Hiroyuki Matsumura

Cellulosic nanocomposites. I. Thermally deformable cellulose hexanoates from heterogeneous reaction

Partially derivatized cellulose esters were prepared from dissolving-grade wood pulp fibers by reaction with a mixed p-toluene sulfonic/hexanoic anhydride system in a nonswelling (cyclohexane-based) reaction medium. The partially derivatized pulp fibers, which failed to undergo a significant change in shape or appearance during the modification, proved to be resistant to swelling (in water), were thermally deformable, and retained their biodegradability. Because X-ray diffractometry provided evidence for the presence of unsubstituted, ordered cellulose with cellulose I morphology, the thermally reshaped and consolidated sheets were found to consist of commingled mixtures of cellulose esters and cellulose I. The transparent or semitransparent consolidated sheets (depending on the degree of substitution) were found to represent composites in which cellulose I serves as a discontinuous inclusion that reinforces a continuous, partially ordered cellulose ester matrix. The composites, which revealed cohesive or adhesive failure at rupture, depending on the degree of substitution, had modulus values and tensile strengths as high as 1.3 GPa and 25 MPa, respectively.

Effects of solvent addition to acetylation medium on cellulose triacetate prepared from low‐grade hardwood dissolving pulp

As cellulose triacetate was prepared from low-grade hardwood-dissolving pulp, a considerable amount of the insoluble residue was present in the acetylation medium of the acetic acid/acetic anhydride/sulfuric acid system, and it consisted mainly of cellulose triacetate (CTA) and xylan diacetate (XDA). As one of the remedies for reducing the insoluble residue, a solvent was added to the acetylation medium and the effects of the solvent addition on the amount of insoluble residue formed were studied. To do so, 17 different solvents were selected so as to cover a wide range of solubility parameters. The obtained results clearly indicated that the addition of the solvent affects the amount of insoluble residue and that, excluding dichloroacetic acid, nitromethane was effective for its reduction, but that neither methylene chloride nor nitroethane were in spite of their effectiveness for softwood-dissolving pulp, which would be due to the intrinsic properties of XDA on the solubility in the acetylation medium. A new acetylation system with such an appropriate solvent would, therefore, provide a clue as to an industrial usage of the low-grade hardwood-dissolving pulps for cellulose acetate production.