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Initiation Mechanisms of Styrene with Methyl Ethyl Ketone Peroxide- Cobalt System
Ruiwei Guo,Yaqi Wang,Yongtao Qi,Auke G Talma,Jianhua Zhang 한국고분자학회 2018 Macromolecular Research Vol.26 No.8
Unsaturated polyester resins (UPR) cured with styrene has been widely used in the various industrial fields. Methyl ethyl ketone peroxides (MEKP)-cobalt(II) system is the most common initiator for the curing of UPR. However, its initiation mechanisms currently remain elusive. In this study, the monomeric MEKP (MEKP-1) was firstly separated out from the commercial MEKP products, and then the radical initiation mechanisms of MEKP-1 catalyzed by cobalt isooctoate in the presence and absence of styrene were comparatively investigated by a combination of nitroxide radical trapping technique and HPLC-ESI/MS (high performance liquid chromatography- electrospray ionization/mass spectrometry). The amount of trapped products originated from methyl radical, ethyl radical and hydroxyl radical was significantly larger than that of trapped products from other radicals. These results indicated that methyl, ethyl and hydroxyl radicals were the dominant intermediate radicals formed in the initiation process of MEKP-cobalt(II) system, which would serve as the primary source to initiate styrene polymerization.