The performance of waferboard bonded with powdered phenol-formaldehyde resins with selected molecular weight distributions

Two liquid phenol-formaldehyde resins, of distinctly low and high molecular weights, were synthesized. Six powdered resins were prepared by blending the low and high molecular weight resins in proportions of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100, and then spray-drying the resins. The molecular weights and functional group characteristics of the powdered resins were determined. The resins were used in the fabrication of waferboard panels and the panels were then evaluated according to the normal standards. Poorest values for the modulus of rupture, the modulus of elasticity, and the internal bond (IB) strength were found for the 100:0 blend. Bending and IB properties improved as the proportion of the high molecular weight fraction of the resin increased. Optimum bending values were found for the 20:80 blend, while optimum IB strengths were found for the 20:80 and 0:100 blends. The 20:80 blend produced significantly less thickness swelling than did the 100:0 blend. These results add to our knowledge of the effects of molecular weight on adhesive performance and will aid in the development of future phenolic resin formulations.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member