| Ultraviolet Curable Coating(UVCC) in recent years is received more and more attention. UVCC has many advantages such as curing speed, environmentally friendly, energy conservation, wide application. UVCC can be divided into free radical system, cationic system and free radical-cationic hybrid system according to the curing mechanism. Radical system cures rapidly but its volumetric shrinkage is high, and it is vulnerable to oxygen inhibition, while cationic system has small volumetric shrinkage, strong adhesion, but its curing speed is small, the raw materials are few and expensive. Hybrid system can include the advantages of free radical system and cationic system. In this thesis, the polymerization kinetics, thermal stability, physical and mechanical properties of hybrid system were studied on the basis of researching free radical system and cationic system.In this thesis, a kind of free radical oligomer with low viscosity named hexahydrophthalic acid diglycidyl acrylate was first synthesized. The conditions of synthesis were determined by investigating the effect of reaction temperature, catalyst type and amount on the reaction process. The structure of raw materials and product was characterized by Fourier Transform Infrared Spectroscopy(FT-IR) and 1H nuclear magnetic resonance(1H NMR). Experimental results showed that expected product was obtained, the conversion rate of reaction was 97.8%.In this paper, the polymerization kinetics of free radical, cationic and hybrid system were studied by real-time FTIR for the first time. Thermal decomposition temperature and glass transition temperature of free radical, cationic and hybrid system curing film were determined by thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC). The best formula of hybrid system and the optimal performance of the curing films were obtained through measuring the hardness, tensile strength, elongation at break, adhesion and volume shrinkage of the three kinds of curing films. Physical and mechanical properties of the three kinds of curing films were analyzed and compared.The results showed that the radical polymerization of double bond and cationic polymerization of epoxy group could occur simultaneously in Hybrid system. The conversion rate of epoxy group for hybrid system was higher than that of epoxy group for cationic system, which demonstrated that the cationic photo-initiator(DPI·PF6) can be sensitized by the free radical photo-initiator (Irgacure 184). The temperature of three kinds of curing film were above 200℃when thermal decomposition 10wt%, which indicated three kinds of curing film had good thermal stability. The glass transition temperature(Tg) of free radical system curing film was 78.5℃, Tg of cationic system curing film was 99.25℃, while hybrid system curing film only had one Tg, and the glass transition region had a very wide distribution. Tg of hybrid system curing film was between that of radical system and cationic system curing film, which illustrated that interpenetrating polymer network was formed during the curing process of hybrid system. The best formula of hybrid system was determined through mixing free radical system and cationic system with the mass ratio of 2:1, the pendulum hardness, adhesion, the volume shrinkage, the tensile strength, elongation at break of the best hybrid system curing film was 0.83, 1 level, 5.23%, 22.15 MPa, 7.29%, respectively. Compared with free radical and cationic system, the hardness and mechanical properties of hybrid system curing film were better than those of the cationic system curing film, while closed to those of free radical system. The volume shrinkage of cationic system was significantly less than that of the radical system, while the volume shrinkage of hybrid system was something in between. |
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