Enhanced Recyclability of Thermoplastic Elastomer Toughened Polyamide 6 via Tri- and Multi-epoxy-Terminated POSS Hybrid Additives

Although widely used polymers, such as polyethylene (PE) and polypropylene (PP), are easily recyclable, complex engineering polymer blends used in the automotive sector involve recycling challenges at the end of life. This study explores the alterations in the properties of compatibilized PA6/TPE blends under multiple thermomechanical recycling conditions, especially for the automotive industry in underhood applications. The compatibilization of PA6/TPE blends was achieved through the incorporation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles, specifically utilizing variants with three and multiple epoxide functional groups (TriEpPOSS and MultEpPOSS, respectively) in their cage structures. Following each recycling step, the blends were pelletized and injection-molded to characterize their morphological, rheological, mechanical, and thermomechanical properties. The findings revealed that the addition of TriEpPOSS significantly improved all properties of PA6/TPE blends throughout successive extrusion cycles. For instance, significant enhancements in Izod impact strength were achieved through the incorporation of TriEpPOSS into the PA6/TPE blend across multiple extrusion cycles. Notably, the 80PA6/20TPE blend with 1 wt % TriEpPOSS demonstrated a remarkable 685% increase in Izod impact strength compared to the same blend without TriEpPOSS following the fourth extrusion cycle. Conversely, the incorporation of MultEpPOSS slightly reduced the rheological and mechanical properties after each extrusion cycle. Nonetheless, it was observed that all properties, particularly rheological characteristics, were superior in blends compatibilized with MultEpPOSS compared to both TriEpPOSS-compatibilized and noncompatibilized blends, owing to the heightened reactivity of MultEpPOSS toward PA6.