A sustainable recycling process and its life cycle assessment for valorising post-consumer textile materials for thermal insulation applications

The textile industry along with construction, electronics and plastic generate huge amounts of waste posing challenges to the adoption of the circular economy. This research presents a sustainable and low-cost recycling technology for conversion of post-consumer textile (denim) wastes to useful insulation materials. To accomplish the objective, nonwoven materials were produced using varying proportions of post-consumer recycled denim (r-denim) fibre and hollow polyester (PET) fibre using different punch densities in the needle punching process. Kowalski, Cornell and Vining mixture design, a special type of design of experiments, was adopted to develop the samples. Developed nonwoven materials were characterised for thermal resistance and tensile properties. The results show that nonwoven materials containing the minimum proportion (20%) of r-denim fibres exhibited the highest thermal resistance (0.131 W^-1m²K). However, by adjusting the process parameter of the nonwovens, that is, the punch density, the same thermal resistance (0.131 W^-1m²K) is also achieved even with 39% r-denim fibres. Additionally, the nonwovens produced from this blend proportion (r-denim:PET = 39:61) demonstrate a reasonable strength of 2.43 cN/tex. Environmental benefits of the developed r-denim/PET nonwovens have been evaluated by the life cycle assessment approach. Results show that the use of ~40% r-denim fibre has reduced the environmental burden significantly. Therefore, the nonwoven materials produced from post-consumer textile wastes hold tremendous potential as an alternative to synthetic fibres in thermal insulation applications. This recycling approach has immense potential to contribute to the efficient utilisation of post-consumer textile waste materials paving the way for environmental sustainability.