Cellulose Whisker/Epoxy Resin Nanocomposites

摘要

New nanocomposites composed of cellulose nanofibers or "whiskers" and an epoxy resin were prepared. Cellulose whiskers with aspect ratios of - 10 and -84 were isolated from cotton and sea animals called tunicates, respectively. Suspensions of these whiskers in dimethylformamide were combined with an ollgomeric difunctlonal diglycidyl ether of bisphenol A with an epoxide equivalent weight of 185-192 and a diethyl toluenediamme-based curing agent. Thin films were produced by casting these mixtures and subsequent curing. The whisker content was systematically varied between 4 and 24% v/v. Electron microscopy studies suggest that the whiskers are evenly dispersed within the epoxy matrix. Dynamic mechanical thermoanalysis revealed that the glass transition temperature (T_g) of the materials was not significantly influenced by the incorporation of the cellulose filler. Between room temperature and 150 °C. i.e.. below T_g the tensile srorage moduli (E') of the nanocomposites Increased modestly, for example from 1.6 GPa for the neat polymer to 4.9 and 3.6 GPa for nanocomposites comprising 16% v/v tunicate or cotton whiskers. The relative reinforcement was more significant at 185 °C (i.e., above T_g), where E' was Increased from -16 MPa (neat polymer) to -1.6 GPa (tunicate) or-215 MPa (cotton). The mechanical properties of the new materials are well-described by the percolation model and are the result of the formation of a percolating whisker network in which stress transfer is facilitated by strong interactions between the whiskers