Studies On Curing Characteristics Of New Copper And Iron Accelerators In UPR/MEKP Systems

Unsaturated polyester resin(UPR)is a versatile thermosetting resin,and accelerator is critical for its room temperature curing.The potential carcinogenicity of cobalt-based accelerators has limited their application,and the development of low-toxic and environmentally-friendly non-cobalt salt promoters has become the focus of research in recent years.New copper accelerator CF12N and iron accelerator CF40 are invented as substitutes for cobalt promoters by Akzonobel corporate,and there is much development and application in the future.It is necessary to further study and improve the curing characteristics.In this study,the promoting properties of CF12N and CF40 on methyl ethyl ketone peroxide(MEKP)in the curing process of UPR and the curing characteristics were studied.MEKP mainly contains three hydroperoxide components,including hydrogen peroxide(H₂O₂),2,2-dihydroperoxybutane(T4)and butanone peroxide(T3).In this paper,H₂O₂,T4 and T3 single-component solutions were prepared by multiple process extractions.The promoting properties of CF12N and CF40 on MEKP and its components was studied by differential scanning calorimetry(DSC),and the reaction process of CF12N and CF40 on MEKP were studied by UV-visible spectrophotometry.The results showed that the promoting activities of CF12N and CF40 on MEKP components is H₂O₂>T4>T3,but the difference in the promoting activity of CF12N on each component is small,so that the DSC curing curve of UPR/MEKP/CF12N system shows a single peak.The DSC curves of UPR/MEKP/CF40 system is multipeak.The high temperature blocking effect accurs on the curing of UPR/MEKP/CF12N in case the dosage of CF12N is low.When the curing temperature is high,UPR curing is incomplete.CF40 shows good low temperature promoting activity to MEKP and the curing is complete.H₂O₂ and T4 play an important role in the low temperature curing activity of CF40/MEKP/UPR.T3 plays an important role in the complete curing of CF40/MEKP/UPR at high temperature.However,high amounts of CF40 will reduce the curing activity at low temperatures and delay the curing process.There is an instability that leads to increase of curing gel time as the storage time increases when the CF12N and UPR are premixed,In this paper,the phenomenon was confirmed by DSC,and the effect of CF12N content on the curing temperature in the premix was studied.The results show that the magnitude of onset temperature decreases with the increase of CF12N premix content.The effects of diethyl maleate and diethyl fumarate as model compound on CF12N were investigated,and the results showed that the gel time of CF12N and UPR premix was prolonged mainly because of the change of copper coordination structure,owing to the reaction of diethanolamine in CF12N and maleate double bonds in the unsaturated polyester.