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

Abstract

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.