High molecular weight polymers are the “backbone” of the flexible packaging industry, although a variety of papers, fabrics, and metallic foils are also employed. Almost without exception, high molecular weight polymers are physiologically inert and, therefore, pose no toxicological problems in themselves. However, monomers and low molecular weight fractions that may be incorporated in certain commercial polymers can be a source of concern, as can be other low molecular weight chemicals purposely added to commercial polymers, in some instances, to modify their processing or functioning characteristics. Conditions of use must also be considered when employing polymeric films (with or without additives) as the food contact components of packages. A polymer may be completely nontoxic and an adequate barrier to other package constituents when used to contain foodstuffs if the resultant package is subsequently stored at room temperature, under refrigeration, or frozen. However, when used as the inner ply of a boil-in pouch, a retortable pouch, or an oven bag, it must be determined that it is not subject to some degree of thermal breakdown or allows permeation of adhesive or ink components not approved for direct contact with food. Finally, if there is a requirement to sterilize packages before filling, as in aseptic packaging, the effect of the sterilizing medium on the packaging material must be fully understood.
A New Formation Process of Poly(phenylsilsesquioxane) in the Hydrolytic Polycondensation of Trichlorophenylsilane. Isolation of Low Molecular Weight Hydrolysates to Form High Molecular Weight Polymers at Mild Reaction Conditions