Study On The Flame Retardancy Of PBS/PBAT System By Carbon Material Composite Montmorillonite

With the development of society,green and environmentally friendly halogen-free flame retardants have gradually replaced traditional halogen-containing flame retardants,and it has become the general trend.Therefore,research on new flame retardants and flame retardant composite systems has become a hot spot today.Biodegradable polymers have the advantages of being environmentally friendly,excellent in comprehensive performance and widely used,but their flammability makes them unable to meet the needs of existing products.Therefore,the development of new environmentally friendly flame retardant biodegradable polymers provides a reference for production and processing.Graphitic phase carbon nitride（g-C₃N₄）,as a new carbon material with the advantages of low price,easy to obtain,non-toxic,visible light absorption and excellent thermal stability,can be used not only as catalysts,coatings but also as photoelectric materials,electrode materials,etc.However,the research on g-C₃N₄ as a flame retardant is very scarce.In this study,g-C₃N₄ was successfully prepared using melamine（MA）as the precursor by a fast and efficient stabilization method,and the g-C₃N₄/MT flame retardant composite system was prepared by loading g-C₃N₄ onto montmorillonite（MT）,and characterized and analyzed as a flame retardant composite system.The flame retardant biodegradable polymer PBS/PBAT/g-C₃N₄ composites and PBS/PBAT/g-C₃N₄/MT composites were prepared by adding g-C₃N₄ and g-C₃N₄/MT flame retardant composite systems to PBS/PBAT through physical blending method.The morphological structure,thermal decomposition behavior and mechanical properties of the composites were investigated by infrared spectroscopy,X-ray diffraction,thermal weight analysis,ultimate oxygen index determination,residual carbon infrared analysis,residual carbon scanning electron microscopy analysis,and tensile property testing,as well as the possible flame retardant mechanism,and the flame retardant properties of PBS/PBAT/g-C₃N₄/MT composites were analyzed for future production and processing As a reference.The main work is as follows.1.Using the physical blending method,PBS and PBAT were mixed to prepare a PBS/PBAT blend material.Through a series of test analysis and related literature review,it was concluded that the difference between PBS and PBAT in PBS/PBAT blend samples of different components was obtained.The mass ratio of 70:30 is the best ratio of comprehensive properties,which is used as the matrix for the research of flame retardant modification in this paper.2.g-C₃N₄ was successfully prepared by using melamine as raw material and using thermal polymerization method,and its chemical structure was demonstrated by a series of test methods.The g-C₃N₄ was filled into PBS/PBAT by physical mixing method to obtain PBS/PBAT/g-C₃N₄ composites.The flame retardant properties of PBS/PBAT/g-C₃N₄composites were characterized by thermal stability test（TG）,residual carbon infrared analysis,limiting oxygen index test（LOI）,and vertical combustion test（UL-94）.The results show that,g-C₃N₄ promotes the carbon formation of PBS/PBAT blends,improves their thermal stability,and slows down the rate of PBS/PBAT thermal decomposition.The LOI value of PBS/PBAT/20%g-C₃N₄ material could reach 33%,and the vertical combustion class was improved from the original no class to V-0.Infrared characterization of the pyrolytic residual carbon of the composites could be concluded that there was incompletely reacted g-C₃N₄,and there were residual g-C₃N₄ and non-combustible gases on the surface of the material,which proved the existence of a gas-phase-condensed-phase flame retardant mechanism.3.The g-C₃N₄/MT flame retardant composite system was produced by direct loading method using g-C₃N₄ and montmorillonite（MT）as raw materials.The PBS/PBAT/g-C₃N₄/MT composite was obtained by filling the g-C₃N₄/MT flame retardant composite system into PBS/PBAT using physical blending method.The flame retardant properties of PBS/PBAT/g-C₃N₄ composites were characterized by residual carbon infrared analysis,limiting oxygen index test（LOI）,and vertical combustion test（UL-94）.The results show that,The LOI of PBS/PBAT was 24%,when 5%g-C₃N₄/MT was added the LOI value was27%,which was a 3%improvement compared to pure PBS/PBAT,and when 20%g-C₃N₄/MT was added the LOI value was 39.8%,which was a 15.8%improvement,and the melt drip phenomenon was significantly suppressed.The IR characterization of the residue shows that the residue contains silicate structure and very little g-C₃N₄.g-C₃N₄/MT decomposes thermally and releases nonflammable gas in the gas phase;the silicate that loses crystalline water in the condensed phase covers the surface of the material to form a protective insulation layer with good stability.