Curing kinetics of polymeric diphenylmethane diisocyanate with different wood species

The effect of wood species on the curing kinetics of diphenylmethane diioscyanate (pMDI)/wood systems under both oven-dry and moisture conditions was investigated. The results indicated that wood species did affect the curing kinetics of the pMDI/wood systems, such as activation energy, reaction rate and reaction enthalpy, under the oven-dry conditions due to the differences in structure and composition. However, the effect of wood species on the curing kinetics became insignificant when moisture was introduced into the pMDI/wood systems, suggesting that the reactions between isocyanate and water dominate the curing process. Wood species seemed not to affect the main reaction mechanism because a similar relationship between the activation energy and the degree of conversion was obtained for all species. The kinetics were also affected by different pMDI/wood ratios for the oven-dried wood system but not for the system with moisture, demonstrating that the hydroxyls in wood were restricted as reactant under the oven-dry conditions.