Study On The Rheological Properties Of SIS And Its Carbon-based Filling System

Unlike purely viscous Newtonian fluids,polymeric fluids tend to be viscoelastic.Rheology can be used to understand the viscoelastic behavior of polymer materials during flow.The change of polymer fluid viscoelasticity was closely related to its internal structure as well as the external field action conditions.Therefore,rheology was an effective tool for detected the evolution of the internal structure of polymeric materials.In this paper,the rheological behavior of SIS triblock copolymers and their carbon-based filled systems was investigated mainly using rotational rheometry,capillary rheometry,and small angle X-ray(SAXS)tests.The effects of two-dimensional layered graphene(FLG)and one-dimensional tubular carbon nanotubes(CNT)on the rheological properties and phase behavior of SIS1209 system were analyzed,respectively.It was found that the filling of carbon-based fillers(CNT,FLG)did not change the microphase separation structure of SIS1209,but CNT affected the microphase separation process of SIS1209.Rheological tests showed that the morphology of CNT and FLG would affect the viscoelasticity(viscosity,modulus,and stress,etc.)of the SIS1209 composite system,and the change of viscoelasticity was more significant in the SIS1209/CNT composite system.This was due to the greater entanglement degree between CNT with high aspect ratio and SIS1209 molecular chain.The viscous flow activation energy of the SIS1209 carbon filled system was also related to the morphology of the filler.In addition,viscoelastic overpermeability occurred in the SIS1209/CNT composite system when the filling of CNT was 1 wt%.The rheological behavior of SIS(SIS1209,SIS5562)/CNT composite systems with different block composition ratios(PS/PI)was investigated,and it was demonstrated that the viscoelasticity of the SIS1209/CNT composite system with PS/PI of 29/71 varied more with the filling of CNT.The SIS5562/CNT composite system with PS/PI of 45/55 not occurred viscoelastic overpermeability when the filling of CNT was 1 wt%.The viscous flow activation energy and stress relaxation behavior of the SIS/CNT composite system were also related to the block composition ratio.The above rheological phenomena were attributed to the different content of the PS microelastic phase acted as a physical entanglement point in the SIS,resulted in different molecular chain motility.The viscous flow curves of SIS with different block composition ratios(SIS1105,SIS1209,SIS5562)at different temperatures were investigated.It was found that the viscous flow curves could be treated by Cross equation with segmental fitting at temperatures lower than the viscous transition temperature of SIS,and the segmental fitted shear rate range was around the critical shear rate of SIS.This was due to the fact that the PS microelastic phase can be disrupted at high shear rates,resulted in a change in the flow pattern of the melt.When the temperature was higher than the viscous flow transition temperature of SIS,the viscous flow curve can be directly fitted by the Cross equation and the melt flow behavior was similar to that of homopolymer.