RESEARCH ARTICLE New high impact polystyrene: Use of poly(1‐hexene) and poly(1‐hexene‐co‐hexadiene) as impact modifiers Davood Nazari 1 | Naeimeh Bahri‐Laleh 1 | Mehdi Nekoomanesh‐Haghighi 1 | Seyed Mehrdad Jalilian 2 | Razieh Rezaie 1 | Seyed Amin Mirmohammadi 3 1 Polymerization Engineering Department, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965/115, Tehran, Iran 2 Polymerization Science Department, Iran Polymer and Petrochemical Institute (IPPI), P.O. Box 14965/115, Tehran, Iran 3 Department of Chemical Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran Correspondence Seyed Amin Mirmohammadi, Department of Chemical Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran. Email: mirmohammadi.sa@gmail.com Funding information Iran National Science Foundation (INSF), Grant/Award Number: 96008930 In this study, polystyrene (PS) was melt blended with different amounts of poly1‐hexene (PH) and poly(1‐hexene‐co‐hexadiene) (COPOLY) and the blends were compared with conventional PS/ polybutadiene (PS/PB) one. Scanning electron microscope revealed that the dispersion of PH and COPOLY in PS matrix was more uniform with the appearance of small particles in PS matrix; however, in the case of PS/PB blends, the fracture surface showed nonhomogenous morphology with the appearance of bigger rubber particles. Based on Differential Scanning Calorimetry (DSC) and dynamic mechanical thermal analysis results, T g of the blends decreased in comparison with it in neat PS. Impact strength of PS/PH and PS/COPOLY blends was considerably higher than that in PS/PB and significantly higher than the value for neat PS. Tensile test showed substantial improvement in stress at yield and better elongation at break for COPOLY containing blend than the samples containing PH and PB rubbers. Also, blending of PS with 10% of the rubbers was considered in the presence of dicumylperoxide as a probable grafting/cross‐linking agent to pro- duce XPS/COPOLY10 and XPS/PB10 samples, respectively. IR results of the nonsoluble solvent extracted gel showed that COPOLY and PB were grafted to PS matrix during melt blending, which caused higher impact strength in the related samples. KEYWORDS copolymer, impact modifier, poly(1‐hexadiene‐co‐hexadiene), poly1‐hexene, polymer blends, polystyrene 1 | INTRODUCTION Polymer blending is one of the cheapest methods of tailoring poly- meric materials for specific applications. The gain in new properties depends on the degree of compatibility or miscibility of the polymers in the intermolecular level. 1-3 Polystyrene (PS) is widely used in packaging, toys, bottles, house wares, electronic appliances, and some industrial components because of its good rigidity and ease of coloring and processing. 4,5 However, because of fragile structure, which limits its applications, some rubbers are used as impact modifier in PS matrix. To obtain an ideal blend with improved properties, the nature and amount of the rubber‐reinforcing phase are of critical importance. In the past few decades, using filler/ rubber systems, focusing on polyolefin‐type rubbers (such as polybuta- diene [PB] and ethylene propylene diene monomer [EPDM]) has attracted a lot of attentions. 6-11 Among the mentioned rubbers, PB was introduced as the most important one in PS toughening; however, its degradation is a major problem in the related blends. The main contribution to photodegradation of PS/PB blends is usually attributed to the PB phase, in which various isomers with different stabilities against degradation are found. To overcome this drawback, PB is usu- ally replaced by saturated rubbers consisting of terpolymers or copol- ymers of propylene and ethylene (such as ethylene propylene rubber [EPR]). 7,12-14 The blends show higher thermal stability than PS homo- polymer, due to the stabilizing effect of EPR part. 6 Although EPR and EPDM are widely used in PS toughening where outdoor applications are intended, 15 investigation on exploring new rubbers is still going on. Polymers of higher α‐olefins have flexible alkyl branches with different lengths, which found various applications in different fields. Low molecular weight poly(α‐olefin)s are used in lubricating oil formu- lation as the base materials while high molecular weight ones are used as drag reducers and pour point depressants. 16-18 It is very difficult for the medium‐sized α‐olefin chains to align side‐by‐side in an orderly manner since the alkyl groups are able to shape themselves in numer- ous conformations. This decreases the intermolecular interactions between polymer chains. 19 Therefore, some poly(α‐olefin)s do not Received: 17 October 2017 Revised: 8 January 2018 Accepted: 9 January 2018 DOI: 10.1002/pat.4265 Polym Adv Technol. 2018;1–10. Copyright © 2018 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/pat 1