Thermal, viscoelastic, solution and membrane properties of sodium alginate/hydroxyethylcellulose blends

Solution and film blend compatibility of carbohydrate polymers, viz. sodium alginate and hydroxyethylcellulose have been studied. Blend solutions were prepared in water. Films of the individual polymers and their blends were prepared by solution casting and crosslinking with glutaraldehyde and urea-formaldehyde-sulfuric acid mixture. Compatibility of blends in solution was studied by density and viscosity, while blend compatibility in solid films was evaluated by differential scanning calorimetry, dynamic mechanical thermal analyzer and scanning electron microscopy. Solution density showed a linear trend with the blend composition. The glass transition of the blends lies in between the individual polymers. The glass transition temperature of sodium alginate was lowered with the addition of HEC in the blend. These results suggested the compatibility of sodium alginate and hydroxyethylcellulose blends. Storage modulus of sodium alginate film decreased after the addition of hydroxyethylcellulose. For the crosslinked blend films, storage modulus was higher than the respective uncrosslinked blend systems. A typical blend film was chosen for the pervaporation separation of water+tetrahydrofuran mixture, while the crosslinked sodium alginate film was tested for the pervaporation separation of water+1,4-dioxane mixture.