Temperature dependence of the thermal conductivity and thermal diffusivity of treated oil‐palm‐fiber‐reinforced phenolformaldehyde composites

The effective thermal conductivity (λ e ) and effective thermal diffusivity (χ e ) of oil‐palm‐fiber‐reinforced treated composites were measured simultaneously with the transient plane source technique from 50 to 110°C. The fibers of the composites were treated with sodium hydroxide alkali, silanol, and acetic acid. The experimental results for the different treated composites showed that there were variations in λ e and χ e over this temperature range. However, the maximum values of λ e and χ e were observed at 90°C, in the vicinity of the glass‐transition temperatures of these composites. An effort was also made to predict the temperature dependence of λ e and χ e through the development of an empirical model. The theoretically predicted values of λ e and χ e for these composites were in excellent agreement with the experimental results over the entire range of investigated temperatures. Sudden increases in λ e and χ e in the glass‐transition region of these composites were indicative of the fact that the crosslinking density decreased and was at a minimum at the temperature at which λ e and χ e showed their maxima. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3458–3463, 2003