Moisture effects on dielectric relaxations of poly (ɛ-caprolactone)/starch biodegradable blends: Local, interfacial and segmental

Abstract

Poly(ɛ-caprolactone)/starch biocomposites in a wide composition range were studied by thermally stimulated depolarization currents, TSDC, during the drying process following the effect on the dielectric relaxations of moisture loss and blend composition. PCL's cooperative chain mobility is unaffected by the presence of water which is mainly located in the starch inclusions as its segmental relaxation is fixed at 207K. The heterogeneities found in the amorphous phase of neat starch are also observed here as a bimodal α relaxation which shifts to higher temperatures as it dries. The blend plasticization by water molecules also affects the blend secondary relaxations showing how the local motions are hindered by the loss of water which is lower in the blend than in pure starch. The interfacial peak which is intermediate between the α relaxations of the two components is affected by the inclusions change from liquid to glassy state as the blend dries.

Keywords: Biodegradable blends; Carbohydrate polymers; Dielectric relaxations; Immiscible blends; Moisture effect in starch blends; Starch.