Thermomechanical properties of cured isophtalic polyester resin modified with poly(ε-caprolactone)

Abstract

The effect of a low profile additive, poly(e-caprolactone) (PCL), on the thermal and mechanical properties of unsaturated polyester resins (UP) was investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile tests. The morphology of the systems has been studied by scanning electronic microscopy (SEM). Two PCL molecular mass were selected (PCL2: M n = 2000 g mol−1 and PCL50: M n = 50000 g mol−1) to analyze the influence of the molecular mass and the content of PCL on the UP resins and to establish the relation between thermomechanical behavior and morphology. DSC and DMTA glass transition temperatures (T g) of the UP cured samples containing PCL indicate that PCL2 is miscible with UP whereas for UP + PCL50 system, T g values are very close to the ones corresponding to neat UP. Besides in UP + PCL2 systems, one phase morphology is observed in which PCL2 would act as solvent of the reacting mixture along curing process; however, UP + PCL50 systems present phase-separated morphology. The presence of PCL2 and PCL50 in UP resin leads to a decrease of the tensile strength and the Young′s modulus as much notorious as the PCL concentration increases. For UP + PCL2 system the elongation at fracture increases in relation to neat UP, increasing as well with the PCL content.