Maleated polypropylene OMMT nanocomposite: Annealing, structural changes, exfoliated and migration

Annealing of maleated polypropylene/organoclay nanocomposites is studied at a range of temperatures from 180 °C to 300 °C under a stream of nitrogen and nitrogen/air mixtures. The study comprises determinations of the migration of clay to the surface by the use of attenuated total reflectance Fourier transform infra red (ATR-FTIR) spectra. The extent of migration is shown to increase with the increase in the percent of maleic anhydride (MA) grafted onto the PP and with the percentage of air added to the nitrogen gas used for purging of the samples during annealing. The extent of migration increases with temperature up to 225 °C. At temperatures of 250-300 °C, the extent of migration decreases. Simultaneously, a change in the structure of the nanocomposites is observed by small-angle X-ray diffraction (XRD), showing a conversion of the nanostructure to the non-colloidal microcomposite. The study conforms to previous findings and indicates that the migrating moiety is composed of exfoliated clay particles. The effect of the decomposition of the grafted MA groups and the evolution of CO2 on the rate of oxidation and migration are observed and discussed. The effect of the evolved CO2 on the stability of the clay particles is pointed out. The role of migration in the elucidation of the structure of nanocomposites is discussed along with other mechanistic considerations.