###### Abstract  
The polymer blends are an effective strategy for materials design with new properties in the plastic industry; such features may depend on the blend components and the processing method. This study aimed to understand the effect of styrene-butadiene-styrene (SBS) content and its architecture on blends based on polyphenylene ether (PPE), high-impact polystyrene (HIPS), and SBS. In addition, this research compared and analyzed the blends formulated by different processing methods: twin-screw extrusion (TSE) and internal mixing (IM). Furthermore, three SBS copolymers, two radial and one linear (with different molecular weights), were used to produce PPE/HIPS/SBS blends, analyzing which SBS copolymer feature provides excellent viscoelasticity, thermomechanical properties, and impact resistance. The findings revealed that the melt processing method played a crucial role in Izod impact resistance of the PPE/HIPS/SBS blends, as well as the molecular architecture, molecular weight, and SBS content. The findings also demonstrated that the TSE process is more effective than the IM. Since the PPE/HIPS/SBS blends displayed higher Izod impact resistance than the PPE/HIPS or PPE/SBS binary blends, a synergistic effect of SBS and HIPS is suggested. polyphenylene ether; HIPS; SBS; internal mixing; polymer blend; twin-screw extruder [PERSON]  
[PERSON], E.I. genated block copolymers (styrene-ethylene-butylene-styrene), enhances PPE toughness, nevertheless, produces two-phase systems owing to polybutadiene (PB) content [4; 8; 9; 10]. Moreover, [PERSON] et al. [11] studied three different SBS ratios for PPE/SBS blends, including 70/30 (SBS1), 60/40 (SBS2), and 30/70 (SBS3). They established that when the SBS contains a larger PB block, the miscibility decreases in PPE/SBS blends, exhibiting phase separation and deterioration of the tensile strength; in contrast, SBS with higher polystyrene (PS) content improves miscibility. Consequently, when the miscibility of the PPE/SBS blend is appropriate, the block of PB is an effective toughener [11]. Nevertheless, a systematic understanding of the effect of structure, molecular weight (M\({}_{\rm w}\)), and SBS content contributes to the physicochemical properties, especially the toughness of PPE, using high-impact polystyrene (HIPS) as a compatibilizer agent, is still lacking. Nonetheless, employing different mixers, varying the processing parameters (mixing, time, and temperature), or both, allows for control phase morphology and, consequently, improves blend performance [5; 11; 12; 13]. [PERSON] et al. [14] prepared blends of polyamide 6 by extrusion and internal mixing (IM), with metallocene rubber as the dispersed phase. Their findings from the rheological and morphological analyses showed that the compounding process had more influence on the mechanical properties than the blend composition. In the same way, [PERSON] et al. [15] compared the viscoelasticity and microstructure of thermoplastic vulcanizate samples prepared by IM and twin-screw extrusion (TSE). Although there was a slight decrease in the extent of cured rubber agglomerates, the samples obtained with TSE revealed a more uniform agglomerate size distribution, which was attributed to a higher stress state in the extruder. Finally, [PERSON] et al. [16] reported the morphology and viscoelasticity of uncross-linked and cross-linked EPDM/PP-based thermoplastic elastomers prepared by IM and a co-rotating TSE. Despite similar average apparent shear rates in both mixing equipment, the intensive flow field in the TSE resulted in a finer morphology. Likewise, despite the shorter residence time in the TSE, compared to the IM, the crosslinking reaction proceeded faster, resulting in more extensive and heterogeneous crosslinked EPDM domains dispersed in the thermoplastic phase. On the other hand, a synergistic toughening effect has been reported by combining two different impact modifiers or through a rigid-toughening (a combination of an elastomer with a rigid polymer) [2; 3; 4].