As a modifier, adding 5–10% of SSBR into SIS/SBS-based hot melt adhesives and pressure-sensitive adhesives can significantly enhance their low-temperature performance, improve bonding strength and flexibility in cold environments, and resolve the pain point of traditional hot melt adhesives being prone to brittle cracking and debonding at low temperatures. However, due to strong intermolecular forces, SSBR tends to experience agglomeration during the hot melt mixing process, leading to uneven dispersion. This not only diminishes the modification efficacy but can also impact the appearance, fluidity, and service performance of the hot melt adhesive. Therefore, effectively preventing SSBR agglomeration is key to ensuring the quality of modified hot melt adhesives. I. Core Techniques for Preventing SSBR Agglomeration 1. Formulation Optimization: Selecting Compatible Grades Formulation design serves as the foundation for preventing SSBR agglomeration, with the core lying in the selection of appropriate SSBR grades. Priority should be given to SSBR products with medium styrene content and high fluidity. Medium styrene content helps balance the rubber's flexibility and compatibility, preventing increased molecular rigidity and aggravated agglomeration tendencies caused by excessively high styrene content. SSBR grades with high fluidity possess better molecular chain mobility, making them easier to disperse within the hot melt system and reducing intermolecular aggregation, thereby lowering the probability of agglomeration from the source. Concurrently, the addition level of SSBR must be controlled within a reasonable range of 5–10%; excessive addition will lead to an overabundance of SSBR molecules in the system, increasing the probability of intermolecular collisions and easily forming agglomerates. 2. Process Improvement: Stepwise Mixing and Scientific Feeding Sequence Adopting a stepwise mixing process of "low viscosity first, high viscosity later," combined with a logical feeding sequence, can effectively prevent SSBR agglomeration. The specific steps are as follows: · First, feed the softening agent and heat it to a molten state to create a low-viscosity system, laying the groundwork for the subsequent dispersion of materials. · Add SIS (or SBS) and agitate until completely melted and dispersed, forming the base adhesive liquid. · Slowly introduce SSBR, feeding it while continuously agitating; utilize the fluidity of the base adhesive liquid to drive the dispersion of SSBR, preventing it from directly contacting the high-temperature melt and forming lumps. · Add fillers, additives, and tackifying resins in sequence, similarly utilizing a feed-while-agitating method to ensure that each material can be uniformly dispersed throughout the system, thereby avoiding localized high concentrations that induce SSBR agglomeration. The entire mixing process must maintain continuous agitation to ensure thorough material contact and uniform dispersion. 3. Parameter Control: Rational Regulation of Shear Force Shear force is a critical parameter influencing the dispersion effect of SSBR. It must be precisely controlled according to the characteristics of different materials to avoid agglomeration caused by insufficient shear force, or molecular structure damage caused by excessively high shear force: · SIS and SSBR Mixing Phase: Control the shear force at a medium-to-high level. This can break the cohesive forces between SSBR molecules and promote their dispersion, while avoiding excessively high shear forces that could cause the cleavage of rubber molecular chains and affect modification performance. · Filler Addition Phase: Control the shear force at a high level. Filler particles are prone to agglomerate, and high shear force can break them apart while preventing filler agglomerates from adsorbing SSBR molecules, indirectly preventing SSBR agglomeration. · Tackifying Resin Addition Phase: Control the shear force at a medium level. This ensures uniform dispersion of the tackifying resin while preventing high shear forces from causing a sudden spike in system viscosity, which would hinder further dispersion of SSBR. II. Summary Preventing the agglomeration of SSBR in hot melt adhesives requires a synergistic effort across three dimensions: formulation, process, and parameters. Selecting SSBR grades with medium styrene content and high fluidity establishes a foundation for dispersion; employing a stepwise mixing and scientific feeding sequence avoids localized high concentrations; and rationally regulating the shear force based on material characteristics promotes the uniform dispersion of SSBR. The combination of these three strategies can effectively resolve the problem of SSBR agglomeration, fully unlock its low-temperature modification potential, and elevate the product performance of SIS/SBS-based hot melt adhesives and pressure-sensitive adhesives.