Structural Characteristics and Thermal Properties of PE-g-MA/MgAl-LDH Exfoliation Nanocomposites Synthesized by Solution Intercalation

Abstract

Exfoliated nanocomposites (PE-g-MA/MgAl-LDH) were synthesized by solution intercalation of polyethylene-grafted-maleic anhydride (PE-g-MA) into the galleries of organo-modified MgAl layered double hydroxide (OMgAl-LDH) under reflux in xylene. Their structural elucidation and thermal characterization were carried out by X-ray diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The molecular dispersion of OMgAl-LDH layers within the PE-g-MA matrix has been verified by the disappearance of d001 XRD diffraction peak of OMgAl-LDH and the observation of TEM image. The OMgAl-LDH layers of about 70-nm length or width show a disordered phase in PE-g-MA matrix. The SAED pattern demonstrates that the MgAl hydroxide sheets of about 0.48-nm thickness have a hexagonal crystal structure with a = 0.305 nm. TGA profiles of the PE-g-MA/MgAl-LDH nanocomposites show a faster charring process in temperature range from 210 to 360 °C and greater thermal stability above 370 °C than PE-g-MA. The decomposition temperature of the nanocomposites with 5 wt % OMgAl-LDH can be 60 °C higher than that of PE-g-MA when 50% weight loss was selected as a measuring point. Dynamic FTIR spectra reveal that this nanocomposite has a slower thermo-oxidative rate than PE-g-MA from 200 °C to 320 °C. This kind of exfoliation nanocomposite is promising for use in flame-retardant polymeric materials.