Supramolecular structure is the critical factor that affects the properties of cellulosic fibers. This article studied the action of Papirindustriens forskningsinstitut (PFI) refining on the molecular aggregation and hydrogen bonding network, and tried to explore the relationship between the crystal packing and hydrogen-bonding network in cellulosic fibers. The results showed that the polymorph, H-bonding distance, and H-bonding energy of various H-bonds remained almost unchanged, while the crystalline index, crystallite size, and content of various H-bonds changed with refining. Therein, the content of the inter-molecular O(6)H⋯O(3') H-bonds was significantly correlated with the crystalline index that was obtained in intensities of the XRD peaks. The Pearson correlation coefficient between them was 0.888 (p < 0.05) for softwood fibers and 0.889 (p < 0.05) for hardwood fibers, respectively. It can be concluded that the variations of accessibility, swelling, and fibrillation were closely related to the supramolecular structure and the intermolecular H-bonds play an important role in the crystal packing of cellulose.
Keywords: Crystallinity; Crystallite size; Hydrogen bonds; mechanical refining; natural cellulosic fibers.