Dissolving Pulp From Eucalyptus Sawdust For Regenerated Cellulose Products

This study assesses the possibility of obtaining regenerated cellulose products (beads and films) from eucalyptus sawdust dissolving pulps produced by non-conventional processes, compared with a commercial dissolving pulp as a reference. Eucalyptus sawdust dissolving pulps were obtained by soda pulping followed by two different TCF sequential bleaching processes OOpZ and OOp (where O is oxygen, Op is oxygen reinforced with hydrogen peroxide, and Z is ozone), followed by a cold soda extraction. The characterization of dissolving pulps involved alpha-, beta- and gamma-cellulose content, alkali solubility with 10 wt% (S10), and 18 wt% NaOH (S18) aqueous solutions, and degree of polymerization. Fock´s method was used to measure cellulose reactivity and the alkali solubility in a 9 wt% NaOH aqueous solution at -5 °C to evaluate the pulps dissolving capacity. Dissolving pulps presented high cellulose content (> 93 %, expressed as a-cellulose) and good reactivity (almost 84 %). The dissolving pulps were adequate raw materials for regenerated cellulose products (beads and films) from two cellulose dissolution methods: direct dissolution in NaOH/urea and cellulose carbamate solution. The sequence OOpE (where E is an alkaline extraction) was determined to be a more economically feasible and straightforward process to produce dissolving pulp than OOpZE. The experimental pulps showed the expected characteristics of the dissolving pulp to obtain regenerated cellulose products. However, it is necessary to deepen the study of producing regenerated cellulose films with enhanced mechanical properties from experimental dissolving pulps, solvents, coagulation, and regeneration conditions.

Crystalline Structure Analysis of All-cellulose Nanocomposites Films Based on Corn and Wheat Straw

The cellulose and nanocellulose which was extracted from corn straw and wheat straw was used to fabricate all-cellulose nanocomposites film (ANF). The crystal structure (CS) of ANFs was analyzed by X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR). The result shows that cellulose-I and cellulose-II are coexisting within regenerated cellulose films (RCF) and ANFs and can transfer each other with the change of nanocellulose content. The characteristics of cellulose transformation depend on the raw material and preparing method of cellulose. When cellulose is prepared from corn straw, under two preparing methods, the cellulose type tends to transform from cellulose-I to cellulose-II with low nanocellulose content and transform from cellulose-II to cellulose-I with high nanocellulose content. However, when cellulose is prepared from wheat straw, under extracting methods, the cellulose type tends to transform from cellulose-I to cellulose-II with nanocellulose content increase; under acid-alkali methods, the transformation is from cellulose-II to cellulose-I. The crystalline index (CI) of RCFs and ANFs is no obvious regularity, and the either content of cellulose-I or cellulose-II alone cannot determine the CI. Based on above result, the transformation characteristics of cellulose type should affect the property of ANFs, but further research methods and strategies are needed on what the effects are.