Special Topics Review

Retrospect and prospect——An analysis of China's hot melt adhesive market in 2025

Zhao Qingfang^1,2

(1. China Adhesives and Tape Industry Association, Beijing  100028, China; 2. Hangzhou Renhe Hot Melt Adhesive Co., Ltd., Hangzhou  310008, Zhejiang, China)

【Abstract】Based on the survey statistics of 77 key enterprises conducted by the China Adhesives and Tape Industry Association, the development status of China's hot melt adhesive industry during the 14th Five Year Plan period (2021-2025) was systematically reviewed in this paper, and the industry trends and plans for the 15th Five Year Plan period (2026-2030) were forecasted. Research showed that in 2025, China's hot melt adhesive industry achieved a sales volume of 1.879 6 million tons and a sales value of 32.322 billion yuan, with year-on-year growth rates of 4.36% and 1.07% respectively. The growth rates significantly slowed compared to previous period, indicating the industry has entered a critical phase of transforming from high-speed scale expansion to high-quality development. In terms of industrial structure, traditional products such as ethylene-vinyl acetate copolymer (EVA), styrene-butadiene-styrene block copolymer (SBS), and polyolefin (PO) hot melt adhesive had seen a steady increase in sales volume, while high-end varieties such as reactive polyurethane (PUR) hot melt adhesive had grown significantly, becoming important structural growth points. In the downstream application market, demands in transportation, packaging, sanitary materials and other fields had maintained good growth, while traditional markets such as construction and woodworking had tended to stabilize. The growth momentum of hot melt adhesive films for photovoltaics had slowed down. The industry was facing challenges such as intensified competition in the form of "involution", increased profit pressure on enterprises, and complex business environment. Looking ahead to the 15th Five Year Plan, China's hot melt adhesive industry would focus on innovation driven and steady development, and strive to promote high-end, green, intelligent and international products. Key technologies such as photovoltaic film (POE), UV/EB cured pressure sensitive adhesive, reactive polyurethane (PUR) hot melt adhesive, bio-based and biodegradable adhesive would be emphasized, and the development goal of achieving a total output of 2.825 million tons and sales value of 47.19 billion yuan by 2030 was planned. This article aimed to provide systematic market data and trend references for industry policy formulation, corporate strategic adjustments, and related research.

【Keywords】hot melt adhesive; market scale; industrial structure; market segmentation; 15th Five Year Plan; development trend

Research progress on optimization of condensation-type silicone sealant process formulation

Li Tao¹, Xie Xiaoyuan¹, Dong Meng¹, Zuo Ting², Zhu Yanbin², Liu Guangming²

(1.Key Laboratory of High Temperature and High Pressure Materials and Welding for Machinery Industry, Dongfang Boiler Co., Ltd., Chengdu  611731, Sichuan, China;2.School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang  330063, Jiangxi, China)

【Abstract】Condensation-type silicone sealant is a high performance sealing material based on hydroxyl-terminated polydimethylsiloxane polymer, which achieves room temperature vulcanization through condensation reaction. The basic process formulation of condensation-type silicone sealant was reviewed in this paper, and the influence of factors such as molecular structure, viscosity, and compounding of the basic polymer polydimethylsiloxane on the construction performance, mechanical properties, and other properties of silicone sealant was introduced. At the same time, the influence of various components such as crosslinking agents, catalysts, reinforcing fillers, adhesion promoters, and plasticizers on the rheological properties, mechanical properties, durability, and functionality of silicone sealant was elaborated. Finally, the future development direction of silicone sealant process formulation was discussed. Through molecular design, interface modification, and multi-component synergistic regulation, the product could effectively achieve rapid curing, low modulus, high elongation rate, and environmentally friendly development. However, the interaction mechanism between multiple components, the balance between high performance and low cost, and the development of new environmentally friendly materials to replace traditional oxime systems were still the main challenges currently faced. Future research should focus on deepening the understanding of structure-activity relationships, developing deep environmental protection and functional integration technologies, and promoting their innovative applications in fields such as new energy and flexible electronics.

【Keywords】silicone sealant; condensation-type; formulation optimization; component regulation; performance impact; development trend

Research on revision of flame resistance standard and testing methods for pressure sensitive adhesive tape for multi-scenario application

Shen Yan¹, Chen Weibin^2,3

(1. Shanghai Institute of Rubber Products Co., Ltd., Shanghai  201702, China; 2. Meixin New Material Co., Ltd., Shenzhen  518053, Guangdong, China; 3. Huizhou Meixin Electrical Co., Ltd., Huizhou  516100, Guangdong, China)

【Abstract】To meet the development needs of pressure sensitive adhesive tape industry and the testing requirements for flame resistance in emerging fields, the current status of flame resistance standards for pressure sensitive adhesive tape issued by international organizations (ISO, IEC) and countries/regions such as the United States and the European Union was systematically investigated in this paper. An in-depth analysis of the deficiencies in China's current national standard GB/T 15903—1995, including aspects of test methods, evaluation systems, timeliness, environmental adaptability, and compatibility with special materials was also conducted. Based on the national standard revision plan, while retaining the original suspension test method, five new test methods of horizontal placement test method, winding test method, horizontal burning test method, vertical burning test method, and roll test method were added. A multi-method, multi-dimensional test and evaluation system was established, with clear specifications for the test principle, test procedure, result calculation, and grade evaluation rules of each method. The revised standard featured comprehensive technical content and test methods that were consistent with international standards. It broke through the limitations of the original standard, such as single test method and weak scenario adaptability, and was suitable for application scenarios in multiple industries including electronics and electrical appliances, automotive wiring harness, and new energy. It could provide technical support for the quality control of pressure sensitive adhesive tape and the high quality development of the industry.

【Keywords】pressure sensitive adhesive tape; flame resistance; standard; test method; multi-scenario application

Research Report

Study on the accelerating effect of sulfaguanidine on the curing behavior of hot melt prepolymeric phthalonitrile resin containing amine

Chen Liangqin¹, Huang Haihong¹, Wu Xiao², Lu Shilong²,

Zhang Xiaoa¹, Wang Chengzhong¹, Zhang Junying¹

(1.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;2.AVIC Research Institute for Special Structures of Aeronautical Composites, Ji’nan  250023, Shandong, China)

【Abstract】To improve the curing efficiency of hot melt prepolymeric phthalonitrile resin containing amine (PNA), the accelerating effect of sulfaguanidine on the curing behavior of PNA was investigated. PNAS resin systems with different sulfaguanidine contents (1-7 phr) by melt blending method were prepared in this study, and their exothermic behavior was analyzed to further explore the curing kinetics, thermal properties, and bonding properties of PNA and PNAS-5. The research results showed that sulfaguanidine significantly reduced the curing temperature and activation energy of PNA. As the dosage increased, the exothermic peak of curing gradually merged from double peaks to a single peak. When the dosage of sulfaguanidine was 5 phr (PNAS-5), the curing peak temperature decreased from 330 ℃ of PNA to 260 ℃, and the main curing temperature zone shifted from above 300 ℃ to 230-300 ℃. Dynamics analysis showed that the average activation energy of PNAS-5 was 67.10 kJ/mol, which was about 31.8% lower than that of PNA (98.45 kJ/mol), and the activation energy was lower at low conversion rates, which was more conducive to low-temperature curing. Under the curing condition of 200 ℃/3 h+220 ℃/3 h, the tensile shear strength of PNAS-5 at 25 ℃ reached 18.2 MPa, which was 61% higher than that of PNA. Sulfaguanidine did not damage the high thermal stability of the system. The initial decomposition temperatures (T_5%) of PNA and PNAS-5 were 479 ℃ and 481 ℃, respectively, and the residual carbon rates at 800 ℃ were all higher than 74%. However, due to the introduction of sulfaguanidine flexible structure, the glass transition temperature (T_g) of PNAS-5 decreased by 42 ℃, resulting in a slight decrease in its high-temperature bonding strength, reflecting the balance between mechanical enhancement and thermomechanical properties. Comprehensive research had shown that sulfaguanidine could effectively promote the low-temperature and efficient curing of phthalonitrile resin containing amine, with excellent thermal stability and room temperature bonding properties.

【Keywords】sulfaguanidine; curing kinetics; phthalonitrile prepolymer; gel time

Study on isosorbide-based organic-inorganic dual network UV-curable adhesive

Liang Guiping¹, Lou Qiaoxiao², Wang Zhongqi², Jiang Yue², Zhang Guona²,

Liang Genglong², Cao Chen², Sun Jia², Li Zhenmei¹, Ye Daiyong¹

（1.School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou  510640, China; 2. Beijing Electric Vehicle Co., Ltd., Beijing  100176, China）

【Abstract】To replace traditional toxic polyurethane raw materials such as toluene diisocyanate, bio-based isosorbide was used as the raw material in this study, and a non-isocyanate polyurethane (NIPU) main chain was constructed through dimethyl carbonate condensation. The organic-inorganic dual network NIPU adhesive (DNIPU) was successfully prepared by utilizing the synergistic effect of hydrolysis condensation of γ-glycidoxypropyltrimethoxysilane (KH-560) and UV curing of γ-methacryloyloxypropyltrimethoxysilane (KH-570)/2-hydroxyethyl methacrylate (HEMA), and then various properties were measured and characterized. The research results showed that a stable chemical bond was formed between the organic phase and the inorganic phase, and a complete dual crosslinked network structure was constructed. The dual network structure significantly improved the crosslinking density and environmental stability of the material. The gel content of the optimized proportion of DNIPU1 in toluene reached 84.09%, which was 2.1 times of the unmodified sample. Its 180° peel strength, shear strength, and tensile strength on polyurethane substrate were 0.831 N/mm, 0.830 MPa, and 3.237 MPa, respectively, which were 13.9 times, 5.1 times, and 4.5 times of the unmodified NIPU, respectively. At the same time, the initial decomposition temperature and glass transition temperature of DNIPU1 reached 207 and 41.68 ℃, respectively, and the water contact angle increased to 65.30°, demonstrating excellent thermal stability and hydrophobicity. This organic-inorganic dual network strategy effectively overcame the shortcomings of low crosslinking density, insufficient bonding and heat resistance of traditional NIPU, providing new ideas for the design of high performance and environmentally friendly structural adhesive.

【Keywords】non-isocyanate polyurethane; isosorbide; silane coupling agent; UV curing; organic-inorganic dual network; adhesive

Process and Application

Study on the bonding performance of p-tert-butylaniline modified epoxy resin to aluminum substrate

He Jinmei¹, Yin Haoyu¹, Li Sheng², Liu Zhengyuan¹, Li Bingshuai¹, Mo Kangnan¹ Bai Yongping¹

(1.School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin  150001, Heilongjiang, China; 2. Institute of Petrochemistry, Heilongjiang Academy of Sciences, Harbin  150040, Heilongjiang, China)

【Abstract】In order to improve the thermal stability and the aluminum-substrate bonding performance of epoxy resin (E-51)/dicyandiamide system, different contents (2.5%, 5.0%, 7.5% and 10.0%) of p-tert-butylaniline (PTBA) were used to modify E-51 in this paper. Combined with infrared spectroscopy characterization and nuclear magnetic resonance hydrogen spectroscopy, it was confirmed that PTBA successfully modified the molecular structure of E-51. The thermal properties and microstructure of the modified and unmodified materials were systematically characterized by differential scanning calorimetry, thermogravimetric analysis, and scanning electron microscopy. The research results showed that the introduction of PTBA significantly increased the glass transition temperature (T_g) of E-51. The T_g of unmodified E-51 was 161.20 ℃, and after 10.0% PTBA modification, the T_g increased to 198.51 ℃. The residual carbon rate of the modified material significantly increased, with 5.0% PTBA modified group achieving a residual carbon rate of 16.9% at 500 ℃, much higher than the unmodified group's residual carbon rate (6.3%). At the same time, the maximum weight loss rate of the modified material decreased from 14.25%/min to 6.98%/min, and the thermal decomposition process was significantly delayed. The bonding performance analysis showed that the tensile shear strength of 5.0% PTBA modified system on the aluminum substrate reached 24.60 MPa, which was an increase of 31.3% compared to the unmodified system (18.74 MPa). Scanning electron microscopy characterization showed that the cross-sectional morphology of E-51 modified with 5.0% PTBA changed from brittle fracture characteristics to a ductile fracture structure rich in wrinkled and stepped textures. The rigid tert-butyl and aniline groups in PTBA molecules formed a strong interaction with the E-51 molecular chain, constructing a rigid cross-linked network that not only limited the thermal movement of the molecular chain but also enhanced the energy gathering within the system, thereby simultaneously optimizing the thermal and mechanical properties of E-51. The comprehensive performance showed that when the PTBA addition was 5.0%, the curing characteristics, thermal stability, and interfacial bonding performance of the resin reached the optimal balance, providing theoretical support and technical reference for its application in high temperature and high demand conditions.

【Keywords】p-tert-butylaniline; epoxy resin; dicyandiamide curing agent; aluminum-substrate bonding

Preparation and performance study of environmentally friendly lignin-glyoxal-phenolic resin adhesive

Huang Rui, Zhuang Junping, Wu Shubin

(School of Light Industry and Engineering, South China University of Technology, Guangzhou  510640, Guangdong, China)

【Abstract】Traditional phenolic resin is prepared by reacting petroleum-based phenol with carcinogenic substance formaldehyde, which poses significant health and safety risks. The mainstream trend in developing green and environmentally friendly wood adhesive is to partially replace phenol and formaldehyde with renewable lignin and bio-based formaldehyde to construct a new type of phenolic resin system. Lignin-glyoxal-phenolic resin (LPGF) adhesive was successfully prepared in this study by using industrial lignin and bio-based formaldehyde as raw materials, replacing some phenol and formaldehyde. The research results showed that the relatively optimal process parameters were the phenol-formaldehyde ratio of 1∶0.7, the substitution rate of 50% for both lignin and formaldehyde, and the hot pressing temperature of 170 ℃. The dry bonding strength of the obtained LPGF adhesive was (1.86±0.33) MPa, with free phenol and free formaldehyde contents of 0.45% and 0.26%, respectively, meeting the requirements of GB/T 14732—2017 standard. Infrared spectroscopy analysis confirmed that formaldehyde underwent crosslinking reaction with lignin and formed ether bonds. Thermal performance analysis showed that the curing peak temperature of LPGF (117.50 ℃) was significantly lower than that of traditional phenolic resin, which was beneficial for reducing energy consumption. However, its thermal stability also decreased, with a lower residual carbon rate (56.43%) and maximum weight loss rate temperature (359.74 ℃) compared to traditional phenolic resin, mainly due to the lower reactivity of formaldehyde reaction, making it difficult to form a dense and stable cross-linked structure like formaldehyde. In summary, this LPGF adhesive significantly reduced the dependence of traditional phenolic resins on petroleum-based phenol and formaldehyde while maintaining good bonding performance, and had good environmentally friendly properties, with potential applications in the field of artificial boards. Subsequent research could focus on the activation modification of lignin and optimization of resin crosslinking structure to further enhance its comprehensive performance.

【Keywords】lignin; glyoxal; phenolic resin; bonding strength

Material Science

Study on toughening epoxy resin with epoxy-blocked polyurethane

Feng Hao, Xiao Wanbao, Zheng Shuai, Zhao Liwei, Wang Dezhi

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

【Abstract】Using diphenylmethane diisocyanate (MDI), polyether polyol, and bisphenol A epoxy resin as raw materials, three different MDI ratios of epoxy-blocked polyurethane were synthesized by the prepolymer method and chain extension with 1,4-butanediol. The synthesized epoxy-blocked polyurethane was used to toughen bisphenol A-type epoxy resin, and its effects on the bonding properties, mechanical properties, thermal properties, dynamic thermomechanical properties, and micro fracture morphology of the modified resin were systematically studied. The research results showed that the synthesized epoxy-blocked polyurethane had good compatibility with epoxy resin, and the curing system formed a homogeneous structure. As the proportion of MDI increased, the glass transition temperature of the system rose and it exhibited good thermal stability at 150 ℃. Microscopic morphology showed that samples with moderate MDI ratios could form fibrous structures and multiple cracks at the fracture surface, effectively promoting plastic deformation and energy dissipation, and significantly improving material toughness. The mechanical performance test showed that sample 4-2# had the best comprehensive performance when the addition amount was 30 phr, with the room temperature shear strength of 34.67 MPa and the peel strength of 4.02 N/mm. This study demonstrated that embedding epoxy segments into polyurethane structures through chemical bonding could achieve interface strengthening and synergistic toughening, providing an effective approach for the design of high toughness and high modulus epoxy resin composites.

【Keywords】epoxy-blocked; polyurethane; epoxy resin; toughening