Catalysts For Esterification Of Cellulose And Its Application

In recent years, thermoplastic materials have been increasingly usedfor various fields. For a long time past, it has resulted in seriousenvironment problem because of its non-biodegradability and thecellulose and natural cellulose fibers as a new reinforcing material inpolymer composites are being paid attention to again. The mechanicalproperties of the final composite strongly depend on the degree ofadhesion between matrix and cellulose. The very high polarity ofcellulose conflicts with the hydrophobic character of most syntheticpolymers, and the obtained composites often show poor properties.In this paper, cellulose acetates with different degree of substitutionhave been synthesized from wood pulp, glacial acetic acid and aceticanhydride using dodecyl benzene sulfonic acid as an esterificationcatalyst. It was knew that dodecyl benzene sulfonic acid can be used as acatalyst for starch acetates by infrared spectra. The spectra of theacetylated samples show the expected acetyl group vibrations at 1750cm^-1,1375cm^-1, 1240cm^-1. The intensity of the acetyl bands increases with reaction time. Also the spectrum of native pulp shows an absorption at1375cm^-1, attributed to the C-H bending vibration. After esterification, theadded contribution of the acetyl (C-CH3)stretching vibration intensifiesthis absorption peak.The reaction mechanism of cellulose acetates was studied. Thekinetic equation of the esterification has been established according to thefirst-order reaction mechanism. And the activation energy was calculatedby experiment. And then the influences of the reaction conditions such asreaction time, reaction temperature, acetic anhydride/cellulose contentand amount of catalyst, on the degree of substitution of the starch acetateshave been investigated. It has been found that the degree of substitutionincreases by prolonging reaction time, increasing temperature, increasingacetic anhydride/cellulose content and the amount of catalyst, however,the productive rate decreases.Finally, the application of catalysts on starch acetate was studied.The result was conclutied as same as cellulose acetate. The influences onthe esterification were investigated. The reaction products were analyzedby infrared spectra. It was knew that dodecyl benzene sulfonic acid canbe used as a catalyst for starch acetates.