The scientific formula for hot-melt pressure-sensitive adhesives

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The main components of pressure-sensitive adhesives are rubber-based materials and polyacrylic substances. Traditional solvent-based pressure-sensitive adhesives cause significant environmental pollution, while water-emulsion type adhesives dry slowly and require special drying equipment. As a result, hot-melt pressure-sensitive adhesives were developed. These adhesives are based on thermoplastic polymers and possess both hot-melt and pressure-sensitive properties; they can be applied in their melted state, and after cooling and curing, they can be bonded quickly by applying pressure. They also allow for easy removal without contaminating the surfaces being bonded. With a 100% solid content, hot-melt pressure-sensitive adhesives are pollution-free during production, easy to use, require a short bonding time, and are also easy to transport and store. They are suitable for modern large-scale production, making them the fastest-growing type of pressure-sensitive adhesive at present. In hot-melt pressure-sensitive adhesives, SBS and SIS are the most widely used components in such formulations. Typically, the materials used in hot-melt pressure-sensitive adhesive formulations consist of three main components: rubber softening oil, thermoplastic elastomers, and tackifiers. All three of these components have a significant impact on the properties of pressure-sensitive adhesives; they can all alter parameters such as the softening point, viscosity, initial tack, cohesive strength, adhesion durability, low-temperature resistance, and high-temperature resistance of hot-melt pressure-sensitive adhesives. Specifically, hot-melt pressure-sensitive adhesives are composed of SBS, SIS, tackifying resins, softening agents, antioxidants, and colorants. The following introduces them separately: 1: SBS and SIS. It is the main component used in the production of hot-melt pressure-sensitive adhesives. Among them, SIS possesses better cohesion, resistance to expansion, good toughness and peel strength, as well as excellent adhesiveness; its resulting adhesive is purer and also more viscous. 2: Viscosity-enhancing resin. Thermoplastic elastomer SIS does not have viscosity on its own; a tackifying resin must be added to it in order to confer pressure-sensitive properties. Therefore, the function of the tackifier is to increase the viscosity of the hot-melt pressure-sensitive adhesive. 3: Antioxidants. The thermoplastic elastomers in hot-melt pressure-sensitive adhesives are prone to aging under the influence of external factors such as oxygen, light, and heat; this aging is particularly likely to occur when the hot-melt pressure-sensitive adhesive is applied at high temperatures. Therefore, by adding antioxidants as the main component of anti-aging agents, the peeling strength of these adhesives is significantly improved. 4: Crosslinking agents – The cohesive strength and adhesion of hot-melt pressure-sensitive adhesives decline rapidly at high temperatures; therefore, certain crosslinking agents must be added to the formula to enhance these properties. 5: Softeners – In hot-melt pressure-sensitive adhesives, in addition to viscosifying resins, a certain amount of softeners is also added. This is done to increase the initial adhesive strength of the adhesive, reduce its viscosity, and speed up the coating process. 6: Colorants – By adding colorants to the formula of hot-melt pressure-sensitive adhesives, it is possible to create various types of such adhesives tailored to the specific requirements of customers. 7: Other additives. To reduce costs or increase the viscosity of certain hot-melt pressure-sensitive adhesives, natural rubber can be used to replace part of the SBS and SIS thermoplastic elastomers. The above is a brief introduction to the materials used in hot-melt pressure-sensitive adhesive formulations.