Effect of Resin Variables on the Creep Behavior of High Density Hardwood Composite Panels

The flexural creep behavior of oriented strandboards (OSB) fabricated with mixed high, density hardwood flakes was investigated. Three types of adhesives, liquid phenolic-formaldehyde (LPF), melamine modified urea-formaldehyde (MUF),.and LPF (face)/MUF (core) were chosen in this investigation. The resin contents (RC) used were 3.5 percent and 5.0 percent. The flakes prepared from white oak, southern red oak and post oak with a mixed ratio of 1: 1: 1 were used for the panel fabrication. Results indicated that the panels fabricated with 5.0 percent RC of MUF had highest bending modulus of rupture (MOR), and the group fabricated with 3.5 percent RC of LPF (face)/MUF (core) was the lowest. Significant differences among the modulus of elasticity (MOE) of each resin type and resin content group were not found. Highest internal bond (IB) strength was observed in the specimens with 5.0 percent RC of LPF (face)/MUF (core) whereas lowest one was found in the group with identical resin combination but with a 3.5 percent RC. The flexural creep behavior of the fabricated OSB under a cyclic RH of 65 percent *, 95 percent at a constant temperature of 75 “F (23.9 “C) was also investigated. The frequency of cyclic RN was 96-hour and the duration of load was 794 hours (approx. 1 month) while the duration of recovery (after unloaded) was 286 hours under constant 65 percent RH at 75 “F. Results indicated that the creep resistance of OSBs are very sensitive to the cyclic RH of 65