Reactive melt‐grafting of maleic anhydride onto olefin block copolymer toward high‐performance polar polyolefin thermoplastic elastomer

The block structure of olefin block copolymer (OBC) elastomer gives it good elasticity and heat resistance relative to other polyolefin elastomers. However, the non‐polar nature of OBC chains limits its comprehensive properties like dyeing and toughening for polar engineering plastics. In this work, maleic anhydride (MA) and dicumyl peroxide (DCP) were selected as a typical polar monomer and a radical initiator to modify the polarity of OBC elastomer. During the melt‐grafting process, the DCP content was tuned to optimize the grafting efficiency while the MA‐to‐OBC ratio was fixed at 5 wt%. It was found that all the melt‐grafting reactions show high efficiency and can be finished in 3 min at 170 °C. With the increase of DCP content, the estimated grafting degree of OBC‐g‐MA elastomer increases from 0.40% to 1.16% along with increased gel content from 4.27% to 22.44%. A suitable grafting process was obtained with a DCP content of 3.0 wt% by balancing grafting efficiency and final mechanical properties. The optimized OBC‐g‐MA elastomer with a grafting degree of 0.92% has a mechanical strength of 17.15 MPa, a Young's modulus of 26.35 MPa, elongation of 1564% and strain recovery of 59.73%. Additionally, the contact angle test shows that polar grafting can increase surface hydrophilicity while excessive crosslinking promotes hydrophobicity. Therefore, our work has demonstrated the feasibility of the reactive melt‐grafting method to prepare OBC‐g‐MA elastomer and can also provide a processing reference for other chemical functionalization of polyolefin thermoplastic elastomers. © 2024 Society of Industrial Chemistry. Maleic anhydride (MA) and dicumyl peroxide (DCP) were selected as a typical polar monomer and a radical initiator to modify the polarity of olefin block copolymer (OBC) elastomer. The optimized OBC‐g‐MA elastomer with grafting degree of 0.92% has a mechanical strength of 17.15 MPa, Young's modulus of 26.35 MPa, elongation of 1564% and strain recovery of 59.73%.