Two kinds of activated carbon spheres-supported metal oxides for reducing smoke release volume and fire hazard in flexible poly(vinyl chloride)

Two kinds of activated carbon spheres (ACS)-supported metal oxides, ACS-supported Fe3O4 (ACS@Fe3O4) and ACS-supported NiO (ACS@NiO), were synthesized and used as flame retardants for reducing smoke release volume and fire hazard in flexible poly(vinyl chloride) (PVC). Scanning electron microscope measurement, Fourier transform infrared spectrum, X-ray diffraction and thermogravimetric analysis (TGA) were utilized to investigate the morphology, chemical structure and stability of the flame retardants. The TGA coupled with mass spectrometry (TG-MS) results of PVC composites showed that ACS could retard the heat and oxygen transfer between gas and polymers. Under the same condition, ACS@Fe3O4 could promote the dehydrochlorination reaction of PVC in lower temperature, while the ACS@NiO could make the dehydrochlorination reaction faster. Therefore, both ACS@Fe3O4 and ACS@NiO effectively promoted the cross-linked carbonization reaction of PVC and then generated a large amount of stable char residues. Limiting oxygen index (LOI) and cone calorimeter test results of the PVC composites showed that ACS@Fe3O4 and ACS@NiO were much more efficient than ACS alone to improve the flame retardancy and smoke suppression of PVC. The incorporation of ACS@Fe3O4 and ACS@NiO increased the LOI from 24.9 to 27.4% and 26.9% and reduced the peak of heat release rate by 47.2 and 30.8%, respectively, compared with pure PVC.