Influence of chlorine content on crystallisation kinetics and mechanical properties of PCL/CPE blends

Abstract

The effects of chlorine content on the crystallisation kinetics and mechanical properties of poly(ε-caprolactone) (PCL) and chlorinated polyethylene (CPE) blends were studied. Thermogravimetric analysis showed that PCL had a single-step degradation, whereas CPE with 25% Cl exhibited a two-step degradation. Differential scanning calorimetry indicated that increasing the CPE content reduced the crystallisation temperature and broadened the peaks, indicating lower crystallinity. The glass transition temperature (T_g) of the blends decreased with increasing PCL content, showing composition-dependent behaviour, and the Fox equation accurately predicted T_g values, especially at lower CPE concentrations. Isothermal crystallisation studies revealed that neat PCL had the highest crystallisation rate, whereas the 60PCL/40CPE blend had the lowest. Melting point analysis indicated partial miscibility between PCL and CPE, with stronger interactions at higher chlorine content. The Hoffman–Weeks method determined the blend's equilibrium melting temperatures, which decreased by nearly 4°C compared to pure PCL. Mechanical testing showed that a higher Cl content in CPE increased ductility and reduced brittleness, with CPE containing 48% Cl showing the greatest strength and rigidity. In comparison, lower Cl content improved the mechanical properties. These results emphasise the significant impact of chlorine content on the thermal, crystallisation, and mechanical properties of the PCL/CPE blends.