Upcycling of industrial footwear waste into nonwoven fibrous structures with thermal and acoustic insulation properties.

The footwear industry significantly impacts the environment, from raw material extraction to waste disposal. Transforming waste into new products is a viable option to mitigate the environmental consequences, reducing the reliance on virgin raw materials. This work aims to develop thermal and acoustic insulation materials using polyester waste from footwear industry. Two nonwoven and two compressed nonwoven structures, comprising 80% polyester waste and 20% commercial recycled polyester (matrix), were produced. The materials were created through needle-punching and compression molding techniques. The study included the production of sandwich and monolayer nonwoven structures, which were evaluated considering area weight, thickness, air permeability, mechanical properties, morphology using field emission scanning electron microscopy, and thermal and acoustic properties. The nonwoven samples presented high tensile strength (893 kPa and 629 kPa) and the highest strain (79.7% and 73.3%) and compressed nonwoven structures showed higher tensile strength (2700 kPa and 1291 kPa) but reduced strain (25.8% and 40.8%). Nonwoven samples showed thermal conductivity of 0.041 W/K.m and 0.037 W/K.m. Compressed nonwoven samples had higher values at 0.060 W/K.m and 0.070 W/K.m. While the sample with the highest conductivity exceeds typical insulation levels, other samples are suitable for thermal insulation. Nonwoven structures exhibited good absorption coefficients (0.640-0.644), suitable for acoustic insulation. Compressed nonwoven structures had lower values (0.291-0.536), unsuitable for this purpose. In summary, this study underscores the potential of 100% recycled polyester structures derived from footwear and textile industry waste, showcasing remarkable acoustic and thermal insulation properties ideal for the construction sector.

Influence of 3D Microstructure Pattern and Infill Density on the Mechanical and Thermal Properties of PET-G Filaments.

This study aims to evaluate the thermal and mechanical performances of PET-G thermoplastics with different 3D microstructure patterns and infill densities. The production costs were also estimated to identify the most cost-effective solution. A total of 12 infill patterns were analysed, including Gyroid, Grid, Hilbert curve, Line, Rectilinear, Stars, Triangles, 3D Honeycomb, Honeycomb, Concentric, Cubic, and Octagram spiral with a fixed infill density of 25%. Different infill densities ranging from 5% to 20% were also tested to determine the best geometries. Thermal tests were conducted in a hotbox test chamber and mechanical properties were evaluated using a series of three-point bending tests. The study used printing parameters to meet the construction sector's specific needs, including a larger nozzle diameter and printing speed. The internal microstructures led to variations of up to 70% in thermal performance and up to 300% in mechanical performance. For each geometry, the mechanical and thermal performance was highly correlated with the infill pattern, where higher infill improved thermal and mechanical performances. The economic performance showed that, in most cases, except for the Honeycomb and 3D Honeycomb, there were no significant cost differences between infill geometries. These findings can provide valuable insights for selecting the optimal 3D printing parameters in the construction industry.