Rheological, thermal and structural behavior of poly(ε-caprolactone) and nanoclay blended films

Abstract

Poly(ε-caprolactone)/nanoclay composite (PCLNC) films were prepared by solvent casting method using a wide range of layered silicate (2.5–10%) and were characterized by different techniques. Nanofiller dispersions in PCL matrix were studied by wide-angle X-ray diffraction (XRD) and transmission electron microscopy (TEM), and results indicated the formation of some intercalated nanostructure of PCLNC. Rheological and thermal properties of PCLNC were measured by parallel-plate oscillatory rheometry and differential scanning calorimetry (DSC), respectively. Rheological study indicated that the predominating liquid-like properties (viscous modulus, G″>elastic modulus, G′) of neat PCL gradually transformed to solid-like (G′>G″) behavior after incorporation of clay in the temperature range of 90–120°C. A plot of G′ vs. G″ provide information on intercalation and microstructure of nanocomposite. Applicability of time–temperature superposition (TTS) principle and van Gurp–Palmen plot (phase angle vs. absolute complex modulus) on rheological data of clay incorporated PCL were employed and found that the results failed to follow the rules. Incorporation of the nanoclay into PCL matrix increased the crystallization temperature (Tc) and melting temperature (Tm) of neat PCL from 28.7 to 32.3°C and 56.3 to 59.2°C, respectively due to the nucleating effect, but the glass transition temperature (Tg) (≈−65°C) was remained unaffected. The decrease in crystallinity with increase in clay concentration was confirmed by both XRD and DSC data.