Non-isothermal crystallization behavior, rheological properties and morphology of poly(?-caprolactone)/graphene oxide nanosheets composite films

In the present study, the non-isothermal crystallization behavior of solution cast poly(?-caprolactone) (PCL)/graphene oxide (GO) nanocomposite (PCL/GO) films was investigated at a different cooling rate. The loading concentration of GO (0.25-1% w/w) increased the crystallization temperature (Tc) of PCL matrix at a constant cooling rate. Various model equations were tested to describe the non-isothermal crystallization kinetics of the PCL/GO blend films. The results indicated that the Avrami analysis modified by Jeziorny equation described well the non-isothermal crystallization kinetics of tested samples. The crystallization activation energy was calculated applying the differential isoconversional method of Friedman, and the values ranged between -250 and -100 kJ/mol with an expected decrease of the energy in depending on the quantity of% GO content. Hoffman-Lauritzen secondary nucleation theory parameters, Kg and U* were evaluated using the isoconversional approach of Vyazonvkin and Sbirazuoli, highlighting a shift for the change of regime I/regime II from 305 to 313 K in dependence of GO content. Oscillatory rheology of PCL/GO blends on melt exhibited a transition of liquid-like to solid-like property. The mechanical strength of the blend improved significantly when the GO concentration was maintained at 0.75 wt% or more. The peak height of the AFM confirmed the doping of GO into the PCL matrix.