Guar gum used as a lubricant for cellulose fibers processed in a twin-screw extruder to obtain a thermocompressible paste for packaging material

This study compares two different types of cellulosic materials to be dried by thermocompression: (i) microfibrillated cellulose (MFC) and (ii) pretretated cellulose fibers mixed to guar gum. Both were produced by twin-screw extrusion at 20 wt% (TSE) from an enzymatically pretreated cellulose fiber pulp. Without guar gum (GG) in TSE, fibers were microfibrillated. MFC drying by thermocompression remained challenging due to shrinkage. However, when GG was added to the fibers prior to extrusion, the fiber length was reduced only after five passes in the TSE (whereas it drastically decreases after one pass without GG) and modest fibrillation and fines content were measured, likely thanks to a lubricating and water retention effect of the GG. In terms of processability, the spreading of the fiber/GG paste was strongly enhanced in comparison to MFC paste. A thermocompressed material with a cohesive quality was successfully produced with the fiber/GG paste with a limited shrinkage.