Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Chemical recycling of waste plastics for new materials production

Abstract

Once referred to as ‘materials of 1,000 uses’, plastics meet demands in everything from clothing and automotive sectors to the manufacturing of medical equipment and electronics. Concomitant with usage, worldwide generation of plastic solid waste increases daily and is currently around 150 million tonnes per annum. Although recycled materials may have physical properties similar to those of virgin plastics, the resulting monetary savings are limited and the properties of most plastics are significantly compromised after a number of processing cycles. An alternative approach to processing plastic solid waste is chemical recycling, the success of which relies on the affordability of processes and the efficiency of catalysts. In this Review, we describe technologies available for sorting and recycling plastic solid waste into feedstocks, as well as state-of-the-art techniques to chemically recycle commercial plastics. These evaluations are followed by a survey of recent advances in the design of new high-performing recyclable polymers.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Prices may be subject to local taxes which are calculated during checkout

Figure 1: The prices of virgin SPI code 1–6 plastics in the United States between 2002 and 2017.
Figure 2: Depolymerization of waste PET can afford a range of useful monomers.
Figure 3: Depolymerization of polyethylene.
Figure 4: Depolymerization of poly(bisphenol A carbonate).
Figure 5: Dynamic covalent materials can undergo topological rearrangements while still maintaining their network integrity.
Figure 6: Steric strain at urea linkers enables hydrolysis of tunable polyurea networks.

References

  1. Singh, N. et al. Recycling of plastic solid waste: a state of art review and future application. Composites B 115, 409–422 (2016).

    Article  CAS  Google Scholar 

  2. Environmental Protection Agency. Plastics. EPAhttps://www3.epa.gov/epawaste/conserve/tools/warm/pdfs/Plastics.pdf (2015).

  3. PlasticsEurope. Plastics — the facts 2016. An analysis of European plastics production, demand and waste data. PlasticsEurope http://www.plasticseurope.org/documents/document/20161014113313-plastics_the_facts_2016_final_version.pdf (2016).

  4. Environmental Protection Agency. Energy impacts. EPAhttps://www3.epa.gov/warm/pdfs/Energy_Impacts.pdf (2015). This number reflects cumulative values for mixed plastic waste, HDPE and PET combined. One barrel of crude oil is 5,535,600 BTU.

  5. Barnes, K. A., Galgani, F., Thompson, R. C. & Barlaz, M. Accumulation and fragmentation of plastic debris in global environments. Phil. Trans. R. Soc. B 364, 1985–1998 (2009).

    Article  CAS  PubMed  Google Scholar 

  6. Jambeck, J. R. et al. Plastic waste inputs from land into the ocean. Science 347, 768–771 (2015).

    Article  CAS  PubMed  Google Scholar 

  7. García, J. Catalyst: design challenges for the future of plastics recycling. Chem 1, 813–815 (2016).

    Article  CAS  Google Scholar 

  8. Huchinson, A. Recycling by the numbers: the truth about recycling. Popular Mechanicshttp://www.popularmechanics.com/science/environment/a3757/4291576/ (2008).

  9. Morris, J. Recycling versus incineration: an energy conservation analysis. J. Hazard. Mater. 47, 277–293 (1996).

    Article  CAS  Google Scholar 

  10. Di Maio, F., Rem, P., Serranti, S. & Bonifazi, G. The W2Plastics project: exploring the limits of polymer separation. Open Waste Manage. J. 3, 90–98 (2010).

    Article  CAS  Google Scholar 

  11. Mantia, F. Handbook of Plastics Recycling (Rapra, 2002).

    Google Scholar 

  12. Carey, J. On the brink of a recycling revolution? Proc. Natl Acad. Sci. USA 114, 612–616 (2017).

    Article  CAS  PubMed  Google Scholar 

  13. Gitschel, G. Mechanized and recovery system for solid waste. US Patent 9061289 (2015).

  14. Montaudo, G., Puglisi, C. & Samperi, F. Primary thermal degradation mechanisms of PET and PBT. Polym. Degrad. Stab. 42, 13–28 (1993).

    Article  CAS  Google Scholar 

  15. Jamdar, V., Kathalewar, M., Dubey, K. A. & Sabnis, A. Recycling of PET wastes using electron beam radiations and preparation of polyurethane coatings using recycled material. Prog. Org. Coat. 107, 54–63 (2017).

    Article  CAS  Google Scholar 

  16. Nakao, T. et al. Method for recycling PET bottle. US Patent 7462649 (2008).

  17. Guclu, G., Yalcinyuva, T., Ozgunu, S. & Orbay, M. Hydrolysis of waste polyethylene terephthalate and characterization of products by differential scanning calorimetry. Thermochim. Acta 404, 193–205 (2003).

    Article  CAS  Google Scholar 

  18. Goto, M. et al. Depolymerization of polyethylene terephthalate in supercritical methanol. J. Phys. Condens. Matter 14, 11427–11430 (2002).

    Article  CAS  Google Scholar 

  19. Kurokawa, H., Ohshima, M., Sugiyama, K. & Miura, H. Methanolysis of polyethylene terephthalate (PET) in the presence of aluminium triisopropoxide catalyst to form dimethyl terephthalate and ethylene glycol. Polym. Degrad. Stab. 79, 529–533 (2003).

    Article  CAS  Google Scholar 

  20. West, S. Improved polyethylene terephthalate decontamination. WO Patent 1995027753A1 (1995).

  21. Grzybowski, P. The method for de-colorization of polyethylene terephthalate pet waste. WO Patent 2016159800A1 (2016).

  22. Fukushima, K. et al. Organocatalytic depolymerization of poly(ethylene terephthalate). J. Polym. Sci. A 49, 1273–1281 (2011).

    Article  CAS  Google Scholar 

  23. Fukushima, K. et al. Advanced chemical recycling of poly(ethylene terephthalate) through organocatalytic aminolysis. Polym. Chem. 4, 1610–1616 (2013).

    Article  CAS  Google Scholar 

  24. Gardea, F. et al. Hybrid poly(aryl ether sulfone amide)s for advanced thermoplastic composites. Macromol. Chem. Phys. 215, 2260–2267 (2014).

    Article  CAS  Google Scholar 

  25. Kartalis, C. N., Papaspyrides, C. D. & Pfaendner, R. Recycling of post-used PE packaging film using the restabilization technique. Polym. Degrad. Stab. 70, 189–197 (2000).

    Article  CAS  Google Scholar 

  26. Vallim, M., Araujo, J., Spinacé, M. & Paoli, M. Polyamide-6/high-density polyethylene blend using recycled high-density polyethylene as compatibilizer: morphology, mechanical properties, and thermal stability. Polym. Eng. Sci. 49, 2005–2014 (2009).

    Article  CAS  Google Scholar 

  27. Jin, H., Gonzalez-Gutierrez, J., Oblak, P., Zupancˇicˇ, B. & Emri, I. The effect of extensive mechanical recycling on the properties of low density polyethylene. Polym. Degrad. Stab. 97, 2262–2272 (2012).

    Article  CAS  Google Scholar 

  28. Andersson, T., Stålbom, B. & Wesslén, B. Degradation of polyethylene during extrusion. II. Degradation of low-density polyethylene, linear low-density polyethylene, and high-density polyethylene in film extrusion. J. Appl. Polym. Sci. 91, 1525–1537 (2004).

    Article  CAS  Google Scholar 

  29. Karian, H. Handbook of Polypropylene and Polypropylene Composites (Marcel Dekker, 2003).

    Book  Google Scholar 

  30. Phuong, N. & Gilbert, V. Preparation of recycled polypropylene/organophilic modified layered silicates nanocomposites part I: the recycling process of polypropylene and the mechanical properties of recycled polypropylene/organoclay nanocomposites. J. Reinf. Plast. Compos. 27, 1983–2000 (2008).

    Article  CAS  Google Scholar 

  31. Wall, L. A., Madorsky, S. L., Brown, D. W., Straus, S. & Simha, R. The depolymerization of polymethylene and polyethylene. J. Am. Chem. Soc. 76, 3430–3437 (1954).

    Article  CAS  Google Scholar 

  32. Sharma, B. K., Moser, B. R., Vermillion, K. E., Doll, K. M. & Rajagopalan, N. Production, characterization and fuel properties of alternative diesel fuel from pyrolysis of waste plastic grocery bags. Fuel Process. Technol. 122, 79–90 (2014).

    Article  CAS  Google Scholar 

  33. Miskolczi, N., Angyal, A., Bartha, L. & Valkai, I. Fuels by pyrolysis of waste plastics from agricultural and packaging sectors in a pilot scale reactor. Fuel Process. Technol. 90, 1032–1040 (2009).

    Article  CAS  Google Scholar 

  34. Abbas-Abadi, M. S., Haghighi, M. N., McDonald, A. G. & Yeganeh, H. Estimation of pyrolysis product of LDPE degradation using different process parameters in a stirred reactor. Polyolefins J. 2, 39–47 (2015).

    Google Scholar 

  35. Achilias, D. S., Roupakias, C., Megalokonomos, P., Lappas, A. A. & Antonakou, E. V. Chemical recycling of plastic wastes made from polyethylene (LDPE and HDPE) and polypropylene (PP). J. Hazard. Mater. 149, 536–542 (2007).

    Article  CAS  PubMed  Google Scholar 

  36. Lal, S., Anisia, K. S. & Kumar, A. Depolymerization of HDPE to wax in presence of catalyst formed by homonuclear macrocyclic zirconium complex chemically bonded to alumina support. Appl. Catal. A 303, 9–17 (2006).

    Article  CAS  Google Scholar 

  37. Wong, S., Ngadi, N., Abdullah, T. A. T. & Inuwa, I. M. Catalytic cracking of LDPE dissolved in benzene using nickel-impregnated zeolites. Ind. Eng. Chem. Res. 55, 2543–2555 (2016).

    Article  CAS  Google Scholar 

  38. Aguado, R., Olazar, M., San José, M. J. & Bilbao, J. Wax formation in the pyrolysis of polyolefins in a conical spouted bed reactor. Energy Fuels 16, 1429–1437 (2002).

    Article  CAS  Google Scholar 

  39. Sakata, Y., Uddin, M. A. & Muto, A. Degradation of polyethylene and polypropylene into fuel oil by using solid acid and non-acid catalysts. J. Anal. Appl. Pyrolysis 51, 135–155 (1999).

    Article  CAS  Google Scholar 

  40. Lin, Y.-H. & Yang, M.-H. Chemical catalysed recycling of waste polymers: catalytic conversion of polypropylene into fuels and chemicals over spent FCC catalyst in a fluidised-bed reactor. Polym. Degrad. Stab. 92, 813–821 (2007).

    Article  CAS  Google Scholar 

  41. Ballice, L. & Reimert, R. Temperature-programmed co-pyrolysis of Turkish lignite with polypropylene. J. Anal. Appl. Pyrolysis 65, 207–219 (2002).

    Article  CAS  Google Scholar 

  42. Achilias, D. S. et al. in Material Recycling — Trends and Perspectives Ch. 1 (ed. Achilias, D. ) 6–7 (InTech, 2012).

    Book  Google Scholar 

  43. Guddeti, R. R., Knight, R. & Grossmann, E. D. Depolymerization of polypropylene in an induction-coupled plasma (ICP) reactor. Ind. Eng. Chem. Res. 39, 1171–1176 (2000).

    Article  CAS  Google Scholar 

  44. Jia, X., Qin, C., Friedberger, T., Guan, Z. & Huang, Z. Efficient and selective degradation of polyethylenes into liquid fuels and waxes under mild conditions. Sci. Adv. 2, e1501591 (2016).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  45. Sadat-Shojai, M. & Bakhshandeh, G.-R. Recycling of PVC wastes. Polym. Degrad. Stab. 96, 404–415 (2011).

    Article  CAS  Google Scholar 

  46. Yu, J., Sun, L., Ma, C., Qiao, Y. & Yao, H. Thermal degradation of PVC: a review. Waste Manage. 48, 300–314 (2016).

    Article  CAS  Google Scholar 

  47. McNeill, I. C., Memetea, L. & Cole, W. J. A study of the products of PVC thermal degradation. Polym. Degrad. Stab. 49, 181–191 (1995).

    Article  CAS  Google Scholar 

  48. Troitskii, B., Troitskaya, L. S., Myakov, N. & Lepaev, A. F. Mechanism of the thermal degradation of poly(vinyl chloride). J. Polym. Sci. Polym. Symp. 42, 1347–1361 (1973).

    Article  Google Scholar 

  49. Lopez-Urionabarrenechea, A., de Marco, I., Caballero, B. M., Laresgoiti, M. F. & Adrados, A. Catalytic stepwise pyrolysis of packaging plastic waste. J. Anal. Appl. Pyrolysis 96, 54–62 (2012).

    Article  CAS  Google Scholar 

  50. Mio, H., Saeki, S., Kano, J. & Saito, F. Estimation of mechanochemical dechlorination rate of poly(vinyl chloride). Environ. Sci. Technol. 36, 1344–1348 (2002).

    Article  CAS  PubMed  Google Scholar 

  51. Vandenhende, B. & Fassiau, E. Process for the solvent treatment of a plastic. WO Patent 2005100461A1 (2005).

  52. Chemical Safety Facts. Polystyrene. Chemical Safety Factshttps://www.chemicalsafetyfacts.org/wp-content/uploads/2014/05/082514_ChemSafety_Print-Polystyrene.pdf (2014).

  53. Wünsch, J. R. Polystyrene: Synthesis, Production and Applications 5 (Rapra, 2000).

    Google Scholar 

  54. Goodier, K. Making and using an expanded plastic. New Sci. 240, 706–707 (1961).

    Google Scholar 

  55. Shah, J., Jan, M. R. & Adnan, A. Tertiary recycling of waste polystyrene using magnesium impregnated catalysts into valuable products. J. Anal. Appl. Pyrolysis 114, 163–171 (2015).

    Article  CAS  Google Scholar 

  56. Marczewski, M. et al. Catalytic decomposition of polystyrene. The role of acid and basic active centers. Appl. Catal. B 129, 236–246 (2013).

    Article  CAS  Google Scholar 

  57. Zhang, Z. et al. Chemical recycling of waste polystyrene into styrene over solid acids and bases. Ind. Eng. Chem. Res. 34, 4514–4519 (1995).

    Article  CAS  Google Scholar 

  58. Yang, Y. et al. Biodegradation and mineralization of polystyrene by plastic-eating mealworms: part 1. Chemical and physical characterization and isotopic tests. Environ. Sci. Technol. 49, 12080–12086 (2015).

    Article  CAS  PubMed  Google Scholar 

  59. Gutiérrez, C., Rodriguez, J. F., Gracia, I., de Lucas, A. & García, M. T. Reduction of the carbon footprint through polystyrene recycling: economical evaluation. Process Saf. Environ. Prot. 101, 144–151 (2016).

    Article  CAS  Google Scholar 

  60. Bajdur, W., Pajączkowski, J., Makarucha, B., Sułkowska, A. & Sułkowski, W. W. Effective polyelectrolytes synthesized from expanded polystyrene wastes. Eur. Polym. J. 38, 299–304 (2002).

    Article  CAS  Google Scholar 

  61. Sato, Y., Kondo, T., Tsujita, K. & Kawai, N. Degradation behaviour and recovery of bisphenol-A from epoxy resin and polycarbonate resin by liquid-phase chemical recycling. Polym. Degrad. Stab. 89, 317–326 (2005).

    Article  CAS  Google Scholar 

  62. Jones, G. O., Yuen, A., Wojtecki, R. J., Hedrick, J. L. & García, J. M. Computational and experimental investigations of one-step conversion of poly(carbonate)s into value-added poly(aryl ether sulfone)s. Proc. Natl Acad. Sci. USA 113, 7722–7726 (2016).

    Article  CAS  PubMed  Google Scholar 

  63. Cowley, P. R. E. J. & Melville, H. W. The photo-degradation of polymethylmethacrylate. I. The mechanism of degradation. Proc. R. Soc. Lond. A 210, 461–481 (1952).

    Article  CAS  Google Scholar 

  64. Chen, Y.-C. Thermal Degradation of Poly(methyl methacrylate) in Solution in Various Solvents. Thesis, Univ. Missouri (1965).

  65. Zheng, Y.-F., Chen, T.-Y., Sun, Y.-L. & Deng, R. L. Method for preparing pure nylon 6 from nylon 6 waste as raw material. CN Patent 105367818 (2016).

  66. Braun, M., Levy, A. B. & Sifniades, S. Recycling nylon 6 carpet to caprolactam. Polym. Plast. Technol. Eng. 38, 471–484 (1999).

    Article  CAS  Google Scholar 

  67. Chaupart, N., Serpe, G. & Verdu, J. Molecular weight distribution and mass changes during polyamide hydrolysis. Polymer 39, 1375–1380 (1998).

    Article  CAS  Google Scholar 

  68. Bryson, L. G. Monomer Recovery from Nylon via Reactive Extrusion. Thesis, Georgia Inst. Technol. (2008).

  69. Howarth, J., Mareddy, S. S. R. & Mativenga, P. T. Energy intensity and environmental analysis of mechanical recycling of carbon fibre composite. J. Cleaner Prod. 81, 46–50 (2014).

    Article  CAS  Google Scholar 

  70. Jiang, G. et al. Characterisation of carbon fibres recycled from carbon fibre/epoxy resin composites using supercritical n-propanol. Compos. Sci. Technol. 69, 192–198 (2009).

    Article  CAS  Google Scholar 

  71. La Rosa, A. D., Banatao, D. R., Pastine, S. J., Latteri, A. & Cicala, G. Recycling treatment of carbon fibre/epoxy composites: materials recovery and characterization and environmental impacts through life cycle assessment. Composites Part B 104, 17–25 (2016).

    Article  CAS  Google Scholar 

  72. Liang, B., Qin, B., Pastine, S. & Li, X. Reinforced composite and method for recycling the same. WO Patent 2013007128A1 (2013).

  73. Tsujii, A., Namba, M., Okamura, H. & Matsumoto, A. Radical alternating copolymerization of twisted 1,3-butadienes with maleic anhydride as a new approach for degradable thermosetting resin. Macromolecules 47, 6619–6626 (2014).

    Article  CAS  Google Scholar 

  74. Kristufek, S. L. et al. Synthesis, characterization, and cross-linking strategy of a quercetin-based epoxidized monomer as a naturally-derived replacement for BPA in epoxy resins. ChemSusChem 9, 2135–2142 (2016).

    Article  CAS  PubMed  Google Scholar 

  75. Hottle, T. A., Bilec, M. M. & Landis, A. E. Sustainability assessments of bio-based polymers. Polym. Degrad. Stab. 98, 1898–1907 (2013).

    Article  CAS  Google Scholar 

  76. Rowan, S. J., Cantrill, S. J., Cousins, G. R. L., Sanders, J. K. M. & Stoddart, J. F. Dynamic covalent chemistry. Angew. Chem. Int. Ed. 41, 898–952 (2002).

    Article  Google Scholar 

  77. Maeda, T., Otsuka, H. & Takahara, A. Dynamic covalent polymers: reorganizable polymers with dynamic covalent bonds. Prog. Polym. Sci. 34, 581–604 (2009).

    Article  CAS  Google Scholar 

  78. Takahashi, A., Ohishi, T., Goseki, R. & Otsuka, H. Degradable epoxy resins prepared from diepoxide monomer with dynamic covalent disulfide linkage. Polymer 82, 319–326 (2016).

    Article  CAS  Google Scholar 

  79. Wu, X. et al. Self-assembly of a ‘double dynamic covalent’ amphiphile featuring a glucose-responsive imine bond. Chem. Commun. (Camb.) 52, 6981–6984 (2016).

    Article  CAS  Google Scholar 

  80. Pettignano, A. et al. Self-healing alginate–gelatin biohydrogels based on dynamic covalent chemistry: elucidation of key parameters. Mater. Chem. Front. 1, 73–80 (2017).

    Article  CAS  Google Scholar 

  81. Lu, Y.-X., Tournilhac, F., Leibler, L. & Guan, Z. Making insoluble polymer networks malleable via olefin metathesis. J. Am. Chem. Soc. 134, 8424–8427 (2012).

    Article  CAS  PubMed  Google Scholar 

  82. Chen, X. et al. A thermally re-mendable cross-linked polymeric material. Science 295, 1698–1702 (2002).

    Article  CAS  PubMed  Google Scholar 

  83. Bergman, S. D. & Wudl, F. Mendable polymers. J. Mater. Chem. 18, 41–62 (2008).

    Article  CAS  Google Scholar 

  84. Scott, T. F., Schneider, A. D., Cook, W. D. & Bowman, C. D. Photoinduced plasticity in cross-linked polymers. Science 308, 1615–1617 (2005).

    Article  CAS  PubMed  Google Scholar 

  85. Higaki, Y., Otsuka, H. & Takahara, A. A thermodynamic polymer cross-linking system based on radically exchangeable covalent bonds. Macromolecules 39, 2121–2125 (2006).

    Article  CAS  Google Scholar 

  86. Wang, T.-N., Yang, G., Wu, L.-B. & Chen, G.-S. Self-assembly of supra-amphiphile of azobenzene-galactopyranoside based on dynamic covalent bond and its dual responses. Chin. Chem. Lett. 27, 1740–1744 (2016).

    Article  CAS  Google Scholar 

  87. Wei, Q. et al. Self-healing hyperbranched poly(aroyltriazole)s. Sci. Rep. 3, 1093–1098 (2013).

    Article  PubMed Central  CAS  Google Scholar 

  88. Chang, X. et al. Dynamic covalent chemistry-based sensing: pyrenyl derivatives of phenylboronic acid for saccharide and formaldehyde. Sci. Rep. 6, 31187–31195 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  89. Fox, C. H. et al. Supramolecular motifs in dynamic covalent PEG-hemiaminal organogels. Nat. Commun. 6, 7417 (2015).

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  90. Wojtecki, R. J. et al. Developments in dynamic covalent chemistries from the reaction of thiols with hexahydrotriazines. J. Am. Chem. Soc. 137, 14248–14251 (2015).

    Article  CAS  PubMed  Google Scholar 

  91. Whittell, G. R., Hager, M. D., Schubert, U. S. & Manners, I. Functional soft materials from metallopolymers and metallosupramolecular polymers. Nat. Mater. 10, 176–188 (2011).

    Article  CAS  PubMed  Google Scholar 

  92. Rossow, T., Hackelbusch, S., van Assenbergh, P. & Seiffer, S. A modular construction kit for supramolecular polymer gels. Polym. Chem. 4, 2515–2527 (2013).

    Article  CAS  Google Scholar 

  93. Krogsgaard, M., Behrens, M. A., Pedersen, J. S. & Birkedal, H. Self-healing mussel-inspired multi-pH-responsive hydrogels. Biomacromolecules 14, 297–301 (2013).

    Article  CAS  PubMed  Google Scholar 

  94. Li, G. et al. Synthesis, self-assembly and reversible healing of supramolecular perfluoropolyethers. J. Polym. Sci. A: Polym. Chem. 51, 3598–3606 (2013).

    Article  CAS  Google Scholar 

  95. Cordier, P., Tournilhac, F., Soulié-Ziakovic, C. & Leibler, L. Self-healing and thermoreversible rubber from supramolecular assembly. Nature 451, 977–980 (2008).

    Article  CAS  PubMed  Google Scholar 

  96. Greenland, B. W., Burattini, S., Hayes, W. & Colquhoun, H. M. Design, synthesis and computational modelling of aromatic tweezer-molecules as models for chain-folding polymer blends. Tetrahedron 64, 8346–8354 (2008).

    Article  CAS  Google Scholar 

  97. Hart, L. R., Harries, J. L., Greenland, B. W., Colquhoun, H. M. & Hayes, W. Healable supramolecular polymers. Polym. Chem. 4, 4860–4870 (2013).

    Article  CAS  Google Scholar 

  98. Montarnal, D., Capelot, M., Tournilhac, F. & Leibler, L. Silica-like malleable materials from permanent organic networks. Science 344, 965–968 (2011).

    Article  CAS  Google Scholar 

  99. Fortman, D. J., Brutman, J. P., Cramer, C. J., Hillmyer, M. A. & Dichtel, W. R. Mechanically activated, catalyst-free polyhydroxyurethane vitrimers. J. Am. Chem. Soc. 137, 14019–14022 (2015).

    Article  CAS  PubMed  Google Scholar 

  100. Snijkers, F., Pasquino, R. & Maffezzoli, A. Curing and viscoelasticity of vitrimers. Soft Matter 13, 258–268 (2017).

    Article  CAS  Google Scholar 

  101. Tsuda, M., Hata, M., Nishida, R. & Oikawa, S. Acid-catalyzed degradation mechanism of poly(phthalaldehyde): unzipping reaction of chemical amplification resist. J. Polym. Sci. A: Polym. Chem. 35, 77–89 (1997).

    Article  CAS  Google Scholar 

  102. Fan, B., Trant, J. F., Wong, A. D. & Gillies, E. R. Polyglyoxylates: a versatile class of triggerable self-immolative polymers from readily accessible monomers. J. Am. Chem. Soc. 136, 10116–10123 (2014).

    Article  CAS  PubMed  Google Scholar 

  103. Sagi, A., Weinstain, R., Karton, N. & Shabat, D. Self-immolative polymers. J. Am. Chem. Soc. 130, 5434–5435 (2008).

    Article  CAS  PubMed  Google Scholar 

  104. Chen, E. K. Y., McBride, R. A. & Gillies, E. R. Self-immolative polymers containing rapidly cyclizing spacers: toward rapid depolymerization rates. Macromolecules 45, 7364–7374 (2012).

    Article  CAS  Google Scholar 

  105. Rajendran, S. et al. Programmed photodegradation of polymeric/oligomeric materials derived from renewable bioresources. Angew. Chem. Int. Ed. 54, 1159–1163 (2015).

    Article  CAS  Google Scholar 

  106. Hong, M. & Chen, E. Y.-X. Completely recyclable biopolymers with linear and cyclic topologies via ring-opening polymerization of γ-butyrolactone. Nat. Chem. 8, 42–49 (2016).

    Article  CAS  PubMed  Google Scholar 

  107. Baker, M. S., Kim, H., Olah, M. G., Lewis, G. G. & Phillips, S. T. Depolymerizable poly(benzyl ether)-based materials for selective room temperature recycling. Green Chem. 17, 4541–4545 (2015).

    Article  CAS  Google Scholar 

  108. Kloxin, C. J. & Bowman, C. N. Covalent adaptable networks: smart, reconfigurable and responsive network systems. Chem. Soc. Rev. 42, 7161–7173 (2013).

    Article  CAS  PubMed  Google Scholar 

  109. Polgar, L. M., van Duin, M., Broekhuis, A. A. & Picchioni, F. Use of Diels–Alder chemistry for thermoreversible cross-linking of rubbers: the next step toward recycling of rubber products? Macromolecules 48, 7096–7105 (2015).

    Article  CAS  Google Scholar 

  110. García, J. M. et al. Recyclable, strong thermosets and organogels via paraformaldehyde condensation with diamines. Science 344, 732–735 (2014).

    Article  PubMed  CAS  Google Scholar 

  111. Taynton, P. et al. Re-healable polyimine thermosets: polymer composition and moisture sensitivity. Polym. Chem. 7, 7052–7056 (2016).

    Article  CAS  Google Scholar 

  112. Taynton, P. et al. Repairable woven carbon fiber composites with full recyclability enabled by malleable polyimine networks. Adv. Mater. 28, 2904–2909 (2016).

    Article  CAS  PubMed  Google Scholar 

  113. Ying, H. & Cheng, J. Hydrolyzable polyureas bearing hindered urea bonds. J. Am. Chem. Soc. 136, 16974–16977 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  114. Murariu, V., Svoboda, J. & Sergeant, P. The modelling of the separation process in a ferrohydrostatic separator. Miner. Eng. 18, 449–457 (2005).

    Article  CAS  Google Scholar 

  115. Bakker, E. J., Rem, P. C. & Fraunholcz, N. Upgrading mixed polyolefin waste with magnetic density separation. Waste Manage. 29, 1712–1717 (2009).

    Article  CAS  Google Scholar 

  116. Xiao, C., Allen, L. III, Biddle, M. & Fisher, M. Electrostatic separation and recovery of mixed plastics. P2RIC InfoHousehttp://infohouse.p2ric.org/ref/47/46175.pdf (1999).

  117. Tilmatine, A. et al. Electrostatic separators of particles: application to plastic/metal, metal/metal and plastic/plastic mixtures. Waste Manage. 29, 228–232 (2009).

    Article  CAS  Google Scholar 

  118. Alter, H. Application of the critical surface tension concept to items in our everyday life. J. Adhes. 9, 135–140 (1978).

    Article  CAS  Google Scholar 

  119. Hu, B., Serranti, S., Fraunholcz, N., Di Maio, F. & Bonifazi, G. Recycling-oriented characterization of polyolefin packaging waste. Waste Manage. 33, 574–584 (2013).

    Article  CAS  Google Scholar 

  120. Gondal, M. & Siddiqui, M. Identification of different kinds of plastics using laser-induced breakdown spectroscopy for waste management. J. Environ. Sci. Health A Tox. Hazard. Subst. Environ. Eng. 42, 1989–1997 (2007).

    Article  CAS  PubMed  Google Scholar 

  121. Sanaee, S. & Bakker, M. Ultrasound for monitoring and quality inspection in MDS plastics recycling. International Solid Waste Associationhttp://www.iswa.org/uploads/tx_iswaknowledgebase/15-191paper_long.pdf (2009).

Download references

Acknowledgements

The authors thank C. H. Fox for insights and discussions.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Jeannette M. García.

Ethics declarations

Competing interests

The authors declare no competing interests.

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Rahimi, A., García, J. Chemical recycling of waste plastics for new materials production. Nat Rev Chem 1, 0046 (2017). https://doi.org/10.1038/s41570-017-0046

Download citation

  • Published:

  • DOI: https://doi.org/10.1038/s41570-017-0046

This article is cited by

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing