Flame retardant grades of polypropylene have various UL ratings. They are more expensive and, because of the addition of the flame retardant fillers, they have lower physical properties and fabricating qualities. Flame retardant clad polypropylene has two outside skin sheets of flame retardant polypropylene that are coextruded onto a center core of polypropylene. This provides a composite material that is tough and with flame retardant exterior surfaces.
