| UV-curable coatings have the excellent characteristics of the fast curing speed, low environmental pollution, low energy consumption, etc. Because of their technical advantage, they have great potential for development in recent years, in which people stress environmental protection and energy saving. However, the UV-curable coatings are difficult to apply to thick films and three-dimensional complex objects. So UV-heat dual curing technologies have emerged to overcome the shortcoming of UV curing technology and to expand the applications scope of the UV curing technology. In this thesis, the UV-heat dual curing coatings were synthesized. Their storage stabilities and curing kinetics were studied.Formulations of resin synthesis and coatings were characterized to analyze their performances including the storage stabilities. The factors that influenced the storage stabilities were investigated. The optimal resin synthesis formula was optimized as the equivalent ratio of carboxyl and epoxy was 1.03:1, the amount of catalyst triethylamine was 0.9 wt%, the amount of inhibitor was 0.02 wt%. The synthesized resin could be conducted an accelerating storage at 50 ℃ for 20 days without a significant viscosity rising, which shows a good storage stability.In order to prepare the UV-curable coatings with excellent storage stabilities, the modified epoxy acrylate resin was synthesized to formulate the UV-curable coating together with a reactive diluent, photoinitiator, inhibitor. The factors effected the storage stabilities were studied. FT-IR and gel permeation chromatography were used to study the change during the storage. The results indicated that when 20-30 wt% reactive diluent and 3 wt% Darocur 1173 were added, the coatings could be stable after an accelerated storage which lasted more than 7 days, which indicated a good storage stability. After a 7-day accelerated storage, the weight-average molecular weight and number-average molecular weight increased by 393 g/mol and 403 g/mol, respectively. The C=C double bond ratio were reduced by 4.9%. There was no difference of coatings properties compared to the previous samples without the accelerated storage.Kinetic of UV-heat dual-curing epoxy acrylate coatings was studied by the way of changing the reactive diluents, photoinitiators, pigment, etc. An effective curing was achieved. The results indicated that the reactive diluents had a great impact on the curing. Gel ratio of films could be up to 90 wt% when the amount of reactive diluents was 10 wt%. Darocur 1173 and Igacure 819 were mixed according to mass ratio of 1:1 to provide a compound initiator, which could broaden the absorbing range of initiator and improve the photoinitiation efficiency. Because of the radical coupling termination, the photoinitiation efficiency declined when the concentration of compound initiator exceeded 4 wt%. After a 10 s UV irradiation, the film gel ratio was up to 90 wt%, the gloss could be 95 to 105, the adhesion grade was 0 to 1, and the pencil hardness was 1 H to 2 H. Films was obtained with great abrasion resistance, alkali resistance and alcohol resistance.With the research of this thesis, not only the UV-curing of three-dimensional subjects and complete curing of thick films could be achieved, but also the storage period of coatings was prolonged, which avoided the properties degradation and coatings gelling because of the unstable storage. The application scopes of both heat-curable and UV-curable coatings were expanded. |
PDF Full Text Request