Study On Microstructure,Dynamic Rheological Behavior And Flame Retardancy Of Halogen-free Flame-retarded Nylon/Montmorillonite Composites

In recent years,polymer/montmorillonite nanocomposites have received extensive attention due to their excellent physical properties and flame retardant properties.However,montmorillonite has limitations in improving the flame retardant properties of polymers.Therefore,it is usually considered to use it with flame retardants.In this paper,flame retardant nylon 6 was prepared by using aluminium salts of diisobutylphosphinicacid(APBA)and inorganic nano-particles montmorillonite/and carbon nanotubes.The rheological behavior and flame retardancy of different flame retardant systems was studied and the structure-activity relationship between the microstructure was illustrated.Three different modified montmorillonites(Na~+MMT,CMMT,CMMTs)/polyamide 6 and montmorillonite/flame retardant polyamide 6 composites were prepared.X-ray diffraction(XRD),transmission electron microscopy(TEM),rotational rheometry,and contact angle measuring instruments were used to systematically characterize the sample structure.The flame retardancy and combustion behavior of the composites were measured by using the oxygen index(LOI)test,vertical combustion(UL-94)and cone calorimeter.The effects of different montmorillonites and their interaction with polymer on the structure,rheological behavior and flame retardancy of flame-retardant nanocomposites were discussed and compared.Studies have shown that when the interfacial tension between CMMT and polymer is the smallest,the interaction is the strongest and the dispersion of montmorillonite in the polymer is best.For the flame-retardant polymer nanocomposites,the strong interaction between the CMMT and the polymer can significantly improve the dispersion distribution of the CMMT in the system and promote the CMMT sheet to form a particle network structure in space,limiting the movement of the molecular chain,and improving the fusion body stability,which ultimately improves the burning behavior of the material.In order to study the effect of different montmorillonite modifiers on the properties of the material,organic barium salt montmorillonite(PMMTsol,PMMTsc)/polyamide 6 and montmorillonite/flame retardant polyamide 6 composite materials were prepared by two different methods.Compared with CMMT flame retardant polyamide 6 nanocomposite system,the structure,rheological behavior and flame retardancy of the composites were studied.The results show that the interfacial tension of PMMT is greater than that of CMMT,and the interaction with polyamide 6is weaker.The dispersity of CMMT in polyamide 6 is better.Due to the weak plasticizing effect of the PMMT system,the melt viscosity of the PMMT system is relatively high,which is conducive to the formation of a denser carbon layer structure,thereby enhancing the condensed phase effect of the system.Compared with CMMT flame retardant polyamide 6 nanocomposite system,PMMT flame retardant polyamide 6 system show more excellent flame retardant performance.Carbon nanotube(MWNT)was used to improve the performance of ammonium salt-modified montmorillonite(CMMT)flame-retardant composites.A series of flame retardant composites with different MWNT contents were prepared.Studies have shown that the addition of a small amount of MWNT can not affect the dispersion of CMMT in composites.The MWNT can interact with CMMT,enhance the network structure of nanoparticles,increase the material melt viscosity,improve the surface structure of the carbon layer,and improve the flame retardancy of the material.