Textile Recycling Technologies, Colouring and Finishing Methods

3.1.2.2 Chemical Recycling 
Chemical recycling pathways for PET have been demonstrated and include processes which break 
down (depolymerize) the polymer into its components (monomers, oligomers, other 
intermediates). Various end products may be formed based on the chosen process and 
depolymerization additives.
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Chemical treatment in the recycling process may also facilitate the 
separation of PET from other materials, such as blended fibres (i.e. elastane or cotton), or dyes and 
chemical finishing, as well as the creation of other end products of equal value.
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For fibre-to-fibre 
recycling, the desired end products to reproduce virgin quality PET resin are the main monomer 
constituents of PET: ethylene glycol and purified terephthalic acid (PTA) or dimethyl terephthalate 
(DMT).
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The most common depolymerization methods include: hydrolysis, methanolysis, 
glycolysis, or hybrid routes.
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Figure 8: Overview of different approaches for chemical recycling of polyester 
(monomer products repolymerized to polyester). 
Modified and reproduced from [6,33]. 
 
Obstacles to the practical application for polyester chemical recycling include, blended fabrics (i.e 
cotton, elastane blends); the use of polymers, dyes, additives, and processing agents in textile 
materials. Difficulties in separating such substances may result in significant degradation of the 
polyester during the recycling processes applied or require the application of a more advanced 
process for their removal. Other issues have included economic feasibility compared to the cost of 
producing virgin fibre, and environmental impacts of applying new chemical processes to recycle 
polyester fibres.

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