Special Topics Review

Research progress of high performance pressure sensitive adhesive

Xing Wenxu, Liu Caizhao, Zhang Xugang, Sun Mingming, Zhang Bin

(Institute of Petrochemistry, Heilongjiang Academy of Sciences, Harbin  150040, Heilongjiang, China)

【Abstract】Pressure sensitive adhesive, as an important functional bonding material, is widely used in electronics, automotive, and packaging industries. The research progress of different types of pressure sensitive adhesive, covering the structural characteristics, performance improvement, and modification methods of acrylate, silicone, natural rubber, hot melt and polyurethane pressure sensitive adhesive was systematically summarized in this article, and the relationship between their molecular structures and adhesion properties was analyzed. At the same time, the application of new modification technologies in improving the performance of pressure sensitive adhesive was explored. Finally, the future development trends of pressure sensitive adhesive were discussed, with a focus on sustainability, intelligence, and multifunctionality research directions. It was hoped that this would provide theoretical basis and practical guidance for the design and development of high performance pressure sensitive adhesive.

【Keywords】pressure sensitive adhesive; acrylate; silicone; research progress

Research status of biomimetic intelligent adhesion interface

Zhou Jianwei¹, Yao Yansheng¹, Kan Honglin^2,3

(1.School of Mechanical and Electrical Engineering, Anhui Jianzhu University, Hefei  230601, Anhui, China; 2.School of Artificial Intelligence, Anhui Polytechnic University, Wuhu  241000, Anhui, China; 3.Anhui Zhengyang Mechanical Technology Co., Ltd., Lu'an  237000, Anhui, China)

【Abstract】The intelligent adhesion interface, especially the interface that switches adhesion force on demand, has shown great potential for applications in wearable devices, robots, and biological detection. Three representative biomimetic objects—gecko, tree frog, and octopus were focused in this article. The JKR model, capillary wet adhesion model, and suction negative-pressure model were used to explain the adhesion mechanisms of three objects, and the various biomimetic intelligent adhesion interfaces and research status in the field of biomimetic switchable adhesion (such as climbing robot, soft fixture, and wearable device) were systematically analyzed. Finally, the future development of biomimetic intelligent adhesion interface was discussed.

【Keywords】switchable adhesion; biomimetic intelligent adhesion interface; micro-nanostructure

Research Report

Influence of the mixing of flake silver/sphere silver on the performance of electrically conductive adhesive

Sang Guangyi, Jiang Chao, Gong Wensheng, Lai Lifeng, Tao, Xiaole, He Yongfu

(Hangzhou Zhijiang Silicone Chemical Co., Ltd., Hangzhou  311200, Zhejiang, China)

【Abstract】An electrically conductive adhesive (ECA) was prepared by using epoxy resin, epoxy diluent, curing agent, curing accelerator, coupling agent, conductive additive, and three times of the aforementioned mass of silver powder (different ratios of flake silver/sphere silver). The influence of micro flake silver /micro sphere silver compounding on the performance of ECA was studied from several aspects of rheological properties, thermophysical properties, electrical conductivity, thermal conductivity, morphology, and bonding strength. The research results showed that, ⑴ The viscosity and thixotropy index were greatly affected by the proportion of sphere silver. The higher the proportion of sphere silver, the lower the viscosity and thixotropy index. Flake silver had a significant effect on improving ECA thixotropy, while sphere silver could effectively reduce viscosity. ⑵ As the proportion of sphere silver increased, the glass transition temperature (T_g) underwent a slight change, with little effect on the coefficient of thermal expansion (CTE-1) before T_g, but a significant decrease in the coefficient  of thermal expansion (CTE-2) after T_g. ⑶ Under the condition of fixed total content of silver powder, sphere silver was not conducive to reducing the volume resistivity, but it could significantly improve the thermal conductivity of ECA. ⑷ The added silver powder exhibited a uniform distribution as a whole, and had a certain degree of randomness and disorder. As the content of sphere silver increased, its filling density in the direction of flake silver gradually became denser from loose, and the degree of shielding of flake silver by sphere silver also increased accordingly. As the proportion of sphere silver increased further, a large amount of sphere silver filled the gaps in the vertical direction of flake silver, which was beneficial for constructing an isotropic and efficient thermal conductivity network. ⑸ Sphere silver had a tighter stacking effect compared to flake silver, and the mechanical reinforcement effect was reflected with the increase of sphere silver content. The optimal bonding strength occurred when the sphere silver content reached 1/3.

【Keywords】electrically conductive adhesive; thermal conductivity; glass transition temperature; coefficient of thermal expansion

Influence of conductive additive and diluent type on the properties of LED die attach adhesive

Jiang Chao, Sang Guangyi, Song Qi, Li Longfa, Gong Wensheng, Chen Dan, Tao Xiaole, He Danwei

(Hangzhou Zhijiang Silicone Chemical Co., Ltd., Hangzhou  311200, Zhejiang, China)

【Abstract】The electrical conductivity, thermal conductivity, and heat resistance reliability of LED die attach adhesive are crucial for the luminescence performance and long-term reliability of high-power LED. LED die attach adhesive was prepared in this article by using epoxy resin, diluent, curing agent, curing accelerator, coupling agent, conductive additive, and silver powder. Then, different samples (E0-E4, R1-R5) were prepared by changing the types of conductive additive and diluent. The influence of conductive additive type on the viscosity, volume resistivity, and thermal conductivity of LED die attach adhesive was investigated, and the influence of diluent type on die shear force at the room temperature and high temperature, residual adhesive rate of chip-silver plating frame, and moisture and heat resistance of LED die attach adhesive were explored. The research results showed that, ⑴ The addition of conductive additive could significantly reduce the viscosity of die attach adhesive. When the conductive additive was adipic acid (dicarboxylic acid), the volume resistivity of die attach adhesive significantly decreased and the thermal conductivity significantly increased. When both carboxyl and hydroxyl groups were present in the conductive additive, the volume resistivity increased, while the thermal conductivity decreased. ⑵ For diluents with strong molecular rigidity (R4) and high crosslinking density (R5), they exhibited poor performance in high-temperature die shear force and residual adhesive rate. For phenyl diluent (R1) with strong rigidity, it achieved excellent balance performance between room temperature/high temperature die shear force and residual adhesive rate. For aliphatic diglycidyl ether diluents (R2, R3) with good flexibility, their comprehensive performance was between the two. ⑶ The high-temperature steaming and moisture and heat aging test showed that the hydrophobic phenyl group in the diluent helped improve the moisture and heat resistance of die attach adhesive.

【Keywords】LED; die attach adhesive; reliability; bonding strength; residual adhesive rate; conductive additive; diluent

Preparation and performance study of Buton rock composite modified asphalt grouting adhesive

Wang Yuanming, Zhao Su

（School of Materials Science and Engineering, Shenyang Jianzhu University, Shenyang  110168, Liaoning, China）

【Abstract】A composite modified asphalt grouting adhesive was prepared by combining Buton rock asphalt with other modifiers in this study. Among them, Buton rock asphalt (BRA), styrene-butadiene-styrene block copolymer (SBS) polymer, rubber powder, compatibilizer, plasticizer, and tackifier were selected for composite modification of matrix asphalt. A six-factor three-level orthogonal experimental design was adopted, and the conventional performance of pavement grouting adhesive was used as the evaluation index. The influence of various factors on the performance of grouting adhesive was explored through range analysis and variance analysis, and the optimal mixing ratio of Buton rock composite modified asphalt grouting adhesive was studied. The optimal construction temperature of the grouting adhesive was determined through the Brookfield rotational viscosity test. The storage aging performance of the grouting adhesive was evaluated through indoor test simulation. The bonding between the grouting adhesive and the aggregate interface was observed using scanning electron microscopy. The research results showed that through the analysis of range and variance in orthogonal experiment, it could be concluded that both Buton rock asphalt and SBS had a significant impact on the conventional performance of pavement grouting adhesive. Buton rock composite modified asphalt grouting adhesive met the technical requirements (JT/T 740—2015) for high temperature grouting adhesive. Compared with other factors, the performance of composite modified asphalt grouting adhesive was greatly affected by Buton rock asphalt and SBS polymer. The optimal ratio (mass fraction ratio) of Buton rock composite modified asphalt grouting adhesive was, m(matrix asphalt)∶m(Buton rock asphalt)∶m(SBS)∶m(waste rubber powder)∶m(compatibilizer)∶m(plasticizer)∶m(tackifier)=100∶16∶20∶10∶2∶2. The optimal construction temperature of grouting adhesive was 195.5 ℃, and the on-site storage time was ≤12 h. Through scanning electron microscopy equipment, it was found that the bonding between the Budun rock composite modified asphalt grouting adhesive and the aggregate interface was good.

【Keywords】Buton rock asphalt; modified asphalt; grouting adhesive

Process and Application

Analysis of tensile performance standards and testing methods for reinforced oriented carbon fiber plate

An Shaodu^1,2, Ma Yanan^1,2, Zhang Mingxuan^1,2, Yao Shufang^1,2, Yan Yuting^1,2, Yan Xinyu^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 reinforced oriented carbon fiber plate formed by infiltration hardening of epoxy resin is a key material in fiber reinforced composite materials, and its tensile performance is of great significance for the safety and durability of the structure. The tensile performance testing methods and technical indicators of carbon fiber plate related standards at home and abroad were compared and analyzed in this article, the factors that affected the tensile performance testing results of carbon fiber plate were investigated, the tensile performance testing data of carbon fiber plate with different thicknesses from different manufacturers were preliminarily explored, and the testing techniques related to the tensile performance testing methods of carbon fiber plate were evaluated.

【Keywords】carbon fiber plate; tensile property; standard; testing technique

Preparation and influence of silane modified polythioether sealant

Peng Yuqing¹, Guo Qingzhao², Wu Songhua¹

（1.BAIMTEC Material Co., Ltd., Beijing  100095, China; 2.COMAC Shanghai Aircraft Design & Research Institute, Shanghai  201210, China)

【Abstract】A silane terminated polythioether rubber (SPSR) structure was obtained by using isocyanate-based silane coupling agent (KH-901) to perform end capping reaction on liquid polythioether rubber, and the corresponding one-component moisture cured polythioether sealant material was prepared. The effect of end capping reaction was analyzed by infrared spectroscopy and nuclear magnetic resonance, and the influence of different types of crosslinking agent and different types of catalyst on the curing behavior of one-component moisture cured polythioether sealant was compared. Finally, the influence of filler system on the performance of one-component moisture cured polythioether sealant was analyzed. The research results showed that, ⑴ The structural characterization indicated that the end capping reaction was complete and the target product was successfully prepared. ⑵ (3-aminopropyl) trimethoxysilane and mercaptopropyl trimethoxysilane could cure the sealant at a faster speed and had strong mechanical properties. They could both be used as crosslinking agents for one-component moisture cured polythioether sealant. After comprehensive consideration, the best curing performance of (3-aminopropyl) trimethoxysilane was ultimately selected as the crosslinking agent for the sealant.⑶ With the increase of crosslinking agent dosage, the tensile strength and elongation at break of one-component moisture cured sealant showed a trend of first increasing and then decreasing. When w(crosslinking agent)=5%, the mechanical properties of the sealant were relatively optimal. ⑷ Dibutyltin dilaurate, as a catalyst for one-component moisture cured sealant, had moderate and stable catalytic efficiency. ⑸ The addition of nano calcium carbonate as a filler could reinforce one-component moisture cured sealant and enhance their mechanical properties. But if the amount of filler added was too much, it would actually lead to a decrease in mechanical properties. As the content of nano calcium carbonate increased, the viscosity of the sealant gradually increased and the flowability decreased, indicating that the addition of nano calcium carbonate had an impact on the construction effect of the sealant.

【Keywords】silane modification; polythioether; sealant; crosslinking agent; catalyst; filler

Preparation and application properties of modified phenolic resin adhesive for computer room construction

Huang Sisheng

(China Railway 23rd Bureau Group Sixth Engineering Co., Ltd., Chongqing  400010, China)

【Abstract】As a place with a high concentration of electronic devices, the computer room has extremely high requirements for temperature and humidity control. In order to cope with the complex and ever-changing construction environment of the computer room, it is necessary to use adhesive materials with good heat resistance and aging resistance. It is difficult for ordinary phenolic resin adhesive to maintain stable bonding performance in harsh environments such as high temperature and high humidity. Therefore, it is particularly important to study the preparation and application performance of modified phenolic resin adhesive for computer room construction. PU/PA nanoparticles were prepared as modifiers by using materials such as polyether polyols, epoxy resin, and dihydroxymethyl propionic acid. Subsequently, basic phenolic resin was synthesized by using raw materials such as phenol and butanone, and PU/PA nanoparticles were added at ratios of 10%, 15%, 20%, and 25%, respectively, to produce phenolic resin adhesive with four different levels of modifier addition. In order to comprehensively evaluate the application performance of these adhesives, diverse testing methods were used for experimental analysis. The research results showed that, in the testing of thermal stability, flexural resistance, compressive resistance, shear resistance, impact resistance, wear resistance, erosion resistance, and construction performance, the concentration of nanoparticles showed a non-linear relationship of "first increasing and then decreasing" with performance. The 20% concentration was the performance inflection point, beyond which the performance deteriorated due to particle aggregation, below this concentration, an effective enhancement network could not be formed due to insufficient particles. In the sample of 20% concentration, uniformly dispersed nanoparticles could form a three-dimensional network structure, significantly improving thermal stability, mechanical properties, and wear resistance. Therefore, adding 20% PU/PA nanoparticles modified phenolic resin adhesive had good application performance, which was conducive to improving the overall quality and durability of computer room facilities.

【Keywords】computer room construction; modified phenolic resin; adhesive; nanoparticles; flexural strength; curing time

Material Science

Research on the influence of different additives on the mechanical properties of epoxy resin and polyamide resin curing system

Pan Maodong, Zhu Lu, Feng Xinglang

（Yangjiang Weiyi Polishing Material Co., Ltd., Yangjiang  529500, Guangdong, China )

【Abstract】The effects of the contents of four different additives (phenolic amine curing agent T-31, curing accelerator DMP-30, silane coupling agent KH-560, and titanate coupling agent NDZ-201) on the mechanical properties of epoxy resin and polyamide resin curing system were investigated in this article. The effects of additives were analyzed by comparing the changes in mechanical properties of cured materials. The research results showed that, for the cured system with T-31, the compressive strength continued to increase, the flexural strength continued to increase, and the tensile strength first increased and then decreased (reaching its peak when the mass fraction of T-31 was 2.53%), the shear strength decreased, while the hardness of the material did not show significant changes. For the cured system with DMP-30, the compressive strength gradually decreased, the flexural strength gradually increased, the tensile strength reached its maximum at 1.25%, the shear strength decreased, while the hardness of the material reached its maximum at 1.25%, then gradually decreased and tended to stabilize. For the cured system with KH-560, the compressive strength and tensile strength gradually decreased with increasing content, the flexural strength reached its minimum at 2.53%, the shear strength decreased, while the hardness of the material showed a gradually decreasing trend. For the cured system with NDZ-201, the compressive strength and flexural strength decreased with increasing additive content, the tensile strength reached its minimum at 2.53%, the shear strength decreased, while the hardness of the material did not show significant changes. Therefore, the optimal dosage of additives needed to be determined comprehensively based on their functional positioning, performance goals, and specific resin curing system.

【Keywords】epoxy resin; polyamide resin; mechanical property; additive; curing

Development of 3,3',5,5'-tetramethyl-4,4'-diphenol diglycidylether

Xiong Gaohu^1,2, Zhang Liang^1,2, Qu Peng^1,2, Liu Yiwu¹

[1.Dongfang Feiyuan (Shandong) Electronic Materials Co., Ltd., Zibo  256300, Shandong, China; 2.Sichuan Dongshu New Materials Co., Ltd., Deyang  618000, Sichuan, China]

【Abstract】3,3',5,5'-tetramethyl-4,4'-diphenol diglycidylether (TMDE) has a high glass transition temperature and excellent heat resistance, and is widely used in composite materials, electronic packaging materials, and nonlinear optical materials. However, the production technology of TMDE in China is not yet perfect, and the products are mainly imported. A method for preparing 3,3',5,5'-tetramethyl-4,4'-biphenyldiol (TMBP) and TMDE was introduced in this article, and the optimal reaction conditions for preparing TMBP and TMDE from TMBP were provided, respectively. The research results showed that, ⑴ It could be demonstrated through structural characterization and other methods that TMBP and TMDE had been successfully synthesized. ⑵ When the oxygen flow rate was 4.48 L/h (the ratio of 2,6-dimethylphenol to total oxygen introduced was 12:1) and the reaction temperature was 80 ℃, the highest yield of TMBP was 93.8%. ⑶ When the reaction ratio m(epichlorohydrin) : m(TMBP) was 2.82:1, the reaction temperature was 62 ℃, and the reaction pressure was 20 kPa, the indicators and consumption of TMDE products were optimal.

【Keywords】3,3',5,5'-tetramethyl-4,4'-diphenol diglycidylether; electronic packaging material; reaction condition