Modification of pine pulp during oxygen delignification by xylan self-assembly.

Self-assembly is a technique of preparing functional materials based on targeted intermolecular interactions involving different macromolecules. In this work, hardwood xylan was disassembled from wood and birch bleached kraft pulp using pressurized hot water extraction (HWX) and cold alkali extraction (CAX), respectively. The extracted biopolymers were characterized using gas chromatography (GC), size exclusion chromatography (SEC) and Fourier transform infrared spectroscopy (FTIR), and subsequently added into an oxygen delignification reactor containing pine kraft pulp. The assembly of xylan-pulp fiber was characterized using advanced time-of-flight secondary ion mass spectrometry (ToF-SIMS) and imaging. The xylan-pine pulp assembly was not significantly removed during the whole elemental chlorine free bleaching sequence or during low consistency refining. Modified fibers had superior mechanical properties compared to the reference pulp. Our concept can be easily applied in the pulp and paper industry, and it opens new possibilities for the utilization of fully bio-based fibers in new materials.