Development of a Renewable Hybrid Resin System by Blending Isocyanate with Novolac Phenolic Resins

Abstract

Abstract The objective of this study was to develop a performance-competitive bio-based hybrid resin system composed of methylene diphenyl diisocyanate (MDI) resin and novolac phenol-formaldehyde (PF) resin for engineered wood panel manufacturing. A novolac PF resin and a bio-oil–modified PF resin were blended with MDI at weight ratios of PF to MDI of 85:15, 75:25, 50:50, and 25:75, respectively. The obtained hybrid resins were examined with Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), and evaluated as plywood binders. The results indicated that the gel times and viscosities of hybrid resins were closely related to the weight ratio of PF resin to MDI. At a ratio lower than 75:25, the viscosities of hybrid resins were appropriate for plywood application. FTIR results showed some reactions between the novolac PF resin and MDI. TGA results showed that reacting novolac PF resin with MDI resin possibly increased the thermal stabilities of hybrid resins in the temperature range of 150°C to 300°C. Panel performance tests showed that blending novolac PF resin with MDI increased both the dry and the wet bonding strength of panels at the optimal ratio of 50:50. Replacing phenol with bio-oil of the hybrid resin had the trend of reducing the hybrid resin gel time and increasing panel dry and wet bonding strength.