Polymer structure of cured alkaline phenol-formaldehyde resol resins with respect to resin synthesis mole ratio and oxidative side reactions

Structural and Physical Changes in Phenol−Formaldehyde Resol Resin, as a Function of the Degree of Condensation of the Resol Solution

“…Kim et al 23 synthesized a wood adhesive-type resol resin with properties similar to those of the resins of this study, and they investigated the structures of the completely cured resols resins with CP/MAS 13 C NMR spectroscopy. They found the methylene group/phenol molar ratios to be 1.35-1.46 in the fully cured resol resins.…”

“…However, the amount of free para sites (0.000) and para methylol groups (0.054) was very low in the NMR spectrum of S230, which strongly indicated the curing reactions of ortho methylol groups with free ortho sites and other ortho methylol groups forming ortho-ortho methylene bridges. These bridge structures were not detected in the 13 C NMR spectra of resol solutions; however, the analyses of the reported CP/MAS 13 C NMR spectra of the resols [23][24][25][26][27] indicated that ortho-ortho methylene bridges could not be completely excluded from the structures of the cured resol resins.…”

Online monitoring of synthesis and curing of phenol–formaldehyde resol resins by Raman spectroscopy

“…Since understanding of the advancement of resol resin synthesis and curing processes is essential for further development of the resins, methylolation and condensation reactions and structures of the resols have been followed and studied by various methods, such as FTIR spectroscopy [5,8,9], gel permeation chromatography (GPC) [10][11][12][13], 13 C NMR spectroscopy [14][15][16][17][18], and differential scanning calorimetry (DSC) [3,7,11,19]. However, none of these methods is well suited for gathering real-time information about the consumption of starting materials or structure of the resins during the resin processes, which could improve the safety and control of the synthesis and result in more uniform resin quality.…”

13C NMR study on structure, composition and curing behavior of phenol–urea–formaldehyde resole resins

“…However, little research has been done on resol type of PUF resins [9]. Due to the insoluble network of the partially cured or completely cured resins, solid 13 C NMR employing cross polarization and magic angle spinning (CP/MAS) has been applied in characterizing the curing process and network structure of the PF resins [17][18][19][20]. However, this technique has not been applied for studying PUF resins.…”