# Opportunities and Limitations in Recycling Fossil Polymers from Textiles
## Recycling Fossil Polymers  
### Polyester  
Polyesters are polymers which contain the ester functional group in their main chain (Figure 3). Although there are many polyesters, in the framework of textile applications the term \"polyester\" as a specific material most commonly refers to polyethylene terephthalate (PET). The PET fibre dominates over 50% of the world synthetic fibre market. Woven polyester fabrics are used in apparel (textile industries) and home furnishings such as bed sheets, table sheets, and curtains. Similarly, industrial polyesters are used in tyre reinforcements, ropes, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements. Polyester fibres are also used to stuff pillows, comforters and cushion padding. To combine functional characteristics with greater comfort in contact with the skin, they are often woven in blends with natural fibres such as cotton. All these characteristics mean that polyester is used pure or mixed with other natural, man-made or synthetic fibres. There are mainly three methods to recycle pure PET textile wastes. These methods can be classified into three groups, respectively: mechanical methods, thermo-mechanical and chemical methods [89], which will be discussed in a general way in Section 3.7. Mechanical methods can be applied to all kind of waste including natural originated wastes such as wood wastes, cotton wastes, etc., and synthetic wastes. The general production steps of the mechanical method are cutting, blending and opening. Mechanical recycling machines gradually break the fabric into small pieces and make it fibrous, and these obtained fibres are reused in the production of yarn or non-wovens. The opened material, which is in web form, is fed into the spinning plants to obtain coarse yams or fed into the non-woven plants. The mechanical method is the simplest and the one in wider use in terms of input textile materials when compared to the other methods. Mechanical methods break down the fabric, and the fibre length is reduced as an unwanted side effect, thereby affecting the spinnability and yarn strength. The main reason for this is the friction between the fibres that causes wear of fibres and melting of synthetic fibres. The fibres will have a shorter fibre length than the original fibres, and some dust will be generated. The costs are low, and generally the economic quality and value of the product is decreased with respect to the starting product. The thermo-mechanical method can be used for synthetic fibre such as PET fibre wastes, polypropylene wastes, polyamide wastes, etc. This method is based on re-melting of wastes to obtain granules, which can then be used for different applications. This method is the most widely used for PET from beverage bottles [90; 91] that is currently used in packaging [92] or textile applications [93]. Moreover, in view of an up-cycling approach,the blending of post-consumer scraps with appropriate rubbery compatibilizers allowed the production of toughened blends [94; 95; 96; 97; 98], not only from post-consumer bottles but also from PET/PE based packaging trays [99], suitable for injection-moulding or thermoforming parts for automotive, household appliance or protection applications [100]. In the case of textile-to textile recycling, granules coming from PET recovered from fabrics can be used in staple fibre production or in the plastic industry. Due to the PET degradation and viscosity drops with respect to bottle grade, granules are basically used in staple fibre production, since that production can also work with a higher melt fluidity. Thermo-mechanical methods are simple, and the economic value of the products is generally higher than that of the simple mechanical method. The thermo-mechanical method is mainly a re-extrusion process. This process consists of several steps: cutting, compacting/drying or drying and feeding to the extruder. Compacting makes the feeding to the extruder easier but extra steps and energy are needed and extra thermal effects occur on PET.