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Tech | April 2018

Recycling of polyester waste

Polyester-based fibres contribute 70 per cent of the total synthetic fibre production worldwide, say RN Turukmane, SS Gulhane and AL Bhongade.

Recycling of polyester waste is an important term used in different industries for reducing waste disposal into the environment. Nowadays, developed and developing countries aim to reduce pre- and post-manufacturing waste and focus on recycling. Waste disposal into environment increases risk for human’s life and so disposal of mechanical, chemical and thermal polymers should be reduced. One of the major advantages of recycling is to reduce the solid waste by converting it into a new product. It is very necessary that every man-made fibre production industry should focus on reducing waste of useful raw material, energy and reuse of east chemical and polymer. Polyester polymer is mostly recycled all over the world and these are fibres, bottles, films, etc. Methods of recycling PET clothes and bottles: mechanical recycling, thermal recycling and chemical recycling.

Mechanical recycling

Food, shelter and clothes are the three basic needs of human being. Population increases ultimately clothes demand also increases and it can be full illed only by developing man-made fibres. The whole world is relying only on PET fibre production, cloth and garment manufacturing. Manufactured polyester fabrics can’t be melt again to polyester. It is an unique method to reprocess the waste polyester fabric by changing its shape to make is reusable ex-torn fabrics like shirts that can be reused by converting it into pillow cover or without changing the chemical structure for other purposes excluding energy recovery or disposal, without changing the chemical structure of the processed material. Collected waste material is shredded and converted into yarn, which can be used in manufacturing different value-added articles.

Thermal recycling

This is the best method of polyester recycling in which the waste PET bottles are initially cuts in to small pieces the washed and melted to spin through the spinneret to get desired polyester filaments, which further converted into fabric and garments.

Chemical recycling

Polymerisation is a process of joining monomers by strong covalent bond to form a long chain called polymerisation. Disposed polyester waste can be treated chemically back to get the monomers the process known as depolymerisation [Shukla, S.R., and Kulkarni, K.S., 2002]. The term chemical recycling is most often applied to the depolymerisation of certain condensation or addition polymers back to monomers. In this method, the polymer is subjected to different processes so as to get the original raw material back i.e. total depolymerisation of polymer, or partial depolymerisation to the oligomers, and again reacting them back, will give a polymer of virgin quality. Depending on the source and morphology of the polymer and fibrous waste, recycling is generally done so that the waste is converted into a polymer or as monomer, which can be reused in the same plant for fibre production or in the production of value-added products like adhesives, resins, thickeners, etc. This is the most widely used and most effective way to recycle PET.

Long chain polymers will be treated with chemicals to interrupt the chains into short segments. Once the treatment is finished to re-create the chemicals from that the polymers were at first created, it’s referred to as feedstock or chemical compound creation. If the treatment breaks the polymers into associate degree assortment of chemical species, the processor will decide whether or not to recover specific chemicals for feedstock use or to use the assortment of chemical species for fuel or to use some combination of each finish product. Benefits of recycling waste include: reducing cost of purchasing materials, increasing profitability, minimising costs of disposal and treatments, minimising environmental impacts by reducing use of new raw materials and producing products from earlier one, textile recycling requires less energy than any other type of recycling, and textile recycling does not create any new hazardous waste or harmful by-products.

Conclusion

Advanced recycling of polymers represents a significant technological advancement. Many of the polymer recycling processes appears to be technically feasible and robust enough to support further development in the future. At this stage the technology is still developing. This recent development in polymer recycling shows promise toward achieving the industry’s goal of increasing the environmentally and economically sound recovery of polymers, and may someday provide viable recycling options beyond conventional.

References

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19. M. Tasdemir, D. Kocak, and I. Usta, et al., 2008,Properties of Recycled Polycarbonate/Waste Silk and Cotton Fiber Polymer Composites. International Journal of Polymeric Materials. 57(8), 797-805.

20. Y. J. Wang, 1999, Utilization of Recycled Carpet Waste Fibers for Reinforcement of Concrete and Soil. Polymer-Plastics Technology and Engineering. 38(3), 533-546.

* R.N.Turukmane, * S.S. Gulhane, # A.L.Bhongade & * A. M. Daberao

*Centre for Textile Functions, Mukesh Patel School of Technology Management and Engineering, SVKM’S NMIMS, Shirpur Campus, Dist. Dhule, Maharashtra, -425405

#Veermata Jijabai Technological Institute, H R Mahajani Marg, Matunga, Mumbai, Maharashtra 400031.

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