AbstractN‐acryloyl–N′‐phenylpiperazine and three of its homopolymers of different molecular weight are tested as low toxicity redox activators in the BPO curing of unsaturated polyester resins. Gel times and other time and temperature parameters drawn from standard exothermal curves are determined with two kinds of resin, at different bath temperatures and amounts of activator. The reciprocal of gel time follows a kinetic equation with average order 0.85 with respect to the activator, and an activation energy of 19 kcal/mol. With polymeric activators it is a simple decreasing exponential function of intrinsic viscosity. Correlations are observed for other parameters relative to the second, faster step of the curing process, in general less sensitive to the mentioned variables. The crosslinked resins show mechanical properties similar to those obtainable with dimethylaniline as ac
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