Scientific Research Report

Preparation and characterization of microencapsulated single-component room temperature curing pressure sensitive adhesive

Tang Rui, Huang Hong, Situ Yue, Fu Heqing

(School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou    510641, Guangdong, China)

【Abstract】Microcapsules coated with epoxy resin and thiol were prepared respectively by in situ polymerization method with melamine-formaldehyde (MF) as the wall material, and single-component epoxy pressure sensitive adhesive was then prepared by mixing two kinds of microcapsules. When the microcapsule walls were ruptured by external force, two kinds of core materials had good mutual solubility, which facilitated their mutual diffusion and homogenization after release to achieve rapid and uniform solidification. The microscopic morphology, size distribution, chemical structure and thermal stability of the microcapsules were characterized, and the curing exothermic process and bonding properties of single-component pressure sensitive adhesive were studied. The research results showed that the prepared microcapsules were all spherical in shape, with a smooth surface and an average particle size of about 8-10 μm, and the encapsulation rate was above 70%. The prepared microcapsules had good storage stability and could be stored for a long time at room temperature without quality change. They could be applied efficiently even when heated to 150 ℃. Microencapsulation of the active components would not damage the reactivity of the core material, and the adhesive had good curing effect at room temperature or even low temperature. Two kinds of microcapsules were mixed to prepare single-component adhesive, and the bonding strength was tested, the results showed that this microencapsulated single-component room temperature curing pressure sensitive adhesive had great potential for development.

【Keywords】microencapsulated adhesive; single-component; room temperature curing

Study on preparation and structure-activity relationship of electronic grade naphthyl epoxy resin

Zhai Ninghui, Cai Xiqing, Zhao Fugui, Cheng Jue, Zhang Junying

(College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing  100029, China)

【Abstract】Three kinds of high-purity electronic grade naphthyl epoxy resin with different sites were prepared by one-step synthesis, dechlorination and molecular distillation process, which were 1,5-dihydroxynaphthalene glycidyl ether (1,5-DNGE), 1,6-dihydroxynaphthalene glycidyl ether (1,6-DNGE) and 2,7-dihydroxynaphthalene glycidyl ether (2,7-DNGE). By controlling the consistency of epoxy value, curing agent and curing procedure, the relationship between the structure and properties of different sites on the naphthalene ring was analyzed. Two curing agents, i.e. polyether amine (D230) and 4-methylhexahydrophthalic anhydride (MEHHPA) were selected to study the curing kinetics of three kinds of naphthyl epoxy resin, and the reactivity of different sites on the naphthalene ring was investigated as well. The research results showed that the three bifunctional high-purity naphthyl epoxy resin prepared with different sites had nearly 100% purity, with the total chlorine, hydrolyzed chlorine, and inorganic chlorine contents below 1 000, 200, and 1 ppm, respectively, which were suitable for the requirements of electronic grade epoxy resin. In the D230 system, the activation energy of 1,6-DNGE was the lowest, while in the MEHHPA system, the activation energy of 2,7-DNGE was the lowest. Since the molecular structure of 1,5-DNGE and 2,7-DNGE was more symmetrical and the crosslinking degree was high, thus the glass transition temperature, rubber elastic modulus, crosslinking density, coefficient of linear expansion, dielectric and thermal weight loss data were better than those of 1,6-DNGE. 1,6-DNGE had the highest storage modulus [E'(50 ℃)>2 600 MPa], loss modulus (tanδ>1.1) and toughness, the processing performance was better, which was very suitable for preparing composite materials with excellent comprehensive performance, providing high-purity electronic grade naphthyl epoxy resin with excellent comprehensive performance and application value for the electronic packaging industry.

【Keywords】naphthyl epoxy resin; structure-activity relationship; curing kinetics; performance

Development of new type of sulfone-containing epoxy resin adhesive

Yang Xinyu¹, Huang Liqian^1,2, Yu Xinhai³

(1. College of Textiles, Donghua University, Shanghai  201620, China; 2.Key Laboratory of Textile Science & Technology, Ministry of Education, Donghua University, Shanghai  201620, China; 3. College of Chemistry and Chemical Engineering, Donghua University, Shanghai  201620, China)

【Abstract】The solvent-free adhesive system prepared from sulfone-containing oligomer (BPA21), epoxy resin, and multifunctional epoxy resin was modified by using thermoplastic carboxyl-containing polymer (PDTD). The performance of modified adhesive was tested and analyzed, and the effect of addition ratio of PDTD on the performance of epoxy adhesive system was explored. The research results showed that the reactivity of adhesive system with the addition of PDTD was increased, and when m(epoxy resin)∶m(PDTD)=100∶10, the reaction rate was the fastest, it needed to be stored separately from the curing agent during storage. With the increase of the proportion of toughening agent, the viscosity of adhesive system was increased in a positive correlation. In order to facilitate the coating, it was necessary to control its addition amount. When m(epoxy resin)∶m(PDTD)=100∶10, the tensile shear strength of epoxy resin adhesive system reached the highest value of 10.74 MPa, which was 29% higher than that without addition, fully achieving the toughening effect. The addition of PDTD could reduce slightly the dielectric properties of epoxy resin adhesive, but all five kinds of adhesive with different ratios of toughening agent showed good dielectric properties. Five kinds of adhesive containing different ratios of PDTD had extremely low water absorption rate and possessed good hydrophobicity, among which when m(epoxy resin)∶m(PDTD)=100∶10 and 100∶8, the water absorption rate was the lowest, making them suitable for storage and application in humid environment. In summary, when m(epoxy resin)∶m(PDTD)=100∶10, the viscosity of epoxy resin adhesive was relatively moderate, the system reactivity was high, it could be cured quickly and had excellent tensile shear mechanical properties, the overall performance was relatively the best, making it the relatively optimal proportion of the formula in this study.

【Keywords】thermoplastic carboxyl-containing polymer; sulfone-containing epoxy resin adhesive; modification; performance

Study on preparation and properties of dimeric acid polyamide hot melt adhesive

Lu Bo, Xue Xin

（School of Materials Science and Engineering, Shenyang University of Chemical Technology, Shenyang  110142, Liaoning, China）

【Abstract】Firstly, dimeric acid-ethylenediamine polyamide hot melt adhesive and dimeric acid-hexamethylenediamine polyamide hot melt adhesive were synthesized, respectively from dimeric acid, ethylenediamine and hexamethylenediamine. The modified polyamide hot melt adhesive was synthesized by copolymerization of polyether diamine instead of partial diamine and adipic acid instead of partial dimeric acid. The effects of the amount of polyether diamine and adipic acid on the properties of polyamide hot melt adhesive were investigated. The research results showed that, (1) The glass transition temperature (T_g), hardness and tensile strength of polyamide hot melt adhesive decreased with the increase of polyether diamine content. The tensile shear strength first increased and then decreased. When the content of polyether diamine was 20%, the tensile shear strength reached the maximum of 4.2 MPa. (2) When m(dicarboxylic acid) : m(ethylenediamine or hexamethylenediamine) : m(polyether diamine)=10 : 6 : 4, part of adipic acid was added into the dicarboxylic acid. With the increase of adipic acid content, the T_g, hardness, tensile strength and tensile shear strength of polyamide hot melt adhesive increased. When the content of adipic acid was 40%, the maximum tensile shear strength was 4.2 MPa, and the maximum T_g was 170.5 ℃. (3) When the content of polyether diamine was 40% and the content of adipic acid was the same, the T_g, hardness, tensile strength and tensile shear strength of dimeric acid-ethylenediamine polyamide hot melt adhesive were all higher than those of dimeric acid-hexamethylenediamine polyamide hot melt adhesive.

【Keywords】dimeric acid; polyamide hot melt adhesive; mechanical property; thermal property

Development and Application  

Effect of temperature-humidity coupling aging on bonding performance of modified silane sealant with PC

Zhang Jing¹, Wang Hao¹, Xu Zhibao², Yang Yang¹, Ni Qiang¹, Zheng Ziqin², Liang Jingheng²

(1.CRRC Qingdao Sifang Co., Ltd., Qingdao  266111, Shandong, China; 2. Yantai Branch of China Ordnance Industry No.52 Research Institute Co., Ltd., Yantai  264003, Shandong, China)

【Abstract】The effect of temperature-humidity coupling aging (70 ℃/100%RH) environment on the bonding performance of modified silane sealant with polycarbonate (PC) used for rail vehicle window & lampshade were investigated by using environmental simulation test chamber, universal tensile tester, infrared spectrometer, contact angle meter and optical microscope. The research results showed that after temperature-humidity coupling aging, the bonding performance between modified silane sealant and PC used for lampshade decreased significantly. The form of adhesive strip peeling failure changed from more than 95% cohesive failure to more than 95% interfacial adhesion failure, and the tensile shear strength decreased by more than 93%. However, the performance reduction of the car window sample after aging was smaller than that of the lampshade sample. After temperature-humidity coupling aging, there was foaming phenomenon between the PC primer and UV coating used for lampshade, which was the main reason for the decrease in the bonding performance of PC used for lampshade. In addition, high temperature accelerated the hydrolysis of ester structures in PC, which may also be one of the reasons for the decrease in bonding performance.

【Keywords】temperature-humidity coupling aging; modified silane sealant; PC; bonding performance; interface cracking

Study on effects of thermal acceleration on mechanical specimens of silicone sealant

Li Ziyong, Chen Bingyao, Song Jiacheng, Liao Yihong, Quan Wengao

(Guangdong Sanhe Holding Co., Ltd., Zhongshan  528400, Guangdong)

【Abstract】At present, the curing time of mechanical specimens of silicone sealant is generally up to 28 d. In order to accelerate the quality monitoring and product development of the company's daily silicone sealant products, the thermal acceleration test on aluminum and glass plate specimens of alcohol type, acid type and ketoxime type silicone sealant was conducted in this study. The research results showed that, (1) The tensile strength of aluminum plate specimens of alcohol type silicone sealant cured at 23 ℃ for 15 days was similar to that cured at 28 days. The mechanical properties of aluminum and glass plate specimens fluctuated under 50 ℃ curing environment. The tensile strength and elongation at break of aluminum and glass plate specimens significantly decreased curing at 70 ℃. (2) The tensile strength of aluminum plate specimens of acid type silicone sealant reached its maximum value after 15 days of curing at 50 ℃. The tensile strength and elongation at break of glass plate specimens of acid type silicone sealant under 50 ℃ curing also continuously improved, and after 15 days, the mechanical properties were closed to those of standard environmental curing. The changes in tensile strength and elongation at break of acid type silicone sealant specimens under the curing environment of 70 ℃ were complex, and this temperature was not suitable as a curing temperature for thermal acceleration. (3) The tensile strength and elongation at break of ketoxime type silicone sealant specimens cured at 50 ℃ for 13 days were similar to those cured in standard environment, and prolonging the curing time led to an increase in tensile strength and a decrease in elongation at break. The mechanical properties of aluminum plate specimens of ketoxime type silicone sealant changed complex under curing environment of 70 ℃, while the mechanical properties of glass plate specimens of ketoxime type silicone sealant showed a gradual upward trend. (4) The thermal acceleration effect of silicone sealant with different formulations was different, manufacturers could conduct thermal acceleration test based on the characteristics of their own products to monitor the quality change of each batch of products.

【Keywords】single component silicone sealant; thermal acceleration; mechanical property

Preparation and property research on thermal conductive silane modified polyurethane adhesive

Chen Wang, Liu Longjiang

[Kangda New Material (Group) Co., Ltd., Shanghai  201419, China]

【Abstract】Polyurethane was synthesized from polyether and diisocyanate, and silane modified polyurethane (SPU) prepolymer was prepared by sealing with silane, and then, thermal conductive silane modified polyurethane adhesive was prepared by adding thermal conductive fillers and additives. The effects of polyether molecular weight, isocyanate, terminated silane, and thermal conductive filler on the performance of SPU adhesive were studied. The research results showed that as the molecular weight of polyether increased, the tensile strength and hardness of adhesive continuously decreased, the elongation at break continuously increased, and the thermal conductivity remained basically unchanged. The benzene ring and symmetrical structure in the isocyanate structure were beneficial for improving the rigidity of adhesive, reducing its toughness, and having little impact on its thermal conductivity. The tensile strength and elongation at break of the adhesive prepared by trimethoxysilane termination were higher than those of the adhesive prepared by hexamethoxysilane termination, and trimethoxysilane was more suitable as terminated agent than hexamethoxysilane. The smaller the alumina particle size, the more favorable to improve the thermal conductivity, and the thermal conductivity of adhesive prepared by the composite particle size was higher than that of the single particle size. In the range of 60-80 parts, as the amount of thermal conductivity filler increased, the thermal conductivity coefficient continued to increase, and the thermal conductivity performance became much better.

【Keywords】silane modified polyurethane; thermal conductivity; adhesive

Preparation and properties of high-temperature resistant cyanate ester adhesive with polyborosilazane as curing agent

Cui Jiuhong¹, Liu Dan², He Tianqi^2,3, Luo Yongming², Xu Caihong^2,3

(1. Research Institute of Aerospace Special Materials and Processing Technology, Beijing  100074, China; 2. Institute of Chemistry Chinese Academy of Sciences, Beijing  100190, China; 3. School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing  100049, China)

【Abstract】A cyanate ester-based high-temperature resistant adhesive was prepared by using cyanate ester as the matrix resin and polyborosilazane precursor as the curing agent, compounding with corresponding fillers. The effect of polyborosilazane dosage on the curing characteristics of cyanate ester, structural changes of cured product, and thermal stability of cured product was studied. The research results showed that compared with traditional cyanate ester adhesive, the curing temperature of cyanate ester catalyzed by polyborosilazane was reduced by 50-100 ℃. Polyborosilazane could catalyze the low-temperature curing of cyanate ester at 150 ℃, and T_5% of cyanate ester cured product catalyzed by 20 parts of polyborosilazane reached a maximum of 476.3 ℃. The highest room temperature bonding strength of the high-temperature resistant adhesive prepared on this basis was 16 MPa. After aging at 400 ℃ for 3 hours, the bonding strength still reached 12 MPa, indicating that the adhesive had good bonding and aging resistance properties. The adhesive prepared in this study had the potential to be used in industries such as aviation, aerospace, and electronics due to its low curing temperature, good bonding performance, and temperature resistance.

【Keywords】adhesive; cyanate ester; polyborosilazane; high-temperature resistant; curing agent

 Special Topics and Review 

Overview and application analysis of damping adhesive materials in China

Gan Lutong¹, Li Yong¹, Liu Xin²

（1.China Adhesives and Tape Industry Association, Beijing  100027, China; 2.China National Chemical Information Center Co., Ltd., Beijing  100029, China)

【Abstract】The classification, preparation methods and main factors affecting damping performance of damping adhesive materials, such as compatibility, temperature, copolymerization, vibration mechanical energy, crosslinking degree, filler, microstructure and material interface were analyzed. The future market applications of damping adhesive materials, such as polyurethane, intelligent terminal, automotive and national defense application were reviewed. Finally the future development was prospected.

【Keywords】damping; phase separation; polyurethane; vibration and noise reduction

Discussion on measurement method of thermal conductivity of applied materials

Tan Yuemin, Xu Jianming, Pang Wenjian, Niu Rong

(Guangzhou Baiyun Chemical Industry Co., Ltd., Guangzhou  510540, Guangdong, China)

【Abstract】With the proposal of the “Dual Carbon” goal, the thermal conductivity of applied materials became one of the important indexes to evaluate whether the materials meet the energy-saving concept. The measurement of thermal conductivity is an important judgment for the thermal conductivity of materials, and it is crucial to choose a suitable measurement method to obtain accurate thermal conductivity. Combined with previous experience, the test principles, instrumentation, influencing factors and test improvement measures of the guarded hot plate method, heat flow meter method, pipe insulation method, thermal impulse method, hot wire method, laser flash method, and transient plane heat source method were summarized in this paper, in order to provide a reference for the selection of the measurement method for applied materials. The selection of testing method for specific material within a reasonable range of application was prospected.

【Keywords】applied materials; thermal conductivity; measurement method