Special Topics Review

Evolution trend and research progress of solvent-free silicone resin in optical fiber and electrical engineering fields

Li Chengbin^1,2, Jia Rubin^1,2, Li Ping^1,2, Ni Yanrong^1,2, Wang Lei^1,2,Wang Guozhu^1,2, Xie Ruiyun^1,2, Zhang Dan^1,2

(1.School of Cable Engineering, Henan Institute of Technology, Xinxiang  453003, Henan, China; 2. Henan Key Laboratory of Wire and Cable Structures and Materials, Xinxiang  453003, Henan, China）

【Abstract】The comprehensive performance of solvent-free silicone resin is outstanding, and it has the performance characteristics of both inorganic and organic materials, which has great potential for application in the fields of optical fiber and electrical engineering materials.In the field of optical fiber, solvent-free silicone resin is particularly suitable as an optical fiber coating due to its advantages such as good thermal stability, high transparency, wear resistance, and moisture resistance. Solvent-free silicone resin is also an essential insulation material in motor and electrical products, which can effectively improve the dielectric, thermal conductivity, safety, and mechanical strength of motor and electrical winding coils. In this article, the development history, molecular structure, performance characteristics, and application and research progress of solvent-free silicone resin in the fields of optical fiber and electrical engineering were reviewed, the development trend of solvent-free silicone resin was summarized, and the prospect for future development was provided.

【Keywords】solvent-free; silicone; electrical insulation impregnating paint; optical fiber coating

Analysis of T-peel testing technology and standards for adhesive used in structural reinforcement

Liu Zhiqi^1,2, An Shaodu^1,2, Zhang Mingxuan^1,2, Yao Shufang^1,2, Ma Haixu^1,2, Zeng Bing^1,2

（1.China Academy of Building Research Co., Ltd., Beijing  100013, China; 2.CABR Testing Center Co., Ltd., Beijing  100013, China）

【Abstract】The T-peel testing regulations and technical requirements stipulated in the relevant standards for adhesive used in structural reinforcement (including steel bonding adhesive, impregnating adhesive, anchoring adhesive, crack adhesive, etc.) were compared and analyzed in this article. The impact of the technical process of the T-peel testing on the measurement results was also discussed. By comparing relevant standards issued both domestically and internationally, the impact of adhesive layer thickness on the peeling performance in steel-steel T-impact peeling length testing was explored. Relevant experiments were conducted, and initial progress was achieved. Finally, the evaluation was conducted based on the testing techniques and methods specified in relevant domestic and international standards. The research results showed that, ⑴ There are significant differences in the standards for different T-peel tests cited in this article, and none of them have specific limitations for structural adhesive used in different industries and fields. Due to significant differences in the performance evaluation and testing techniques of materials themselves, there is still a lot of work to be done in the formulation and revision of standards to standardize the application of T-peel testing methods in the adhesive industry. ⑵ The current standards related to adhesive T-peel reinforcement, both domestically and internationally, do not explicitly specify the range of adhesive layer thickness for test specimens. The adhesive layer thickness is only recorded during the test of T-peel length, and the recorded value of adhesive layer thickness does not affect the judgment of the results. The T-impact peeling ability is an important indicator for measuring the toughness of structural adhesive, and the thickness range of the adhesive layer will significantly affect the T-impact peeling ability. The lack of clarity in the standard in this regard is not conducive to the determination of T-impact peeling length or impact resistance, and nor can it objectively reflect the true test of adhesive toughness. ⑶ The current domestic standards for T-peel testing of reinforcement adhesive are not detailed, uniform, and sometimes unreasonable in terms of testing methods, which have caused significant confusion for manufacturers, design units, and testing institutions. Therefore, it is necessary to strengthen the research on T-peel testing, introducing more comprehensive standards, enhancing its scientificity and applicability, and promoting technological advancements in the evaluation of reinforcement adhesive performance and the healthy development of the industry.

【Keywords】adhesive; T-peeling; standard; testing technology

Current status and strategies of China's participation in international standardization activities in the field of sealants

Qian Lumin^1,2

(1.Shanghai Plastics Research Institute Co., Ltd., Shanghai  201702, China; 2.Shanghai Rubber Products Research Institute Co., Ltd., Shanghai  201702, China)

【Abstract】The current status and development trend of China's participation in international standardization activities in the field of sealants were analyzed in this article. Guided by the “National Standardization Development Outline” and “ISO Strategy 2030”, the ways and strategies for China's participation in international standardization activities in the field of sealants at the current stage were summarized. At the same time, the prospects of international standards in the field of sealants were put forward.

【Keywords】sealant; international standard; ISO; strategy

 Research Report 

Research on the strength correlation of corn starch adhesive

Zeng Jing¹, Li Shuang¹, Li Wei¹, Xu Feng¹, Qiao Xiangdong¹, Jiang Wei², Liu Xinghai³, Han Xiaoxue^1,,3

(1.Xiangyang Hongyan Industrial Co., Ltd., Xiangyang  441000, Hubei, China; 2. Hubei Xinye Tobacco Slice Development Co., Ltd., Wuhan  430056, Hubei, China; 3. Electronic Information School, Wuhan University, Wuhan  430072, Hubei, China.)

【Abstract】A corn starch adhesive with strong bonding strength for corrugated box was prepared by using corn starch as the main raw material, borax as the crosslinking agent, sodium hydroxide as the oxidant, aluminum sulfate octadecahydrate as the waterproofing agent, polyvinyl alcohol modified urea-formaldehyde resin as the bonding strength enhancer, and water as the solvent. The formulation of corn starch adhesive for corrugated box was optimized and studied. The single-factor variable method was used to investigate the effects of factors such as the amounts of corn starch, borax, sodium hydroxide, aluminum sulfate octadecahydrate, polyvinyl alcohol modified urea-formaldehyde resin and water on viscosity and bonding strength. At the same time, the central composite design (Box-Behnken Design) in response surface methodology was used to study the impact of the more influential components in the formulation on the bonding strength of corn starch adhesive, with bonding strength and viscosity as the indicators, and the optimal formulation was selected based on actual production. The research results showed that the optimal formulation (mass ratio) was as follows: 12.5% corn starch, 3.7% sodium hydroxide solution, 0.42% borax, 0.15% aluminum sulfate octadecahydrate, 1.75% polyvinyl alcohol modified urea-formaldehyde resin, and 81.48% water. The preparation process was stable and reliable, with low preparation costs and certain practical value.

【Keywords】adhesive; corn starch; bonding strength; viscosity; response surface optimization methodology

Optimization of preparation process of dehydrated castor oil/maleic anhydride adduct and its application in pressure sensitive adhesive

Liu Xingyu¹, Wang Yan¹, Sun Yuewen¹, Ye Zihan², Xu Panpan¹, Bi Yanlan¹, Li Jun¹

(1. Key Laboratory of Henan Province, School of Food Science and Technology, Henan University of Technology, Zhengzhou  450001, Henan, China; 2. School of International Education, Henan University of Technology, Zhengzhou  450001, Henan, China)

【Abstract】Using dehydrated castor oil and maleic anhydride as raw materials, with acid value as the evaluation index, the optimal preparation process of dehydrated castor oil/maleic anhydride adduct was optimized by studying the effects of substrate ratio (molar ratio) of maleic anhydride to dehydrated castor oil, reaction temperature, and reaction time on the degree of Diels-Alder reaction addition. The research results showed that, ⑴ The substrate ratio, reaction temperature, and reaction time all had a significant impact on the degree of addition of dehydrated castor oil/maleic anhydride adduct, and the order of influencing factors was: reaction temperature>substrate ratio>reaction time. The optimal preparation process was: the substrate ratio of 12∶10, reaction temperature of 120 ℃, and reaction time of 3.0 h. At this point, the performance of the adduct was optimal, and the acid value of the adduct could reach 60.9 mg KOH/g. ⑵ Dehydrated castor oil and maleic anhydride effectively underwent DA reaction, and the adduct formed by the reaction of one molecule of dehydrated castor oil and one molecule of maleic anhydride was the main one. ⑶ Dehydrated castor oil/maleic anhydride adduct had good fluidity and thermal stability, and the introduction of maleic anhydride increased its glass transition temperature. ⑷ The introduction of maleic anhydride endowed dehydrated castor oil with more polar functional groups, thus enhancing the peel strength and tack of pressure sensitive adhesive when copolymerized with epoxy soybean oil. Compared with epoxy soybean oil-based pressure sensitive adhesive, the peel strength of pressure sensitive adhesive prepared by copolymerizing dehydrated castor oil/maleic anhydride adduct with epoxy soybean oil was increased by about 2 times, and the tack was increased by about 10 times.

【Keywords】dehydrated castor oil; maleic anhydride; Diels-Alder reaction; acid value; structural characterization; pressure sensitive adhesive; bonding strength

Development of high performance epoxy-bismaleimide adhesive

Wan Chuansong, Li Yadong, Yu Xinhai

(College of Chemistry and Chemical Engineering, Donghua University, Shanghai  201620, China)

【Abstract】Five kinds of high performance epoxy-bismaleimide adhesives (K-1~K-5) with excellent comprehensive properties were prepared by using different epoxy resins, epoxy chain extenders, bismaleimide resins, curing agents, initiators, etc. The viscosity, gelation time, apparent activation energy, dielectric property, tensile shear strength at variable temperature, water absorption rate and other indicators were tested. The research results showed that, ⑴ The five different epoxy adhesives prepared had low viscosity at room temperature, and their viscosity was below 400 mPa·s after exceeding 70 ℃, which made them easier to mix, apply and penetrate with other materials. ⑵ The activation energy of five epoxy resin adhesives ranged from 61.5 to 71.0 kJ/mol, demonstrating a high level of reactivity. ⑶ The dielectric loss of five formulation adhesives was less than 2.1%, and the dielectric constant of the materials was between 3.9 and 4.5, demonstrating good dielectric properties. ⑷ Among five formulations of epoxy adhesives, K-5 had overall better shear strength at high and low temperatures than the other four, with a shear strength of over 12 MPa at both high and low temperatures. It had excellent high and low temperature stability and could meet the basic requirements of matrix resin strength and high and low temperature resistance and was a high performance epoxy adhesive. ⑸ The water absorption rate of five formulations of epoxy adhesives ranged from 0.29% to 0.57%, all below 1.00%, indicating good hydrophobicity. Among them, K-5 had a water absorption rate of 0.29%, which was the lowest among five epoxy adhesives, and could meet the electrical performance requirements as well as various demands in humid environments.

【Keywords】epoxy resin; bismaleimide; adhesive; high performance

 Process and Application 

Research on the selection of UV adhesive for VR optical module lens bonding

Li Ke¹, Song Hanyu¹, Liu Meiyan¹, Chen Wen¹, Liu Chaohong², Rao Yi¹, Yang Chun¹, Li Jiyin¹

(1. Goertek Optical Technology Co., Ltd., Weifang  261031, Shandong, China; 2.Goertek Inc., Weifang  261031, Shandong, China)

【Abstract】Cycloolefin copolymer (COC) is commonly used in VR product lenses, with the characteristics of low water absorption and ultra-low stress. However, the bonding difficulty of COC materials is high, and there is relatively little research on such bonding problems. In order to better study the key factors of UV adhesive selection in VR optical module, the characteristics of VR optical module structure and Pancake lens COC material were focused in this study. By simulating the application environment of VR optical modules, two key conditions of high temperature and humidity, and temperature shock were designed in the laboratory. 30 kinds of UV adhesive (G1-G30) from different manufacturers were selected and tested for the durability of modules assembled with adhesive with different thermal expansion coefficients, glass transition temperature (T_g), toughness, and storage modulus at low temperature under these simulated conditions. And by analyzing the relevant parameters such as the elongation at break and T_g of UV adhesive at room temperature, the relationship between them and the final bonding effect were explored, in order to provide reference for the practical selection and application of COC material lens bonding adhesive. The research results showed that by exploring four key factors of UV adhesive, including thermal expansion coefficient, T_g point, toughness, and storage modulus at low temperature, it was found that G2 and G3 had two T_g points above and below zero, low storage modulus at low temperature (less than 1 000 × 10⁶ Pa), and good toughness (elongation at break greater than 400%, Young's modulus less than 60 × 10⁶ Pa), which could resist cold and hot temperature impacts, and exhibited good thrust and optical performance. G2 and G3 could maintain the stability of VR module optical imaging and solve the problem of adhesive cracking in VR module temperature shock testing. A feasible selection basis for the adhesive of COC material bonding was provided in this article, which had certain guiding significance in practical production.

【Keywords】UV adhesive; VR module; glass transition temperature; temperature shock; cycloolefin copolymer

Preparation and properties of polyurethane hot melt adhesive for laser holographic hot stamping

Chen Junhua^1,2, Liu Can¹, Shen Xiao¹, He Guangying¹, Tang Weican¹, Zhu Sheng³, Li Xiang^1,2

(1.School of Environmental and Chemical Engineering, Zhaoqing University, Zhaoqing  526061, Guangdong, China; 2.Guangdong Provincial Key Laboratory of Environmental Health and Land Resource, Zhaoqing  526061, Guangdong, China; 3.Guangdong Leibao Optoelectronic Technology Co., Ltd., Sihui  526200, Guangdong, China)

【Abstract】In this article, isocyanates, polyols, and polypropylene glycol were used to prepare prepolymers with different isocyanate indices (R values), and then crosslinking agents were added to synthesize one-component polyurethane hot melt adhesive. After conducting tests on its —NCO content, viscosity, adhesion, and hardness, the one-component polyurethane resin with good adhesion was synthesized. Then, self-made polyurethane resin, acrylic resin, terpene resin, and surfactant were blended and modified to prepare polyurethane hot stamping adhesive, and the hot stamping performance of the laser holographic hot stamping film made of polyurethane hot stamping adhesive was studied. The research results showed that, by comparing the viscosity, adhesion, and hardness of polyurethane resin with different R values, it was found that the one-component polyurethane resin (PU203) prepared with R=1.3 had better comprehensive properties. The laser effect of polyurethane hot stamping adhesive coating was clearer and the pattern was more complete. The use of polyurethane hot stamping adhesive could significantly improve the hot stamping performance of laser holographic hot stamping film.

【Keywords】polyurethane; hot melt adhesive; one-component; hot stamping adhesive

Effect of polyurethane resin on the heat resistance bonding properties of one-component moisture curing sealant

Guo Meng¹, Zhao Zhaolin¹, Bian Feng¹, Zhou Yamin², Peng Xiaolan²

(1.Guangdong Pustar Adhesives and Sealants Co., Ltd., Dongguan  523646, Guangdong, China; 2.School of Chemical Engineering and Energy Technology, Dongguan University of Technology, Dongguan  523808, Guangdong, China)

【Abstract】Different types of end —NCO polyurethane resins were synthesized, and the effects of polyurethane resin content, R value, isocyanate type, and polyether polyols with different molecular weights on the heat resistance bonding of polyurethane sealant were discussed. The research results showed that, ⑴Polyurethane sealants with different polyurethane resin contents had a bonding surface of 100% CF after curing at room temperature for 7 d, but after high temperature treatment at 120 ℃, some polyurethane sealants and primers exhibited detachment. ⑵ The heat resistance bonding of sealant was greatly affected by the —NCO% content. When the —NCO% content of sealant was greater than 1.10%, the holding time of 90% CF could reach 18 hours.⑶ The addition of monomers could enhance the heat resistance bonding, and the HDI trimer with moderate reactivity and suitable structure had the best effect. ⑷ The sealant prepared with MDI had the best heat resistance bonding effect, followed by HDI and TDI, and IPDI was the worst. ⑸ Changing the relative molecular weight of polyether polyols had a slight difference in the heat resistance bonding of the sealant, but the impact was not significant.

【Keywords】polyurethane; heat resistance bonding; sealant; —NCO group

 Material Science 

Study on polymerization behavior and properties of meta-substituted benzoxazine resin

Ren Shitong^1,2, Wu Aiyan¹, Tong Tong¹, Tian Fangjing¹, Du Yonggang^1,2

(1.School of Materials Science and Engineering, Shijiazhuang Tiedao University, Shijiazhuang  050043, Hebei, China; 2.Hebei Key Laboratory of Advanced Materials for Transportation Engineering and Environment, Shijiazhuang  050043, Hebei, China)

【Abstract】The polymerization behavior and properties of benzoxazine resin are closely related to its molecular structure. Current research has mainly focused on the effects of para-substituents on the polymerization behavior and properties of benzoxazine resin, while studies on meta-substituted benzoxazine resin are relatively scarce. In order to further investigate the structure-property relationship of benzoxazine resin, bis-functional benzoxazine resins using meta-substituted anilines and meta-substituted phenols as raw materials were prepared in this paper. The molecular structure of benzoxazine resin was characterized by Fourier transform infrared spectroscopy (FT-IR), and the polymerization behavior, thermomechanical properties, and thermal stability of different structures of benzoxazine resin were studied by differential scanning calorimetry (DSC) and dynamic thermomechanical analysis (DMA), respectively. The research results showed that, ⑴ Meta-substituted benzoxazines were successfully synthesized from meta-substituted anilines and meta-substituted phenols. ⑵ For meta-substituted aniline type benzoxazines, the introduction of meta-substituent lowered the polymerization temperature of benzoxazines. For meta-substituted phenol type benzoxazine, the electron-donating methyl substituent significantly increased the polymerization temperature of benzoxazines, while the electron-withdrawing methoxy and chlorine substituents significantly decreased the polymerization temperature, especially when the substituent was methoxy, the polymerization temperature was the lowest. ⑶ The influence of meta-substituents on the thermomechanical properties of benzoxazine resins was more complex. The introduction of electron-withdrawing substituents at the meta position of phenol reduced the thermal stability of the polybenzoxazine, and aromatic diamine type polybenzoxazine had better thermal stability compared to diphenol type polybenzoxazine.

【Keywords】meta-substituent; benzoxazine; polymerization behavior; thermomechanical property