Effect of nanofiller's type on the thermal properties and enzymatic degradation of poly(ε-caprolactone)

Poly(ε-caprolactone) (PCL) nanocomposites containing different types of montmorillonite, fumed silica nanoparticles or carbon nanotubes were prepared by the melt mixing technique. The nanofiller content was 2.5 wt% in all the materials. From the tensile properties study, it was found that the Young modulus increased in the nanocomposites, while the stress as well as the elongation at break decreased. The WAXD patterns of the materials showed no significant change in the crystal structure caused by the addition of the filler. The non-isothermal crystallization of the nanocomposites was studied with differential scanning calorimetry (DSC). In all cases, especially for MWCNTs, it was found that the addition of nanoparticles can increase the nucleation activity as well as the crystallization rates of the nanocomposites compared to those for neat PCL. This is a proof that the nanoparticles act as nucleating agents. From the enzymatic hydrolyses tests in the presence of lipases it was found that PCL has the highest mass loss from all tested samples and it is completely degraded after 8 days of hydrolysis. For the same time of hydrolysis, all nanocomposites showed lower mass loss, proving that addition of the nanoparticles decreased the hydrolysis rates of PCL. The delay depends on the used type of nanofillers. However, GC-MS analysis evidenced that nanofillers did not alter the hydrolysis mechanism of PCL, since for all the nanocomposites 6-hydroxy-hexanoic acid was the main byproduct.