Study on blends of thermoplastic polyurethane and aliphatic polyester: morphology, rheology, and properties as moisture vapor permeable films

Blends of Estane® thermoplastic polyurethane (TPU) and aliphatic polyester were prepared via melt blending and blend films were prepared via blow molding. The morphology, thermal properties and rheology of the blends, and the properties as moisture vapor permeable films were studied. Differential scanning calorimetry and Fourier transformed infrared spectroscopy investigation indicated that the TPU was compatible with the aliphatic polyester. Scanning electron microscopy (SEM) micrographs exhibited a particle-dispersed type of the morphology, in which the aliphatic polyester was finely dispersed as regular spherical particles in the TPU matrix when the content of the aliphatic polyester was below 30 wt%; however, the dispersed domain presented an irregular form owing to aggregation when the content of the aliphatic polyester reached 40 wt%. Evaluation of the properties of the blend films demonstrated that incorporation of the aliphatic polyester could significantly enhance the adhesive strength and the tensile properties of the TPU film, but the moisture vapor permeability and the waterproofness deteriorated. The blend films will still have a balance of comfort and laminating processability as long as the aliphatic polyester content is controlled to an appropriate level, i.e. below 20 wt%.