Fast curing PF resin mixed with various resins and accelerators for building composite materials

The objective of this research is to investigate the fast curing effect of phenol–formaldehyde (PF) resin by employing three methods: mixing with novolac phenol–formaldehyde, adding amino-based resin and the use of accelerators. The effects of shorting phenolic resin curing time and adhesion strength were determined. The gelation time of phenolic resin mixed with novolac resin shortened the curing time by 20–50% compared to that of the phenolic resin itself (at 100 °C). The hot-press time of the phenolic resin was considerably lessened by varying the composition of the amino-based resin, but it introduced the problem of low bonding strength of waterproof layer for plywood constructed with the radiata-pine solid veneer. Among the various phenolic resin types of curing accelerators, sodium carbonate was the most effective and was able to shorten the curing time by 30% when applied to the plywood process. The addition of sodium carbonate as the curing accelerator of a phenolic resin gave a bonding strength of waterproof layer equal to that of phenolic resin (no sodium carbonate addition) and shortened the hot-press time by about 30 s/mm (135 °C). These test results suggested 4–5% as a suitable addition level for sodium carbonate in phenol use.