Thermal properties and interactions in blends of poly(ε-caprolactone) with unsaturated polyester resins

Blends of two linear unsaturated polyester (LUP, commercially named AL-100 and 6603) with poly(ε-caprolactone) (PCL) were prepared by the casting method. Differential scanning calorimetry (DSC) has been used to study the miscibility, melting behaviour and crystallinity of 6603+PCL and AL-100+PCL blends. Two different heat treatments (Method 1 and Method 2), were carried out, in both systems. Only by following Method 2 a crystallization temperature (Tc) was selected before monitoring the glass transition and melting behaviour of the blends. When samples were scanned under Method 1, a unique Tg intermediate between the Tg’s of the pure polymers in all the blends studied was found. It indicates that the PCL is miscible with both unsaturated resins in the whole composition range. Nevertheless, when samples were scanned following Method 2 the Tg–composition dependence exhibited an asymmetric behaviour that could indicate a certain lack of homogeneity in the blends at intermediate compositions.