The Influence of Refining on Molded Pulps from Banana Pseudostem Waste After NH₄OH-KOH Based Pulping and Single-Stage Bleaching

The low environmental impact NH4OH-KOH pulping process was used to extract pulp from banana pseudostem waste (BNW). The extracted BNW pulp was then single-stage bleached using a mixture of NaOH and H2O2 to increase brightness of the pulp. The Valley beater was further used to refine the obtained pulp (at a speed of 500 and 700 rpm) which resulted in fiber delamination, fibrillation, cutting, shortening as well as creation of fines leading to considerable higher total surface area for fiber-fiber bonding as revealed by SEM. XRD patterns of the bleached and refined BNW pulps indicated unchanged cellulose I structure with a minor increase in the crystallinity index (79-82%). The Canadian Standard Freeness (CSF) of the refined BNW pulps was sharply decreased, suggesting a much greater swelling ability of fibers from internal fibrillation after refining. Still, it was found that only a speed of 700 rpm in refining could dominate positive effects on the pulp fiber characteristics and enhance overall mechanical properties of the pulp sheets, exhibiting the highest tensile index of 76.66 Nm/g and tear index of 10.89 mNm(2)/g. In addition, the molded sheet prepared with BNW pulp refined at 700 rpm, having smoother surface and denser structure (reduced porosity), showed a visible increase in surface water resistance (as confirmed by dynamic contact angle measurement).