Preparation and Properties of New UV-curable Naphthyl Epoxy Acrylates

New UV-curable di-functional naphthyl epoxy acrylates (DNEA) and multifunctional naphthyl epoxy acrylates (MNEA) were synthesized from naphthyl epoxy, acrylic acid, and hydroquinone as an inhibitor, and N,N´-dimethylbenzylamine (DMBA) as a catalyst. Different UV-curable liquid compositions were developed with naphthyl epoxy acrylates, different reactive diluents, active amine monomer and 1-hydroxycyclohexylphenyl ketone (Irgacure 184) as a photoinitiator. Thin films were prepared by curing these composite solutions using a high pressure mercury lamp. The change of double bond absorption band was identified by Fourier transform infrared spectra during the UV-curing process. Gel content, water absorption, the pendulum hardness, mechanical properties (static and dynamic) and thermal characterizations of the UV-cured films were investigated. The characteristic C=C absorption of the unsaturated acrylic groups at 1635 cm-1 gradually disappeared with UV-cured time and was no longer detectable after irradiation for 10 s. The gel content and the pendulum hardness increased with increasing irradiation time, and these gradually turned to constant values with increasing the irradiation time as the degree of polymerization reached its saturation. With the increase of mono-functional reactive diluents butyl acrylate in the compositions, the gel content, the pendulum hardness and mechanical properties of UV-cured films decreased, except for the water absorption. It was found that the glass transition temperature and the storage modulus of MNEA compositions were higher than those of DNEA compositions by the dynamic mechanical measurements, and the glass transition temperature of MNEA compositions was 142°C. The thermogravimetric analysis of UV-cured films revealed that films prepared from naphthyl epoxy acrylates exhibited excellent thermal stability.