Effect of compatibilizer type on the properties of thermoplastic elastomers based on recycled polyethylene at high ground tire rubber content

In this study, compatibilized thermoplastic elastomers (TPE) based on recycled high-density polyethylene (HDPE) and high ground tire rubber (GTR) content (70, 80 and 90 wt%) were prepared by twin-screw extrusion followed by injection molding. The main objective of the work was to use three different compatibilizers and to compare their efficiency: ethylene-octene copolymer (Engage 8180), styrene-ethylene-butylene-styrene grafted with maleic anhydride (SEBS-g-MA) (Kraton FG1901X) and a trans-polyoctenamer (Vestenamer 8012). A morphological analysis showed that the addition of a compatibilizer produced more homogeneous structures, significantly improving mechanical performance compared with their uncompatibilized counterparts. This modification had a direct effect on all the properties, especially the tensile properties which were evaluated at different crosshead speeds (10, 50, 100 and 500 mm/min) to better see differences in the interfacial state. High elongations at break exceeding 100 % for highly filled recycled blends (up to 90 wt% of GTR) with Kraton FG1901X were obtained, highlighting superior compatibility efficiency. In general, adding GTR to recycled PE produced a more elastic TPE. Increasing the GTR concentration led to lower modulus (from 300 MPa for R-PE to 50 MPa for 70 % GTR). The main conclusion of the work was that injection molding of TPE with high GTR content (above 70 %) was only possible by adding compatibilizers. Nevertheless, the best performance to produce high GTR content TPE was obtained using Kraton FG1901X probably due to its grafted functionality (maleic anhydride, MA) leading to better interfacial interactions between the phases.