Er types of chain extenders have also been investigated, which include diisocyanates [312], diphosphates [313], and silicones [314]; the final ones are particularly efficient to raise the flexibility of rPET, facilitating the extrusion course of action. Effects of Mechanical Recycling on PET Properties The thermal and mechanical properties of rPET are hard to define since they strongly depend on the sources on the PET waste, the presence of contaminants, and the recycling circumstances. Badia et al. [315] investigated the influence of mechanical recycling on the vPET properties. They emphasised the significance of chain scissions, which have been revealed by a higher variety of -OH groups, which explains the yellowing elements of rPET. In addition they studied the influence of recycling cycle number on the viscosity and polydispersity index (PDI) (Figure 16a), crystallinity (Figure 16b), and mechanical properties (Figure 16c,d) of PET. Some authors also studied the influence of contaminant polymers on the final properties of rPET [45,316]. Itim and Philip [316] investigated the influence of 5 wt of PP contamination in bottle grade PET multicolour waste. With this contaminant, the crystallinity degree and crystallisation rate had been decreased in comparison to neat rPET and that decreased additional together with the variety of recycling cycles. Additionally they highlighted that below these circumstances crosslinking predominated over chain scissions. Torres et al. [45] compared the properties of vPET and rPET from homogeneous blue bottles, and rPET from heterogeneous wastes contaminated by PVC. Their unique results are summarised in Table four. They Methyl acetylacetate Epigenetics reported that rPET was more sensitive to hydrolytic degradation than vPET because of the presence of contaminants and moisture.Energies 2021, 14, x FOR PEER REVIEW24 ofEnergies 2021, 14,23 ofFigure 16. Impact of mechanical reprocessing 20-HETE In stock cycles on on (a) PDI and viscosity,crystallinity, (c) effect and Young’s modFigure 16. Impact of mechanical reprocessing cycles (a) PDI and viscosity, (b) (b) crystallinity, (c) impact and Young’s modulus, (d) stress and and strain at break of PET. Reproduced with permission [315], 2012, Elsevier. ulus, and and (d) stress strain at break of PET. Reproduced with permission [315], 2012, Elsevier. Table 4. Comparative properties of vPET and rPET. Reproduced with permission [45]. Table 4. Comparative properties of vPET and rPET. Reproduced with permission [45].vPETvPETrPET from Blue BottlesMw (g/mol) Young’s Young’smodulus modulus (N/mm2) (N/mm2) Elongation at break Elongation at break Charpy effect strength Charpy effect strength (notched, 20 C, J/m2) (notched, 20 , J/m2) Aspect of test bars Aspect of test barsMw (g/mol)42,42,rPET from Wastes rPET from Blue Bottles Contaminated by PVC Contaminated by PVC 37,900 31,300 37,900 31,2170 (84) five.4 (.6) two.4 (.5) OpaquerPET from Wastes2140 (06) 270 (7)2140 (06) 270 (7)2170 (84) 5.4 (.6)1996 (10)three.0 (.4) 1.8 (.3) Opaque1996 (10)3.0 (.4)3.0 (.two)3.0 (.2)two.four (.5) Opaque1.eight (.three) OpaqueTransparentTransparent5.3. Compatibilization of rPO and rPET Blends five.3. Compatibilization of rPO and rPET Blends The blending of rPET with other virgin/recycled polymers which include POs can make The blending of rPET with other virgin/recycled polymers including POs can produce a material with beneficial versatile mechanical and barrier properties and processability, material with beneficial versatile mechanical and barrier properties and processability, a overcoming the rPET limitations and decreasing the.
