The effect of formaldehyde/phenol (F/P) molar ratios on function and curing kinetics of high‐solid resol phenolic resins

Abstract A series of high‐solid resol phenolic resins (HSRPRs) were synthesized with different molar ratios (1.6, 1.8, 2.0, 2.2, and 2.4) of formaldehyde to phenol using calcium oxide and sodium hydroxide as catalyst. The effects of F / P molar ratios on physical properties, free formaldehyde and phenol, activity, structure, and thermally resistant properties of HSRPRs were fully investigated by chemical assays, liquid and solid 13 C‐NMR, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The curing kinetics of different F / P molar ratios were explored with differential scanning calorimeter at four different heating rates (5, 10, 15, 20°C/min) from 35 to 200°C. Overall, HSRPRs with F / P = 2.0 had excellent comprehensive properties. The study was significant in solving the wastewater problem during the process of industry‐scale preparation of HSRPRs. We believed that the experimental findings would provide a new avenue for further study and application of HSRPRs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013