Flame Retardancy of Thermoplastic Polyurethane and Polyvinyl Chloride by Organoclays
Thermooxidative stability and peak of heat release rates of thermoplastic polyurethane nanocomposites are improved by organoclays; but time to ignition of these composites is reduced. A cable with a thermoplastic polyurethane nanocomposite jacket does not pass a simple flame spread test by a Bunsen burner, indicating that the reduction of the peak of heat release rate does not prevent the flame spread. Polyvinyl chloride (PVC) with organoclays shows a fast HCl release by an accelerated chain-stripping reaction of the polymer catalyzed by the quaternary ammonium compound within the organoclays resulting in strong discolorations. Synthesis routes based on ethylene-vinyl acetate copolymer (EVA) or thermoplastic polyurethane (TPU) masterbatches of organoclays strongly diminish the darkening of the PVC compounds. Cone calorimeter experiments do not show remarkably improved flame retardancy properties of PVC filled with organoclays.