Performance of flakeboard bonded with three PF resins of different mole ratios and molecular weights

Structural flakeboards (strandboards) were bonded with phenol-formaldehyde (PF) resins containing different formaldehyde/phenol (F/P) mole ratios (2.00, 2.25, and 2.50). The physical characteristics and molecular weight distributions of the resins are described. Evaluations of the resins were carried out by performing strength tests on the flakeboards. The flakeboard tests included internal bond and static bending (modulus of rupture, MOR). The MOR was measured on both dry specimens and specimens subjected to accelerated-aging wet-dry cycles. Effects of some resin characteristics on flakeboard strength properties were tested statistically. Generally, increasing resin viscosity and polydispersion ratio resulted in increased internal bond strengths for flakeboards. Increasing resin molecular weights were associated with decreasing internal bond strengths. Other data are shown on the relationships of resin F/P mole ratio, viscosity, and molecular weight to subsequent resin-bonded panel dry MOR and accelerated-aging MOR strength retention properties. These data will help researchers in designing and formulating PF resins to meet certain performance properties.

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