Special Topics Review

Research progress on high refractive index optical resin

Yang Yutong¹, Wu Shufang^1,2, Liu Xiaoxuan¹

(1. School of Materials and Energy, Guangdong University of Technology, Guangzhou  510006, Guangdong, China; 2. Guangdong Shenzhan Industrial Co., Ltd., Jieyang  522061, Guangdong, China)

【Abstract】In recent years, high refractive index (n) optical resins have received widespread attention due to their excellent properties and have been widely used in advanced optoelectronic manufacturing. In this article, the design concept of increasing the n-value and Abbe number (υ) of optical resins was emphatically introduced, and the basic methods and important parameters for developing high n-value optical resins were briefly introduced. The research progress of high refractive index resins in the past decade was reviewed, and the design principles of high refractive index optical resins as well as the research status of sulfur-containing, halogenated, phosphorus containing, organic-inorganic hybrid high refractive index optical resins were summarized. Some applications of high refractive index optical resins in optical adhesives, light-emitting diode (LED) packaging materials, optical lenses, etc were also listed. Finally, the future development of high refractive index optical resins was prospected.

【Keywords】high refractive index; optical resin; research progress

Research and application of epoxy resin curing accelerator

Li Shuan^1,2, Zhang Baoyan¹, Yang Jiping², Zhang Si¹, Bai Yu¹, Wang Weihan¹

(1.AVIC Manufacturing Technology Institute Composite Technology Center, Beijing  101300, China; 2. School of Materials Science and Engineering, Beihang University, Beijing  100191, China)

【Abstract】Epoxy resin has been widely used in the fields of adhesives, coatings, and composite materials due to its excellent properties. In order to improve the curing rate, and for some heat sensitive components, temperature is an important indicator, it is necessary to lower the curing temperature. Therefore, it is necessary to add curing accelerator. In this article, the research progress and application of curing accelerators for epoxy resin, including tertiary amine and its salt curing accelerators, triphenylphosphine and its salt curing accelerators, substituted urea curing accelerators, imidazole and its salt curing accelerators, boron trifluoride amine complex curing accelerators, etc. were mainly summarized, and the future development direction was pointed out.

【Keywords】epoxy resin; curing rate; heat sensitive; curing temperature; curing accelerator; development direction

Progress of epoxy resin AB adhesive for LED encapsulation

Wang Qingyuan, Wang Wenjun

（Dalian Kaihua New Technology Engineering Co., Ltd., Dalian  116318, Liaoning, China）

【Abstract】In this paper, the development process of epoxy resin AB adhesive for LED encapsulation in China, from the initial application of liquid bisphenol A epoxy resin to cycloaliphatic epoxy resin, and recently the application of silicone hybrid cycloaliphatic epoxy resin was introduced. The formulation, performance, and research progress of epoxy resin adhesive for direct-insertion LED and digital tube encapsulation, epoxy resin AB adhesive for SMD RGB encapsulation, and epoxy resin AB adhesive for Mini LED encapsulation (such as compound amine cured epoxy resin AB adhesive, epoxy resin AB adhesive for matte display screen encapsulation, heat cation-cured epoxy resin AB adhesive, and anhydride-cured silicone hybrid cycloaliphatic epoxy resin AB adhesive, etc.) both domestically and internationally were shared in details. The development requirements and trends of future new epoxy resins were also discussed.

【Keywords】LED; epoxy resin; anhydride; silicone hybrid epoxy resin

 Research Report 

Preparation and performance study of multiple hydrogen bonds-based self-healing optical adhesive

Ye Dihui^1,2, Wang Jiasheng¹, Tang Fangcheng¹, Qiao Ligen^1,2, Qi Shengguang^1,2, Zeng Xiyang^1,2

(1.Guangzhou Lushan New Materials Co., Ltd., Guangzhou  510530, Guangdong, China; 2.Guangzhou Lushan Advanced Materials Co., Ltd., Guangzhou  510530, Guangdong, China)

【Abstract】Under the rapid development trend of consumer electronics and 5G communication, the demand for OCA optical adhesive in the field of optoelectronics continues to increase. However, during the use or processing of OCA optical adhesive, the problem of deterioration of material properties due to material defects often occurs, even further leading to the scrapping of materials, which makes OCA optical adhesive with self-healing ability show great market potential. In this paper, 2-ureido-4[1H]-pyrimidinone methacrylate (UPyMA) monomer containing quadruple hydrogen bonds was prepared, and UPyMA with mass fractions of 5%, 10%, 15%, and 20% was introduced into a copolymer system of polyurethane acrylate, 2-ethylhexylacrylate and isobornyl acrylate, respectively. A series of OCA optical adhesives with self-healing function were prepared by UV induced polymerization, with 2-hydroxy-2-methylphenylpropane-1-ketone as the photoinitiator and g-glycidoxypropyltrimethoxysilane as the tackifier coupling agent. Their structures, light transmittance, rheological properties, tensile properties, and self-healing properties were measured or characterized. The research results showed that, ⑴UPyMA and a series of OCA optical adhesives with self-healing function were successfully prepared. ⑵ All OCA optical adhesives did not produce bubbles or crystal dots, and their haze was all less than 0.50, which could meet the demand for OCA optical adhesives in the field of touch display products. ⑶ The 180° peel strength of OCA optical adhesives with different mass fractions (0-20%) of UPyMA was tested on stainless steel plates. When the UPyMA content was 15%, the bonding power was the highest (25.5 N). ⑷ The temperature dependence of storage modulus (G') and loss modulus (G") of OCA optical adhesives with different contents of UPyMA was analyzed. All OCA optical adhesives had good flowability and interfacial wetting properties at room temperature, which endowed OCA optical adhesives with good bonding properties. ⑸ The self-healing efficiency was significantly improved after adding UPyMA, providing favorable conditions for extending the service life of the material. ⑹ The high-temperature and high humidity aging resistance test showed that the prepared products could meet the application requirements, indicating that they had good aging resistance under high-temperature and high humidity conditions.

【Keywords】OCA optical adhesive; UPyMA monomer; UV induced polymerization; self-healing

Study on water resistance of amino acid functionalized molybdenum disulfide/epoxy resin composite materials

Cao Yuxin¹, Wu Mianyuan¹, Zhao Ming^1,3, Zhang Bin^1,2, Sun Mingming¹, Zhang Xugang¹, Zhang Xue¹, Li Jianhui¹

(1.Institute of Petrochemistry, Heilongjiang Academy of Sciences, Harbin  150040, Heilongjiang, China; 2. Harbin Engineering University, Harbin  150001, Heilongjiang, China; 3.Harbin University of Science and Technology, Harbin  150040, Heilongjiang, China)

【Abstract】Epoxy resin has made significant progress in various high-tech fields due to its excellent physical and chemical properties. In recent years, with the increasing demand for materials science in certain extreme environments, the need to improve the water resistance of epoxy resin has become increasingly urgent. In this paper, glycine (Gly) modified molybdenum disulfide (MoS₂) nanosheets were first prepared, and then they were used to modify epoxy resin, and Gly-MoS₂/epoxy resin composite materials were obtained. The structure, microstructure, mechanical properties, thermomechanical properties, and water absorption rate were characterized. The research results showed that, ⑴ The target products were successfully prepared, and MoS₂ nanosheets that had been exfoliated and modified by glycine were more evenly dispersed in the resin matrix. While ensuring appropriate lateral dimensions, the thickness was thinner and the compatibility with the matrix resin was better. ⑵ With the increase of the addition amount of nanosheets, the shear strength, tensile strength, and impact strength of resin systems at room temperature and high temperature after boiling were all improved. This was because the modified nanosheets were uniformly dispersed in the matrix and formed a more stable sea-island structure with the epoxy group, thereby improving the water resistance of the material itself. ⑶The thermomechanical performance tests showed that Gly-MoS₂ nanosheets played an important role in enhancing the temperature resistance of materials after water boiling. The water absorption test showed that Gly-MoS₂ greatly improved the water resistance of epoxy resin, and the water absorption rate decreased with the increase of Gly-MoS₂ nanosheets. The water resistance of the 1.00% Gly-MoS₂/epoxy resin system was the best, with a final water absorption rate of only 1.2% after boiling for 192 h.

【Keywords】nanocomposite material; polymer-based composite material; water resistance; mechanical property

Study on foam formation mechanism and application performance of pressure sensitive adhesive emulsion

Zhang Peng, Li Ying, Jia Yonghua, Wang Lege, Guo Ning,

Zhang Huiqin, Cheng Jingxuan, Li Huaxin, Lin Yuhui

(Hubei Aerospace Chemical New Materials Co., Ltd., Xiangyang  441003, Hubei, China)

【Abstract】Acrylic emulsion with different emulsifier dosages was prepared. The synthesis process of acrylic emulsion formula and the mechanism of foam formation were analyzed. The influence of emulsifier dosage, emulsion surface tension, emulsion solid content and defoamer on the foam and application performance of pressure sensitive adhesive emulsion was discussed. It was clear that the main reasons for foam formation were the high foaming rate of emulsifier, the high surface tension of foam, the high rotational viscosity because of high solid content of emulsion, and the selection and amount of defoamer. The research results showed that, ⑴ The emulsifier dosage not only had a great impact on the weather resistance of pressure sensitive adhesive and the stability of emulsion polymerization, but also had a great impact on the foam formation. Taking all factors into consideration, it was advisable to control the dosage of emulsifier at 0.50%. ⑵ The control of surface tension in the pressure sensitive adhesive emulsion system was directly related to the change of foam surface tension, and the emulsion surface tension should be controlled within the range of 38-40 mN/m. ⑶ The solid content of pressure sensitive adhesive emulsion had a direct impact on the rotational viscosity of emulsion and foam content, and also had a crucial impact on the application performance of emulsion. ⑷ Adding an appropriate amount of defoamer was the best scheme to improve the defoaming ability of pressure sensitive adhesive emulsion, and the application conditions were convenient. Different systems of defoamers had good effects on the elimination of foam. Mineral oil defoamer-A and polyether defoamer-C could provide good defoaming performance, weather resistance and film forming performance when the mass fraction was 0.05%, and their comprehensive application effect was better than other systems of defoamers. ⑸ The addition mode of defoamer could affect the dispersion performance of defoamer. The emulsification dispersion mode of emulsion could improve the dispersion of defoamer, reduce the foam of emulsion, and improve the film forming performance of emulsion.

【Keywords】pressure sensitive adhesive emulsion; foam; defoamer; emulsifier; surface tension

Research and development of UV-curing strippable pressure sensitive adhesive tape

Feng Xiao^1,2, Chen Yaqin^1,2, Zhang Xufeng^1,2, Hu Yongqi², Wang Zhihong², Li Yuchuan²

(1.Shandong Aozo New Materials Co., Ltd., Tengzhou  277599, Shandong, China; 2.Lu’nan Research Institute of Beijing Institute of Technology, Tengzhou  277599, Shandong, China)

【Abstract】The UV-curing strippable pressure sensitive adhesive tape was prepared by using polyacrylate pressure sensitive adhesive as the base adhesive, adding oligomers, multifunctional active diluents, and photoinitiators to form the adhesive solution, and then coating it on the PET-based film. The influence of the dosage of oligomers, multifunctional active diluents and photoinitiators on the properties of adhesive tape was studied. The optimal dosage of each component was optimized by testing the 180° peel strength and residual adhesive situation, and the UV curing process was characterized by using Fourier transform infrared spectroscopy. The research results showed that, ⑴ When the matrix of polyacrylate adhesive 129A was 100 parts, the amount of oligomer was 30 parts, the amount of active diluent was 50 parts, and the amount of photoinitiator was 0.8 parts, the UV-curing strippable adhesive tape prepared had outstanding adhesive reduction effect, no residue, and excellent comprehensive performance. The initial adhesion force with the wafer was as high as 10.3 N/25 mm, but it instantly lost adhesion after UV light irradiation, with an adhesion force of 0.3 N/25 mm. It was easy to peel off and met the special processing requirements of the chip. ⑵ The UV curing reaction process was characterized by using Fourier transform infrared spectroscopy. As the light curing process progressed, the infrared absorption peak of the carbon-carbon double bond gradually weakened to disappeared, and the carbon-carbon double bond crosslinking reaction occurred in the system, forming the crosslinked structure and causing the adhesive to change from "sticky" to "non sticky".

【Keywords】pressure sensitive adhesive; UV curing; oligomer; active diluent

 Process and Application 

Performance and influencing factors of polythiourethane sealant

Peng Yuqing, Qin Pengbo, Zhang Jianzheng

(AECC Beijing Institute of Aeronautical Materials, Beijing  100095, China)

【Abstract】In this paper, 5 different diisocyanates and 5 different catalysts were used to vulcanize polythioether system, and a new type of polythiourethane sealant material was produced. The composition of the material was analyzed by infrared spectroscopy, and the effects of different types of curing agents, catalysts, and polythioether raw adhesive on the mechanical and process properties of the material were compared. The research results showed that choosing IPDI and HMDI as the vulcanization systems for polythiourethane was relatively suitable. The catalytic efficiency of PC-41 and 1-methylimidazole was relatively moderate, and their catalytic efficiency for the reaction of isocyanates with water was not high, making them suitable as catalysts for the vulcanization of polysulfides. By characterizing the structure of polythiourethane sealant before and after vulcanization, it was demonstrated that the entire vulcanization reaction was complete. As the molecular weight of polythioether raw adhesive decreased, the tensile strength of the corresponding polythiourethane sealant increased, while the elongation at break decreased. Through the study of mechanical properties and oil resistance, it was found that the performance of polythiourethane sealant prepared by HMDI was superior. Compared with ordinary polythioether sealant, its mechanical properties had been improved while retaining oil resistance, and it had certain application value in the aerospace field.

【Keywords】polythiourethane; sealant; mechanical property; process performance

Preparation and properties of single component epoxy adhesive for electronic component bonding

Gong Qiuyan, Li Jiming, Qian Renjie, Wei Yunfeng, Wang Changyong

(Suzhou Adhesive Technology Co., Ltd., Suzhou  215101, Jiangsu, China)

【Abstract】The single component medium & low-temperature curing epoxy adhesive was prepared for electronic component bonding. The effects of different types of epoxy resins, fillers, and curing accelerators on their tensile shear strength, tensile strength, elongation at break, and curing properties were mainly studied. The research results showed that the single component epoxy adhesive prepared based on bisphenol F-type epoxy resin exhibited better bonding strength and lower hardness compared to bisphenol A-type and polyurethane modified epoxy resin. When used in combination with calcium carbonate, the tensile shear strength was significantly improved compared to silicon micro powder and kaolin, and the elongation at break reached about 55%, indicating a certain degree of elasticity. Using the same amount of accelerator, the curing promotion rate was in the order of modified urea accelerator > modified amine accelerator > imidazole accelerator. The developed single component epoxy adhesive product could be stored normally for 3 weeks at room temperature, was easy to use, had good curing efficiency and excellent mechanical properties, which could be applied to the structural bonding of electronic components.

【Keywords】epoxy resin; filler; accelerator; tensile shear strength; storage stability; medium & low-temperature curing

Effect of nano TiO₂ on the performance of oral adhesive

Su Jiafeng, Wu Feng, Li Qian, Zhang Xiaoxiao, Guo Qiaoling, Tian Guobing

(Department of Prosthodontics, Shanxi Medical University School and Hospital of Stomatology, Taiyuan  030006, Shanxi, China)

【Abstract】The oral adhesive was prepared by using 2,4,6-trimethylbenzoyl diphenyl phosphine oxide as the photoinitiator, methyl methacrylate as the monomer, white carbon black as the reinforcing filler, and nano titanium dioxide(TiO₂) particles as the antibacterial filler. The effects of nano TiO₂ size and addition amount on the mechanical and antibacterial properties of the adhesive were studied. The research results showed that, ⑴ The size of nano TiO₂ was an important factor affecting the mechanical properties of adhesive, and it was more suitable to use TiO₂ with a particle size of 30 nm for filling. ⑵ The addition amount of nano TiO₂ was another important factor affecting the mechanical properties of adhesive. When the addition amount of TiO₂ was 5.0%, the mechanical properties of the adhesive were significantly improved. ⑶ The size and addition amount of nano TiO₂ were important factors affecting its antibacterial performance. When the particle size of nano TiO₂ in the adhesive was 30 nm and the addition mass fraction was 5.0%, the antibacterial rate reached 97.46%, meeting the requirements of industry's antibacterial rate standard.

【Keywords】titanium dioxide; adhesive; photocatalysis; mechanical property; antibacterial performance

 Material Science 

Preparation of modified novel coating materials and their anticorrosion properties

Zhang Binying, Ye Yiming, Wen Zhenxing, Chen Jiayu, Qi Tao, He Xiaohong, Ma Aili

(Beijing Institute of Technology, Zhuhai  519088, Guangdong, China)

【Abstract】In order to solve the dispersion effect of nano SiO₂ and hexagonal boron nitride (BN) solid fillers in resin, surface treatment was carried out on both by using silane coupling agent (KH-560). By adding coupling agent as compatibilizer in the blend system, the compatibility with polydimethylsiloxane (PDMS) and epoxy resin was increased. The composite system was fully dispersed by using ultrasound to enhance the properties of the filler, resulting in the anticorrosion epoxy composite coating with hydrophobic effect. The in-depth research on its formula composition and various properties of coating samples was conducted by using orthogonal experiment, and its structure, contact angle, adhesion, electrochemistry, and resistance to medium corrosion were tested and analyzed. The research results showed that, ⑴ Silane coupling agent KH-560 was successfully grafted onto nano SiO₂ and hexagonal BN, with good compatibility in the resin. ⑵ Based on the analysis of the test indicators of the sample coating, the influence degree and optimal level of each filler addition on various performance indicators were determined. ⑶ The introduction of fillers significantly increased the contact angle of the coating, and the contact angle, i.e. the hydrophobicity of the coating, showed a positive correlation trend with the addition amount of three fillers. Range analysis showed that the optimal level for all three fillers was the fourth level, and the level of modified hexagonal BN addition had the most significant effect on the hydrophobicity of the coating. ⑷ According to the test results of acid, alkali and salt media resistance, it could be seen that the coating sample had better protection ability against alkaline and concentrated salt media than against acidic media, and there was basically no foaming, damage or corrosion phenomenon in alkaline and concentrated salt media. ⑸ The optimal formula in the orthogonal experiment was: PMDS addition of 0.5 g, modified nano SiO₂ addition of 2.0 g, and modified hexagonal BN addition of 1.00 g.

【Keywords】anticorrosive coating; hydrophobicity; formulation; surface modification; composite material