Miscibility of TPU(PCL diol)/PCL blend and its effect on PCL crystallinity

Poly(epsilon-caprolactone) (PCL) was melt blended with thermoplastic polyurethane based on polycaprolactone diol (TPU(PCL diol)). The amount of PCL was varied from 20% to 50% by weight. A single composition dependent glass transition temperature (from DSC) shows the miscibility of system. Also the negative value of polymer-polymer interaction density, obtained from the analysis of the equilibrium melting point depression, confirms the blends' miscibility. T-c and T-m of the PCL component in the blend decrease significantly with an increase in the TPU content, in comparison with that of pure PCL. The position of the diffraction peak related to (110) planes of PCL in the blends using WAXS has been shifted to lower value. This means the b-axis of orthorhombic unit cell of PCL is spread out in the blends. On the whole, increase of TPU content in the blend decreases crystallization ability of PCL compared to pure PCL.