No abstract

Unsaturated and saturated organic acids with 11 and 18 carbon atoms, respectively, were used in a heterogeneous esterification reaction in the pyridine/ toluene sulfonyl chloride system to prepare fibrous cellulose esters with different degrees of substitution. Highly bleached sulfite cellulose fibers were esterified during a 1-or 2-h reaction time with the following organic acids: undecylenic acid, undecanoic acid, oleic acid, and stearic acid. In all cases, the heterogeneous esterification yielded partially substituted cellulose esters retaining their fibrous structure. The substitution reaction was confirmed by diffuse reflectance infrared spectroscopy and the chemical structures of cellulose esters were identified by solid-state CP/MAS 13 C-NMR (75.3 MHz). X-ray diffraction analyses showed broadening of the diffraction peaks with a higher degree of substitution of cellulose esters, which suggests structural changes within the cellulose fibers. Because the broadening peaks of X-ray spectra or the unassigned C-4 region of substituted cellulose chains in NMR spectra do not allow the calculation of dimensional changes of cellulose crystallites in cellulose esters, the lateral dimensions of crystallites in only cellulose fibers were calculated. The value derived from NMR (4.6 nm) differs by about 11% when compared with the value calculated from X-ray diffraction data (4.1 nm).

Unsaturated and saturated organic acids with 11 and 18 carbon atoms, respectively, were used in a heterogeneous esterification reaction in the pyridine/toluene sulfonyl chloride system to prepare fibrous cellulose esters with different degrees of substitution. Highly bleached sulfite cellulose fibers were esterified during a 1‐ or 2‐h reaction time with the following organic acids: undecylenic acid, undecanoic acid, oleic acid, and stearic acid. In all cases, the heterogeneous esterification yielded partially substituted cellulose esters retaining their fibrous structure. The substitution reaction was confirmed by diffuse reflectance infrared spectroscopy and the chemical structures of cellulose esters were identified by solid‐state CP/MAS 13C‐NMR (75.3 MHz). X‐ray diffraction analyses showed broadening of the diffraction peaks with a higher degree of substitution of cellulose esters, which suggests structural changes within the cellulose fibers. Because the broadening peaks of X‐ray spectra or the unassigned C‐4 region of substituted cellulose chains in NMR spectra do not allow the calculation of dimensional changes of cellulose crystallites in cellulose esters, the lateral dimensions of crystallites in only cellulose fibers were calculated. The value derived from NMR (4.6 nm) differs by about 11% when compared with the value calculated from X‐ray diffraction data (4.1 nm). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1354–1365, 2000

No abstract

Composites were prepared by compounding linear low-density polyethylene (LLDPE) with cellulose fibers as reinforcing filler. Effect of a small addition of unsaturated or saturated long chain organic acid cellulose esters (cellulose undecylenate, undecanoate, oleate, stearate) with partial degrees of substitution and the presence of dicumyl peroxide (DCP) as a polymer crosslinking initiator was investigated on the rheological and tensile properties of hybrid composites. No grafting of polyethylene onto fibers surfaces occurred under processing conditions; however composites with DCP showed significant increase in tensile properties. The use of unsaturated cellulose esters in composites containing DCP was more effective in maintaining stress at yield and in progressive increase of energy to yield with higher cellulose esters content and degree of substitution in comparison with composites containing only cellulose fibers. The tensile properties decreased sharply in composites containing saturated cellulose esters.