Special Topics Review

Research progress of high-temperature resistance acrylate pressure sensitive adhesive

Xue Gang, Xue Shuangle, Zhang Xugang, Sun Mingming, Bai Xuefeng, Wang Lei, Zhao Ming, Zhang Bin

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

Abstract】Acrylate pressure sensitive adhesive is limited in many application fields due to its insufficient high-temperature resistance. In recent years, many studies have emerged in the industry to improve its temperature resistance through modification. In this paper, the recent research on the high-temperature resistance modification of acrylate pressure sensitive adhesive was reviewed, and the test methods on high-temperature resistance performance were summarized and compared. Various modification methods such as the study of crosslinking agent and crosslinking method, silicone modification, acrylamide compound modification, fluorine-containing compound modification, and heterocyclic heat-resistant monomer modification were analyzed and summarized. Finally, the development direction of high-temperature resistance acrylate pressure sensitive adhesive was prospected.

Keywords】acrylate; pressure sensitive adhesive; high-temperature resistance; summarize

Research progress on optical adhesive for electronic display screen

Du Yuxin1, Bai Yongping1, Meng Linghui1, Bai Yang2

(1.School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin  150001, Heilongjiang, China; 2. Wuxi Trillion Stars New Material Technology Co., Ltd., Wuxi  214100, Jiangsu, China)

AbstractsThe touch display screens of cell phones, tablet PCs, smart watches, and other electronic products are composed of many complex thin layers with different structures and functions, in which optical adhesive plays an important role. With the iteration of screen technology, the touch display screen is developing in the direction of edge-to-edge screen, foldable screen, as well as curled and stretchable screen, which puts forward higher requirements for optical adhesive. In this review, the characteristics and research status of polyurethane optical adhesive, epoxy resin optical adhesive, acrylate optical adhesive, and silicone resin optical adhesive for 3C product screens were introduced, and the development and problems of various types of optical adhesive were discussed. An in-depth exploration was conducted on the preparation and properties of acrylate optical pressure-sensitive adhesive, and the latest research progress on optical pressure-sensitive adhesive for flexible foldable screens in recent years was summarized. The application, challenges, and future development directions of optical pressure-sensitive adhesive for electronic display screen were proposed, providing reference for subsequent research work.

Keywords】touch display panel; foldable screen; optically clear adhesive; research progress

Research progress and discussion on the thermal conductivity of thermal conductive adhesive

Hu Xiaowei1,2, Yang Junling2, Zhao Dandan1, Zhang Zhentao2,

Li Xiaoqiong2, Chang Hong3, Zhang Wenxia3, Fang Zhanzheng4

(1.College of Food Science and Biology, Hebei University of Science and Technology, Shijiazhuang  050018, Hebei, China; 2.Technical Institute of Physics and Chemistry, CAS, Beijing  100190, China; 3. State Power Investment Corporation Science and Technology Research Institute Co., Ltd., Beijing  102200, China; 4.Beijing Jingkai Integrated Smart Energy Co., Ltd., Beijing  102600, China)

AbstractWith the rapid popularization of consumer electronic products and the continuous progress of technology, the thermal conductive adhesive market demand continues to increase, and the development potential is huge. However, while miniaturization, integration, and portability of electronic products are rapidly developing, higher requirements are also put forward for the thermal conductivity of thermal conductive adhesive. Therefore, in this article, the thermal conductivity mechanism of filled thermal conductive adhesive was introduced, the application scope of traditional thermal conductivity models, and the method of finite element simulation to predict the thermal conductivity coefficient were discussed. The research achievements of thermal conductive adhesive colloids in recent years were reviewed, and the type, shape, particle size, modification of thermal conductive adhesive fillers, as well as the influence of the mixed use of thermal conductive fillers on the thermal conductivity coefficient of thermal conductive adhesive were described emphatically, and the methods for improving the thermal conductivity coefficient of thermal conductive adhesive were summarized.

Keywordsthermal conductive adhesive; thermal conductivity coefficient; thermal conductivity model; thermal conductive filler; adhesive

Research Report

Synthesis of organosilicone acrylate prepolymer and its application in

UV curing acrylate pressure sensitive adhesive

Chen Keyu1, Lin Xiaodan1, Wang Lei1, Liao Pingxiang2

(1.School of Materials Science and Engineering, South China University of Technology, Guangzhou  510641, Guangdong, China;2.Hunan Hexiangrun New Materials Co., Ltd., Yongzhou  266400, Hunan, China)

AbstractOrganosilicone acrylate prepolymer containing urethane groups were prepared by using single-terminated hydroxysilicone oil, isophorone diisocyanate and hydroxyethyl acrylate. Using this prepolymer as a hard monomer, 2-ethylhexyl acrylate as a soft monomer, and low biotoxicity 2,4,6-trimethylbenzoylphenylphosphonate ethyl ester (TPO-L) as a photoinitiator, acrylate pressure sensitive adhesive with excellent water absorption, water permeability, water resistance, and bonding properties was prepared by UV curing polymerization. The optimal process parameters for the synthesis of prepolymer, such as temperature, time, and catalyst dosage, were investigated by using the reverse titration method with dibutylamine. The effects of illumination time, types and amounts of photoinitiators on the curing degree of pressure sensitive adhesive, as well as the effects of prepolymer content on the bonding performance, water absorption, and moisture permeability of pressure sensitive adhesive were studied. The research results showed that in the synthesis of organosilicone acrylate prepolymer, the first step reaction temperature was 40 ℃, the second step reaction temperature was 50 ℃, both the reaction time was 60 minutes, and the optimal catalyst dosage was 0.10% (mass fraction). In the preparation of modified pressure sensitive adhesive, when the illumination time was 120 s, the photoinitiator TPO-L dosage was 3% (mass fraction), the prepolymer content was 20%, the photocuring degree of pressure sensitive adhesive was relatively high, the initial adhesion force was 21# ball, the 180° peel strength was 5.7 N/(25 mm), the holding power exceeded 360 h, and the 180° peel strength for non-polar surface of PP board was 3.2 N/(25 mm). The modified pressure sensitive adhesive had good water absorption and moisture permeability.

Keywordshydroxysilicone oil; isophorone diisocyanate; hydroxyethyl acrylate; prepolymer; UV curing; pressure sensitive adhesive

Synthesis and performance study of dimethyl p-xylylene cyanate

Shen Dongliang, Wei Yunzhao, Wu Jianwei, Fu Gang, Zhao Yuyu, Wang Guan

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

Abstract】Dimethyl p-xylylene phenol (DMPXPh) was synthesized by using p-phenyldimethyl ether as the raw material, and a new type of dimethyl p-xylylene cyanate (DMPXCy) was prepared by the cyanogen chloride-phenol method, and the structure was measured. The thermal properties, moisture and heat resistance, dielectric properties, and mechanical properties of the material were investigated, and compared with bisphenol A cyanate (BADCy). The research results showed that, ⑴ The characterization by infrared and nuclear magnetic resonance spectroscopy confirmed that the target phenolic intermediate was successfully prepared, and the phenolic intermediate was synthesized into cyanate monomer through cyanate esterification. ⑵ The study on the curing behavior and thermal performance of DMPXCy showed that the reaction activity of DMPXCy was lower than that of BADCy resin, and the addition of organic metal catalysts significantly reduced the curing temperature, allowing for stepwise curing within 280 ℃. In addition, the glass transition temperature of DMPXCy resin was lower than that of BADCy resin, and its thermal stability was basically the same. However, the residual carbon rate of DMPXCy was higher, indicating a certain degree of ablation resistance. ⑶ The research on mechanical properties showed that the overall mechanical strength of DMPXCy resin was similar to that of BADCy, with slightly lower tensile strength. ⑷ The research on the moisture absorption and dielectric properties of DMPXCy resin showed that DMPXCy resin exhibited excellent dielectric properties and low moisture absorption, the dielectric constant (ε) and dielectric loss tangent (tanδ) were 2.650 and 0.004 50, respectively, the saturation moisture absorption rate was 0.70%, which were much lower than the dielectric loss and moisture absorption rate of BADCy resin. DMPXCy resin had good application potential as a resin matrix for low dielectric transparent materials or high-precision aerospace composite materials and adhesive.

Keywordscyanate; dimethyl p-xylylene type; synthesis; dielectric performance; low moisture absorption

 

Process and Application

Study on preparation and performance of polyurethane potting sealant

with high thermal conductivity and high flame retardancy

Li Ping1, Yan Qiming2, Cong Helei3

(1.School of Cable Engineering, Henan Institute of Technology, Xinxiang  453003, Henan, China; 2.Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China, Fuzhou  350108, Fujian, China; 3. Kangda New Materials (Group) Co., Ltd., Shanghai  201419, China)

AbstractThe modified alumina and modified ammonium polyphosphate were prepared by using n-hexyltrimethoxysilane (HTTS) as surface activator, which improved the dispersion of alumina and ammonium polyphosphate in polymer matrix. On this basis, the two-component polyurethane potting sealant was prepared by using polypropylene glycol and castor oil as hydroxyl components, modified alumina as thermal conductive filler, modified ammonium polyphosphate as flame retardant, polymethylene polyphenyl isocyanate as curing agent, as well as adding catalyst, defoamer, and molecular sieve. The effects of HTTS, R value, the addition of thermal conductive filler and flame retardant on the performance of polyurethane potting sealant were studied. The research results showed that when the addition amount of HTTS was 2.0% and 2.5%, respectively, the activation effect of alumina and ammonium polyphosphate was relatively excellent. When the R value was 1.15, the tensile strength of polyurethane potting sealant was 2.76 MPa, and the elongation at break was 254%. When the addition amounts of modified alumina and modified ammonium polyphosphate were 70% and 8%, respectively, the thermal conductivity of the polyurethane potting sealant was 2.11 W/(m·K), the flame retardant level reached UL-94 V0 grade, and the limiting oxygen index was 28.5%. In addition, the prepared polyurethane potting sealant had excellent stability. When stored at 50 ℃ for 30 d, the rotational viscosity of component A and component B fluctuated within a reasonable range of 18-26 Pa·s and 400-700 mPa·s, respectively. Finally, the volume resistivity of the prepared polyurethane potting sealant was 5.1×1013 Ω·cm, the water absorption was 0.21%, the gel time was 49 min, and the Shore D hardness was 52. After curing, the adhesive surface was flat without bubbles, indicating that the performance of the potting sealant could meet the requirements in the field of electronic potting.

Keywordsalumina; ammonium polyphosphate; two-component polyurethane potting sealant; thermal conductivity; flame retardant

Preparation and application of one-component self-crosslinking

solvent-based acrylate pressure sensitive adhesive

Zhou Lijun1,2, Liu Mingzhu2, Liu Congpeilin2, Cheng Jingxuan2, Huang Lun1,2, Yao Kun2, Gong Lulu2

(1.Hubei Longzhong Laboratory, Xiangyang  441138, Hubei, China; 2.Hubei Institute of Aerospace Chemical Technology, Xiangyang  441003, Hubei, China)

AbstractA kind of one-component self-crosslinking benzene-free solvent-based acrylate pressure sensitive adhesive was prepared by free radical polymerization using a self-crosslinking functional monomer N-hydroxymethylacrylamide (NMA). The effects of self-crosslinking monomer content on the peel strength, viscosity, holding power, and conversion rate of pressure sensitive adhesive were systematically studied, and the optimal amount of NMA was selected. The research results showed that when the mass fraction of self-crosslinking monomer NMA added was 0.2%, the peel strength and viscosity of pressure sensitive adhesive met the requirements, and the temperature resistance performance was excellent. The high-temperature holding time at 65 ℃ increased to 10 h, and the monomer conversion rate was high (up to 95.2%). The prepared pressure sensitive adhesive was coated on the substrate and applied to the carpet protective film. After 30 days, there was no curling phenomenon, and the solvent used was toluene-free, which had the advantages of environmental protection and low toxicity, proving that this product had certain application prospects.

Keywordsone-component; self-crosslinking; N-hydroxymethylacrylamide; acrylate; solvent-based pressure sensitive adhesive

Material Science

Studies of UV-cationic hybrid system and its application in inkjet solder resist

Liu Yuan1, Yao Lu1, Liu Xiaoxuan1, Han Dong2, Liao Zhengfu1

(1. School of Materials and Energy, Guangdong University of Technology, Guangzhou    510060, Guangdong, China; 2. Shenzhen Inkbank Graphic Technology Co., Ltd. Shenzhen    518100, Guangdong, China)

Abstract】Inkjet printing is a relatively novel non-contact printing technology and has broad development prospects with its high efficiency, economy and environmental features in solder resist process. In this study, the curing speed, adhesion, and hardness of UV cured coating were compared, and 3,4-epoxycyclohexylformate-3',4'-epoxycyclohexylmethyl ester (TTA-21) as the cationic monomer for the hybrid system was selected from five commercially available cationic monomers. The TTA-21/1,6-hexanediol diacrylate (HDDA) hybrid system with a mass ratio of 2:3 was selected as the research object, and its reaction conversion rate, curing degree, thermal performance, thermal stability, and the application of the prepared ink in solder resist were studied. The research results showed that: ⑴ Under LED illumination, both free radical and cationic components underwent polymerization reactions. The reaction rate of the free radical system was faster and the conversion rate of the reaction was higher. The reaction rate of cationic system was slow and the conversion rate was relatively low. Continuous light exposure in a short period of time could not significantly improve the conversion rate of cationic system. Under photothermal dual curing, the degree of reaction between cationic epoxy ring opening polymerization and free radical double bond addition reaction increased, and the curing process was more thorough. ⑵ The cured products of the hybrid system had two phases, but the thermogravimetric curve showed only one weight loss curve, indicating that the hybrid system may form an interpenetrating cross-linked network structure after LED heating and baking. There was a certain microphase separation structure between the epoxy component and the acrylic component, which enhanced the overall performance of the cured film. ⑶The application study showed that the prepared qualified solder resist ink had the viscosity of 8-14 mPa·s (45 ℃), the surface tension of around 22 mN/m, and the particle size range of 135-150 nm. Its solvent resistance, acid and alkali resistance, and solder resistance could all meet the requirements of solder resist ink.

Keywords】UV curing; cationic; hybrid system; inkjet printing; solder resist ink

 

Preparation and performance study of barium phenolic resin modified by KH-560

Li Panpan, Liu Xiaoli, Gao Guosheng, Duan Wanze, Zhang Le, Zhao Jianyu

(Beijing Xinfeng Aerospace Equipment Co., Ltd., Beijing  100854, China)

AbstractIn order to improve the high-temperature resistance and mechanical properties of barium phenolic resin, silane coupling agent KH-560 was used to chemically modify the resin in this study. Various performance characterizations were conducted on the resin before and after modification, with a focus on the thermal stability, mechanical properties, and adhesion of the modified resin. The research results showed that, ⑴KH-560 was successfully and stably connected to the molecular chain of barium phenolic resin through chemical bonds. ⑵ The optimal addition amount of KH-560 was 15%. Compared with pure barium phenolic resin, the Tmax2 of modified barium phenolic resin increased by about 25 ℃, and the thermal performance was significantly improved. ⑶ KH-560 could effectively improve the mechanical properties of barium phenolic resin. The tensile strength of barium phenolic resin modified by 15% of KH-560 increased by about 32.5%, the tensile modulus increased by about 11.7%, and the adhesion increased by about 30.4%.

KeywordsKH-560; barium phenolic resin; modification; thermal stability; tensile property; adhesion

Influence of aggregate acidic composition and temperature on asphalt/aggregate adhesion

Zhu Zhenxiang1, Wei Hui2, Fan Liang2, Wang Lin1, Li Yongzhen2

(1.Shandong High-Speed Co., Ltd., Ji’nan  250014, Shandong, China; 2.Shandong Transportation Research Institute, Ji’nan  250100, Shandong, China)

Abstract】In order to quantitatively characterize the influence of acidic composition in aggregate on asphalt/aggregate adhesion, the adsorption law of acidic component on asphalt was studied first by simulated mineral and infrared spectroscopy. Then, three types of petroleum asphalt and five types of aggregate were selected to investigate the influence mode of actual acidic components on adhesion, as well as the influence characteristics of application temperature on adhesion. The research results showed that the SiO2 content of the acidic component and the total content of SiO2+Al2O3 in actual mineral aggregate could exhibit the Logistic function relationship with the adhesion characterization parameter-spalling rate. When the SiO2 content was less than 50%, or the content of SiO2+Al2O3 was less than 63%, the spalling rate of asphalt on the aggregate surface was generally less than 5%, which was the first stable zone. When the SiO2 content was between 50%-73%, or the content of SiO2+Al2O3 was between 63%-87%, the spalling of asphalt on the aggregate surface accelerated with the increase of acidic component content, which was a sensitive zone for adhesion. The adhesion grade of asphalt could rapidly decay from level 4 to level 3 or 2. When the SiO2 content was greater than 73%, or the content of SiO2+Al2O3 was greater than 87%, the adhesion grade of asphalt was below level 2 or level 1, which was the second stable zone. In some low-temperature climate areas, acidic aggregates such as granite could be utilized normally by using ordinary asphalt mixture design methods or with appropriate anti-spalling measures.

Keywords】asphalt adhesion; aggregate mineral composition; acidic component; influence law