Revealing the impacts of recycled urea–formaldehyde wastes on the physical–mechanical properties of MDF

Recycling of the urea–formaldehyde (UF) products mainly obtained from adhesive wastes of wood industries is vital and requires a high level of attention due to the environmental and human health impacts of formaldehyde and other chemicals. In this study, the complete polymerized resin, as undesired waste product of Chassbsaz company, has been recycled and reused in the manufacturing process of medium density fiberboards (MDF). The results demonstrated that by adding recycled polymerized powder in sub-micron size to urea–formaldehyde control resin and replacing 1 wt% of the 55% solid content resin, the curing time of the resin significantly decreased. Fourier transform infrared spectroscopy (FTIR) demonstrated the chemical stability of the UF resins after adding 1 wt% recycled polymerized resin. In addition, there were substantial improvements in physical–mechanical properties [i.e., modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB) strength and thickness swelling (TS)] of the newly manufactured board compared to that of the control board. Analysis of variance (ANOVA) was employed to study the dependency and significance of the physical–mechanical properties of the MDF on the concentration of the recycled polymer. Moreover, the production capacity was expected to significantly increase as the curing time decreased while maintaining the outstanding mechanical characteristics of the boards.