Influence Of Montmorillonite Interlayer Compounds On Flame Retardancy In Polymer

Montmorillonite(MMT)has been widely used in various fields,such as organic absorption and flame retardant nano-materials,due to its excellent barrier effect and interlayer ion exchange ability.However,it has high flammability and poor compatibility with polymers,which extremely restrict its further application.To solve these problems,in this study,a series of montmorillonite intercalation metal compounds(MIMC)were designed and fabricated.MIMC possesses the barrier effect of MMT and the excellent catalytic charring performance of transition metals.MIMC was modified by chitosan or ?-cyclodextrin to further expand their interlayer distance and promote the char yields.Subsequently,the polymer/organic MIMC nanocomposites were prepared.The effect on the thermal stability and flame retardant properties of polymer nanocomposites as well as their mechanism was studied.To improve the flame retardancy of PP/IFR composites,organic montmorillonite intercalation cobalt compounds(CTS-Co-OMT)were prepared and modified by chitosan.Subsequently,the PP/IFR/CTS-Co-OMT nanocomposites were prepared via melt blending.The results indicated that cobalt compounds and chitosan were successfully intercalated into inter-layers of MMT.The results indicated that PP/IFR composites only reached V-2 rating and the LOI value was 26.5.With addition of 4 wt% CTS-Co-OMT,the nanocomposites passed UL-94 V-0 rating and the LOI value was 32.1.The notably improving flame retardant was attributed to the well-dispersion of Co-OMT with layered structure and excellent catalytic performance in PP matrix,which promoted the fully cover of consolidated and compact residual layers on the surface of polymer during combustion.The consolidated and thick char layer which significantly reduced heat and mass transfer and thus significantly enhanced the flame retardancy.Meanwhile,montmorillonite intercalation nickel compounds(Ni-MMT)and the clathrate(?-CD-CTAB)combing ?-cyclodextrin(?-CD)and cetyltrimethylammonium bromide(CTAB)were designed and prepared.Then the clathrate ?-CD-CTAB was successfully intercalated into the interlayers of the Ni-MMT to form the organic compounds labeled as Ni-OMT.The EP /Ni-OMT nanocomposites were prepared.The results indicated that the LOI value of the EP nanocomposites containing 5 wt% Ni-OMT increased by 10% compared with pure EP.Moreover,their char residues dramatically increased by 21% and their total heat release(THR)decreased by 7.7%.The reason was ascribed to barrier effect of the MMT and the excellent catalytic charring of the nickle compounds.Thus promoting the hard and compact char yields can protect the underlying polymeric materials from action of the flame,heat and oxygen.Similarly,the montmorillonite intercalation iron compounds(Fe-MMT)were designed and synthesized,then modified by phosphorylated chitosan(PCTS).Hereafter,the EP/ organic montmorillonite intercalation iron compounds(PCTS-Fe-OMT)nanocomposites were prepared.The thermal and flame retardant properties of EP nanocomposites were investigated.The cone calorimeter tests results confirmed that total heat release(THR)and total smoke production(TSP)of containing 5 wt% PCTS-Fe-OMT of EP nanocomposites decreased by 17 % and 11% compared with those of pure EP,respectively.The notably improving flame retardant and smoke suppression properties were mainly attributed to the barrier effect and the excellent catalytic charring performance of the PCTS-Fe-OMT;Secondly,the phosphorous contained in PCTS,can capture the PO· and HPO· free radicals in gas phase,thus interrupting the combustion.