Graphene-Embedded Hybrid Network Structure to Render Olefin Block Copolymer Foams with High Compression Performance
Yanting Li, Yunjie Liu, Pengjian Gong, Yanhua Niu, Chul B. Park, Guangxian Li
Abstract
Graphene has abundant interactions with polymers by adhering to macromolecular chain segments, facilitating heterogeneous crystal nucleation and adsorbing free radicals. Hence, a hierarchical network structure using graphene as the anchor could be formed in an olefin block copolymer (OBC)/low-density polyethylene (LDPE) blend together with cross-linking points and entanglement points. Then, a nanocomposite foam was fabricated by supercritical CO2 foaming. In this work, a graphene-embedded hybrid network structure was designed to effectively control OBC/LDPE foaming. The strategy is as follows: (1) Macromolecular free radicals triggered by peroxide were adsorbed on the surface of graphene to form a dentritic-on-plate structure. (2) Both OBC and LDPE molecular chain segments were adhered to graphene to form a hybrid physical network. (3) Long-branched chains of LDPE formed entanglement points with both molecular chains whose segments adhered to graphene and macromolecular free radicals adsorbed on graphene. Finally, an optimized graphene content of 0.5 wt % in the obtained nanocomposite foam would maximize its compression stability (hysteresis loss of 53%) with a high resilience of 60%.