Process for forming a thermally and chemically inert multilayer film

The process according to any preceding claim, wherein non-fluorinated silane compound is chosen from chloro- bromo- or iodo-alkoxysilanes, aminosilanes such as APTES, APDEMS, APDMES, APTMS, glycidoxysilanes such as GPMES, and mercaptosilanes such as MPTMS, MPDMS and alkoxysilanes;

• and preferably is a tetraalkoxysilane such as TEOS.

The process according to any preceding claim, wherein the fluorinated silane compound is chosen from perfluoroalkylsilanes bearing at least one perfluoroalkyl group, at least one non-hydrolyzable group and at least one reactive group, preferably from perfluoroalkylsilanes bearing at least one perfluoroalkyl group, at least one alkyl or aryl group and at least one alkoxy group, a halogen atom, hydroxyl group, amine or substituted amine group.

The process according to any preceding claim, wherein the composition comprising one or more copolymers of tetrafluoroethylene further comprises a perfluorinated solvent dissolving the copolymers of tetrafluoroethylene, such as for example perfluorinated alkanes or cycloalkanes, perfluorinated heterocyclic compounds, or mixtures thereof

The process according to any preceding claim, wherein the copolymer of tetrafluoroethylene is chosen from copolymers of tetrafluoroethylene and perfluoro-2,2-dimethyl-1,3-dioxole.

A substrate comprising on at least part of its surface a thermally and chemically inert multi-layer film comprising in this order

• a. a continuous layer comprising at least partially fused inorganic oxide material;
• b. a layer comprising a copolymer of tetrafluoroethylene;
• wherein the continuous layer comprising an at least partially fused inorganic oxide material is in contact with the substrate, and the layer comprising a copolymer of tetrafluoroethylene is in contact with the porous or non-porous continuous layer comprising at least partially fused one or more inorganic oxide material.