical properties of blends of pectin and poly(vinyl alcohol)

Abstract

Blends of citrus pectin and several types of poly(vinyl alcohol) were investigated to determine the effects of compositional variables and polymer type on film properties. Some films were also plasticized with glycerol. Films were cast from water onto Lexan™ plates, dried, and removed. Thermomechanical properties were obtained using a dynamic mechanical analyzer, and thermodynamic transitions were also obtained using a differential scanning calorimeter. Increasing the amount of poly(vinyl alcohol) in the blends reduced the storage and loss modulus of the films above the glass transition temperature (Tg). The Tg values observed decreased as the amount of PVOH in the blend increased. Addition of glycerol depressed the PVOH Tg and merged it into the Tg of the pectin/glycerol blend. Changes in the molecular weight and degree of ester hydrolysis of poly(vinyl alcohol) exerted a rather small effect on the blends. © 1996 John Wiley & Sons, Inc. 1 Reference to a brand or firm name does not constitute an endorsement by the U.S. Department of Agriculture over others of a similar nature.