Polymer blends of polyamide-6/Spandex fabric scraps and recycled poly(ethylene terephthalate)

In the textile industry, scraps of natural and synthetic polymers in the shape of fibres and yarns are commonly discarded as trash. In order to follow the trends of environmental preservation, we prepared melt-extrusion blends of underwear fabric scraps—made of polyamide-6 and Spandex—and recycled poly(ethylene terephthalate) at five different proportions. The hydrogen low-field nuclear magnetic resonance analysis revealed that there was variation in the molecular mobility of the blends, indicating the interaction of the precursor polymers. The differential scanning calorimetry showed that the crystallization and melting temperatures, and the degree of crystallinity of the recycled polymers, depended on the composition of the blend. The thermogravimetric analysis showed the variation on the initial and maximum degradation temperatures according to the composition of the materials. Through the dynamic mechanical analysis, we observed two intermediate glass transition temperatures, resulting in blends with at least two phases. After selective corrosion, the SEM images revealed voids in the interfacial region of poly(ethylene terephthalate) and polyamide-6 phases. The highest elastic modulus was found for the polyamide-6/Spandex-recycled poly(ethylene terephthalate) (20/80 mass/mass%) blend. In this context, the results suggested the contribution of interchange reactions between ester–amide groups and possibly additional ones (acidolysis, alcoholysis and aminolysis) during the molten processing. The detection of two glass and melting temperatures led to deduce that polyamide-6/Spandex-recycled poly(ethylene terephthalate) formed a partially miscible blend. Thus, this work is line with the sustainability concept, and the material can be reuse for other textile applications.