Fragment analysis of different size-reduced lignocellulosic pulps by hydrodynamic fractionation

Abstract

Micro-and nanocelluloses are typically produced using intensive mechanical treatments such as grinding, milling or refining followed by highpressure homogenization to liberate individual nanoand microcellulose fragments. Even though chemical and enzymatic pretreatments can be used to promote fiber disintegration, the required mechanical treatments are still highly energy consuming and very costly. Therefore, it is important to understand the kinetics and factors affecting the disintegration tendency of cellulose. In this study, the disintegration tendency of three different wood cellulose pulps with varying chemical composition processed in a PFI mill was examined by analyzing the fractional composition of the microparticles formed. The fractional compositions of the microfibrils and microparticles formed were measured with novel analyzers, which fractionated particles using a continuous water flow in a long tube. The hydrodynamic fractionators used in this study gave valuable information about different size of particles. Results showed that the amount of lignin and hemicelluloses clearly affected the kinetics and the mechanics of cellulose degradation. The P and S1 layers were peeled off from the Kraft fibers, causing the S2 layer to be cropped out. The thermomechanical pulp (TMP) fibers were first degraded by comminution and delamination from the middle lamella and the primary wall. As the refining process progressed, the fibers and fiber fragments began to unravel. Surprisingly, the semi-chemical pulp (SCP) fibers degraded more like Kraft fibers than TMP fibers despite their high lignin and extractive content.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse

“…However, the mechanical fibrillation process caused a more significant reduction in the value of the degree of polymerization of the fibrillated pulps containing lignin (410 for fibrillated unbleached fiber) compared to the bleached pulp (435 for fibrillated and bleached fiber). The presence of hemicelluloses and lignin favor mechanical fibrillation [ 51 , 53 ]. Due to their hydrophilic nature, hemicelluloses aid the swelling of fibers, whereas lignin, due to its hydrophobic nature, aids fibrillation since it counteracts the recombination reactions between cellulose molecules.…”