关键词: 邻甲基酚醛环氧树脂, 紫外光固化, 深层固化, 光固化动力学

Abstract: " Ultraviolet (UV) curing technology serves as a rapid curing method for liquid materials, where UV-irradiated photocurable resins undergo rapid crosslinking polymerization to form solid materials with a three-dimensional crosslinking network. Compared to traditional thermal curing technology, UV curing technology boasts notable advantages such as fast curing speed, low energy consumption, excellent gloss and hardness of the cured film, strong environmental friendliness, and a broad range of applications. Consequently, it has found widespread use in fields such as coatings, adhesives, copper-clad laminates, and electronic packaging. However, during the UV curing process, due to the absorption, scattering, and reflection of UV light by the surface layer, the light intensity significantly diminishes in deeper layers, resulting in insufficient crosslinking of the resin in these areas and thus compromising overall performance. Although UV-heat and UV-moisture dual-curing technologies can to some extent enhance the overall crosslinking degree of the resin, both methods have inherent limitations: UV-heat curing requires longer time and higher energy consumption and is unsuitable for heat-sensitive applications; UV-moisture curing is constrained by longer curing times and dependence on ambient humidity. Therefore, achieving efficient deep curing of resins solely through UV curing and enhancing overall performance has become a key area of research. To address issues such as low deep UV curing efficiency, poor thermomechanical properties, and weak adhesion in resin, a photosensitive o-cresol novolac epoxy acrylate resin (EOA) was successfully synthesized using o-cresol novolac epoxy resin and acrylic acid as raw materials. This was achieved by introducing double bonds through the reaction between the carboxyl groups of acrylic acid and the epoxy groups. Using EOA as the main resin, a systematic study was conducted on the effects of type I photoinitiator 907, type II photoinitiator ITX, and their dosages on the double bond conversion rates in both the surface and deep layers of the EOA cured film. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the photopolymerization kinetics of the surface and deep layers of the EOA cured film. Additionally, key indicators such as the thermomechanical properties, pencil hardness, and adhesion of the EOA coating film were evaluated. The results showed that when the photoinitiators 907 and ITX were combined in a 10:1 ratio at a total dosage of 4 wt%, the EOA cured film exhibited optimal comprehensive performance. Under these conditions, the double bond conversion rates for the surface and deep layers of the EOA cured film were 96.5% and 76.2%, respectively. The glass transition temperature (Tg) was 161.6 ℃, the storage modulus was 3,259.5 MPa, the coating film hardness was 5H, and the adhesion was rated at grade 0. The EOA coating film prepared using the aforementioned method not only overcomes the shortcomings of traditional UV curing technology, such as insufficient deep crosslinking and degraded overall performance, but also significantly enhances the crosslinking degree, thermodynamic properties, and mechanical performance of the coating film. By optimizing the ratio and amount of photoinitiators, this study achieves efficient deep curing of the resin solely through UV curing. Compared to traditional UV-heat or UV-moisture dual-curing processes, this approach offers notable advantages including ease of operation, high efficiency, and strong environmental friendliness."

Key words: o-cresol novolac epoxy resin, UV curing, deep curing, photocuring kinetics