Poly ( e-caprolactone) nanocomposites : study of crystallization behavior

Abstract

Consulta en la Biblioteca ETSI Industriales (8128)

[EN] 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. Differential scanning calorimetry (DSC) is used to investigate the influence of moisture on the isothermal crystallization behavior of polycaprolactone samples. It can be concluded that a dry sample starts to crystallize before the wet samples. 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 (Cp excess). The influence of nanofiller loading on the melting behavior after quasi isothermal crystallization is also studied. Experiments to study crystallization kinetics are conducted with DSC using different cooling rates. It is observed that as the rate of cooling increased the crystallization temperature (Tc) shifts to lower temperatures. However, no significant difference in the enthalpy of crystallization values is observed. The PCL nanocomposites used in this work were prepared by melt mixing techniques (extrusion). DSC is used to study the influence of this process on the isothermal crystallization of PCL. It is observed that the extruded samples start to crystallize earlier than the granule sample as is. After isothermal crystallization experiments at different Tc, the melting behavior of the samples is recorded with DSC. With increasing the isothermal crystallization temperature, the melting peak moves to higher temperatures for PCL samples. Most of the samples prepared in this thesis were made using one PCL batch. To study the influence of the molecular weight on the thermal properties (crystallization temperature, enthalpy and melting temperature) obtained via DSC measurements, PCL batches with different molecular weights are used. No significant differences in glass transition temperature (Tg) values are obtained.