Special Topics Review

Marine mussel-inspired self-healing polymeric adhesive with strong dry/wet adhesion

Yang Haoyu^1,2, Zhang Qing¹, Huang Jijun¹

(1.College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing  100049, China; 2.Department of Chemical and Materials Engineering, University of Alberta, Alberta, Canada)

【Abstract】Inspired by the extraordinary adhesion properties of mussel adhesion proteins, researchers have introduced the main functional group dopamine (mainly catechol groups) in mussel adhesion proteins into polymer materials, synthesizing many biomimetic polymer materials with different molecular structures and functions, significantly expanding their application scope. The composition and function of mussel foot silk protein were first described in this article, then the current applications of mussel biomimetic materials in underwater adhesive, self-healing materials, anti-fouling materials, and biomedical materials were introduced. Finally, the application prospects of mussel biomimetic materials were provided.

【Keywords】mussel biomimetic; adhesion protein; dopamine; catechol; functional polymer

Research status of addition-type silicone optical adhesive

Wang Dongzhe,Zhuang Rui,Chen Dianlong,Zhang Jingjing,Huang Rui,Li Rui,Wang Yuanrong,Su Yaping

(Yellow River Delta Chambroad Institute Company Limited, Binzhou  256600, Shandong, China;)

【Abstract】The hydrosilylation reaction is an important method for synthesizing silicone compounds, and its typical application in the field of optical adhesive is the addition-type silicone optical adhesive. This type of material is widely used in fields such as electronics, electrical engineering, and optics due to its excellent performance. Taking high refractive index addition-type silicone optical adhesive as the research object, the research progress of its key components (vinyl polysiloxane, hydrogen containing crosslinking agent, catalyst, and reinforcing filler) was systematically reviewed in this article, and the influence of key factors such as the molar ratio of Si—H and Si—V and curing procedures on product performance was deeply analyzed. On this basis, further prospects were made for the future development direction of this material.

【Keywords】hydrosilylation reaction; silicone; optical adhesive; high refractive index

Research Report

A study on low-temperature curing thiol-epoxy/episulfide adhesive based on photo base generator catalysis

Yang Yutong¹, Li Zhiquan^1,2, Liu Xiaoxuan^1,2

（1.Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, Guangzhou  510006, Guangdong, China; 2.School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, Guangdong, China）

【Abstract】A thiol-epoxy/episulfide curing system based on photo base generator catalysis was developed in this study to solve the problems of poor storage stability and high post-curing temperature in traditional photo base generator catalyzed adhesive systems.A highly active episulfide monomer (BADGE-S) was synthesized by nucleophilic substitution reaction between potassium thiocyanate (KSCN) and bisphenol A diglycidyl ether (BADGE), and was compounded with BADGE and tetra(3-mercaptobutyric acid) pentaerythritol ester (PE-1) crosslinking agent. A novel thiol epoxy/ episulfide photopolymerization system triggered by 365 nm LED was constructed by introducing photo base generator (PB-DBU) and photosensitizer 2-isopropylthioanthraquinone (ITX). A photo curing adhesive with high storage stability, low-temperature rapid curing, and excellent bonding strength was prepared, and its various properties were characterized. The research results showed that, ⑴ Multiple characterizations such as FT-IR and NMR confirmed that the epoxy groups were completely converted into episulfide structure. Compared with epoxy precursors, BADGE-S exhibited higher base catalytic activity due to its lower ring opening energy barrier of episulfide groups and easier polarization of sulfur atoms towards electrons, providing an ideal monomer for subsequent low-temperature rapid curing. ⑵ The study of light absorption performance showed that PB-DBU was only absorbed by deep ultraviolet light sources. After introducing ITX, the system exhibited broad and strong absorption at 350-400 nm, with an extinction coefficient of 6.86×10³ L/(mol cm) at 383 nm. The triplet state (³ITX*) lifetime was extended, and the sensitization efficiency was improved. Under 365 nm LED irradiation, a single electron transfer occurred from ³ITX* to PB-DBU, causing the C—N bond to break. Within 3.5 min, the pH increased from 7.8 to 9.5 and stabilized. Phenol red color change simultaneously confirmed the rapid release of DBU, providing strong base catalysis for subsequent low-temperature thiol-epoxy/episulfide click polymerization. ⑶ Through the study of polymerization kinetics, it was found that as the content of episulfide monomer increased to 20%, the peak polymerization temperature of the system decreased from 173 ℃ to 165 ℃, and the epoxy conversion rate increased from 13.81% to 53.33% after light irradiation. The bonding strength significantly increased by nearly 10 times under low-temperature conditions of 80 ℃ (from 0.164 MPa to 1.532 MPa). ⑷ Through the study of storage stability, it was confirmed that the PB-DBU photo base generator system exhibited excellent storage stability, maintaining low viscosity even after 144 h of storage at 40 ℃ in the dark, which was significantly better than the commercial PL-DBN system. ⑸ The thiol-epoxy/episulfide curing system based on photo base generator catalysis constructed in this study combined high storage stability, low-temperature curing characteristics, and excellent bonding properties, providing a new material selection for precision electronic packaging and optical device assembly.

【Keywords】photo base generator; episulfide; thiol-epoxy; low-temperature curing; adhesive

Preparation and curing kinetics study of a new high-performance epoxy/BAPP-BMI adhesive

Wen Manying, Fan Tianhua, Yu Xinhai

(College of Chemistry and Chemical Engineering, Donghua University, Shanghai  201620, China)

【Abstract】Long chain ether bonded 2,2-bis[4-(4-maleimidophenoxy) phenyl] propane (BAPP-BMI) was synthesized by using 2,2-bis [4-(4-aminophenoxy) phenyl] propane (BAPP) and maleic anhydride (MA) as raw materials. A series of epoxy/BAPP-BMI adhesive were prepared by mixing bisphenol A-type epoxy resin (E-51), self-made BAPP-BMI, epoxy chain extender (SD-248), curing agent (MTHPA), and curing accelerator (2E4MI), and their structures and properties were analyzed. The research results showed that BAPP-BMI monomer was successfully synthesized, and its structure was confirmed by FT-IR, which was then used to prepare epoxy/BAPP-BMI adhesive. Moderate addition of BAPP-BMI could significantly improve the comprehensive performance of the cured material. It exhibited high reactivity at 30 ℃, with a maximum tensile shear strength of 15.4 MPa, and effectively improved the toughness (67% increase in maximum impact strength), mechanical strength, and hydrophobicity (water absorption rate<0.10%, with a minimum of 0.02%) of the material. The curing kinetics analysis showed that the activation energy of the reaction was 77.52 kJ/mol, and the reaction order was 0.9. Meanwhile, this series of adhesive exhibited stable low dielectric constant (3.84-4.26) and low dielectric loss (2.02%-2.20%) at high frequencies, with capacitance values ranging from 4.97-5.52 pF, demonstrating excellent dielectric properties and potential applications in fields such as electronic packaging.

【Keywords】BAPP-BMI; adhesive; mechanical property; dielectric property; curing kinetics

Research on toughening and flame retardant modification of melamine-formaldehyde resin adhesive

Feng Yan¹, Mashanlo Abdurakhman¹, Lin Zhiqian¹, Shen Jiahao¹, Chen Fengqing^1,2, Dai Jinfeng^1,2

(1.College of Chemistry and Materials Engineering, Zhejiang A&F University, Hangzhou  311300, Zhejiang, China; 2.Key Laboratory of Wood Science and Technology of Zhejiang Province, Hangzhou  311300, Zhejiang, China)

【Abstract】Despite exhibiting good heat resistance, the high brittleness of melamine-formaldehyde (MF) resin adhesive restricted its utilization in impregnated paper decorative materials. In this study, polyborosiloxane (PBS) was synthesized by polycondensation of boric acid and hydroxysilicone oil, and was used to modify MF for toughning and flame retardancy. The influence of PBS addition amount on the mechanical properties, flame retardancy and toughness of modified MF adhesive was systematically investigated. The research results showed that the Si—O—B flexible segments in PBS significantly enhanced the toughness of MF through physical entanglement and hydrogen bonding, and the bonding strength and flame retardancy of modified MF adhesive were both enhanced. When the PBS addition amount was 5%, the limit oxygen index (LOI) of modified MF sample reached 34.3%, which was 4.6% higher than that of pure MF. The burning through time of impregnated paper veneer was extended to 106 seconds (an increase of 253%). The dry/wet bonding strength reached 2.98 and 3.11 MPa, respectively, an increase of 36.1% and 5.8% compared to pure MF. Meanwhile, the elongation at break of 5% PBS modified MF increased from 4.2% to 26.5%, demonstrating excellent flexibility and crack resistance. This study provided a new strategy for developing MF adhesive with high strength, high toughness, and flame retardant properties, which was of great value for expanding the application of MF adhesive in customized decorative materials.

【Keywords】melamine-formaldehyde resin; polyborosiloxane; toughening modification; flame retardancy

Process and Application

Factors affecting yellowing of room-temperature vulcanized silicone rubber

Liu Bin, Qin Ying, Cao Junru, Zhao Zhipeng, Xie Zhijian, Wang Yunran

(1.China Bluestar Chengrand Chemical Co., Ltd., Chengdu  610041, Sichuan, China;2.National Silicone Engineering Technology Research Center, Chengdu  610041, Sichuan, China)

【Abstract】One-component room-temperature vulcanized silicone rubber was prepared by using hydroxyl-terminated polydimethylsiloxane as the base polymer, fumed silica as the reinforcing filler, ketoxime silane as the crosslinking agent, and dibutyltin dilaurate as the catalyst. The effects of ketoxime crosslinking agent, silane coupling agent, pigment, antioxidant, and heat-resistant agent on the yellowing of silicone rubber were investigated. The research results showed that, ⑴ A comparative study was conducted on the effects of three crosslinking agents on the yellowing of silicone rubber. To control the yellowing degree of silicone rubber, it was recommended to prioritize the use of methyl tributone oxime silane (D-30) as a crosslinking agent and avoid prolonged exposure of silicone rubber to high temperature as much as possible. ⑵ The influence of four silane coupling agents on the yellowing of silicone rubber was investigated. When KH-560 or KH-570 was used as an adhesive coupling agent in deoxime-type room-temperature vulcanized silicone rubber, the yellowing degree was relatively low. ⑶ The combination of titanium dioxide and permanent purple pigment could effectively mask or neutralize the yellow color generated by chromophores, improved the appearance of silicone rubber, and further reduced the degree of yellowing. ⑷ The combination of antioxidant and heat-resistant agent had a synergistic effect, which could effectively reduce the yellowing degree of silicone rubber in high temperature environment. ⑸ The yellowing mechanism of silicone rubber could be considered as a model of "free radical oxidation reaction - accumulation of chromophores". By adding pigment, antioxidant, and heat-resistant stabilizer to deoxime-type silicone rubber, the yellowing degree of silicone rubber at room temperature and high temperature could be significantly reduced, and the application of silicone rubber in high-end fields such as 5G base station sealing materials and new energy vehicle battery pack protective parts could be expanded.

【Keywords】silicone rubber; bonding sealant; silane coupling agent; antioxidant; heat-resistant agent; yellowing

Preparation and research of a bio-based polyurethane structural adhesive applied

 in the field of new energy battery

Li Renpu, Zhang Zhijun, Liu Bin, Lu Chunlan, Zhou Gang

(Guangdong Pustar Material Technology Co., Ltd., Dongguan  523646, Guangdong, China)

【Abstract】Polyol (A) component and curing agent isocyanate (B) component were prepared, respectively in this article by using polyhydroxy castor oil, long-chain castor oil, and bio-based prepolymers as raw materials. The bio-based polyurethane material was obtained by mixing with a volume ratio of V_A∶V_B=1∶1 after curing. The properties of the prepared bio-based polyurethane were characterized through infrared spectroscopy, surface drying time, hardness, tensile strength and elongation at break, shear strength, and "double 85" weather resistance testing. The research results showed that, ⑴ When the content of polyhydroxy castor oil was 30% (relative to the mass of component A), the surface drying time of the material was 33 min, the hardness was 60D, the tensile strength was 13.7 MPa, the maximum elongation at break was 68%, the shear strength was 14.0 MPa, and the "double 85" weather resistance attenuation rate was 5.1%. ⑵ When the content of long-chain castor oil was 30% (relative to the mass of component A), the bio-based content of the material was high, the surface drying time was 37 min, the hardness was 57D, the tensile strength was 11.7 MPa, the maximum elongation at break was 73%, the shear strength was 13.4 MPa, and the "double 85" weather resistance attenuation rate did not exceed 10%. ⑶ When the content of bio-based prepolymer was 60% (relative to the mass of component B), the bio-based content of the material was high, the surface drying time was 36 min, the hardness was 62D, the tensile strength was 14.2 MPa, the maximum elongation at break was 63%, the shear strength was 14.1 MPa, and the "double 85" weather resistance attenuation rate did not exceed 10%. ⑷ In summary, when the content of polyhydroxy castor oil was 30%, the content of long-chain castor oil was 30%, and the content of bio-based prepolymer was 60%, the bio-based polyurethane material prepared had the relatively highest bio-based content and the relatively best comprehensive performance.

【Keywords】new energy battery; bio-based; polyurethane; structural adhesive

Material Science

Preparation and properties of high performance PBAT/PPC/PLA composite films compatibilized with PAPI

Gao Yuan, Shen Xing

(College of Aerospace Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing  210016 Jiangsu, China)

【Abstract】The issues of “white pollution” and energy crisis have made the development of functionalized biodegradable polymer materials an urgent strategic need. Polybutylene adipate terephthalate (PBAT) has excellent toughness, good processability, and complete biodegradability, but its tensile properties, gas barrier properties, and UV aging resistance are poor, limiting its widespread application. Blending PBAT with other biodegradable polymer materials and introducing light stabilizers are effective ways to improve the aforementioned performance issues. PBAT/PPC/PLA composite films with different ratios were prepared in this study by using extrusion blending and casting processes. Reactive compatibilizer polyaryl polymethylene isocyanate (PAPI) was added to the blending system, and the microstructure and various properties of composite materials were systematically analyzed. The research results showed that, ⑴ Simple ternary blending had limited improvement on material properties, while introducing PAPI could significantly improve the overall performance of the system. When the component ratio of each group was m(PBAT): m(PPC): m(PLA): m(PAPI)=60:30:10:0.7, the tensile strength, Young's modulus, and water vapor barrier performance of composite films were improved by 59%, 122%, and 62%, respectively, compared to pure PBAT film. ⑵ Rheological testing and torque analysis indicated that the compatibilizer PAPI could undergo chain extension reactions with PBAT, PPC, and PLA, and its reaction activity was higher than that of the compatibilizer ADR4468. ⑶ The results of infrared spectroscopy, scanning electron microscopy, and dynamic mechanical analysis further indicated that PAPI effectively enhanced the compatibility between the blending components and promoted the crystallization behavior of PBAT. ⑷ PAPI had a relatively small impact on the transparency of composite films, and while maintaining the original transparency, it delayed the degradation rate of the material. ⑸ In summary, PAPI as an efficient reactive compatibilizer, significantly optimized the structure and comprehensive properties of PBAT/PPC/PLA composite films.

【Keywords】PBAT film; biodegradable film; reactive compatibilizer