Preparation of a self-repairing, recyclable, and high-performance crosslinked polymer for the development of anisotropic thermally conductive adhesive films

Abstract

Thermal interface material (TIM) is a widely used composite adhesive film whose adhesion and vertical thermal conductivity are critical to its application. Alumina (Al₂O₃) is now the most commonly used thermal filler in the industry, due to its high-cost performance. However, the spherical morphology of Al₂O₃ particles poses a significant challenge for the straightforward development of anisotropic thermal conductivity structure within a polymer substrate. This study aims to design a single-layer Al₂O₃ distribution structure to improve the vertical thermal conductivity of TIM. To accomplish this objective, a copolymer grafted with ethylene-vinyl acetate copolymer (EVA) and isobutylene-isoprene rubber (IIR) was synthesized via CC bonding. This EVA@IIR copolymer exhibits excellent self-repairing, adhesion, heat resistance and recyclability. Subsequently, the coating technology is employed to regulate the thickness of the adhesive film, thereby establishing a single-layer Al₂O₃ distribution structure within the polymer substrate. Under the single-layer distribution structure, the particle size of Al₂O₃ and the vertical plane (Z) thermal conductivity increase proportionally. At a 70 μm Al₂O₃ loading of 70 wt%, the vertical thermal conductivity of the film increased by 129.3 % compared to the EVA@IIR substrate, and its thermal conductivity performance(Z) was superior to that of non-single-layer distribution structure films under the same loading. Therefore, this is conducive to effective heat transfer between heaters and heat sinks.