It is provided a phyllosilicate having a layered structure in the form of platelets and comprising an intercalating agent between the platelets, wherein the intercalating agent is a polyester of a molecular weight of 274 to 30,000 g/mol, and wherein the phyllosilicate is other than a phyllosilicate modified through ionic interchange. It is also provides a polymer nanocomposite comprising a polyethylene terephthalate (PET) polymer an the phyllosilicate mentioned above, as well as preparation processes for the preparation of the intercalated phyllosilicate and the PET nanocomposite. The PET nanocomposite is particularly useful for packaging, particularly for food and drink packaging.