Three Key Formulation Tips To Prevent Oil Bleeding in TPE Pellets During Hot Summer Temperatures

As summer approaches and temperatures rise, TPE products such as bicycle grips and overmolded sports equipment handles often exhibit oil bleeding under high-temperature exposure. This not only leads to a sticky surface and poor user experience but may also cause uneven coloration, affecting the product’s appearance and overall quality. How can we adjust the TPE pellet formulation to prevent this issue? Here are three effective strategies:

1. Select Appropriate Oil-Filling Materials and Optimize the Oil-Filling Process

  To prevent oil bleeding during TPE pelletizing, it is essential to use high-viscosity, high-flash-point white oil—such as 500# paraffin oil—as the oil-filling material. High viscosity helps the paraffin oil remain stable within the TPE system, reducing oil separation due to heat. A high flash point ensures good thermal stability under high-temperature conditions, minimizing volatility and oil bleeding risks.  

  The recommended oil dosage should be 0.7 to 2 times the weight of SEBS to ensure adequate fusion between the oil and SEBS and form a stable matrix. Additionally, allowing the oil-filled mixture to rest for over 6 hours improves the homogeneity and significantly enhances the anti-bleeding performance of the final product.

2. Add Nano-Silica to Enhance Molecular Adsorption  

  Incorporating a small amount of surface-treated nano-silica into the TPE formulation is another critical method to prevent oil bleeding under high temperatures. In hot conditions, free small molecules in TPE tend to migrate to the surface, causing oil bleeding. Nano-silica has a large specific surface area and strong adsorption capacity, enabling it to effectively capture these free molecules and inhibit their migration.  

  Surface-treated nano-silica disperses well in the TPE system and avoids agglomeration, maximizing its adsorption function. A dosage of 1–3% strikes a balance between effective oil control and preserving the mechanical and processing properties of the TPE material.

3. Choose Suitable SEBS Grades and Optimize Blending  

  The type of SEBS used has a direct impact on the oil-locking ability of TPE products. High-molecular-weight SEBS grades such as YH-503T, 533, or 604T should be prioritized. These grades offer tighter molecular structures that better encapsulate paraffin oil, reducing oil bleed at elevated temperatures.  

  For special TPE performance requirements, SEBS can be blended with 10–20% SEPS (e.g., YH-4052, 4053). SEPS features a unique molecular structure that, when blended with SEBS, further optimizes the molecular chain network of the TPE system. This enhances the binding capability to paraffin oil and achieves superior oil-locking performance.

In actual pelletizing operations, manufacturers can flexibly adjust parameters and processing methods based on specific product requirements and production conditions to achieve optimal oil resistance.

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