# Opportunities and Limitations in Recycling Fossil Polymers from Textiles
## 5 Conclusions and Perspectives  
The recycling of fossil polymers present in waste textiles could be highly beneficial to save fossil resources and so prolong the life cycle of these materials, but it is difficult because textile products are often the combination of different polymers. Despite sorting technologies being developed to support efficiently the online rapid selection of materials, the separation of single polymers is difficult. Some alternatives for recycling monomaterial textiles such as PET, PA and acrylics, such as attempting up-cycling approaches through mechanical or thermo-mechanical methodologies are possible, but these methodologies are less promising for mixed materials. Thus, separation by chemical or enzymatic methodologies could be promising to separate/eliminate some polymeric fractions (Figure 8). \begin{table}
\begin{tabular}{c c} \hline \hline
**Recycling Method** & **Limitations** \\ \hline
**Mechanical recycling** & Shorter fibres, coarse yarns and lower quality of products (mainly non-woven). Preliminary sorting can be useful for a better reliability of the process. \\ \hline
**Thermo-mechanical recycling** & Its quality depends on composition; thus, it is better for homogenous polymers or for some specific blends/composites with reliable composition. For this kind of recycling, preliminary sorting is necessary. \\ \hline
**Chemical recycling** & With the exception of pyrolysis, it requires the use of solvents or chemicals, hence generally high investments, including suitable measures for protecting health and environment, are necessary. In the case of pyrolysis, a solid absorbent and gases are obtained. Their market demand should be high in order to create a profitable supply chain. \\ \hline
**Enzymatic recycling** & It can be applied to ester, amide, ether or glycoside linkages; thus, it can be applied to polyesters, polyamide or cotton. Polyaddition polymers (acrylics, polyolefins, etc.) generally could not be decomposed by enzymatic paths. Preliminary homogeneization and reduction of dimensions is useful. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Limitations of the different textile recycling methodologies. Despite more work being necessary to explore new specific recycling chains, several possibilities can be currently considered for final applications based on the updated literature. The application in textiles seems difficult, especially due to the high thermo-mechanical performance required for re-spinning fibres. Non-wovens, used in personal protective equipment, filtration devices, packaging and furniture, allowing the use of shorter fibres, can be considered a good alternative for mechanical recycling. Composites are another interesting field where recycled textiles can be used in the form of single fibres, fabric or non-woven, depending on the specific requirements (insulation, soundproofing, rigidity, strength, etc. ), and in some cases the preliminary separation of different polymers can be skipped. It should be noticed that a high durability should be preferentially considered for final applications, so that the polymeric carbon is stored for a long time and the occurrence of the product in waste is not only slightly postponed. Chemical modification processes resulting in specialty chemicals can also be considered. In this case the conversion of polymers into oligomers or monomers is considered. In the form of oligomers, polymers can be employed in the production of materials, (for instance, polyurethanes from waste PET oligomers used as diols) or components for glues, binders, coatings and adhesives. Other specific applications can certainly be developed in the near future, as well as new studies that will show their sustainability. Policy initiatives should promote these research activities that could contribute to converting a fossil-based industrial system into a circular one.