Preparation of carbon microspheres coated magnesium hydroxide and its application in polyethylene terephthalate as flame retardant

Abstract

A novel flame retardant, carbon microspheres coated magnesium hydroxide (Mg(OH)2@CMSs) was synthesized. The morphology and structure of Mg(OH)2@CMSs was characterized by scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FTIR). Then, Mg(OH)2@CMSs was added into polyethylene terephthalate (PET) to improve the flame retardancy of PET. The prepared composite (Mg(OH)2@CMSs/PET) with only 1 wt% Mg(OH)2@CMSs obtained a LOI value of 27.5% and reached UL94 V-0 rating. The flame retardant mechanism was studied by cone calorimeter measurement, thermogravimetric analysis (TGA), SEM and FTIR. The results showed that Mg(OH)2 and CMSs had synergistic flame retardant effect on PET. And there were two effects for Mg(OH)2@CMSs to improve the flame retardancy of PET. On one hand, CMSs and MgO as the bridge supporting points were dispersed into the basic framework of char layer in order to further strengthen the three-dimensional network structure of char layer. Thus a continuous and compact protective layer was formed, resulting in the decrease of pk-HRR and pk-MLR. On the other hand, the FTIR spectra of Mg(OH)2@CMSs/PET char residues showed that Mg(OH)2@CMSs induced PET degrading into small molecules with CC, which prevented PET from further decomposition, thus increased the amount of residue and decreased the THR value.