The Production of Improved Plastic Materials by Chaotic Mixing of Polymer Melts Recovered from Environmental Waste

Abstract

Over the past thirty years, plastics have become among the most common and preferred materials for the manufacture of products ranging from packaging films to structural components. Largely because of the very large molecular weights of the molecules comprising them, plastic melts can be very viscous and consequentially difficult to process into finished goods. Industrial devices, such as shown in Fig. 1, have been developed to forcefully melt and mix different types of plastics, or plastics and additives, either in batches or continuously in devices commonly referred to as screw extruders. Ingredients are introduced into these devices in pelletized or flake form. The pellets and flakes melt as a result of contacting heated surfaces and viscous dissipation in strong shear flows. The molten blend can subsequently be forced through a die to produce tubes or fibers, for example, or into a mold to produce large parts such as automotive dashboards. Polymer recycling is an area of growing interest. For example, polyethylene (PE) and polystyrene (PS) blends are major constituents of plastic waste, which respectively consist of about 60% and 15% by weight of all recycled plastics [2]. Creating PE / PS blends and other types of plastic blends with favorable microstructures and thereby attractive mechanical properties is important for reducing plastic wastes. Unfortunately, present-day processing techniques most often provide blends with deficient properties due to the droplet microstructures that typically result [3] or strong dependencies between microstructures and composition.