Eucalyptus Fiber Morphology and Inter Fibre Hydrogen Bond Density
Eucalyptus fiber collapse and hydrogen bond density dictate sheet tensile strength, bulk retention, and landed sheet cost in commercial packaging grades.
Glucuronoxylan
Hemicellulose Composition
Polysaccharide chains form the matrix surrounding cellulose microfibrils in the cell walls of hardwood and softwood species. Glucuronoxylan acts as the primary hemicellulose found in deciduous trees, contributing to the structural integrity of the plant by linking with lignin through covalent bonds. Removal or alteration of this polymer occurs during the chemical pulping process when alkaline conditions hydrolyze the glycosidic linkages.
Bonding Mechanism
Xylose units constitute the linear backbone of the molecule with alpha-D-glucuronic acid residues attached at frequent intervals along the chain. These acidic side groups provide the negative charge necessary for fiber swelling in water, which aids internal fibrillation during the refining process. Printers evaluate this property when adjusting mechanical beating cycles for heavy weight folding boxboard.
Higher amounts of this polymer relative to cellulose allow for faster sheet densification, although excessive concentrations impede drainage rates on the fourdrinier wire.
Converting Impact
Moisture sensitivity correlates with the presence of uronic acid groups along the xylan chain, affecting how a substrate behaves during high speed converting operations. Increased solubility of the polymer in caustic solutions dictates the chemical recovery load in a pulp mill and influences the potential for dimensional instability in finished print stock. Controlling the retention of this component during the bleaching stage stabilizes the opacity and physical strength of high quality office paper.