Effect of Mechanical-Chemical Pretreatment at Room Temperature on Properties of Cellulose and Cellulose Solution

The high degree of polymerization (DP) of cellulose makes it difficult to dissolve the cellulose fibers and increases the viscosity of the dissolved cellulose solution, which limits the ability to produce small particles of beads by using small needles or nozzles by dropping or spraying methods. This study explores the development of a technology to control the DP of cellulose of a chemical pulp through a mechanochemical pretreatment at room temperature. The chemical pulp was pretreated by three methods (ethanol-hydrochloric acid pretreatment, ball milling pretreatment, or acid-ball milling pretreatment), and the effects on fiber and cellulose properties, cellulose solution properties, and bead size were explored. Our findings reveal that wet ball milling pretreatment with acid is more effective in reducing DP of cellulose than acid treatment or ball milling treatment alone. The DP of cellulose of chemical pulp was reduced from 1400 to 400 after 1 h of acid-ball milling treatment at room temperature. The reduction in the DP of cellulose decreased the viscosity and surface tension of the cellulose solution, which affected the size of cellulose beads. In addition, the acid-ball milling pretreatment resulted shortening of fiber length and external fibrillation, and did not affect the crystal structure of cellulose-I, unlike the ball milling treatment, which destroyed the fiber morphology and the cellulose crystal structure.