Several RF pressing trials were successfully conducted in the pilot plant at the Vancouver lab of FPInnovations, which aimed at thick LVL manufacturing, use of lignin-based PF resin as a binder and new plywood pressing method. A number of 3.5-in thick LVL billets were first RF-pressed for heavy-duty packaging applications with a pressing time of being shortened to about 25 min but with satisfactory bending MOE and MOR properties. Lignin PF resin (with 20wt% phenol replacement ratio) was prepared and used to make 13-ply spruce LVL. Compared to the control, there was no significant difference in both panel flatwise and edgewise bending MOE and MOR, as well as panel delamination resistance, when the lignin-based PF resin was applied. Further plywood RF heating trials with aluminum plate separation of panels demonstrated that the inclusion of the plates can help increase the thickness uniformity of plywood panels pressed with RF heating.
Economic analyses were conducted to determine the benefits of RF pressing for manufacturing LVL and plywood, and RF preheating of plywood. For RF pressing of LVL preliminary calculations demonstrated that RF pressing would generate aoubt $3.0 million CAD operating profit per year. It would also have 3.3% higher internal rate of return (IRR) and 1.25 years shorter payback period. For RF pressing of plywood, preliminary calculations indicated about $1.0 million CAD increase in operating profit annually for the RF pressing option, yielding a payback period of 3.95 years for purchasing and installing the new RF equipment. For RF pre-heating of plywood, the analysis showed that an increase of $4.7 million CAD in operating profit can be achieved annually and payback period is only 0.4 year. However, some further pilot plant work is required to establish the maximum closed assembly time of pre-heated plywood panels for industrial applications. PF adhesive formulations may also need to be changed in order to prevent glue dry-out after preheating.