Recycling of Pretreated Polyolefin-Based Ocean-Bound Plastic Waste by Incorporating Clay and Rubber

Abstract

Plastic waste found in oceans has become a major concern because of its impact on marine organisms and human health. There is significant global interest in recycling these materials, but their reclamation, sorting, cleaning, and reprocessing, along with the degradation that occurs in the natural environment, all make it difficult to achieve high quality recycled resins from ocean plastic waste. To mitigate these limitations, various additives including clay and rubber were explored. In this study, we compounded different types of ocean-bound (o-HDPE and o-PP) and virgin polymers (v-LDPE and v-PS) with various additives including a functionalized clay, styrene-multi-block-copolymer (SMB), and ethylene-propylene-based rubber (EPR). Physical observation showed that all blends containing PS were brittle due to the weak interfaces between the polyolefin regions and the PS domains within the polymer blend matrix. Blends containing clay showed rough surfaces and brittleness because of the non-uniform distribution of clay particles in the polymer matrix. To evaluate the properties and compatibility of the blends, characterizations using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and small-amplitude oscillatory shear (SAOS) rheology were carried out. The polymer blend (v-LDPE, o-HDPE, o-PP) containing EPR showed improved elasticity. Incorporating additives such as rubber could improve the mechanical properties of polymer blends for recycling purposes.

FDM-based additive manufacturing of recycled thermoplastics and associated composites

“…It was found that the 3D printed R-HDPE/ R-PP (70:30) blend alone shows 34% improvement in Young’s modulus, while the addition of 20% bio-carbon in the blend shows improvement by 11–15% in the mechanical properties. Martey et al [ 71 ] compounded ocean-bound waste (o-HDPE and o-PP), virgin polymer (low-density polyethylene (LDPE) and polystyrene (PS)) with functionalized clay, styrene multi-block-copolymer (SMB) and ethylene–propylene-based rubber (EPR) additives. It was observed that adding clay particles to the polymer matrix creates a rough surface and causes brittleness in the final material.…”

“…It was observed that adding clay particles to the polymer matrix creates a rough surface and causes brittleness in the final material. At the same time, incorporating EPR and rubber in the polymer significantly enhances the elasticity and mechanical performance of the composite [ 71 ]. SEM images of fractured surfaces in Fig.…”

“…SEM images of fractured surfaces in Fig. 10 shows that the blend with no additives had larger void content, while adding an additive reduces the void with a large chunk of EPR [ 71 ]. Similarly, Yap et al blended recycled polystyrene extracted from Styrofoam waste with LDPE and extruded filament for 3D printing.…”

“…10 SEM images of fractured surface of 3D printed composite specimens. a Neat blend (o-HDPE/o-PP/v-LDPE (in ratio 30:30:30); b o-HDPE/o-PP/v-LDPE/clay (in ratio 30:30:30:10); c o-HDPE/o-PP/v-LDPE/EPR (in ratio 25:25:25:25) [ 71 ] …”

“… HDPE PP R-HDPE/R-PP/soy hull Biocarbon (size: 2 µm) Twin screw 1.75 Lulzbot Taz 6 38–40 Developing cost-effective composite enhances the analytical properties and develops lightweight composites Addition of biochar creates porous structure and lightweight material (spectacle frame, elliptical gears) [ 70 ] 3. HDPE PP o-HDPE/o-PP/V-HDPE/V-LDPE/clay/EPR 3-Devo 350 Composer 1.75 Creality 3-D printer 21.4 ± 0.9 Improving the compatibility among immiscible blends Addition of EPR increased elasticity of material [ 71 ] 4. Expanded PS R-PS/LDPE Single screw 1.5–1.75 Creality Ender-3 V2 25–30 Enhancing the printability and thermal stability of final material TS decreased with increase in ductility [ 117 ] 5.…”