Mechanical properties of acrylate-grafted henequen cellulose fibers and their application in composites

The properties of cellulose fiber and PMMA- or PBA-grafted cellulose fibers are investigated as a function of the initiator (ceric-ammonium nitrate) concentration and the amount of grafted polymer onto cellulose fiber. The molecular weight of cellulose decreases while the crystallinity increases with an increment of initiator concentration because of the partial degradation of the amorphous zone of the fibers exposed to the oxidation by the initiator. This results in a reduction of the elastic modulus and tensile strength at high initiator concentrations. Degradation of cellulose is partially inhibited during the grafting process and, therefore, the effect of initiator on the mechanical properties is less notorious in the grafted cellulose fiber. The grafting of PMMA or PEA on the fiber results in lower mechanical properties than those of the ungrafted cellulose fiber. The reduction of the elastic modulus is independent of the amount of grafted PMMA or PEA, but the tensile strength decreases with the PEA content on the PBA-grafted fiber. Either the grafted or the ungrafted cellulose fibers improve the mechanical properties of plasticized PVC composites, and the best results are obtained for PMMA-grafted cellulose fibers because of the better fiber-matrix adhesion. The Halpin-Tsai equation seems to better agree with the experimental data when there is a good fiber-matrix adhesion. In contrast, for poor fiber-matrix adhesion the experimental data has a better agreement with the parallel arrangement equation. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.