In attempts to improve the properties of post-consumer commingled plastics waste a variety of additives that could potentially act as compatibilizers/impact modifiers were evaluated. The feedstock was representative of a model curbside collection program and contained a variety of polymers, mostly polyethylenes with PET, PP, PVC, etc., in smaller amounts. The ground mixed plastics were first compounded and melt filtered in a counter-rotating nonintermeshing twin-screw extruder and then combined with different amounts of additives in a corotating intermeshing twin-screw extruder. Additives included unmodified and maleated polyolefin elastomers and styrene/olefin block copolymers. Blends were analyzed for thermal and mechanical properties, and processability. The most effective modifier in terms of impact strength improvement was a styrenic block copolymer with very similar rheological characteristics to the commingled plastics matrix. The experimental observations were interpreted by considering the complex morphological features of the injection molded multicomponent, multiphase systems.

In attempts to identify potential applications for refined commingled postconsumer plastics, a feedstock containing about 80% polyethylene (PE) and lesser amounts of poly(ethylene terephthalate) (PET), polystyrene (PS), polypropylene (PP), and poly(vinyl chloride) (PVC) was modified through functionalization with maleic anhydride in a co‐rotating intermeshing twin‐screw extruder. The modified and unmodified blends were compounded with various fillers and reinforcements such as glass fibers, mica flakes, talc, and calcium carbonate. Injection molded composites based on the modified matrix had, in general, superior mechanical and thermal properties. These findings are discussed in view of the improved adhesion resulting from reactions and/or enhanced polar interactions at phase boundaries. Several compounds prepared in this work had overall property data comparable to, or approaching those, of equivalent commercial HDPE molding compounds that are commonly used in “durable” applications.

Samples of a concentrated suspension were systematically collected from the mixing volume of a continuous processor. The large amplitude oscillatory shear behavior of the samples was found to be significantly affected by the screw configuration employed and the location. Microstructural analyses employing nuclear magnetic resonance imaging, wide‐angle X‐ray diffraction and X‐ray radioscopy revealed substantial entrainment of air into the suspension during continuous processing. The volume fraction of the entrained air increased with geometries and operating conditions leading to partially full channels. Overall, air entrainment is identified as a dominant factor in the development of the microstructure and the rheology of concentrated suspensions and should be considered in their optimum processing.

A novel approach to the extrusion of high‐density, rigid PVC foam uses commercial RPVC compounds with inert‐gas physical blowing agents (carbon dioxide and argon). The process was developed on a segmented single‐screw extruder with L/D of 40. On‐line monitoring of process variables was also carried out. This technique provides an alternative to conventional processing methods using chemical blowing agents.

A 1.25" segmented single screw extruder was custom designed and used for foaming polystyrene with physical blowing agent such as carbon dioxide, nitrogen, and argon. The type of gas, the pressure, nucleating agents, and the extrusion conditions were found to be of significant importance affecting density cell size, cell size distribution, and foam stability. The lowest density achieved was3 lbs/cu.ft. Melt pressure oscillation was found to be a problem, which could be addressed by the addition of talc or endothermic nucleating agents.