Keywords: Automotive interior; Flexible adhesive film; SEBS; SEPS I. Application Scenarios and Core Requirements Flexible interior parts such as automotive seat leather, door panels and sun visors are mostly processed via high-speed automated production lines for soft lamination, with core requirements for cleanliness, efficiency and cost-effectiveness.SEBS based hot melt adhesive films have been widely used to replace traditional solvent borne adhesives due to their advantages of being solvent free, low in VOC and compatible with multi material lamination. For the assembly of high end flexible interior parts, the core demands for high bonding strength and high temperature resistance of adhesive films must be met through precise formulation optimization, balancing flexibility, process compatibility and mass production cost effectiveness.This ensures reliable performance under harsh conditions such as high temperature exposure and long term service without delamination.Compared with TPU based and PA based adhesive films, SEBS based adhesive films offer superior cost effectiveness. II. Key Formula Optimization 1.Selection and Optimization of Elastomer Base Materials High molecular weight SEBS (Mooney viscosity ML1+4@100℃ ≥ 80) is preferred. Its long molecular chains and tight entanglement structure can significantly improve the cohesive strength of the adhesive film, laying a foundation for high bonding strength, while maintaining excellent flexibility to meet the deformation requirements of interior parts.If necessary, blend with 5%–8% high molecular weight SEPS. SEPS exhibits better heat resistance (long term service at 110–120℃) than SEPS,which can synergistically enhance the high temperature resistance and low temperature flexibility of the adhesive film, avoiding softening and bonding failure at high temperatures.SEPS also has excellent compatibility with SEBS and does not affect system stability. 2.Optimization of Tackifying and Reinforcing System A hydrogenated C5/C9 hybrid resin system (ratio 7:3 or 8:2) is adopted for the tackifying resin. Hydrogenated resins with a high softening point (105–115 °C) can improve the high-temperature holding power and wettability on various substrates, making them suitable for mainstream interior materials such as leather, PP, and ABS, and achieving substrate-failure bonding. The hybrid system ensures good compatibility and high bonding strength, while avoiding the problem of high-temperature bleeding caused by single resins. Add 1%–1.5% composite coupling agent (KH 560 : heat resistant titanate NDZ 201 = 1:1). One end binds with the molecular chains of SEBS/SEPS, and the other end forms chemical bonds with the substrate, greatly improving interfacial bonding strength. The bonds remain stable and do not fail at high temperatures. Add 1%–2% hydrophobic fumed silica. The nanoparticles are uniformly dispersed in the system, providing light reinforcement without sacrificing flexibility, while improving the high-temperature creep resistance and cohesive strength of the adhesive film, thus reducing the risk of high-temperature shrinkage and delamination. 3.Adjustment of Auxiliary System Use ultra-high viscosity white oil (dosage 5%–7%) to reduce small molecule migration and improve high-temperature stability. A quaternary composite antioxidant system (1010 + 168 + 1098 + DLTP) is adopted to prevent thermal degradation of elastomers and tackifying resins, and extend the service life of the adhesive film. A heat and weather resistant composite system is added to avoid yellowing and performance degradation of the adhesive film after exposure. III. Process Adaptation and Performance Targets The optimized formulation remains compatible with existing extrusion casting and hot pressing processes.Only minor adjustments are required: extrusion temperature 165–170 °C, hot pressing temperature 130–160 °C, holding pressure 0.8–1.2 MPa, making it suitable for high speed production lines.