| In this paper, zinc nitrate, aluminum nitrate and cerium nitrate were employed as raw materials to prepare Zn Al Ce-LDH(N-LDH) by hydrothermal method. The conditions of synthesis reaction were explored on the basis of large interlayer spacing. The characterization of polymorph, composition, morphology and thermal performance of N-LDH were studied By XRD, FT-IR, SEM, TG, etc. The test results revealed that a single crystalline phase and the interlayer spacing of0.90 nm of N-LDH were successfully achieved by adjusting the reaction conditions, and N-LDH possessed high thermal stability.To improve the dispersion and compatibility between LDH and polymer matrix, the Fc(COOH)2 and sodium dodecyl benzene sulfonate(SDBS) were selected as organic intercalation agents to prepare modified N-LDH(F-LDH and S-LDH). The influencing factors on synthesis conditions of F-LDH and S-LDH have been detailedly discussed. The resulting modified LDHs were characterized by XRD,FT-IR, NMR, SEM and TG measurements. The results showed that the SDBS and Fc(COO-)2 anion were successfully intercalated into the interlayers of LDHs by co-precipitation. Comparing with N-LDH, the basal d-spacings of F-LDH and S-LDH increased from 0.90 nm to 1.58 nm and 3.02 nm, and the increased d-spacings are 0.68 nm and 2.12 nm,respectively, which indicated that Fc(COO-)2 oriented at 44° angle with respect to the plane of the clay sheets and SDBS arranged in vertical orientation in the interlayers of LDH. Furthermore, the F-LDH and S-LDH possessed high thermal stability, and about 50% char residue yield can be formed at 800 o C. The plate structure of F-LDH can also be observed in SEM image.A novel intumescent flame retardant polypropylene(PP)composites has been prepared via melt blending by incorporating IFR(APP/PER, a mass ratio of 3:1) and various LDHs. The structure and properties of final PP composites were characterized by XRD, AFM, TG,tensile and impact test. The XRD curves reflected that three kinds ofLDHs were greatly dispersed in the PP matrix, and the addition of various LDHs would not change the crystal form of PP. The TG data revealed that the different atmosphere N2 and air has great effect to the process of thermal degradation of PP and PP composites. The initial decomposition temperature was improved about 30 o C for IFR/PP and IFR/S-LDH/PP composites in air atmosphere. Furthermore, the addition of LDHs would improve the mechanical property of PP composites.The synergistic effect between LDH and IFR on fire retardancy and thermal behavior of PP were also investigated. Diversified flame retarding PP composites(IFR/S-LDH/PP) were characterized by limiting oxygen index(LOI), vertical combustion test(UL-94), cone calorimeter test(CC) and thermogravimetry analysis(TG) in this work,respectively. The LOI and UL-94 test data revealed that an optimal synergistic effect between IFR and LDH could be achieved under the certain proportion of 24 wt% IFR, 1 wt% S-LDH, the LOI value of 31%and V-0 rating. Compared with neat PP, the peak heat release rate(PHRR) of IFR/S-LDH/PP is reduced by about 63.2%. In this work,flame-retardant mechanism has been discussed detailed. The photos of residue of IFR/PP 、 IFR/LDHs/PP composites after cone calorimeter testing. For IFR/PP composite, the compact and some holes can be observed. In comparision with IFR/PP composite, the char layer of IFR/LDHs/PP composites are more intact with no holes, and the white substance is mainly the zinc, aluminum and cerium oxide(LDO)produced from the LDHs thermal decomposition. The hinder effect of compact char played an important role in flame retardancy. According to the result of EDX, For IFR/N-LDH/PP and IFR/S-LDH/PP composites, the carbon content achieve 31.59% and 38.93%, which ere largely higher than that of IFR/PP formulation(26.02). It indicated that N-LDH and S-LDH considerably improve the carbonization ability of IFR/N-LDH/PP and IFR/S-LDH/PP composites, and S-LDH was definitely superior to N-LDH. |
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