Nonisothermal curing of a solid resole phenolic resin

Abstract

A commercial solid resole phenolic resin was thoroughly characterized with Fourier transform infrared spectroscopy, NMR, and gel permeation chromatography, and its nonisothermal curing reaction was studied systematically with differential scanning calorimetry at a series of heating rates (bs) of 3, 4.5, 5.7, and 10 C/min. The results show that the solid resole had a higher molecular weight than conventional liquid resoles, and its reactive hydroxymethyl (CH 2 AOH) and dibenzyl ether (CH 2 AOACH 2 ) functionalities participated in the crosslinking reaction upon heating. The nonisothermal curing reaction of the solid resole exhibited a relatively constant reaction heat, whereas the onset, peak, and end curing temperatures increased gradually with increasing bs. In addition, the reaction kinetics of the solid resole was analyzed with an nth-order reaction model, the global activation energy was determined with the Kissinger method, and the reaction order was derived from the Crane equation. The obtained rate equation was applied to simulate the reaction time, conversion, and reaction rate, with a good fit achieved between the experimental data and the model predications. In conclusion, this study provided us with new knowledge on solid resoles at a molecular level and was also a great help for the curing procedure design, property optimization, and practical application of this commercial solid resole.

Kinetic Analysis of One-Step Solid-State Reaction for Li4Ti5O12/C

“…According to Crane formula, , normald .25em ln nobreak.25em normalφ normald ( 1 / T normalp ) = − E n R − 2 T normalp When E / nR ≫ 2 T p , the integral of Crane formula can be described as eq . ln nobreak.25em normalφ = − E n R × 1 T p + C …”

Curing mechanism of resole phenolic resin based on variable temperature FTIR spectra and thermogravimetry-mass spectrometry

“…Typically, the nonisothermal activation energy of the curing reaction of phenolic resin was determined to be 72.23 kJ/mol with the Kissinger equation by Zhou and his coworkers. 24 The curing reaction kinetics was analyzed with an nth-order reaction model and n was calculated to be 0.92 from the Crane equation. The main curing reaction is condensation between the hydroxymethyl and unsubstituted active hydrogen of phenol ring, cleavage reaction of ether bond, accompanied with the gas release of water and formaldehyde.…”

Methylol‐functional benzoxazines as precursors for high‐performance thermoset polymers: Unique simultaneous addition and condensation polymerization behavior

“…Thus, this early weight loss in o HBA‐ddm is attributed to the condensation reaction byproducts produced from the polymerization of methylol groups in a similar way as in traditional phenolic resin. This indicates that the first exothermic peak is due to the condensation reaction of methylol in the same way as a resole‐type phenolic resin, which shows an exothermic peak around this temperature range 35, 36. Furthermore, a methylol group blocks the preferred ortho‐reaction site, and consequently, the polymerization is forced to proceed through the less favorable para‐position37 which justifies the high temperature required for the second peak to undergo the polymerization.…”