Yutthana Tirawanichakul, Jutarut Tasara, and Supawan Tirawanichakul

pp. 69 - 80

Abstract

Knowledge of the temperature and relative humidity (or water activity) dependence of moisture sorption phenomena
of agro-industrial products provides valuable information about changes related to the thermodynamics of the system. Thus
the moisture sorption characteristics in terms of equilibrium moisture contents (EMC), enthalpy and entropy of heat sorption
of natural rubber (NR) for producing STR 20 and skim block rubber were investigated. Simulation modeling of water sorption
isotherms was performed using the 10 non-linear regression EMC models and the multilayer artificial neural network (ANN)
approach. The results showed that the predicted EMC results using the modified Oswin model was the best fitting model for
both NR samples. However, the predicted values of ANN model were more accurate than those predicted results using nonlinear regression method. Finally, enthalpy and entropy of heat sorption for both NR samples were evaluated by applying the
Clausius-Clapeyron equation showing as the negative exponential function of moisture content.