Special Topics Review

Research progress on high-temperature resistance pressure-sensitive adhesive

Xu Dan¹, Zhang Junying², Niu Donghua¹, Ma Jiefang¹, Liu Tong¹, Cheng Jue², Song Jiayun¹

(1.Beijing Tianyu Aerospace New Material Technology Co., Ltd., Beijing  101407, China; 2.College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing  100029, China)

【Abstract】The application fields of high-temperature resistance pressure-sensitive adhesive were introduced in this study, and the commonly used high-temperature resistance pressure-sensitive adhesive from three categories was described, i.e. high-temperature resistance acrylic pressure-sensitive adhesives (metal chelate crosslinking, polyisocyanate crosslinking, polycyclic oxygen compound crosslinking, and radiation crosslinking), high-temperature resistance polyurethane pressure-sensitive adhesives, and high-temperature resistance silicone pressure-sensitive adhesives. The high-temperature resistance modification methods and research progress of three types of pressure-sensitive adhesives were introduced, respectively.

【Keywords】acrylate; silicone; polyurethane; high-temperature resistance pressure-sensitive adhesive

Research progress of silane modified polyether sealant from a patent perspective

Wang Xiaoming¹, Wang Ya¹, An Jingyi², Zhang Xiaoa²

[1.Patent Examination Cooperation (Beijing) Center of the Patent Office, CNIPA, Beijing  100160, China; 2.Key Laboratory of Carbon Fiber and Functional Polymers of Ministry of Education, College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing  100029, China]

【Abstract】In this article, the patent application status of silane modified polyether sealant in recent years from the dimensions of research direction, technical region, and applicant situation was first analyzed. Then, the research progress on the synthesis of silane modified polyether, the preparation of silane modified polyether sealant, and the improvement of the properties of silane modified polyether sealant (bonding properties, mechanical properties, transparency, modulus, flame retardancy, heat resistance, curing properties, etc.) and its applications (construction, automotive, etc.) were summarized from the applied patents, and the future development prospects were also discussed.

【Keywords】silane modified polyether; sealant; MS adhesive; patent

Research progress on modified dicyandiamide cured epoxy resin

Yang Yuxin¹, Lou Chunhua^1,2, Yu Jingjing¹, Wang Huixiao¹

(1.College of Chemistry and Chemistry Engineering, Qiqihar University, Qiqihar  161006, Heilongjiang, China; 2.Key Laboratory of Composite Materials, Heilongjiang Province, Qiqihar University, Qiqihar  161006, Heilongjiang, China)

【Abstract】As one of the earliest latent curing agents, dicyandiamide has excellent mechanical properties in cured epoxy resin, but still has defects such as high curing temperature. In response to this deficiency, domestic and foreign literature from two aspects: reducing the electron withdrawing ability of the cyanide group on dicyandiamide to enhance curing activity, and introducing similar functional groups to enhance the compatibility between dicyandiamide and epoxy resin, was summarized in this article. The application prospects of modified dicyandiamide cured epoxy resin were also discussed.

【Keywords】dicyandiamide; epoxy resin; curing activity; compatibility; cyano group

Research Report

Preparation and application of visible light LED sensitive photobase generator system

Wan Mengdi¹, Zhu Weite¹, Li Zhiquan^1,2, Liu Xiaoxuan^1,2

(1.School of Materials and Energy, Guangdong University of Technology, Guangzhou  510006, Guangdong, China; 2.Guangdong Laboratory of Chemistry and Fine Chemical Industry Jieyang Center, Jieyang  522000, Guangdong, China)

【Abstract】In response to the current problem of short absorption wavelength of photobase generator, which was difficult to match with commonly used visible light LED sources, based on the photosensitization mechanism, in this paper, a non-ionic photobase generator (PL-DBN) was synthesized by reducing amidine photobase generator, and its structure was characterized. It was compounded with photosensitizers (CQ, COU and ITX), three kinds of visible light sensitive photobase generator systems (PL-DBN/CQ, PL-DBN/COU and PL-DBN/ITX) were prepared, and their photophysical and photochemical behaviors were systematically investigated. The research results showed that, ⑴ The nuclear magnetic hydrogen spectrum indicated that the target product PL-DBN was successfully prepared. ⑵ By studying the light absorption properties of three kinds of photosensitizers, it was decided to select photosensitizers (CQ, COU and ITX) with different absorption ranges to be compounded with PL-DBN, respectively. ⑶ The efficiency of photolysis of different photosensitizers under 405 nm light source was investigated through steady-state photolysis experiments. Among them, PL-DBN/ITX showed a faster photolysis rate under 405 nm LED light source irradiation, making it more suitable for use in composite photobase generator systems. ⑷ Through the changes in UV-visible absorption spectra, it was found that the alkaline substances produced by the photolysis of the photobase generator system underwent acid-base neutralization reaction with phenol red, proving that PL-DBN could undergo photo induced alkali production reaction under 405 nm light source irradiation. ⑸ The effect of irradiation time on the kinetics of thiol-epoxy polymerization was investigated by using differential scanning calorimetry and Fourier transform infrared spectroscopy. The initial curing temperature of the system could be reduced by 23 ℃ after 10 minutes of irradiation, and the conversion rate of thiol and epoxy functional groups could slowly increase to over 95% during a short period of heating after 10 minutes of light irradiation. ⑹ The bonding strength of the thiol-epoxy system after photothermal dual curing was tested. The thiol-epoxy system catalyzed by photobase generator had dark curing characteristics and could be applied in delayed curing adhesive, which had certain potential for future applications.

【Keywords】photobase generator; amidine; photosensitization; thiol-epoxy; anionic photopolymerization

Preparation and properties of acrylate prepolymer and its pressure sensitive adhesive

Huang Yi^1,2,3, Cai Jiehong², Zhang Yihui², Chu Yuehuan³, Wang Linge¹

(1.School of Emergent Soft Matter, South China University of Technology, Guangzhou  510640, Guangdong, China; 2.Polomo New Material Technology Development Co., Ltd., Dongguan  523185, Guangdong, China; 3. School of Chemistry and Materials Engineering, Huizhou University, Huizhou  516007, Guangdong, China)

【Abstract】Acrylate polymer was synthesized through free radical polymerization using methyl methacrylate (MMA), isooctyl acrylate (2-EHA), acrylic acid (AA), and hydroxyethyl acrylate (HEA) as comonomers, azobisisobutyronitrile (AIBN) as initiator, and ethyl acetate (EA) as solvent. Then, acrylate prepolymer was systhesized by grafting isocyanate ethyl acrylate (AOI) monomer, which was used to prepare UV curable pressure sensitive adhesive (PSA). The effects of structural properties and reaction temperature on the relative molecular weight and distribution of prepolymers, as well as low dosages of functional monomer AA and crosslinking monomer AOI, and weight average molecular weight (M_w) on PSA performance were investigated. The research results showed that, ⑴ Infrared spectroscopy analysis showed that almost all prepolymers and monomers participated in the polymerization reaction. The analysis of relative molecular weight and distribution showed that the mass average molecular weight (M_n) and weight average molecular weight (M_w) decreased with the increasing reaction temperature, but the distribution coefficient (PDI) remained between 3.56~3.79, and there was no obvious correlation between the change of PDI and temperature. The T_g determined by DSC analysis was -63.53 ℃, which was much lower than the T_g of PSA reported in other studies (-30~-50 ℃), and the applicable temperature lower limit was significantly reduced. ⑵ Overall, when the dosage of AA and AOI was 1.0% and 0.16%, respectively, and the M_w of prepolymer was about 457,000, the comprehensive performance of PSA was relatively optimal. The rheological properties at different frequencies explained the intrinsic relationship between pressure-sensitive performance and viscoelasticity.

【Keywords】acrylate prepolymer; pressure sensitive adhesive; crosslinking monomer; acrylic acid; viscoelasticity

Research on failure mode of conductive adhesive under high temperature aging and temperature shock

Liu Hao^1,2, Zhang Weiwei², Liu Jiahao^1,3, Zhu Shuyan², Zhao Dingwei², Liu Zhao², Chen Hongtao¹

[1.Harbin Institute of Technology (Shenzhen), Shenzhen  518055, Guangdong, China; 2.Beijing Santel Technology & Trading Co., Ltd., Beijing  100854, China; 3.Electronic Fifth Research Institute of the Ministry of Industry and Information Technology, Guangzhou  510610, Guangdong, China]

【Abstract】In response to the widely used HD-903 modified epoxy resin conductive adhesive in China's aerospace industry, high-temperature aging and temperature shock were used in this study to accelerate the changes of the conductive adhesive in the service environment, thus conducting research on the reliability of the conductive adhesive. During the experiment, the morphology and organization of the conductive adhesive sample were observed, and its volume resistivity and chip shear strength were measured to reflect the inherent changes of the conductive adhesive through changes in its properties. The research results showed that during the aging process at 150 ℃, the volume resistance of the conductive adhesive first decreased and then continuously increased, while the shear strength of the chip first increased and then decreased. After 5 000 hours of high temperature aging, the volume resistivity increased by 81.0% compared to before aging, and the shear strength of the chip was 56.5% of before aging. After 3 000 temperature shocks, the volume resistivity of the conductive adhesive increased by 77.2% compared to before the test, and the chip shear strength was only 13.8% of before the test. Analysis suggested that conductive adhesive mainly underwent oxidation of silver powder and aging of resin matrix during high temperature aging. On the one hand, this destroyed the interface structure between silver powder and resin matrix. On the other hand, the aging of resin matrix caused severe relaxation, resulting in a significant increase in volume resistivity and a decrease in adhesive strength. During the temperature shock process, due to the difference in thermal expansion coefficients between the conductive adhesive and the chip, as well as Kovar gold-plated substrate, creep and fatigue of the adhesive joint were induced under alternating stress loads. Cracks gradually propagated on the side of the joint near the chip and the side near the substrate, resulting in a significant decrease in joint strength.

【Keywords】electrically conductive adhesive; failure mode; high temperature aging; temperature shock

Process and Application

Study on the reliability of polypropylene adhesive resin for steel wire composite pipe

Wu Jinkui^1,2,3, Ni Fengyao^1,2,3, Kong Tao^1,3, Sun Zhizhuang^1,3,

Kong Debin^1,3, Kong Zhiyong^1,3, Wu Teng³, Kong Deliang³

(1.National Enterprise Technology Center of Shandong Donghong Pipe Industry Co., Ltd., Qufu  273100, Shandong, China; 2.Department of Chemistry and Chemical Engineering, Jining University, Qufu  273155, Shandong, China; 3.Shandong Donghong Pipe Industry Co., Ltd., Qufu  273100, Shandong, China)

【Abstract】Polypropylene adhesive resin was prepared by using maleic anhydride grafted polypropylene, polypropylene pipeline specific materials, and elastomers as raw materials. The steel wire configuration of the reinforcement layer of polypropylene steel wire pipe was designed by force balance method, and the polypropylene adhesive resin was used for the composite of polypropylene steel wire pipe. The reliability of polypropylene adhesive resin to polypropylene steel wire composite pipes was studied through peeling test, flattening test, high and low temperature cycling, blasting test, and static hydraulic pressure test. The research results showed that, the shear strengths of polypropylene adhesive resin for steel wire bonding at room temperature and 80 ℃ were 24.1 and 15.6 MPa, respectively. The peel strength of the pipe was 19.1 N/mm. Flattening test and high and low temperature cycling test confirmed that polypropylene adhesive resin had good bonding effect on the steel wire of the core tube, outer layer, and reinforcement layer of the pipe. The burst pressure of polypropylene steel wire pipe was 9.36 MPa, which met the requirement of a burst pressure greater than 3 times the nominal pressure. The polypropylene steel wire pipe passed the 20 ℃/3 PN/1 h static hydraulic pressure test, indicating that the polypropylene adhesive resin exhibited excellent composite effect on the polypropylene steel wire pipe.

【Keywords】polypropylene adhesive resin; steel wire composite pipe; composite effect; peel strength

Preparation and properties of anti-static coating based on potassium titanate whiskers/silicone rubber

Huang Hailong^1,2, Zhu Liangming¹, Luo Yuhan^1,3, Cheng Jingxuan^1,2, Li Shenghua^1,3, Guo Fan^1,3

(1.Hubei Institute of Aerospace Chemical Technology, Xiangyang  441003, Hubei, China; 2.Science and Technology on Aerospace Chemical Power Laboratory, Xiangyang  441003, Hubei, China; 3.The Key Laboratory of Emergency Rescue and Safety Protection Technology of Hubei Province, Xiangyang  441003, Hubei, China)

【Abstract】By combining the color and whisker structure characteristics of FT-3000 titanium dioxide and potassium titanate shiskers (PTWs), a light colored anti-static coating of potassium titanate whiskers/silicone rubber (PTWs/SR) was prepared by using silicone rubber (SR) as the resin matrix and PTWs and FT-3000 as anti-static fillers. The effects of PTWs on the anti-static properties, mechanical properties, and thermal stability of silicone rubber anti-static coating were studied, the anti-moisture and heat aging properties of the prepared PTWs/SR anti-static coating, as well as their interfacial bonding properties to different substrates were characterized. The research results showed that, ⑴ The whisker structure of PTWs could compensate for the small contact area of conductive fillers caused by the continuous distribution of FT-3000 conductive powder dots. Through the synergistic effect of the two, the volume resistivity of the silicone rubber coating was further reduced, forming a more complete conductive network together. ⑵ The tensile strength and elongation of PTWs/SR showed an increasing trend with the increase of PTWs dosage, and the improvement tended to plateau after 7 parts. When the dosage of PTWs was 7 parts, the tensile strength was 5.71 MPa and the elongation was 83.9%, which was 102% and 26% higher than the silicone rubber coating filled with FT-3000 alone. ⑶ Under the combined action of PTWs and FT-3000, the heat resistance of PTWs/SR coating was significantly improved. Compared with the blank silicone rubber coating, the thermal decomposition temperature was increased by 223 ℃. ⑷ PTWs/SR coatings had excellent interfacial bonding stability and good bonding performance to various materials such as specialty rubber, organic coatings, and metals at normal, high, and low temperatures, with good applicability. ⑸ After aging at 85 ℃ and 85%RH for 1 000 hours, the mechanical properties of PTWs/SR coating showed some degradation, and the decrease in elongation was greater, but overall it was controllable. The volume resistivity of PTWs/SR coating changed from 5.25×10⁶ Ω·cm to 8.19×10⁶ Ω·cm, indicating its good resistance to moisture and heat aging.

【Keywords】potassium titanate whiskers; silicone rubber; anti-static coating; preparation

Effect of fly ash on the properties of magnesium oxychloride inorganic plywood

Li Xiwang^1,2, Yu Hongwei^1,2

（1.College of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou  311300, Zhejiang, China; 2.National Engineering Technology Research Center for Comprehensive Utilization of Wood Resources, Hangzhou  311300, Zhejiang, China）

【Abstract】In this study, fly ash was selected as a modifier to prepare inorganic plywood using magnesium oxide, magnesium chloride, and poplar veneer as raw materials. The physical and mechanical properties, elastic modulus, and modulus of rapture of plywood were measured by using a universal mechanical tester, and the impregnation peeling and flame retardant properties of plywood were also determined. The research results showed that, ⑴ X-ray diffraction analysis showed that when the content of fly ash was 9%, the formation of gel like 518 phase crystal led to the improvement of water resistance of magnesium oxychloride plywood. Therefore, the addition of an appropriate amount of fly ash could improve the water absorption of magnesium oxychloride cement, thereby enhancing the water resistance of plywood. ⑵ Scanning electron microscope (SEM) characterization showed that the addition of fly ash reduced the density of the adhesive structure, resulting in many pores and gaps, leading to a decrease in the mechanical properties of the plywood. ⑶ After adding fly ash, the internal bonding strength of the plywood decreased to a minimum of 0.46 MPa at a fly ash addition of 6%. The addition of fly ash might affect the hydration rate of magnesium oxychloride adhesive, and the decrease in hydration reaction rate of adhesive under air hardening conditions would affect the strength of the adhesive. ⑷ After adding fly ash, the overall elastic modulus and modulus of rapture of plywood showed a decreasing trend. When fly ash was added to 9%, the elastic modulus and modulus of rapture were the lowest. ⑸ After adding different amounts of fly ash, the nail holding force on both the front and side of the plywood decreased. When the amount of fly ash added was 15%, the nail holding force on both the front and side of the plywood reached its minimum value. ⑹ After adding different amounts of fly ash, the 24 h water absorption rate and impregnation peeling length of the plywood decreased, and the water resistance significantly improved. When the amount of fly ash added was 9%, the 24 h water absorption rate of the plywood decreased to 21.7%, and the impregnation peeling length decreased to 12 mm, indicating the best water resistance of the plywood. ⑺ With the addition of fly ash, the flame retardant performance of the plywood decreased. When the amount of fly ash added was 15%, the temperature rise on the back of the plywood reached 180 ℃ in only 520 s.

【Keywords】magnesium oxychloride adhesive; fly ash; inorganic plywood; property

Material Science

 Structural study of ethylene-acrylic acid and ester copolymers

Du Wenbo, Shen Heyu, Guo Sen, Zhang Yue, Liu Zhenyu, Jiang Wenjun

(Research Institute of Maoming Branch Company, SINOPEC, Maoming  525011, Guangdong, China)

【Abstract】In order to further investigate the differences in branched structure of ethylene-methyl acrylate copolymers obtained by free radical polymerization and coordination copolymerization, and to explain the essential reasons for the differences in branched structure, the melting point, melting index, molecular weight, polar monomer insertion rate, and micro chain structure of imported ethylene-acrylic acid and ester copolymers were characterized and analyzed in this study. The research results showed that, ⑴ The melting point range of ethylene-acrylic acid and ester copolymers was 64.1~98.4 ℃. The melting index range was 2.81-10.50 g/10min. The average molecular weight (M_w) of EMA, EEA and EBA was almost around 200 000, and the molecular weight distribution (M_w/M_n) was less than 5.0. ⑵ The polar monomer MA in EMA copolymers coexisted on the polyethylene chain in two forms: the branched end and the main chain, with the branched end being the main form. MA did not have a continuous insertion structure in polyethylene chains, and was mainly inserted into polyethylene in a random form. ⑶ The imported EMA copolymer was obtained through high-temperature and high-pressure free radical polymerization, and the EMA copolymer chain contained butyl, pentyl, and long branches, while the EMA copolymer obtained through coordination polymerization contained short and long branches such as methyl, ethyl, and propyl. There were significant differences in the micro chain structure of EMA polymers obtained by two polymerization methods.

【Keywords】ethylene-acrylic acid and ester copolymers; semi-crystallization; structure; characterization

Influence of biomass carbon source on flame retardancy and bonding properties of EPDM

Liu Yanbin, Niu Lili, Zhao Xiaoya, Wang Zheng, Qi Shuangchun

(Department of Chemistry, Hengshui University, Hengshui  053099, Hebei China)

【Abstract】In order to further investigate the differences in branched structure of ethylene-methyl acrylate copolymers obtained by free radical polymerization and coordination copolymerization, and to explain the essential reasons for the differences in branched structure, the melting point, melting index, molecular weight, polar monomer insertion rate, and micro chain structure of imported ethylene-acrylic acid and ester copolymers were characterized and analyzed in this study. The research results showed that,⑴ Glucose, dextrin, cyclodextrin, and starch were used as carbon sources, combined with ammonium polyphosphate and melamine, the carbonization effect of EPDM could be significantly improved. To further improve the flame retardancy, it was necessary to add substances with significant expansion effects. ⑵ Glucose, dextrin, cyclodextrin, and starch were all rich in hydroxyl groups and had high polarity, which could significantly improve the bonding properties of EPDM. However, the poor compatibility with EPDM led to a significant decrease in the tensile strength of the rubber body. To further improve bonding properties, finding suitable compatibilizers was the main breakthrough. ⑶ The amount of ammonium polyphosphate was fixed as 25 parts. Through comparison of oxygen index, tensile properties and bonding properties, cyclodextrin had the best comprehensive performance, and the optimal dosage was around 25 parts. Dextrin followed, with an optimal dosage of around 35 parts. The optimal dosage of glucose and starch was around 15 parts. However, the melting point of glucose was too low and the sulfurization temperature was relatively high, making it unsuitable as a flame retardant carbon source. And dextrin, cyclodextrin, and starch all had good application prospects.

    【Keywords】ethylene propylene diene monomer; biomass carbon source; flame retardancy; bonding property; mechanical property