Sorption Isotherm of Southern Yellow Pine High Density Polyethylene Composites
Temperature and relative humidity (RH) are two major external factors, which affect equilibrium moisture content (EMC) of wood plastic composites (WPCs) In this study, the effect of different durability treatments on sorption and desorption isotherms of southern yellow pine (SYP) high density polyethylene (HDPE) composites was investigated. All samples were equilibriumed at 20 degC and various RHs including 16% 33% 45% 66% 75% 85% 93% and100% EMCs obtained from desorption and absorption for different WPC samples were compared with Nelson's sorption isotherm model predictions using the same temperature and humidity conditions. The results indicated that the amount of moisture absorbed increased with the increases in RH at 20 degC. All samples showed sorption hysteresis at a fixed RH. Small difference between EMC data of WPC samples containing different amount of ultraviolet (UV) stabilizers were observed. Similar results were observed among the samples containing different amount of zinc borate (ZB) The experimental data of EMCs at various RHs fit to the Nelson's sorption isotherm model well. The Nelson's model can be used to predicate EMCs of WPCs under different RH environmental conditions.
Materials