Keywords: hot-melt adhesive; SIS; polarity I.SIS hot-melt pressure-sensitive adhesives exhibit poor adhesion to polar materials. SIS has low polarity, so its bonding strength with polar materials is usually not high. Polar materials generally have high surface energy and strong intermolecular forces, making it difficult for SIS hot-melt pressure-sensitive adhesives to form a firm bond. For example, when SIS hot-melt PSA is used as an adhesive at high temperatures or for bonding polar substrates such as shoes, wood, TPU, and PVC, its bonding performance is limited. II. Several methods to improve the polarity of SIS To improve the bonding performance of SIS hot-melt adhesives on polar materials, the polarity of SIS must first be enhanced. There are three main methods: For low-to-moderate requirements: Add an appropriate amount of coupling agent to the SIS hot-melt adhesive formula to improve bonding strength. Epoxidation of SIS: Epoxidize SIS first to increase its polarity. UV or electron beam modification: Irradiate SIS with electron beam or ultraviolet light, followed by polymerization, grafting, and crosslinking to improve the polarity of SIS.