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Acceptable alternatives of cobalt-free promoters in UPR: Gelation and exotherm behavior

Authors: Matušková Eliška | Honzíček Jan | Vinklárek Jaromír

Year: 2022

Type of publication: ostatní - přednáška nebo poster

Page from-to: nestránkováno

Titles:

Language	Name	Abstract	Keywords
eng	Acceptable alternatives of cobalt-free promoters in UPR: Gelation and exotherm behavior	The curing of unsaturated polyester resins is a free-radical polymerization initiated by organic peroxides and accelerated by a curing agent. During the curing process, the resin is transforming from a liquid structure into a rigid one [1]. Commonly used cobalt accelerator was established as a carcinogen in many studies [2]. Due to the toxicity of cobalt, the use just of cobalt-free alternatives is expected. The catalytic activity of potential cobalt-free alternatives was confirmed in a commercial polyester/styrene/methyl ethyl ketone peroxides system. In general, transition metal compounds are used as a curing agent for their ability to accelerate peroxide decomposition. Synthesized compounds based on iron and vanadium were tested and compared to the commercially available accelerators. Evaluation of gel time and exothermic behavior indicates the course of the cross-linking process. Due to the peroxide decomposition accelerated by the promotor, an exothermic process was observed. The production of free radicals supports a sharp increase in viscosity of the resin system due to cross-linking. Subsequently, the gel time meter record adequate resistance, and the gelation part continue to the final curing. In a thermally isolated system, the exothermic behavior of the studied system was achieved by the use of K-type thermocouples. Through the high-temperature rise upon the curve, the degree of cure was determined. Subsequently, the inflection point was set based on the results of the derivative curve derivation. At this specific point, the maximum rate of the temperature rise at an appropriate time gives an overview of the catalytic activity of potential cobalt-free alternatives. All tested synthetized promoters proved to catalyze the curing process of unsaturated polyester resin and are comparable to commercial.	resin