Evaluation of UF resin content in MDF boards after hot-pressing by Kjeldahl method

Abstract

Understanding resin behavior during hot pressing of medium density fiberboard (MDF) is important to optimize panel properties. Before gelation, the mobility of the resin can affect its distribution and penetration on the wood cells during pressing. The resin in MDF boards occurs as coverage on the fibers surface and also penetrates within the fibers. In this paper, the effect of final resin content and physical–mechanical properties of MDF panels was measured under different conditions of press time, temperature and initial resin content. The measurements were performed by the Kjeldahl method. Results showed that a higher amount of initial resin led to a higher resin content in MDF boards. At the same amount of initial resin, a higher final resin content was obtained by increasing the pressing temperature. Furthermore, the final resin content affects the board properties such as internal bond strength and modulus of rupture. The results showed good correlation between mechanical properties and thickness swelling.