Application of peroxides to the control of the crosslinking rate of epoxide oligomers with the phenolic Mannich base
The effect of the peroxide-type compounds (benzoyl peroxide, isopropylbenzene hydroperoxide, methylethylketone peroxide, tert-butyl perbenzoate) on the crosslinking rate of epoxide resin of the ED-20 type with 2-dimethylaminemethylphenol (FZM-1) was investigated. It was found that at room temperature peroxides distinctly inhibit the crosslinking reaction. This was explained by the formation in their presence from FZM-1 of compounds more hindered sterically than the initial FZM-1 and capable therefore of blocking the active centres of the curing agent. In the temperature range however in which the FZM-1/peroxide system can generate active radicals (120—140°C), peroxides accelerate the crosslinking reaction. The catalytic effect of peroxides at an elevated temperature can be attributed to the formation during their decomposition of proton donors (e.g. of benzoic acid from benzoyl peroxide or dimethylphenylcarbinol from isopropylbenzene hydroperoxide), these proton donors being capable of accelerating the reaction of curing of epoxide oligomers.
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