Modification Of Layered Double Hydroxides And Its Application In Flame Retardant Polyolefin

Layered Double Hydroxides (LDHs) as a kind of layered anion inorganicmaterial have been developing fast in recent years. Much attention has been paidto its applications as green fire retardants thanks to its regulated structure, ionexchangeability, thermal stability and flame retardant properties.Mg-Al LDH was modified by sodium dodecyl sulfate (SDS) and2-carboxyethyl (phenyl) phosphinic acid (CEPPA) by co-precipitation, ion-exchange and regeneration method. The structure and thermal decompositionbehaviors of modified LDHs were characterized by X-ray diffraction (XRD),fourier transformed infrared spectroscopy (FTIR), scanning electron microscope(SEM) and thermogravimetric analysis (TGA). Polyolefin based composites wereprepared by melt-blending method and master-bathch method, respectively. Thestructure, crystallization and thermal degradation behaviors of composites wereinvestigated by XRD, SEM, transimission electron microscopy (TEM),differential scanning calorimetry (DSC) and TGA. Modified LDHs were appliedin intumescent flame retardant PE, whose properties were evaluated in terms offlame retardant property and mechanical property.The results reveal that modified LDH with SDS and CEPPA can besuccessfully prepared by coprecipitation method, ion exchange method andregeneration method. The interlayer distances of modified LDHs are2.7nm(SDS-LDH) and1.2nm (CEPPA-LDH), larger than LDH (0.8nm). With modifiedLDH, nanocomposites based on polyethylene (PE) and maleic anhydride graftedPE (PEgMA), PE/PEgMA/SDS-LDH and PE/PEgMA/CEPPA-LDH, are obtainedby master-batch method which is confirmed to promote the delamination anddispersion of LDH and modified LDH in polyolefin matrix in comparison withmelt-blending method. Nanocomposites show well crystallization and thermal stability. In intumescent flame retardant polyolefin, CEPPA-LDH improves theflame retardant property while SDS-LDH favours the mechanical property.