As NEVs evolve toward lightweight and modular designs, hot melt adhesives are being used more widely across interior components, filtration materials, and wire harness accessories. Yet NEV cabins present a tougher thermal challenge—summer sunlight can send interior temperatures soaring. Under these conditions, conventional SIS-based hot melt adhesives may lose cohesion, creep, or leave adhesive residue, potentially resulting in loose wire harnesses, displaced interior materials, sagging labels, and other quality issues. This creates a growing need for hot melt adhesive systems that combine high heat resistance, high cohesion, clean removability, and stable performance across a wide temperature range. For these demanding applications, selecting the right SIS grade is critical. 1. High-Heat, High-Cohesion SIS: Key Performance Advantages Our high-heat-resistant SIS is designed with a balanced molecular structure, featuring approximately 30% styrene and controlled diblock content. This structure delivers high hardness, dimensional stability, and balanced adhesion. Excellent High-Temperature Storage Modulus The SIS demonstrates excellent storage modulus performance in the 120–170°C range, with a slower decrease in modulus at elevated temperatures and relatively high storage modulus maintained around 150°C. Its higher proportion of PS hard segments creates more physical crosslinking points within the polymer network. As a result, the adhesive structure remains more stable at elevated temperatures, supporting improved thermal stability and cohesive strength. High Cohesion with Low Residue High cohesive strength helps keep adhesive failure within the adhesive layer rather than transferring excessive adhesive onto the substrate. This makes the material well suited to automotive interior applications where clean removability and low residue are important, particularly for components that may require maintenance or replacement. Enhanced Heat Resistance Compared with conventional SIS grades, this high-heat SIS provides significantly improved resistance to shear failure at elevated temperatures. It is therefore suitable for applications exposed to intermittent high-temperature conditions, such as automotive interiors subjected to intense summer sunlight. Broad Formulation Compatibility The SIS offers a broad formulation window with hydrogenated tackifying resins and other elastomers, allowing formulators to balance initial tack, holding power, flexibility, and heat resistance according to specific application requirements. 2. Building a High-Performance Hot Melt Adhesive Formulation Selecting a high-heat SIS is only the first step. A well-designed formulation is essential for achieving the required balance of tack, cohesion, flow, and thermal stability. Hydrogenated tackifying resins further improve high-temperature holding power while enhancing compatibility and thermal stability. They also help reduce resin migration and bleed-out under elevated temperatures. For applications requiring improved initial tack and wetting, high-flow, high-cohesion SIS can be incorporated into the formulation. This improves adhesive wet-out on rough or irregular substrates and enhances elongation, compensating for potential limitations in flow or initial tack when using a single high-heat-resistant SIS grade. The elastomer, tackifier, and antioxidant ratios should then be optimized according to the specific application. For automotive adhesives, an effective antioxidant system is particularly important to suppress thermal-oxidative aging and maintain long-term adhesive performance. 3. Typical NEV Assembly Applications 3.1 Headliner and Interior Auxiliary Fixation Hot melt adhesives are used for the auxiliary fixation of headliner foam, felt, sound insulation materials, and wire harness accessories. The adhesive needs to resist creep under high cabin temperatures, preventing interior materials from shifting or delaminating. At the same time, low-residue removability helps facilitate maintenance and replacement without contaminating the substrate. 3.2 Masking Tapes for Automotive Lamp Painting and Baking Automotive lamp housings may undergo painting and baking processes involving short-term exposure to elevated temperatures. A high-cohesion adhesive helps prevent edge lifting and tape displacement during heating, while clean removability after baking minimizes adhesive residue on painted surfaces. 3.3 Semi-Structural Bonding of Air-Conditioning Filter Media Hot melt adhesives can be used to bond automotive air-conditioning filter media to filter frames. As a semi-structural bonding application, the adhesive must resist creep and maintain long-term bonding performance under repeated temperature fluctuations. In this application, long-term cohesion is often more important than extremely high pressure-sensitive tack. 3.4 High-Temperature Wire Harness Wrapping Tapes For interior wire harness wrapping tapes, the adhesive must withstand intermittent high temperatures as well as shear forces generated by vehicle vibration. High cohesion helps prevent tape loosening and displacement, reducing the potential for wire harness movement and associated noise. This application is primarily intended for vehicle interiors rather than continuously high-temperature areas such as engine compartments. 3.5 Other Potential Applications Beyond NEV assembly, high-heat-resistant SIS can also be considered for: High-temperature-resistant carton sealing tapes Summer-grade shipping and logistics labels Elastic attachment and hook-and-loop fastening in hygiene products Fixation of electrical and thermal insulation materials Other hot melt adhesive applications requiring high cohesion and heat resistance Conclusion As NEV manufacturers continue to pursue lightweighting, modular assembly, and higher reliability, adhesive materials face increasingly demanding performance requirements. For hot melt adhesive applications exposed to elevated temperatures, SIS selection plays a key role in balancing heat resistance, cohesion, tack, removability, and formulation compatibility. DZBH provides high-heat-resistant SIS grades for demanding adhesive applications, together with technical support for grade selection, formulation development, and application testing. Looking for a more reliable hot melt adhesive solution for high-temperature applications? Contact our technical team to discuss your requirements and explore the right SIS grade for your formulation.