Organic Modification Of Mg-Al Hydroxide And Its Effect On Mechanical And Flame Retardant Properties Of Functiona Materials

Layered magnesium aluminium hydroxide,also known as hydrotalcite,is considered as one of the effective ways to achieve green flame retardant because of its non-toxic,smoke suppression and other advantages.Nevertheless,there are still some problems in the hydrotalcite used at present,such as poor flame retardant effect,great influence on the mechanical and physical properties of functional materials.Therefore,it is of great theoretical and practical significance to further study and improve the compatibility and flame retardancy of functional materials.Firstly,Mg/Al-CO3-LDHs precursor were prepared by double-titration coprecipitation method using magnesium nitrate,aluminum nitrate,sodium hydroxide and sodium carbonate as raw materials.Then the compound modified hydrotalcites(ITA-LDHs)with itaconic acid and titanate coupling agent NDZ-201 were prepared by anion exchange method.ITA-LDHs were characterized by FTIR,XRD,TGA and SEM.The results showed that itaconic acid and titanate coupling agents have been incorporated into the interlayer of hydrotalcite.Flame retardant polypropylene(PP)composites were prepared by melt blending.The flame retardancy and mechanical properties of the composites were investigated by measuring LOI,UL-94,thermogravimetric curves and cone calorimetry.The results showed that both unmodified and modified LDHs have flame retardant effect on PP with the increase of hydrotalcite content,and the LOI value,melt drop resistance time,thermal stability and charring rate of modified LDHs are significantly improved.When thecontent of hydrotalcite was 30%(based on the quality of polypropylene),the LOI of ITA-LDHs reached 27.5%,UL-94 reached V0,which was obviously superior to that of unmodified LDHs.By testing the bending strength and tensile strength of the material,it can be seen that compared with the unmodified hydrotalcite,the unfavorable effect of the modified hydrotalcites on the bending strength and tensile strength of the material have been significantly improved.Then,functional magnesium aluminium hydrotalcite(STA-LDHs)with oxidized starch,sodium dodecyl sulfate(SDS)and titanate coupling agent(NDZ-201)as modifiers were prepared.The structure of STA-LDHs were characterized by FTIR,XRD,TGA.STA-LDHs were added to pulp as filler to improve the flame retardancy of paper.The LOI,thermogravimetric curves,cone calorimetry and mechanical properties of the flame retardant paper were measured.The results showed that the flame retardancy,thermal stability and charring ability of the modified hydrotalcites were improved.When the content of the modified hydrotalcite was 25%,the LOI of STA-LDHs reached 27.8%.The effect of the modified hydrotalcite on the strength of the flame retardant paper was significantly reduced,and the whiteness of the paper was significantly increased to 83%.