Core-shell structured rubber toughener CSR: a high-end modification material for epoxy systems

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CSR Toughening Agent: A High-End Modification Material for Epoxy Systems. I. Product Definition: CSR, short for Core-Shell Structure Rubber Toughening Agent, refers to rubber toughening particles with a core-shell structure, where the interior consists of an elastic rubber core and the exterior is a shell layer equipped with compatible or reactive functional groups. CSR is primarily used as an impact modifier or toughener to improve the fracture toughness, impact resistance, fatigue resistance, and adhesion properties of brittle resin systems. It generally results in a smaller increase in viscosity compared to traditional liquid rubber toughening systems, and it helps to maintain the Tg and thermal properties of the cured system. Unlike conventional impact modifiers for general engineering plastics and the like, CSR is designed specifically for epoxy resins and epoxy composites. Its key features are efficient toughening at extremely low addition levels, minimal impact on the viscosity of the system, and almost no reduction in the matrix’s Tg; it is a functional additive for high-end epoxy systems. II. Application Areas 1. Copper Clad Laminate (CCL): In M9-grade copper clad laminates, CSR core-shell rubber serves as a key toughening component. The core layer, made of an elastomer, is responsible for absorbing energy and providing impact resistance, while the shell layer, composed of a rigid polymer, helps to disperse particles and bond with the M9 hydrocarbon resin matrix. This results in the formation of micro-nano buffering structures within a system with high levels of silicon micropowder, thereby enhancing the overall mechanical properties. The M9 grade uses hydrocarbon resins, with CSR toughener being an important component of its resin formula. NVIDIA’s next-generation products are expected to enter mass production as early as the second half of 2027; they are currently in the stage of initial material testing and evaluation. Testing of copper-clad plate samples of the M10 grade began in January 2026. 2. Automotive structural components: Toughening of carbon fiber/epoxy and glass fiber/epoxy composites, primarily used for the toughening and modification of resin materials such as epoxy resins or composite materials in industries like automobiles, copper-clad laminates, wind power, and packaging. 3. Wind turbine blades: CSR tougheners can improve the fatigue resistance and resistance to wind and sand impact of the epoxy matrix, thereby extending the lifespan of the blades. 4. Electronic semiconductor packaging: Used to toughen the epoxy encapsulation material for chips, reduce internal stresses, prevent cracking, and meet the requirements for precise packaging. III. Production Process and Technical Source 1. Main process: The preparation of CSR via the emulsion polymerization–coagulation method employs a seed emulsion polymerization process. The core layer is formed by polymerizing monomers such as butadiene and butyl acrylate in the presence of a crosslinking agent to create an elastic core ； The shell is formed through graft polymerization using monomers such as methyl methacrylate (MMA) and styrene, creating a rigid outer shell. Subsequently, the CSR product is obtained through processes such as condensation, washing, and drying. 2. Source of technology and domestic breakthroughs: Japanese Kaneka, American DOW, and French Arkema hold the core patents; the technical barriers associated with CSR products are high, and currently China relies heavily on imports for these products. Domestically, Ruifeng High-Performance Materials’ CSR toughening agents achieved breakthroughs in 2025; samples of products produced using pilot-scale production lines were sent to downstream customers, and their quality was recognized by those customers. IV. Major Manufacturers and Production Capacities 1. Overseas leaders: Japan’s Seiko Kagaku, Evonik, and Resinous Kasei (Japan). Among them, Nippon Shokubai Chemical holds a dominant position in the global CSR market and is the largest CSR supplier in the world. 2. The domestic company Ruifeng High-Tech is a leader in the CSR industry in China, and it is also one of the companies with the most extensive presence in the M9 CSR sector in the country. The company has planned a production capacity of 10,000 tons for its CSR toughening agent products, as part of an overall capacity of 60,000 tons per year for engineering plastic additives. The project will be built in two phases: the first phase will cover a production capacity of 20,000 tons per year for engineering plastic additives (including 5,000 tons per year for CSR products), with operation expected to begin by the end of 2026 ； Phase 2: a 40,000 tons per year production facility for engineering plastic additives (including a capacity of 5,000 tons per year for CSR), with commencement expected in 2027. V. Product Profitability 1. Overall industry profit level: In 2025, the average gross margin in the global core-shell rubber (CSR) industry was between 30% and 35%. CSR is a high-margin premium product, significantly higher than ordinary engineering plastic additives. 2. Profits from domestic substitution: The unit price of Ruifeng High-Tech’s CSR products is 3–5 times that of ordinary toughening agents, resulting in high added value. The current tight supply of imported products and rising prices have accelerated the process of replacing them with domestic alternatives. After localization, the price is expected to be significantly lower than that of imported products (40,000+ yuan per ton for powdered forms, and 80,000+ yuan per ton for liquid forms); domestic companies can thus enjoy higher profit margins thanks to their cost advantages. VI. Market Supply and Demand 1. Global Market By 2025, the global market size for core-shell rubber (CSR) is expected to be around $0.96 billion, with sales volume of approximately 7,530 tons, and an average price of $12,685 per ton. It is estimated that by 2032, the global market size will reach $199 million, with a compound annual growth rate (CAGR) of 12.5% between 2026 and 2032; the average gross margin in this industry lies between 30% and 35%. In the Chinese market, Ruifeng High-Tech is working on expanding its production capacity. With the commissioning of a 5,000-ton CSR production capacity by the end of 2026, domestic supply capacity will increase significantly. Currently, there is a tight supply of imported products, leading to rising prices; thus, there is significant room for domestic substitution. Summary: As a key material for high-level modification of epoxy systems, CSR toughening agents feature high technical barriers and high added value, making domestic substitution an urgent need. Domestic companies such as Ruifeng High-Performance Materials have achieved technological breakthroughs; by 2025, they plan to complete pilot-scale tests and start delivering products in small quantities, while also working on expanding production capacity on a larger scale. With the commissioning of a production capacity of 5,000 tons per year by the end of 2026, along with the ongoing growth in demand from sectors such as AI servers and new energy vehicles, the CSR industry is entering a new phase characterized by accelerated adoption of domestic alternatives