Improvement of the physical and mechanical properties of HIPS by SEBS and PIB

Document Type : Regular Article

Authors

1 Department of Chemical Engineering, Ah.C., Islamic Azad University, Ahar, Iran

2 Department of Chemistry, Ta.C., Islamic Azad University, Tabriz, Iran

10.22034/ijche.2026.588882.1601
Abstract
Objective: The aim of this study was to investigate the combined effects of styrene–ethylene–butylene–styrene (SEBS) and polyisobutylene (PIB) on the thermal, mechanical, and morphological properties of high-impact polystyrene (HIPS) and to evaluate their effectiveness in improving the performance of HIPS through binary and ternary blend formulations.
Methods: Binary and ternary HIPS/PIB/SEBS blends containing 1–2 wt% PIB and 1–5 wt% SEBS were prepared using twin-screw extrusion followed by injection molding. The blends were characterized by the melt flow rate (MFR) test, Vicat softening temperature(VST) test, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), Izod impact test, and environmental stress crack resistance (ESCR) test based on elongation-at-break measurements before and after immersion in oil.
Results: PIB acted primarily as a plasticizer, resulting in increased melt flowability, whereas SEBS significantly enhanced the thermal stability and toughness of HIPS.VST dropped from 95.3 to 94.5 and 93.1, then increased to 96.4 and 96.5 in blends No. 1-8 and No. 9-13 respectively. The thermogravimetric analysis demonstrated improved thermal degradation resistance with increasing SEBS content (the highest result achieved at 446.9 C for HI-3), while DSC results indicated good compatibility among the blend components. SEM observations revealed finer elastomer dispersion and a fracture morphology with greater ductility. Furthermore, the simultaneous addition of PIB and SEBS markedly improved the impact strength up to 19.2 j/m and environmental stress crack resistance, with the best overall performance achieved for blends containing 1 wt.% PIB and 2 wt.% SEBS.
Conclusion: The incorporation of SEBS and PIB provides an effective strategy for simultaneously improving the flowability, toughness, thermal stability, and environmental stress crack resistance of HIPS. The proposed ternary blends offer enhanced performance and demonstrate promising potential for engineering applications to improve mechanical and environmental durability.

Keywords

Subjects

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