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Oxygen Permeability of Novel Organic-Inorganic Hybrid Coatings

Matteo Minelli1, Maria Grazia De Angelis2, Ferruccio Doghieri1, Michele Marini3, Maurizio Toselli4, and Francesco Pilati3. (1) Department of Chemical Engineering, Mining and Environment Technology, Alma Mater Studiorum - University of Bologna, Via Terracini 34, Bologna, Italy, (2) Department of Chemical Engineering, University of Bologna, Via Terracini 34, Bologna, Italy, (3) Department of Materials and Environmental Engineering, University of Modena and Reggio Emilia, Italy, (4) Department of Applied Chemistry and Material Science, Alma Mater Studiorum - University of Bologna, Bologna, Italy

The oxygen barrier properties of composite materials, consisting of a 45 μm thick LDPE substrate coated by a thin layer (0.7-1 μm) of nanostructured hybrid organic/inorganic materials based on SiO2 and polyethylene-polyethylene glycol (PE-PEG) block copolymers, obtained via a sol-gel technique have been characterized at 35°C and 50°C. A significant decrease (25-40%) of the oxygen transfer rate has been observed for coated samples with respect to bare substrate both at 35°C and 50°C.

The barrier effect was further improved by adding of a second organic component capable of forming hydrogen bonds, namely poly(4-hydroxy styrene) (PHS): use of PHS leads to a remarkable decrease (50 - 70 %) of the oxygen transfer rate both at 35°C and 50°C. It has been determined that the optimal formulation is the one containing 22% of PHS and 33% of silica; the thickness required for the multilayer sample to have the same barrier properties as a 45 μm thick, homogenous film composed of HDPE, oPP and PLA is equal to 2.5, 0.2 and 0.1 μm respectively.