Initiation Mechanism And Curing Properties Of Methyl Ethyl Ketone Peroxide And New Copper Promoters

Unsaturatured polyester resin(UPR)is widely used in many fields,such as aircraft and polymeric composites,because of its excellent mechanical properties and good chemical resistance.The most commonly used initiating system for curing UPR is methyl ethyl peroxide(MEKP)catalyzed by transition metal salts.On account of multiple components interactions making the reaction more complex,and the mechanism changes with the developments of new type initiating systems,so it is instructive to research on the reaction mechanism for extending application of UPR.The curing process of UPR with different copper promoters were studied by non-isothermal DSC.The results indicated that copper promoters consumed a part of radicals during curing process leading to the retardation effect at high temperature.The influence of CF12 n dosage and heating rate for UPR/MEKP/CF12 n system were studied.The results showed the accelerating activity increased when adding more dosages of CF12 n to the system.Compared the accelerating ability of the two copper promoters,we concluded that CF12 n is more effective promoters for curing UPR.And effect of additives(Vit C and diacetone)to CF12 and CF12 n in the process of curing UPR were also investigated,we discovered that the accelerating ability of CF12 n can be improved by adding a little amount of diacetone.The initiation mechanisms of T4-copper(II)system for the radical polymerization of different monomers(St,MA,MMA)were investigated in detail by a combination of nitroxide radical trapping technique and HPLC-ESI/MS in the presence of radical scavenger(4-benzyloxy-2,2,6,6-tetramethyl-piperidinyloxy).The trapped products formed in the T4/Cu(II)reaction can be identified by HPLC/ESI-MS.With the interaction of Cu(II),methyl,ethyl,hydroxyl and acetoxyl radical were the dominant initiating radicals.Compared the effect of CF12 and CF12 n,we indicated that the accelerating activity of CF12 n is better than CF12 under room temperature.Nitroxide radical trapping technique and HPLC-ESI/MS were combined to investigate the initiation process of MIPKP-copper(II)system for the radical polymerization of different monomers(St,MA,MMA),indicating that methyl,isopropyl,acetoxyl were the main radical which can initiate the monomer polymerization.And we proposed the possible initiation mechanism of this system.Unfortunately,the various components in commercial MEKP makes it harder to research on its decomposition and initiation process.In this article,we separated the components monomeric MEKP(T4)and 2,2’-dihydroperoxy-2,2’-dibutyl peroxide(T3)by a multistep extraction method.The catalytic reaction between peroxides(T4 or T3)and copper salt complex(CF12 or CF12n)were investigated by UV-vis.And we compared the reaction activity differences of CF12 and CF12 n under different temperature,the experiments results indicated that CF12 had a stronger temperature dependency than CF12 n.We also investigated the effect of different additives for the redox reaction of initiating systems.These results will provide guidance for improving performance of copper promoters and development of new promoter systems.