The effect of several hot pressing parameters on the internal mat environment was

investigated by using the mathematical model and the results were compared to data collected experimentally. The different pressing parameters included three initial mat moisture contents (5, 8.5, 12 %), three final panel densities (609, 641, 673 kg/m3 or 38, 40, 42 lb/ft3), two press platen temperatures (150, 200 °C), and three press closing times (40, 60, 80 s). The variation of temperature and total gas pressure during the press cycle at six points in the vertical mid-plane of a single layer, random mat structure was predicted with the heat and mass transfer model using the different pressing conditions. Twenty-four boards were manufactured according to the same

specifications, and the temperature and internal gas pressure were measured with thermocouples and gas pressure probes at the same six locations. The model predicted data described the major trends during the hot-compression operation qualitatively. However, further work is needed to make quantitative predictions.

A hot-compression model was developed based on fundamental engineering principles. The material physical and transport properties were the best available values from the literature or best estimates based on engineering judgment. A sensitivity study assessed the relative importance of the different transport properties during the hot-compression process. The response of selected variables of the hot-compression model for a perturbation of the parameter values was investigated. The sensitivity analysis of the model parameters revealed

that the thermal conductivity and gas permeability of the mat have the greatest influence on model results. The assessment of these transport properties experimentally, as a function of mat structure, is highly desirable and can considerably improve the model predictions.EFFECT OF HOT PRESSING ON THE INTERNAL MAT ENVIRONMENT.pdf (2.7% u)