Preparation Of Composite LDHs Flame Retardants And Its Application In Polypropylene

In this dissertation, MgAl layered double hydroxides (MgAl-LDHs) was synthesizedby coprecipitation method. The MgAl-LDHs used as precursour was modulated with asmall amount of ammonium polyphosphate (APP) to prepare APP–LDHs and theinfluence of APP at different mass fractions on the crystallization of MgAl-LDHs wasinvestigated. When the addition of APP in LDHs suspension was0.8wt%, theAPP2–LDHs was mixed with pentaerythritol (PER) and silane coupling agent KH-550via ball milling and the modified LDHs (marked as PER–APP2–LDHs) was completedultimately. The as-prepared LDHs samples were added into polypropylene (PP) toobtain Retardant/PP flame retardant composites. X-ray powder diffraction (XRD),Fourier transform infrared (FT-IR) spectroscopy (FT-IR), scanning electronicmicroscope (SEM) and thermogravimetry (TG) were utilized to characterize thesamples. UL-94vertical burning test, limiting oxygen index (LOI) and tensile, flexuraland notch impact test were used to investigate the influences of flame retardant additionon the flame retardant and mechanical properties of Retardant/PP composites.Additionally, the as-prepared samples and several inorganic substances used as synergistwere compounded with decabromodiphenylethane (DBDPE) and the influences ofsynergist/DBDPE compound system on flame retardant and mechanical properties ofRetardant/PP composites were studied. The results demonstrated that the as-preparedMgAl-LDHs that exhibit regular laminate structure was obtained at Mg2+/Al3+ratio of31, the pH value of11and reaction temperature of65°C. The crystal growth of LDHswas inhibited along the stacking direction in the presence of APP, but the grain sizewhich represents layer growth remained unchanged. The MgAl-LDHs showedsheet-like structure and the resultant PER–APP2–LDHs showed as a regular powderwith particle size of100~250nm. PP filled with20%mass fraction of MgAl-LDHs,APP–LDHs and PER–APP2–LDHs burnt without droplet and the surface of LDHs/PPcomposites residue were covered with an expanded char network. PER–APP2–LDHs/PPcomposites exhibited superior retardant properties, flexural strength and notch impactstrength. In addition, the Retardant/PP composites could achieve a UL-94V-1or V-0rating in vertical burning test with the addition of PER–APP2–LDHs, meanwhile, thePER–APP2–LDHs considered to be more significant to improve the LOI value of flameretardant composites. The compound effect between DBDPE and APP was proved to bebetter than other synergist, when the ratio of DBDPE and APP was21(30wt%total amount), the compound system achieved better synergistic flame retardant effect.