the present invention provides an improved polymer additive which may be used to increase the high temperature viscosity of an asphalt , without deleteriously affecting the low - temperature viscosity of the asphalt . the polymer additive may also be used to improve the stiffness of certain asphalts . the polymer additive is produced from readily available polymer blends by a thermal process . the invention additionally provides an improved polymer modified asphalt . in its preferred embodiments , the invention also provides an environmentally acceptable method for recycle of post consumer carpet and bottles .