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Wear resistant all-PE single-component composites via 1D nanostructure formation during melt processing

 
: Hee, Timo; Zhong, Fan; Koplin, Christof; Jaeger, Raimund; Mühlhaupt, Rolf

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Polymer 151 (2018), S.47-55
ISSN: 0032-3861
Englisch
Zeitschriftenaufsatz
Fraunhofer IWM ()
composite; nanofiber; blend; self-reinforcement; wear resistance

Abstract
Melt-flow-induced crystallization of polyethylene blends having tailored ultrabroad molar mass distribution affords extended-chain ultrahigh molar mass (UHMWPE) nanophases resembling nanofibers which effectively reinforce the polyethylene matrix. Unparalleled by state-of-the-art high density polyethylene (HDPE), the resulting melt-processable all-polyethylene single component composites exhibit simultaneously improved wear resistance, toughness, stiffness and strength. Key intermediates are trimodal blends prepared by melt compounding HDPE with bimodal UHMWPE/HDPE wax reactor blends (RB) readily tailored by ethylene polymerization on supported two-site catalysts. Whereas HDPE wax, varied up to 54 wt.-%, serves as processing aid lowering melt viscosity, UHMWPE varied up to 63 wt.-% accounts for improved blend properties. UHMWPE platelet-like nanophase separate during ethylene polymerization and readily melt during injection molding of RB/HDPE blends producing extended-chain fiber-like UHMWPE nanostructures of 100 nm diameter as shish which nucleate HDPE and HDPE wax crystallization to form shish-kebab-like structures. At 32 wt.-% UHMWPE content shish-kebab-like reinforcing phases account for massive polyethylene self-reinforcement as reflected by improved Young's modulus (+420%), tensile strength (+740%) and notched Izod impact strength (+650%) without impairing HDPE injection molding. All-PE composites exhibit high wear resistance entering ranges typical for polyamide and monomodal UHMWPE which is not processable by injection molding under identical conditions.

: http://publica.fraunhofer.de/dokumente/N-521492.html