Effect of Blending SBS with PE And PS on Material Performance

 

SBS (styrene–butadiene–styrene) is a triblock copolymer widely used as a thermoplastic elastomer (TPE). Due to the molecular structure similarity—both PE (polyethylene) and butadiene are linear olefins, and PS (polystyrene) shares styrene units with SBS—SBS shows good compatibility when blended with PE and PS. Through blending modification, several physical properties of SBS can be effectively enhanced.

(1) PE / SBS Blends

PE features excellent processability, low‑temperature flexibility, bending resistance, superior chemical resistance, low water and air permeability, and outstanding electrical insulation properties. Blending PE with SBS can significantly:

• Increase abrasion resistance, hardness, weatherability, and tear strength.

• Slightly improve melt flow rate (MFR).

• Maintain high tensile strength and elongation at break.

For example:

• When SBS is blended with HDPE or LDPE, reducing the rubber–plastic ratio typically lowers tensile strength, elongation at break, and MFR, but greatly improves hardness and abrasion resistance.

• Adding ultra‑high molecular weight polyethylene (UHMW‑PE) as a high‑molecular wear‑resistant modifier—due to its long carbon‑chain structure—can further improve wear resistance (wear length < 7 mm), making SBS soles as durable as polyurethane soles.

Using SBS and LDPE as the base and applying partial dynamic vulcanization techniques can produce SBS/LDPE blended TPEs. An optimal rubber–plastic ratio around 70/30 results in high mechanical strength, large elongation at break, and good recyclability.

(2) PS / SBS Blends

PS is known for easy processing, low shrinkage, low moisture absorption, and good thermal properties. SBS and PS exhibit excellent compatibility, with strong interfacial adhesion that increases as the styrene content in SBS rises.

In SBS/PS blends:

• As PS content increases, tensile strength and elongation at break tend to decrease.

For SBS/PS = 100/10, tensile strength can reach ~22.5 MPa and elongation at break ~530%.

For SBS/PS = 100/40, tensile strength drops to ~20.3 MPa and elongation to ~380%.

• This reduction is due to PS having a much higher molecular weight (~300,000) than the PS blocks in SBS (10,000–30,000). As a result, PS molecules cannot penetrate SBS PS micro‑domains, forming a third phase that disrupts the morphology and reduces transparency.

• As PS content rises, phase separation occurs, decreasing elongation at break.

• PS addition slightly increases blend hardness and significantly boosts MFR.

Additional Processing Notes

• SBS must be oil‑extended when blended with PS or PE to improve processability.

• High SBS + oil ratios produce TPE or TPR compounds; lower SBS content can act as an impact modifier for plastics.

• SBS shows excellent toughening effects on PS, while effects on ABS, SAN, PP, and nylon are moderate; grafted compatibilizers are often required to enhance compatibility and impact performance.

Summary

Blending SBS with PE or PS tailors the final material's hardness, abrasion resistance, MFR, and impact strength, expanding applications in footwear, automotive parts, household goods, and engineering plastics modification. Understanding molecular interactions and optimizing blend ratios are key to maximizing performance.

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