Enhanced strength, stiffness and elongation potential of paper by spray addition of polysaccharides

The effects of spray additions of alginate, cationic guar gum, or chitosan on paper properties were determined. The aim of this study was to enhance the mechanical properties of papers after unrestrained drying, while maintaining or increasing the extraordinarily high elongation potential of these papers. The mechanical characteristics of the different polysaccharides were determined by tensile test of model films. Alginate resulted in very strong and stiff films with low strain at break values, while cationic guar gum and chitosan resulted in significantly weaker and softer films with high strain at break. The polysaccharide solutions were sprayed onto wet handsheets, and the paper properties were measured after restrained and unrestrained drying. The spray additions increased the tensile index, density, and tensile stiffness of the handsheets. Spray addition of alginate resulted in stiffer and stronger paper than the other tested polysaccharides. Alginate was able to increase the tensile index of the paper by 54% and the tensile stiffness by 32% after restrained drying. All strain at break values in this study correlated linearly with paper shrinkage during drying. Alginate, which gave extremely strong and stiff model films, enhanced paper shrinkage, effectively lowered the air permeability of the paper, and formed a polysaccharide film on top of the paper, was found to be the most promising candidate for future packaging applications.