Gelation and isoconversional kinetic analysis of synthesis of lignin–resorcinol–glyoxal resin curing

Abstract

and 72 %, for LRFR and LRGR, respectively. These values were compared to those calculated from Flory and Stockmayer equation and found to be close to each other.

Resorcinol in high solid phenol−formaldehyde resins for foams production

“…24 The second peak appeared at a higher temperature, which was because of the condensation reaction of hydroxymethyl groups formed through reaction of phenol and resorcinol with an excess of formaldehyde. 24,25 Figure 4(a) and Table IV show that, as the R/P molar ratio increased, the first curing exothermic peak shifted to lower temperature and the reaction enthalpy ᭝H 1 increased, while the second curing exothermic peak moved to higher temperature and the ᭝H 2 decreased, which were due to high reactivity of resins caused by the incorporation of resorcinol. The trends were consistent with the trends of previous literature.…”

“…The first broader exothermic peak around 150 to 160 °C corresponded to the addition reaction between the hydroxymethyl groups and the active hydrogen in the ortho ‐ and para ‐free positions of resorcinol and phenol . The second peak appeared at a higher temperature, which was because of the condensation reaction of hydroxymethyl groups formed through reaction of phenol and resorcinol with an excess of formaldehyde …”

Biobased Resins Using Lignin and Glyoxal

“…Ammar et al and Esfandiyari et al developed lignin–glyoxal resins with 100 wt % substitution of phenol by lignin. ,, From Table , it can be observed that much lower viscosities and higher gel times were obtained for these adhesives compared to the reported LPG resins. It is difficult to compare the amount of added glyoxal as this is expressed as wt % relative to lignin.…”

“…21,22,24,144 In some studies, the staged addition of catalyst (NaOH) is also described during synthesis of LPG resins. 145,146 During production of resoles, both formaldehyde and glyoxal can react via Cannizzaro and form, respectively, formic and glycolic acids ( Figure 5B). However, the reaction mechanism differs for both reactions: an intermolecular and intramolecular rearrangement, respectively, for formaldehyde and glyoxal.…”

“…For LPG resins, glyoxal is also added in a dropwise fashion to the reaction mixture which is preheated at 80–100 °C followed by resinification under reflux conditions for a certain time. ,,, In some studies, the staged addition of catalyst (NaOH) is also described during synthesis of LPG resins. , …”