| Mg-Al layered double hydroxides were synthesized by urea method. Organic-modified LDHs were prepared by co-precipitation method, ion-exchange method and calcinated-hydration method, respectively, using Lauryl alcohol phosphoric acid ester potassium as organic modifier. LDHs and organic-LDHs were characterized by XRD, FT-IR, TGA. The PP/organic-LDHs and PP/organic-LDHs/BZn nanocomposites were prepared by melt blending method. The structures and properties of nanocomposites were characterized by XRD, TEM, TGA, cone calorimeter, limited oxygen index (LOI), and UL94 test.The XRD results of LDHs indicated that the well crystalline LDHs could be synthesized at 105℃for 24h, while the ratio of urea to nitrate anion to urea was 1:3. The TGA result shown that the carbonate anion in the in-terlayer of LDHs began to decompose at 420℃, and Maximum decomposition rate of LDHs was at 450℃.The results of organic-LDHs indicated that the interlayer space of organic-LDHs obtained by co-precipitation method, ion-exchange method and calcinated-hydration method increase from 0.76nm of LDHs to 3.15nm, 3.89nm and 3.89nm, respectively. The FT-IR data shown that there existed the carbonate anion, which could not be completely replaced by the MAPK in the interlayer of organic-LDHs obtained by ion-exchanged method due to the strong electrostatic force of LDHs'interlayer, but the carbonate anion were not observed in the interlayer organic-LDHs obtained by other two methods.The basal space of organic-LDHs obtained by three preparation methods analyzed from the XRD data had increased after melt blending with PP, but the preparation process of organo-LDHs have a decisive in-fluence on the structure of PP/organic-LDHs nanocomposites, which is intercalated or exfoliated. TEM im-ages shown that the dispersion of organic-LDHs obtained by three preparation methods in the nanocompo-sites was well. The data from TGA study indicated that the onset temperature and thermal decomposition temperature of PP/LDHs composites and PP/organic-LDHs nanocomposites have no significant change. But compared with pure PP, the amount of nonvolatile residue for the PP/organic-LDHs nanocomposites while remains at 600oC are significantly higher than pure PP, and also higher than the theoretically calculated value. The cone calorimetric results of PP/organic-LDHs nanocomposites indicated that the PHRR of PP/organic-LDHs nanocomposites, in which organic-LDHs were obtained by co-precipitation method, ion-exchange method, and calcinated-rehydration method, respectively, had decreased to 21%, 33%, 30%,the ALMR decreased from 15.3g/sec m2 of pure PP to 14.0 g/sec m2, 11.8 g/sec m2, 12.9 g/sec m2, but the PHRR and ALMR of PP/LDHs composites had no significantly change, compared with pure PP, respectively. The LOI value of PP/LDHs composites and PP/organic-LDHs nanocomposites increased from 17.2 of pure PP to 17.8, 19.9, 20.9, 20.8. UL94 test results shown that all of the material can reach UL94HB grade, but can not meet the requirements of UL94V.The results of XRD data indicated that the basal spacing of organic-LDHs obtained by co-precipitation method in the PP/organic-LDHs/BZn nanocomposites increased from 3.15nm to 3.37nm, but the XRD dif-fraction peaks of organic-LDHs obtained by the other two methods disappeared. TEM images shown that organic-LDHs obtained by three methods were well dispersed in the nanocomposites. The results from TGA analysis revealed that the onset temperature and thermal decomposition temperature of PP/LDHs/BZn com-posites and PP/organic-LDHs/BZn nanocomposites have no significant change. But compared with pure PP, the amount of nonvolatile residue for the PP/organic-LDHs/BZn nanocomposites while remains at 600oC are significantly higher than pure PP and PP/organic-LDHs nanocomposites. The PHRR of PP/LDHs/BZn composites and PP/organic-LDHs/BZn nanocomposites , in which organic-LDHs in the nanocomposites ob-tained by co-precipitation method, ion-exchange method and calcinated-hydration method, respectively, de-creased 37%, 58%, 55%, 63%, respectively, compared with the PHRR of pure PP. Meanwhile, The ALMR of PP/LDHs/BZn composites and PP/organic-LDHs/BZn nanocomposites decreased from 15.3g/sec m2 of pure PP to 9.8g/sec m2 of composites, to 9.4 g/sec m2, 9.5 g/sec m2, 8.3 g/sec m2 of three nanocomposites, respec-tively. The LOI value of composites and nanocomposites increased from17.2 of pure PP, to 19.8?20.4?20.8?21.0 of three nanocomposites, respectively. All the samples could achieve UL94HB grade, but not achieve UL94V grade.
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