Study On The Crystal Morphology And Crystallization Kinetics Of Poly(ε-caprolactone)/graphene Composites

Poly(ε-caprolactone)(PCL)/graphene composites was prepared by ultrasonicallymixing PCL with graphene oxide (GO), graphene (GE) or graft graphene (gGE) inN,N-dimethylformamide (DMF). The crystalline morphology, isothermal crystallizationand thermal stability of PCL and PCL/graphene composites were investigated by usingpolarized optical microscopy (POM), differential scanning calorimetry (DSC) andthermogravimetric analyzer (TGA). POM results revealed that the crystalline morphologyof PCL/GO, PCL/GE and PCL/gGE composites was spherulite, showing a typical maltesecross extinction image. The nucleation densities of composites was significantly increasedcompared to pure PCL, the grain boundary was increased too. DSC results show that themaximum crystallinity (Xmax) of the composites decreases when the content of GO, GE andgGE increased, PCL/GE system decreased the most. This will be conducive to biologicaldegradation of PCL. Isothermal crystallization kinetic results investigated by DSC showedthat GO, GE and gGE accelerate the crystallization rate of PCL effectively due to theirnucleation effect. Maximum crystallization rate was obtained when the content of GO orgGE is0.2wt%. Combination of DSC and POM results, the increase of the totalcrystallization rate of composites is the nucleation density and spherulite growth rateincreased. It is show that the add of GO, GE and gGE conducive to molecular motion ofPCL. It will also accelerate the degradation rate of PCL in the environment. The meltingpoint and equilibrium melting point of PCL composites decreased gradually with theincrease of the concentration of GO, GE, gGE. From TGA data, the thermal stability ofPCL is enhanced when GO, GE or gGE was added. The thermal stability of PCL isenhanced significantly when GO was added, and gradually enhanced with the increase ofthe concentration of GO.