2 CHEMICAL MATERIALS BASED ON SILANES AND/OR POLYSILOXANES FOR COATING PLASTICS, METAL, GLASS, PORCELAIN, ENAMEL, CONCRETE, AND NATURAL MATERIALS SUCH AS WOOD, SILK, HEMP, SISAL, SANDSTONE, AND MINERALS FOR PROTECTION AGAINST DIRT, WATER, UV RAYS, MECHANICAL, THERMAL, AND CHEMICAL INFLUENCES