The effect of brominated epoxy on epoxy/phenolic reactive blends

Abstract

Innovative reactive blends containing epoxy and brominated epoxy (BE) incorporated with resole-type phenolic were studied with the aim to elucidate the curing kinetics and the final thermomechanical characteristics of this unique system. Curing kinetics was investigated by means of the activation energy determined using differential scanning calorimetry (DSC ) at various heating rates analyzed by the Arrhenius equation. Both DSC and Fourier transform infrared revealed that bromine elimination at elevated temperatures (above 220 C) had lowered the activation energy in the case of BE containing phenolic blends. The thermomechanical properties showed that the addition of conventional epoxy to resole decreased its thermal properties and modulus compared to neat resole. Distinctively, BE/resole blends exhibited increased glass-transition temperature, compared to diglycidyl ether of bisphenol A/resole blends in combination with higher elongation and toughness compared to neat resole. It was concluded that BE/epoxy resin/phenolic reactive systems offer high T g , mechanical properties and toughness and hence are applicable for structural adhesives and for matrices of polymer-fiber composites.

Acid catalyzedepoxy–methylolphenolthermosets: Astructure–propertystudy

“…The methylol groups of the resole moiety can undergo self-condensation, react with the epoxy groups, and react with the hydroxyl groups of the high molecular weight epoxy resin. 15,16 The thermal degradation temperature of resole-epoxy networks, as defined by the temperature at which 5% weight loss occurs, is reported to be around 400 C 17 and the glass-transition temperatures (T g ) range from 89 to 200 C. 10,11,[17][18][19] Laza et al reported that the presence of an acid catalyst facilitates the reaction between epoxy and resole resins for stoichiometric compositions. 10 Such networks show an increase in T g when the amount of phenolic component increases.…”

“…10 Epoxy-resole networks usually exhibit Young's moduli that are on the order of 2.5 GPa, tensile strengths of 36-90 MPa, and tensile elongation of 2.2%-7.5%. 19,23,24 Several studies have been reported on network formation of epoxy-resole networks using high molecular weight precursors. [25][26][27] Low molecular weight methylolphenols have been used as model systems to study the reaction mechanism and kinetics of the resole synthesis and cure behavior.…”

“…When the phenolic content in epoxy‐resole formulations is increased from 50% to 90%, distinct T g s at 220–260°C were observed due to homo crosslinking of the resole component 10 . Epoxy‐resole networks usually exhibit Young's moduli that are on the order of 2.5 GPa, tensile strengths of 36–90 MPa, and tensile elongation of 2.2%–7.5% 19,23,24 . Several studies have been reported on network formation of epoxy‐resole networks using high molecular weight precursors 25–27 …”

Molecular structure effects on the mechanisms of corrosion protection of model epoxy coatings on metals

“…Moreover, this result presented an important insight into the crosslinking reactions of the epoxy and phenolic resins, which was previously believed to take place mainly through the epoxides ring-opening reaction with the phenolic hydroxyls. [61][62][63][64] If this were the main crosslinking mechanism, type 7 coating would be expected have a higher degree of crosslinking than type 9, and hence a higher T g , due to its shorter chains providing more functional epoxides to cure. Instead, the fact that we observe the opposite, suggests that in addition to the epoxides ring opening reaction, the phenolic methylol groups react with the hydroxyl groups in the epoxy repeating unit forming a more crosslinked network for the higher molecular weight type 9.…”

Hexahydrotriazine derivative containing imidazole for fast curing, improved mechanical strength, and flame retardancy of epoxy

“…Epoxy resin (EP) is one of the most representative thermo-setting resins and has excellent properties such as electrical and thermal insulation; it is also used as an adhesive in various industrial fields. [1][2][3][4][5] EP creates a three-dimensional cross-linked structure with a network structure by exothermic reaction with amine or acid anhydride molecules. We call this reaction the curing process.…”