Polypropylene (PP)/Postconsumer recycled poly(ethylene terephthalate) (rPET) blend has gained much attention as an environmentally friendly and economical material in various industrial applications. The aim of this study is to improve the properties of PP/rPET blend with talc, glass fiber, and carbon fiber mixture to be included by twin-screw extrusion followed by injection molding. Maleic anhydride grafted polypropylene (PP-g-MA) and chain extender (Joncryl ADR 4368) were used as the coupling agent. The effects of various coupling agents were evaluated in terms of the mechanical, morphological, electrical, and thermal properties of the PP/rPET hybrid composites. The mechanical properties of the composites were characterized by tensile and Charpy impact tests. Scanning electron microscopy (SEM) was used to assess the fracture surface morphology and the dispersion of the filler. The thermal properties of the composites were characterized using differential scanning calorimeter (DSC), heat deflection temperature (HDT), and Vicat softening temperature (VST) tests. The results showed that the composites morphology was dramatically affected by the addition of coupling agent. Tensile and impact strength increased in the presence of coupling agent of the composite due to the improved interaction at the interface of polymers. HDT and VST of the composite were increased significantly in the presence of PP-g-MA.

Production and consumption of plastic materials have increased in recent decades. The increase in plastic production and consumption has been largely responsible for the increase in plastics waste production. The problem of plastics waste is quite important in terms of environmental sustainability and solid waste management. Plastics recycling require the separation of materials insofar as being almost pure. To achieve this goal in an economical way, technologies developed in mineral processing are of great help. Each method has certain capabilities and limitations. Instance separation of PET and PVC by gravity techniques is practically not applicable, due to slight differences in density. In this research, separation of PET and PVC by selective floatation was studied. The use of floatation for plastic separation is particularly challenging because of inherent hydrophobic nature of plastics surfaces. To separate PET and PVC, from the mixture of the two, by floatation should make one of them hydrophilic and wettable by water. This can be achieved by several methods among which the addition of a wetting agent that interacts with the surface layer is one of many techniques designed. In this study, tannic acid was employed as the depressant of PET. The results showed that, virgin materials can be separated with 99.62% efficiency. In the case of post-consumer PET and PVC, 88.40% separation efficiency was achieved at optimum conditions. Also, in virgin and Postconsumer materials, difference in the contact angles of PET and PVC increased as tannic acid dosage increased. Besides, the results indicated that the pH of the conditioning step is vital with respect to separation efficiency. 

The effect of a high-density polyethylene grafted amine alcohol (HDPE-g-DMAE) as compatibilizer on the mechanical, rheological and morphological characteristics of polyethylene/polyethylene post-consumer recycled blends (HDPE/rHDPE) reinforced with nanoclay was studied. Blends of HDPE with high rHDPE contents, more than 60% (wt) of rHDPE, were evaluated. HDPE bottles were manually separated from municipal solid waste, washed, grinded, and finally compounded at various concentrations with virgin HDPE and nanoclay. The effect of this HDPE-g-DMAE was compared with conventional polyethylene maleic anhydride (HDPE-g-MA) compatibilizer. FTIR characterization confirmed the formation of this HDPE-g-DMAE compatibilizer. The mechanical properties of uncompatibilized blends decreased with increasing rHDPE content, whereas these properties were significantly enhanced when HDPE-g-DMAE was used compared with HDPE-g-MA compatibilizer and with uncompatibilized blends. Scanning electron (SEM) micrographs of the fractured surfaces when using HDPE-g-DMAE showed improvement in the interfacial adhesion and interaction between recycled and virgin polyethylene. The nanocomposites compatibilized with PE-g-DMAE had better clay exfoliation–, intercalated structure compared to PE-g-MA-compatibilized nanocomposites. The novelty of this work is based on the use of PE-g-DMAE as a compatibilizer in HDPE/rHDPE/nanoclay composites with improved mechanical properties. This compatibilizer promoted the adhesion between recycled and virgin polymer phases in the blend and increased the interactions between compatibilizer and hydroxyl groups on the clay surface, as well as oxidized groups in the recycled polymer. This indicates that recycled Postconsumer HDPE could replace, in larger proportions, part of the virgin HDPE for certain applications with better mechanical performance than uncompatibilized blends. This is an option to bring recycled plastics back into the market and increase the versatility of products manufactured with recycled polymers.