Heterogeneous bubble nucleation in PCL/clay nanocomposite foams

Nanocomposites based on biodegradable polycaprolactone (PCL) and organically modified layered silicates (organoclay) have been prepared by melt mixing. The isothermal crystallisation of polycaprolactone/clay nanocomposites showed that the well-dispersed organoclay platelets acted as nucleating agents in the PCL matrix, as confirmed by a remarkable reduction of the crystallisation half-time t_1/2. The nanocomposites showed much higher complex viscosity than that of the neat PCL and pseudosolid-like behaviour in the low frequency range. The foaming process of PCL/clay nanocomposites containing 2%wt and 5%wt of clay were investigated by using a batch process. The results showed that the presence of clay resulted in an increase in cell density and a reduction of cell size compared to pure PCL and higher densities due to the higher viscosity of the melt.