Synergistic blends of natural polymers, pectin and sodium alginate

Abstract

AbstractA wide range of Pectin and Sodium Alginate blends have been investigated by casting films from aqueous solution. Blends showed synergy both in mechanical properties and water vapor permeation rate. Previously observed synergism in gels at low pH is also maintained in cast films of blends having up to 40% Pectin. Films were made water‐insoluble by post‐treatment with CaCl2, which develops physical crosslinks among the molecules of both polymers. After CaCl2 treatment, mechanical properties are drastically changed due to development of physically crosslinked tie points in the molecular network structure. The modulus and tensile strength of the resulting network structure are dependent on the nature of the polymers. Even in water insoluble films, synergism in mechanical and water barrier properties is retained in films having up to 20% Pectin content. Structural reorganization before and after CaCl2 treatment was investigated by X‐ray and dynamic mechanical analysis. The synergism observed in mechanical properties of the films before and after CaCl2 treatment is attributed to reduction in molecular mobility and change in molecular network structure. Structural reorganization in CaCl2‐treated films, and thereby film properties, is dependent on the compositions of the blends; blended films show sharp glassy‐rubbery transition in the storage modulus—temperature plot, which is not the case in untreated films. Film flexibility increases with increasing Pectin content in the blends. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011