A polymer film is made by mixing pellets of starch and of PVA together, and then thermoplastically extruding the mixture. The mixture should contain at least 10% and preferably at least 25% (by weight) of each polymer, and extrusion generates a homogeneous film which appears uniform. It can be as thin as 20 |jm. The resulting film is readily biodegradable, water-soluble or water-dispersible, and has good physical properties. This same pellet mixing extrusion process, followed by injection moulding, can be used to form other objects.