Thermomechanical properties of bionanocomposites based on polycaprolactone and halloysite clay nanotubes

Abstract Bionanocomposites based on polycaprolactone and halloysite clay nanotubes were prepared by melt blending procedure. The nanofiller content was systematically varied in a wide range (from 5 to 60 mass%). We studied the effect of halloysite Addition on the thermal properties of polycaprolactone by thermogravimetric analysis and differential scanning calorimetry. Both techniques evidenced that the thermal characteristics of the nanocomposites depend on the biopolymer/halloysite composition. We observed that the polymer degradation temperature is not affected by halloysite for concentrations up to 15 mass%, while a further addition of the clay nanotubes generated a decrease of the thermal stability of polycaprolactone. Similar results were detected for the polymer melting enthalpy in agreement with a reduction of the polycaprolactone crystallinity. On the other hand, the melting temperature of the polymer was not influenced by halloysite for all the investigated compositions. We studied the viscoelastic properties of the nanocomposites at variable temperatures by dynamic mechanical analysis. These experiments revealed that the presence of the nanotubes can preserve the elastic component of the polymer within a larger temperature range compared to native polycaprolactone. According to this observation, we can conclude that the addition of halloysite nanotubes to the synthetic and biodegradable polycaprolactone matrix is promising for obtaining bionanocomposite materials suitable for technological applications, such as absorption of pollutants for remediation and conservation of cultural heritage.