The Synthesis, Characterization, and Application of Polysaccharides-Based Additives to Increase the Dry Strength of Paper

Paper recycling is a very visible and highly important conceptual framework in any effort to address environmental concerns, reduce expanding landfills, and reduce the need for virgin fiber manufacture with the concomitant expenditure of energy and resources. The major problem with recycling paper is the loss of its strength properties due to reduced inter-fiber bonding of reclaimed fibers relative to virgin wood pulp fibers is generally attributed to the drying phase of the first papermaking cycle. Petroleum-based dry strength agents are widely used for improved recycle paper strength properties. The widespread use of petroleum-based dry strength agent in the paper making industry has raised environmental concerns and prompted efforts towards developing alternatives.;The goal of this study is to therefore develop a new (natural and environmentally friendly) polysaccharide derivative to produce a polysaccharide-based dry strength additive featuring high strength recycled paper. These new polysaccharide dry strength additives are expected to significantly improve inter-fiber bonding and improve the antimicrobial activity of the final product. Soy flour is a very cheap complex polysaccharide, but it has a low number of free functionalities and poses a bacterial digestion problem as manifested by bad odors and potential paper strength losses. This dissertation is a fundamental study that focused on the modification (synthesis) of polysaccharides (soy flour, cornstarch, hydrolyzed protein and carbohydrate-based nano materials) with five different types of crosslinking agents for the introduction of carboxylic or and amine groups. The modified polysaccharides were complexed with chitosan as part of a general chemical strategy to reduce the bacterial digestion of modified polysaccharides (especially soy protein flour) and improve its incorporation into a recycle pulp matrix to increase inter-fiber bonding.;To confirm the improvement properties of modified polysaccharide additive-treated pulp sheet, the inter-fiber bonding strength, amount and type of bond formation between additive and pulp fibers, mechanical strength, and antimicrobial activity were tested. The inter-fiber bonding strength increased 2.5-3 times, mechanical strength (tensile, bursting, and STFI index) increased 38-52%, the ester bonds formed were found to be 1.82-1.90 mmol/100g after curing at 110 °C, and a significantly enhanced antimicrobial activity was observed for both modified polysaccharide and modified polysaccharide additive-treated pulp sheet compared to the control sample (untreated pulp sheet). The composition and structure of additive-treated pulp sheet was also analyzed by TGA, DMA, FT-IR and SEM.;The current results confirm that modified polysaccharides have a potential opportunity in the papermaking industry as dry strength agents for paper.