A thermoplastic, biodegradable polymer blend having a high surface energy and good adhesion without the need for pretreatment, is made up of starch in the range 10% to 60% by weight of the polymer blend, at least one further carrier polymers in the range 40% to 90% by weight of the polymer blend and one or more process aids in the range 0% to 0.5% by weight of the polymer blend. The polymer blends typically have a surface energy after processing of at least 40 mN/m.