Virgin Hardwood Pulp Sizing Chemistry and Fibre Hydrogen Bonding Properties
Virgin hardwood sizing requires balancing high surface hydroxyl density against AKD and ASA steric interference to maintain internal bond and Cobb holdout.
Styrene Acrylic Acid
Synthetic Polymer
Synthetic copolymer dispersions enhance water resistance and ink receptivity when applied to paperboard surfaces during sizing operations. Styrene acrylic acid acts as a polymeric surface sizing agent that regulates liquid penetration and improves surface strength. The copolymer film binds surface fibers together while imparting hydrophobic properties to the paperboard web.
Surface Sizing
Paperboard mills apply liquid sizing formulations at the size press or metering coater to control aqueous liquid absorption. Styrene acrylic acid copolymers contain hydrophobic styrene segments that face outward to repel water and hydrophilic carboxyl segments that anchor to cellulose fibers. Application of this copolymer increases Cobb test resistance, preventing water-based inks and adhesives from penetrating too rapidly into the substrate.
The polymer coating also increases surface pick resistance, preventing fiber picking during offset printing operations. Modern sizing formulations run styrene acrylic acid alongside starch to achieve high water holdout without compromising surface printability. Converting plants rely on consistent copolymer application to maintain gluability on high-speed packaging lines.
Concentration Limit
Chemical performance metrics evaluate water repellency and surface strength in treated paperboard. Styrene acrylic acid applications do not extend to wet-end internal sizing or wet-strength pulp additions. Surface characterization stops when board surfaces receive continuous barrier polymer extrusions.
Performance drops if size press drying temperatures fall below film-forming thresholds.