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Application of SEBS in improving impact resistance of PP

June 15,2022

Compared with SBS, SEBS has higher main chain saturation.

 Due to the high entanglement of the segments after block hydrogenation of polybutadiene, SEBS has a large cross-linking effect per unit volume, so it has a high modulus and is not easy to degrade. Therefore, it has become a popular product among styrene block copolymer elastomers, and is widely used in the fields of adhesives, coatings, plastic modifiers, automotive parts, wires and cables, food, medical treatment and leisure products.

SEBS has better stability, heat resistance, oxidation resistance, weather resistance and solvent resistance than SBS due to its high saturation of main chain. The service temperature of SEBS can be as high as 130 ℃ (SBS is only 65 ℃), and its processing temperature is higher than that of polypropylene. SEBS is used as a high-quality wire and cable material because of its good electrical insulation performance. SEBS has good blending property, and can be blended with PP, polystyrene (PS), high density polyethylene (HDPE), polycarbonate (PC), polyamide (PA), polyphenylene oxide (PPO) and many other polymers, and its impact properties can be greatly improved.

The transparency of SEBS blended with paraffin oil, naphthenic oil and PP was better.

1. Compared with most pp/ rubber blends, pp/sebs blends have higher service temperature and better solvent resistance. Although the toughness of PP / SEBS blends was improved, the tensile strength and yield stress decreased. In order to ensure toughness and achieve certain strength and rigidity, another kind of plastic, such as PS, HDPE, PC, etc., is usually mixed.

2. In pp/ps/sebs blends, SEBS had good compatibility with PP, while PP had poor compatibility with PS, and the blends were prone to deformation. After mixing SEBS, the melt viscosity of the blend system increased and the deformation trend of the extrudate decreased. It can be seen that SEBS and PP have good compatibilization due to their compatibility. When the mass ratio of pp/ps/sebs is 85:10:5, the best performance combination can be obtained: the tensile strength is 24.4mpa, the bending modulus is 810.6mpa, the impact strength is 82, 0j/m, and the melt flow index is 12, 7g/10min.

3. The yield deformation of pp/hdpe/sebs blends increased more than that of pp/ps/sebs blends. Because HDPE has certain compatibility with PP and hydrogenated polybutadiene block, the stress concentration is less than that of PS which is incompatible with PP; Pp/hdpe/sebs is superior to pp/ps/sebs blends in tensile strength and modulus. At the same time, the melt elastic effect and extrusion deformation trend of pp/hdpe/sebs system were lower than that of pp/ps/sebs system. Obviously, in the two groups of blends, the blending effect of SEBS Elastomer is more fully reflected in pp/hdpe/sebs system. The practical results show that pp/hdpe/sebs system should be selected first from the aspects of cost reduction and tensile strength.

4. Pp/pc/sebs system, rubber toughened thermoplastic usually reduces the tensile and bending properties of materials. Using pp/pc/sebs system is also an effective method to obtain toughness and ensure its strength and rigidity. Pp/pc system is a typical crystalline / amorphous blend system with poor interfacial adhesion. PC is compatible with SEBS. SEBS has certain compatibility with PP, so SEBS blending can not only toughen, but also improve the compatibility of the system to a certain extent. Mixing PC and SEBS into PP have opposite influence on the change of its properties. Therefore, the best performance combination can be obtained by properly adjusting the ratio of PC and SEBS. A better performance combination can be obtained when the amount of PC is not too low and the amount of SEBS is not too high. The amount of PC is related to the proportion of pp/sebs. For example, when the PC content is 10%, if the material wants to meet the high tensile properties, the pp/sebs feeding ratio of 90:10 is better; To meet the bending performance, the pp/sebs feeding ratio can be 95:5.

5.Pa/pp/sebs and maleic anhydride (MA) grafted SEBS (SEBS-g-MA) system have strong polarity of amide group on PA main chain, and can form hydrogen bond to promote crystallization, which makes it have good wear resistance and solvent resistance, but also increases the moisture absorption of PA and affects the dimensional stability of products. PA has poor impact performance and small elastic modulus in dry state and low temperature. The blending of PP with it not only reduces the cost, but also improves the impact of PA and reduces the hygroscopicity of PA. However, PP has no thermodynamic compatibility with strongly polar PA, and the blending modification effect is poor. The reaction between polar amide group on PA main chain and Ma grafted compatibilizer can increase the interfacial adhesion, such as Ma grafted EPDM (epdm-g-ma), SEBS-g-MA, etc. through experimental comparison, compared with soft epdm-g-ma, hard SEBS-g-MA is a more efficient compatibilizer for blends, which can significantly improve the strength and toughness of pp/pa6 blends without affecting its hardness.SEBS

This shows that the new elastomer SEBS is a kind of plastic modifier and compatibilizer with excellent performance, especially after functionalization (such as maleic anhydride, sulfonation, chloromethylation, hydroxymethylation), it shows remarkable compatibility with specific systems