The effect of nanofiller type and dispersion state on the thermal and rheological properties of poly(e-caprolactone) nanocomposites

Poly(e-caprolactone) (PCL) is a biodegradable synthetic resin which - besides relatively high crystallization rate, fair mechanical performance and good processability - exhibits a high degree of biocompatibility. Resins based on aliphatic polyesters such as PCL find application as compost bags as well as in a number of medical products. Its use in additional fields is however restricted due to moderate barrier properties and low modulus. A simple approach to overcome these limitations consists of incorporating low amounts of nanosized filler particles.
Processing conditions and nanocomposite preparation method influence the degree of filler dispersion. For a given type of nanocomposite, the thermodynamic compatibility between the polymer matrix and the nanofiller (effect of the filler modification) plays another key role.
The PCL nanocomposites used in this work were prepared by melt mixing techniques. Various layered silicates, treated by different organic modifiers on their surface, and carbon nanotubes (CNT) were used as nanofillers.
An advanced thermal analysis methodology (Modulated Thermal Differential Scanning Calorimetry, MTDSC) is employed for the characterization of PCL nanocomposites. During quasi-isothermal crystallization, the presence of high aspect ratio nanofillers strongly affects the amount of crystalline-amorphous interface, thus increasing the recorded excess heat capacity (Cpexcess).
A clear link between Cpexcess, rheological data and/or conductivity data evidences the effect of dispersion quality on the nanocomposite properties. As such the use of Cpexcess from advanced thermal analysis provides a new methodology to quantitatively assess the filler dispersion state.