The influence of regranulated material on the mechanical properties and thermoformability of extruded polypropylene sheet

The economic and environmental success of many thermoforming operations is highly dependent on the efficient recycling of process waste and its reintroduction into the production stream. The action of both heat and shear imposed by the extrusion process promotes the degradation of polypropylene resins, As a result, it may be anticipated that the incorporation of regranulated skeletal sheet waste may compromise the mechanical properties of subsequent extruded sheet feedstock for thermoforming. This paper discusses the influence of recycled material on the mechanical properties of nucleated polypropylene sheet. Evidence is presented which suggests that a dramatic deterioration in sheet properties is not incurred by the addition of regranulated process waste. This result is in keeping with previous studies conducted on un-nucleated polypropylene.