Improvement of the thermal latency for epoxy-phenolic resins by novel amphiphatic imidazole catalysts

Abstract

Novel amphiphatic imidazole compounds were evaluated as thermal latent catalysts for the polymerization of diglycidyl ether of bisphenol A (DGEBA). Amphiphatic compounds 5-9, two commercially available catalysts 1 and 2, and compounds 3 and 4 were used to cure epoxy resin systems for an investigation of their thermal latency and storage stability. The results from the cure activation energy and viscosity-storage time of the catalysts, the order of thermally latent activity was 3-phenylpropanoic acid (4) > 2-amino-3-phenylpropinoic acid (5) > 2-amino-3-(imidazole-4-yl)-propionic acid (H-His-OH, 8) > N-tert-butoxycarbonyl-histidine (9) > imidazole-4-acrylic acid (6) > 3-(imidazole-4-yl)propionic acid (7) > 1-cyanoethyl-2-ethyl-4-methyl-imidazole (2) > 2-ethyl-4-methylimidazole (1) > histamine (3). From the results, the amphiphatic imidazole catalysts 5-9 showed better thermal latency than commercialized catalysts 1 and 2, basic catalyst 3 and acidic catalyst 4. Concerning the glass transition temperature (T g ), the use of amphiphatic imidazole catalysts 5-9 provided complete or near complete curing systems at temperatures ranging from 152-163 o C, which were similar to two commercially available catalysts (151-152 o C, 1 and 2) and histamine (159 o C, 3). On the other hand, the T g for compounds 4 and 5 could not be detected at 30-300 o C from the temperature scans because of their weak nucleophilicity and low cross-linking reactivity.

Investigation of soluble PEG-imidazoles as the thermal latency catalysts for epoxy-phenolic resins

“…From Table 1 imidazole (35.2 kJ/mol) [19]. Their tendency is consistent with the viscosity measurements.…”

“…metals acetylacetone-imidazole complex) [15,16], the formation of 1,3-disubstituted imidazolium salts and 1-substituted imidazole derivatives [17], and the modification by blending with the intermolecular acids (e.g. benzoic acid, isophthalic acid, and trimellitate) [18] or intramolecular acidic groups (carboxylic or amino acid groups) [19]. In this study, a series of novel soluble PEGimidazole compounds were synthesized and investigated as thermal latent catalysts for the polymerization of diglycidyl ether of bisphenol A (DGEBA) under liquid-liquid or liquid-solid (≥ PEG1000) phaseseparated systems [20,21].…”

Thermal Decomposition Kinetic Study of Non-Recyclable Paper and Plastic Waste by Thermogravimetric Analysis

“…The findings of both methods stated that the E a is dependent on conversion. The higher complexity of dehydration process, the greater the variation of E a [40]. Thus, Subcoal™ PAF ignition point is considerably low compared to RDF or SRF.…”

Curing behavior, thermal, and mechanical properties of epoxy resins cured with a novel liquid crystalline dicarboxylic acid curing agent

“…Epoxy resins have mainly been crosslinked with primary aromatic diamines as the curing agents . In some studies, catalytic crosslinking of epoxy resins has been done using trialkyloxonium tetrafluoroborates , iodonium salts , and imidazoles catalysts . The advantage of catalytic systems is that they require a small proportion of curing agent, e.g., <5 wt%, but allow the epoxy resin can be cured at lower temperature and shorter curing time than that of without using catalyst.…”