Polyolefin nanocomposites containing inorganic components show improved properties in various applications. A common route to nanocomposites is their preparation from composite nanoparticle dispersions. Usually, aqueous dispersions from surfactant-free heterophase polymerization are employed, in which the inorganic nanoparticles are adsorbed to the polymer particles’ surface and ensure colloidal stability by Pickering stabilization. However, for the case of polyethylene, free-radical dispersion polymerization requires high pressures and catalytic aqueous polymerizations have become available more recently only. The high hydrophobicity of polyethylene additionally impedes its interaction with Pickering stabilizers and thus dispersibility in aqueous media. Aqueous dispersions of ethylene copolymers with polar comonomers are of practical interest, e.g. as additives for paints or water-based adhesives.<br/><br/>We report on the synthesis of aqueous, Pickering stabilized dispersions of polyethylene and copolymers of ethylene and polar comonomers at relatively mild conditions (300 atm, 85°C). The added inorganic particles effectively stabilize the polyolefin particles formed and also support particle formation during the aqueous polymerization reaction. In polymerizations in the presence of vinyl acetate, acrylates, methacrylates, acrylamides or ionic vinyl or (meth)acrylate copolymers with polar comonomer contents of 0.1 up to 10 mol-% were obtained. The degree of incorporation of comonomers into polyethylene allows tuning of its adsorptive properties which is decisive for Pickering stabilization efficiency of polymer particles with clay. Mechanistic insights on particle formation and stabilization are discussed.

Aqueous dispersions of polyethylene and ethylene-copolymers and their clay nanocomposites from free-radical dispersion polymerization

2019 Fall National Meeting

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