Special Topics Review

Research progress on surface modification of silver powder and performance improvement of epoxy resin conductive adhesive

Li Xiaojuan^1,2, Gao Yunfei^1,2, Sun Tong^1,2, Wang Hong^1,2

(1.China Bluestar Chengrand Co., Ltd., Chengdu  610041, Sichuan, China; 2.China Bluestar Chengrand Chemical Co., Ltd., Chengdu  610041, Sichuan, China)

【Abstract】Conductive adhesive is a type of adhesive that combines conductivity and bonding properties. Due to its low processing temperature, low viscosity, and ability to form stable conductive pathways after curing, it is widely used in the fields of electronics and microelectronics. Epoxy resin conductive adhesive uses epoxy resin as the matrix resin and achieves excellent conductivity by adding conductive fillers (such as silver powder). However, there are differences between silver powder and epoxy resin, which may lead to insufficient dispersion and stability of silver powder in the resin, thereby affecting the performance of conductive adhesive. By surface modification of silver powder, its compatibility in resin can be significantly improved, thereby enhancing the conductivity and bonding properties of conductive adhesive. Common surface modification methods for silver powder, such as removing surface organic layers, treating with surface modifiers, and designing core-shell structures were summarized in this article, and the effects of modified silver powder on the dispersibility, conductivity, mechanical properties, and environmental adaptability of epoxy conductive adhesive were also described. Finally, the future development of silver powder surface modification and epoxy resin conductive adhesive was discussed.

【Keywords】surface modification of silver powder; conductive adhesive; epoxy resin; conductivity; bonding property

Application and prospect of PUR hot melt adhesive in coated abrasive tool industry

Meng Xia, Meng Qiang

(Zibo Sankyo Rikagaku Co., Ltd., Zibo  255086, Shandong, China)

【Abstract】With the increasing demand for environmental protection, the coated abrasive tool industry is accelerating its transformation towards environmentally friendly adhesive. Reactive polyurethane hot melt adhesive (PUR) has become one of the important development directions in the industry due to its flexibility and environmental advantages brought by its moisture curing properties. The application progress of PUR in coated abrasive tool was summarized in this article. Firstly, the core advantages of PUR in curing environmental protection, flexibility and adjustability, low application temperature, and wide adaptability were outlined. At the same time, the technical challenges it faced were analyzed, mainly including long curing and life time, limited temperature and humidity resistance, insufficient fluidity, high costs, and poor storage stability. In response to these issues, the relevant achievements of previous researchers in significantly improving the comprehensive performance of PUR through strategies such as raw material modification, filler reinforcement, and additive regulation were summarized in this article. On this basis, it was further proposed that in the future, through collaborative innovation in the industrial chain, development of bio-based raw materials, and integration of multi mechanism curing technologies, PUR could be developed towards higher performance, environmental friendliness, and more composite functions, in order to meet the stringent application requirements of the coated abrasive tool industry.

【Keywords】polyurethane; hot melt adhesive; coated abrasive tool

Research Report

Oriented boron nitride nanosheets to enhance the thermal conductivity of polyacrylate composite pressure sensitive adhesive

Liu Kai¹, Zhao Haichuan², Xie Yanlin³, Qu Xiongwei⁴

（1. Hebei Provincial Polyolefin Composite Pipe Technology Innovation Center, Langfang  065800, Hebei, China; 2. Kemibond Advanced Materials (Tianjin) Co., Ltd., Tianjin  300383, China; 3. Hebei Provincial Engineering Machinery Rubber and Plastic Hose Technology Innovation Center, Hengshui  053200, Hebei, China; 4. Hebei Key Laboratory of Functional Polymers, School of Chemical Engineering and Science, Hebei University of Technology, Tianjin  300401, China）

【Abstract】The traditional method of constructing a thermal conductive network requires expensive equipment and complex processes. A strategy for constructing oriented boron nitride nanosheets (BNNSs)/polyacrylate composite pressure sensitive adhesive (PSA) through calendering process was proposed in this article. Polyacrylate pressure sensitive adhesive was prepared by the method based on UV initiation and bulk polymerization, combined with the calendering process, and one to five layers of composite pressure sensitive adhesive (m-BNNSs/PSAs-Ori) were successfully prepared. Compared with the emulsion and solvent-based pressure sensitive adhesive, the preparation process did not contain organic solvents and media that need to be dried, and was environmentally friendly. Its thermal conductivity, orderliness, microscopic morphology, pressure sensitivity, viscoelasticity, thermal diffusion ability, electrical insulation properties were also studied. The research results showed that, ⑴ The thermal conductivity of composite pressure sensitive adhesive increased with the increase of thermal conductive filler content, and the composite material coated with only a single layer of pressure sensitive adhesive had the lowest thermal conductivity. Increasing the number of coating layers could significantly improve the thermal conductivity of composite pressure sensitive adhesive. When the filler content was 25%, the thermal conductivity of the composite pressure sensitive adhesive coated with 3 and 5 layers was increased by 474% and 543% respectively compared to pure pressure sensitive adhesive. ⑵ After multiple coatings and double roll shear treatments, the orderliness of organic boron nitride nanosheets (m-BNNSs) was improved, which was beneficial for promoting phonon transport and reducing phonon scattering. ⑶ With the increase of coating times, the nanosheets gradually tended to form parallel arrangements along the "plane" direction, which was consistent with the conclusion of X-ray diffraction analysis. ⑷ With the increase of coating times, the 180° peel strength of the material was correspondingly improved, the interlayer interaction of the adhesive was enhanced, and its cohesion was also improved. The introduction of modified boron nitride nanosheets (m-BNNSs) filler would result in a slight decrease in loop tack force of the material. ⑸ The addition of modified boron nitride nanosheets reduced the tanδ value of the composite pressure sensitive adhesive, with the lowest tanδ value observed when coated with 5 layers of composite pressure sensitive adhesive. The glass transition temperature (T_g) of the sample coated with 5 layers was also higher than that of pure pressure sensitive adhesive. ⑹ The thermal responsiveness of composite pressure sensitive adhesive increased with the increase of filler content, and the thermal conductivity effect was significant, further confirming the importance of increasing the amount of coating and shearing for improving thermal conductivity. ⑺ Compared with single-layer pressure sensitive adhesive, the surface resistivity and volume resistivity of the adhesive coated and sheared 5 times showed a slight decrease, with little difference in surface resistivity and a more obvious decrease in volume resistivity. However, it could fully meet the electrical insulation performance requirements of microelectronic devices for internal diaphragm materials. ⑻ In summary, when the filler content in the oriented boron nitride nanosheets/polyacrylate composite pressure sensitive adhesive (m-BNNSs/PSA-Ori) was 25%, the thermal conductivity of the sample coated with 5 layers reached 0.955 2 W/(m·K). Compared with the single-layer composite pressure sensitive adhesive, the thermal conductivity of the m-BNNSs/PSA-Ori composite pressure sensitive adhesive was significantly improved while maintaining the material's pressure sensitive properties, providing a new idea for the industrialization of thermal interface bonding materials.

【Keywords】boron nitride nanosheets; light-initiated polymerization; thermal conductivity; orientation; pressure sensitive adhesive

Preparation and characterization of reusable acrylate-type impregnating sealant

Wang Bo¹, Zheng Li¹, Song Lu², Xiang Shanglin²

(1. Nanjing ABNEN New Materials Co., Ltd., Nanjing  211299, Jiangsu, China; 2. College of Materials Science and Engineering, Nanjing Tech University, Nanjing  211816, Jiangsu, China)

【Abstract】The reusable acrylate-type impregnating sealant was prepared in this article by using materials such as isodecyl acrylate, hydroxyethyl methacrylate, trimethylolpropane triacrylate, reactive surfactants, benzoyl peroxide, and benzoquinone. The recycling efficiency and performance comparison of the impregnating sealant before and after recycling were tested, and the kinetics of the impregnating sealant before and after recycling were studied by differential scanning calorimetry, and the kinetic parameters such as reaction activation energy were obtained. The research results showed that the absorption peaks of the main functional groups of the impregnating sealant before and after recycling were basically the same, indicating that its main chemical components remained stable during the recycling process and had not undergone significant changes. As the amount of trimethylolpropane methacrylate increased, the recycling speed of the impregnating sealant slowed down and the recycling rate also decreased. The performance of the recycled impregnating sealant was not significantly different from that before recycling, so the reusable acrylate-type impregnating sealant had good application prospects and market promotion value.

【Keywords】acrylate; impregnating sealant; recycling; performance

Synthesis and properties of nano calcium carbonate modified polyacrylate emulsion

Zhuang Yuwei¹, Li Xiaoli², Zhang Yanchang¹, Wang Huafen¹,Du Juan³, Wang Man¹, Chen Baoyuan⁴, Liu Zhijie⁴

(1.High & New Technology Research Center of Henan Academy of Sciences, Zhengzhou  450002, Henan, China;2.Zhengzhou Industry Technicians College, Xinzheng  451150, Henan, China; 3. Institute of Materials, Henan Academy of Sciences, Zhengzhou  450046, Henan, China; 4. Henan Zhongbao Technology Co., Ltd., Zhengzhou  450002, Henan, China)

【Abstract】Using ammonium persulfate (APS) as the initiator, alkylphenol polyoxyethylene ether (OP-10) and sodium dodecyl sulfate (SDS) as the composite emulsifiers, vinyl acetate (VAC), ethyl acrylate (EA), butyl acrylate (BA), methacrylic acid (MAA) and hydroxyethyl methacrylate (HEMA) as the main monomers, ammonia solution as the pH regulator, and introducing surface modified nano calcium carbonate (CaCO₃) emulsion, a nano calcium carbonate modified polyacrylate emulsion was synthesized by the semi continuous seed emulsion polymerization method at a certain temperature. The effects of monomer dosage, initiator dosage, emulsifier dosage, reaction temperature, and nano calcium carbonate dosage on polymer properties were investigated. The polymer structure was characterized by using Fourier transform infrared spectroscopy and band assignment analysis was performed. The optimal experimental conditions were determined as follows: monomer dosage of 45%, initiator dosage of 0.20%, emulsifier dosage of 0.50%, polymerization reaction temperature of 72 ℃, and nano CaCO₃ dosage of 3.0%. In the future, the preparation process and application prospects of new formaldehyde-free environmental friendly wood adhesive with nano calcium carbonate modified polyacrylate emulsion as the substrate will be further studied.

【Keywords】nano calcium carbonate; polyacrylate emulsion‌; modification; synthesis; property

Process and Application

Study on the influence of nano calcium carbonate on the properties of single-component dealcoholized silicone sealant

Jiang Jinbo¹, Chen Jianjun^1,2, Huang Hengchao¹

（1.Guangzhou Baiyun Technology Co., Ltd., Guangzhou  510440, Guangdong, China; 2.Guangdong Baiyun Technology Co., Ltd., Foshan  528143, Guangdong, China）

‌【Abstract】Four representative types of nano calcium carbonate available on the market were selected in this article, and their BET specific surface area, particle morphology, and particle size were tested and characterized. Four types of nano calcium carbonate were applied to single-component dealcoholized silicone sealant, and the influence of different filling ratios of nano calcium carbonate was systematically investigated by designing experimental formulas. On this basis, the extrusion performance, tensile bonding performance, and tensile modulus of four types of nano calcium carbonate in single-component dealcoholized silicone sealant were discussed and analyzed. The research results showed that in the application of silicone structural sealant, it was recommended to choose calcium carbonate with moderate specific surface area, regular particle morphology, and narrow particle size distribution. In the application of weather-resistant silicone sealant, calcium carbonate with smaller specific surface area, regular particle morphology, larger particle size, and narrower distribution could be considered.

‌【Keywords】‌nano calcium carbonate; silicone sealant; dealcoholized; performance study

Analysis of factors affecting the application performance of polyether-based two-component

polyurethane adhesive

Zhang Peng, Xia Kui,Wang Lege, Luo Daoqi, Pang Panting, Mao Shenghua, Wu Peng, Zhou Zhihao

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

【Abstract】Starting from the formulation process and application environment, theoretical analysis and experimental research were conducted on polyurethane adhesive from multiple aspects such as synthesis process design and environmental temperature and humidity. The synthesis formulation process of polyether-based two-component polyurethane adhesive and the bonding process of thermoplastic polyurethane elastomers (TPU) airbags were analyzed, and it was clarified that the glass transition temperature (T_g) of polyester polyols, the proportion of trimethylolpropane (TMP), the selection of diisocyanate structures, and R value design were the main factors affecting the adhesive performance. The influence of environmental temperature and humidity on the bonding properties during the application process was also discussed. The research results showed that, ⑴ The setting of T_g, TMP ratio, and R value of polyester polyols directly affected the crosslinking density, weather resistance, and cohesive strength of adhesive, and played a core role in meeting the requirements of bonding performance and interface rigidity. The study suggested that the T_g of polyether polyol should be set at 67 ℃, the ratio of polyether polyol resin to TMP should be controlled at 100∶3, and the R value should be set at 1.1. At this point, the cohesive strength, weather resistance, and crosslinking density of the adhesive reached a relatively optimal level. ⑵ The structure of diisocyanates was an important factor affecting the anti-bending performance of adhesive at the bonding interface of airbags during the application stage, as well as their polymerization stability. To cope with the impact of repeated deformation of airbags on the bonding interface and ensure the polymerization stability and storage performance of the adhesive, it was recommended to use isophorone diisocyanate (IPDI) as the key crosslinking monomer. ⑶ Polyurethane adhesive, due to its special formula design, had a direct impact on the crosslinking density, interfacial strength, curing time, and operating window period of the adhesive with the changes in environmental temperature and humidity. It was proposed that the optimal application performance should be achieved when the environmental temperature was controlled between 20-25 ℃ and the environmental humidity was controlled between 40%-60%RH.

【Keywords】polyurethane adhesive; TPU airbag; bonding strength; polymerization stability

Study on preparation and properties of silane modified polyether-epoxy hybrid adhesive

Luo Xubiao¹, Chen Jianjun^1,2, Gao Minhua¹, Huang Hengchao¹, Miao Mingsong¹

(1.Guangzhou Baiyun Technology Co., Ltd., Guangzhou  510440, Guangdong, China; 2.Guangdong Baiyun Technology Co., Ltd., Foshan  528143, Guangdong, China)

【Abstract】A series of two-component silane modified polyether-epoxy hybrid adhesive were prepared by using silane modified polyether resin as the main component and epoxy resin as the system reinforcing agent. The effects of silane modified polyether polymers (MS1, MS2), calcium carbonate (NCC, GCC) ratios, and silane coupling agent types (KH-550, KH-560, KH-792) on the properties of hybrid adhesive were studied. The research results showed that, ⑴ In this hybrid system, resin MS2 had a faster reaction rate compared to resin MS1, while also having higher tensile strength, elongation at break, and shear strength. Taking into account the opening time of construction and the curing speed of adhesive, it was suitable to choose a ratio of n(MS1): n(MS2)=1:3 for the MS polymer in the formula. ⑵ Under the condition of constant total amount of calcium carbonate, NCC exhibited better mechanical properties (tensile strength, elongation at break, shear strength) and droop (anti sagging) than GCC, but GCC showed better workability (extrusiveness) than NCC. Taking into account both factors, the optimal ratio of n(NCC): n(GCC)=3:1 was chosen as the formula filler. ⑶ Compared to epoxy-based and monoamino-based silane coupling agents, the catalytic rate of diamino-based silane coupling agent KH-792 was higher, and the hybrid adhesive prepared exhibited superior mechanical properties in terms of tensile strength, shear strength, and hardness.

【Keywords】silane modified polyether resin; epoxy resin; hybrid adhesive; mechanical property

Study on machine adaptability of high-weight trademark paper with new packaging adhesive

Liu Youwei, Cao Changqing, Yan Xiaodong

(Shanghai Tobacco Group Co., Ltd., Shanghai  201315, China)

【Abstract】In response to the demand for high-speed cigarette packaging, the compatibility and machine adaptability of new type (type 100-B) water-based packaging adhesive for cigarette with different weights of Zhonghua (Soft) trademark paper were studied. Through practical packaging machine tests, the comprehensive effects of adhesive properties (viscosity, solid content, open time, glass transition temperature, initial tack) and trademark paper weight on packaging quality (bonding strength, substrate damage), production process stability (defect rejection rate, paper breakage rate, equipment adhesive accumulation), and sensory evaluation of finished cigarette packs (gripping feel, premium quality perception) were investigated. The research results showed that the initial tack, flowability, glass transition temperature, and open time of packaging adhesive were key factors affecting high-speed adaptability. The increase in the weight of trademark paper significantly reduced the bonding effect and production stability, but enhanced sensory evaluation. Under the premise of ensuring high-speed and stable production, the combination of 112 g/m² trademark paper and type 100-B packaging adhesive was currently the optimal solution to enhance the sensory and risk control of Zhonghua (Soft) packaging. If pursuing more significant sensory enhancement, 127 g/m² trademark paper had the potential, but resources need to be invested to solve the process stability challenges it brought. This study provided practical basis for the application of high weight packaging materials in high-speed cigarette machines and the performance design of supporting adhesive.

【Keywords】cigarette packaging adhesive; water-based adhesive; trademark paper weight; machine adaptability; bonding strength; sensory evaluation; high-speed packaging

Material Science

Determination of hydroxyl content in CO₂-based polycarbonate polyols

Yu Yujian^1,2, Qin Yu¹, Liu Gandong¹, Guo Yongchun¹, Zhang Lujun^1,3

(1. Institute of Chemistry Co., Ltd., Henan Academy of Sciences, Zhengzhou  450002, Henan, China; 2. Henan Keqin New Materials Co., Ltd., Jiaozuo  454000, Henan, China; 3.Henan Academy of Sciences, Zhengzhou  450046, Henan, China)

【Abstract】The prominent problems in the determination of hydroxyl content by chemical methods were summarized in this article, three methods (national standard method, industry standard method, catalytic method) were explored, and the stability and accuracy of hydroxyl values of different types of CO₂-based polycarbonate polyols by using a six parallel test method were tested. Based on the test results, polyurethane materials were prepared by using isocyanate index (R value) of 1.01 and diphenylmethane diisocyanate (MDI) according to their hydroxyl content. The synthesized polyurethane material was analyzed by —NCO content measurement, Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR). The research results showed that, ⑴ Three methods were used to measure the hydroxyl value of sample 2 in six parallel tests, and the repeatability standard deviation was less than 0.4 mg KOH/g. Among them, the catalytic method had best repeatability and stability. ⑵ Sample 4 was selected as the raw material to synthesize polyurethane material, further verification was carried out through testing such as —NCO content, infrared spectrum, and nuclear magnetic resonance hydrogen spectrum. It was found that the test results of catalytic method could meet the hydroxyl value testing requirements for synthesizing polyurethane materials, and had high reliability and accuracy. ⑶ The catalytic method for determining hydroxyl values had the advantages of good repeatability, small deviation, and more accuracy. It also avoided the use of toxic reagents such as odors and carcinogens, was more friendly to humans and the environment, had high testing efficiency, simple operation, and wide applicability. It met the needs of CO₂-based polycarbonate polyol enterprises for rapid and accurate testing of hydroxyl values in production and experimental research processes.

【Keywords】CO₂-based polycarbonate polyols; hydroxyl value; secondary hydroxyl; 4-dimethylaminopyridine