Feedstock agnostic upcycling of industrial mixed plastic from shredder residue pragmatically through a composite approach

Abstract

Shredding of a vehicle or an electrical and electronic equipment at its end-of-life (EOL) is a common practice to extract valuable critical raw materials. Unfortunately, this has the unintended consequence...

Immiscible Polymer Blends Made from Industrial Shredder Residue Mixed Plastic with and without Melt Blending

“…It also follows that the tensile work of fracture, defined as the area under the tensile stress–strain curve, is higher for the mixed plastic blend manufactured without using a prior melt-blending step (1.14 J cm –3 compared to 0.26 J cm –3 for the mixed plastic blend produced with prior melt blending). It must be mentioned at this point that virgin PP, PE, ABS, and PS, which are the major constituents of this batch of mixed plastic, possess a tensile strain-at-failure and work of fracture of 578% and 38 J cm –3 , 416% and 40 J cm –3 , 77% and 7.5 J cm –3 , as well as 5% and 2 J cm –3 , respectively . The lower tensile work of fracture of the mixed plastic blends compared to their virgin counterparts is attributed to the incompatibility between the different polymers, with Δδ PS/PP = 5.3 (J/mL) 0.5 , Δδ ABS/PP = 3.8 (J/mL) 0.5 , Δδ ABS/PS = 2.0 (J/mL) 0.5 , and Δδ PS/PE = 4.4 (J/mL) 0.5 .…”

“…Mixed plastic blends produced without using a prior melt-blending step possessed a large variation in material density distribution, which appeared in the form of concentric ellipsoids (i.e., deformed “onion-like” structures). The formation of such heterogeneous microstructure is hypothesized to be a combination of (i) the absence of intimate polymer mixing, (ii) the difference in melt rheology of the polymers during processing (PP and PE melt at ∼165 and ∼110 °C, respectively, , while ABS and PS are amorphous), and (iii) the characteristic fountain flow arising from the injection molding process. , Due to the absence of intimate polymer mixing, large molten single polymer domains with a size corresponding to one or more granules (see Figure for example) are expected to form in the barrel of the injection molder. During the injection molding process, the molten material experienced shear and elongational stresses. ,,, At the nozzle exit and inside the mold, the pressure exerted caused the molten material to move in the radial direction, forming concentric ellipsoids.…”

“…Based on the data provided, this batch of mixed plastic composed of 40–50 wt % acrylonitrile butadiene styrene (ABS), 30–40 wt % polystyrene (PS), 10–15 wt % polypropylene (PP), 3 wt % rubber, 2 wt % polyethylene (PE), and the remainders are unidentifiable. The different types of granules had been previously hand sorted and characterized based on their color and rigidity . The mean diameter ( D 50 ) of the granules was found to be 4 mm by using a sieving tower.…”

“…The profile of the screws is also illustrated in Figure . A processing temperature of 210 °C and a screw speed of 30 rpm were used based on our previous study . After melt blending, the extrudate was then pelletized (Haake VariCut, Thermo Fischer Scientific, Karlsruhe, Germany) and fed into a piston injection molding system (Haake MiniJet Pro, Thermo Fischer Scientific, Karlsruhe, Germany).…”

“…To divert this shredder residue mixed plastic waste from landfill and incineration, the easiest method is to repurpose it as it is. , However, most polymers are incompatible and immiscible at the molecular level. − Consequently, enthalpic repulsion between the different immiscible polymers becomes dominant, leading to poor adhesion at this boundary between the immiscible polymers and causing earlier onset failure. This produces a polymer product with inferior mechanical properties compared with their virgin counterparts.…”