Application of EVA Compatibilizer in High-End Cable Materials: Mechanisms, Advantages, and Prospects

Abstract: With the increasingly stringent requirements for performance, safety, and environmental friendliness of cables in high-end equipment fields such as new energy and rail transit, traditional cable materials face severe challenges. Using ethylene-vinyl acetate copolymer (EVA) as the carrier, maleic anhydride grafted compatibilizers, as efficient polymer interfacial modifiers, have successfully addressed the core technical bottleneck of poor compatibility between polar fillers and non-polar matrices in halogen-free flame retardant (HFFR) cable compounds through their unique "bridging" mechanism, becoming a key material driving the development of special cable compounds. This article aims to systematically elaborate on the mechanism, performance advantages, and typical applications of EVA compatibilizers in the high-end cable field.

I. Introduction: The Core Role of Compatibilizers in Cable Compound Modification
In the field of polymer blend modification, the compatibility between different components is key to determining the final properties of the material. Compatibilizers, as functional additives, improve the bonding state of multiphase interfaces through molecular design, playing an irreplaceable role in enhancing the comprehensive performance of blend systems. In the cable compound industry, especially for the development of special compounds for demanding applications such as high performance, low smoke zero halogen (LSZH), oil resistance, and weather resistance, EVA-based compatibilizers have become indispensable core components in formulation design due to their excellent balanced properties.

II. Preparation, Structural Characteristics, and Mechanism of EVA Compatibilizers
Typical EVA compatibilizers, such as the commonly used model LC 331 in the industry, are prepared using EVA resin as the main substrate. Through multi-component melt grafting technology, strongly polar monomers like maleic anhydride (MAH) are grafted onto its molecular chain, resulting in milky white or slightly yellow granules.

The technical core lies in precise control of the grafting rate, typically optimized within the range of 0.8% to 1.2% for MAH. This design endows the material with a unique amphiphilic structure: the EVA backbone has good compatibility with non-polar polyolefin cable matrices (e.g., polyethylene, polypropylene); while the grafted MAH functional groups can form strong chemical bonds or hydrogen bonds with the surface of polar halogen-free flame retardant fillers (e.g., aluminum hydroxide, magnesium hydroxide).

During cable compound processing, adding only 6% to 10% of such a compatibilizer enables it to migrate and enrich at the interface layer between the matrix resin and the filler. Its molecules act like a "bridge," anchoring one end in the resin and bonding the other end tightly with the filler, thereby significantly reducing interfacial tension, improving filler dispersion, and transforming simple physical blending into robust interfacial adhesion. This fundamentally solves the problems of decreased mechanical properties and processing difficulties in highly filled HFFR systems caused by weak interfaces.

III. Performance Enhancement Advantages Brought by EVA Compatibilizers
The introduction of EVA compatibilizers brings comprehensive performance improvements to cable compounds:

Excellent Mechanical Properties: Significantly increases the tensile strength and elongation at break of the material, enhancing the cable's toughness and resistance to mechanical damage, ensuring its long-term reliability during installation and use.

Enhanced Flame Retardancy and Safety Performance: By improving filler dispersion and interfacial bonding, it promotes the more efficient action of flame retardants, helping to increase the oxygen index (LOI) of the system. It also ensures the formation of a strong, dense char layer during combustion, achieving superior low smoke zero halogen flame retardant effects.

Improved Processing Performance: Effectively reduces the melt viscosity of highly filled systems, enhancing the fluidity and extrusion processability of the material, leading to more stable production and a smoother surface finish.

Enhanced Resistance to Specific Environments: Its strengthened interface structure can effectively prevent the ingress of media such as oils and moisture, thereby improving the cable's resistance to oil, chemical corrosion, and weathering.

IV. Analysis of Typical Application Scenarios
Based on the above advantages, EVA compatibilizers are widely used in cable fields with extreme requirements for performance and safety:

Photovoltaic Cables: Used in LSZH photovoltaic cable compounds, ensuring the cable maintains excellent insulation and mechanical strength even under long-term outdoor exposure to harsh conditions like UV radiation and high-low temperature cycles.

Rail Transit Cables: Used in oil-resistant LSZH cable compounds for railway vehicles, providing excellent resistance to fuels and lubricating oils while meeting strict flame retardancy ratings.

New Energy Vehicle Cables: Serves as a coupling agent for TPE/polyolefin materials used in electric vehicle charging pile cables and in-vehicle high-voltage cables, ensuring electrical stability, heat aging resistance, and flame retardant safety under high-voltage, high-current operating conditions.

General High-End Cables: Commonly applied to various types of insulation and sheathing materials requiring low smoke zero halogen properties, enhancing the overall safety level of cables used in data centers, high-rise buildings, public places, etc.

V. Conclusion and Outlook
In summary, EVA-based maleic anhydride grafted compatibilizers, through their ingenious molecular structure and excellent interfacial modification function, have become a core key to overcoming the technical challenges of high-performance HFFR cable compounds and achieving material upgrades. They not only solve the long-standing industry problem of filler-matrix compatibility but also drive cable products to continuously evolve towards higher safety, better reliability, and greater environmental friendliness.

In the future, with the advancement of the "dual-carbon" goals and the rapid development of industries such as new energy and smart grids, the demand for special cables will continue to grow. The development of EVA compatibilizers will also move towards higher grafting efficiency, lower addition cost, more environmentally friendly preparation processes, and specialization for specific resin systems (e.g., polyamide, polyester), continuously providing critical material support for innovation and progress in the cable compound industry.