Research And Preparation Of LLDPE/Flame Retardant/OLDHs Nanocomposites

In this thesis, the synthesis of flame retardant and the organic modified LDHs with laurylether phosphate counter anion were firstly investigated. The preparation methods of polymer/flame retardant and polymerr/flame retardant/layered double hydroxide (LDH) nanocomposites were described, morphology structure and properties of these nanocomposites were also characterized. The LLDPE/flame retardant (SPDD) and LLDPE/flame retardant (SPDD)/OLDHs nanocomposites were synthesized by melt intercalation methods. Synergistic effects of LDHs with IFR of flame retardant (SPDD) on the flame retardant, thermal properties and flame retardation have been studied.(1) Based on the molecular design, we synthesized a new intumescent flame retardant, spirocyclic pentaerythritol diphosphonate dinitroguanidine (SPDD), on the basis of pentaerythritol, phosphorus oxychloride and nitroguanidine, and the chemical structure of flame retardant (SPDD) was characterized by FTIR,1H-NMR and TGA. The results of thermal analysis showed that flame retardant (SPDD) had excellent thermal stability and char-forming ability, yielding55.5%char residue at600℃in air atmosphere.(2) The laurylether phosphate organic modified LDHs (OLDHs) were obtained using solution intercalation method. The XRD result showed that the laurylether phosphate was intercalated into the gallery of the LDHs and resulted in an enlargement of interlayer distance. In addition, the enlargement of interlayer distance increased with different metal ion.(3) The LLDPE/flame retardant (SPDD) nanocomposite was prepared by melt intercalation method and characterized by XRD、 FTIR、LOI、SEM and TGA. From the results of LOI, it can be found that LLDPE material with the suitable content of flame retardant (SPDD) has a better flame retardant properties and a higher fire safety. The results of SEM and TGA show that flame retardant properties of LLDPE improve substantially compared with that of pure LLDPP. Flame retardant (SPDD) can form an intumescent system to protect the matrix from further burning, so the flame retardant properties of LLDPE improve.(4) The LLDPE/flame retardant (SPDD)/OLDHs nanocomposites were prepared by melt intercalation method. The results of TGA show that the weight loss for the LLDPE/flame retardant (SPDD)/OLDHs samples occur at region of low temperature, which is due to the evaporation of absorbed water physically in the layers and the loss of hydroxide of LDHs layers. Compared with pure LLDPE, the thermal stability of different divalent cations improves substantially, the reason is that LDHs and flame retardant (SPDD) cut off oxygen as well as other volatile products. The results of SEM show that fracture surfaces of different LDHs are distinctly different, because different LDHs in LLDPE/flame retardant (SPDD)/OLDHs have different dispensability in resin small cracks and interstices of the material surface.