Recycling bovine ear tags for phase change material encapsulation via electrospinning

Abstract

In this study, thermoplastic polyurethane (TPU) from waste bovine ear tags has been processed and recycled as shell material to encapsulate phase change materials (PCMs), enabling the fabrication of thermoregulating core-shell nanofibers via coaxial electrospinning. Notably, this process was achieved in few steps and without the need for heating equipment to melt the injected materials, enhancing its simplicity. Two PCMs were selected based on their melting points; octadecane (OCTA) near room temperature and eicosane (EICO) near body temperature. Composite fibers were prepared at different core solution concentrations (10, 20, 40 and 80 % w/v), with the highest encapsulation efficiency and thermal properties obtained for samples with 80 % (w/v). TPU/PCM electrospun nanofibers were observed by scanning electron microscopy (SEM) with average diameters between 400 and 700 nm. The Fourier transform infrared spectroscopy (FTIR) suggested no further chemical reactions during the fabrication process. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) demonstrated good thermal stability, with latent heats of 62.9 2 J/g and 81.4 J/g for TPU/OCTA80 and TPU/EICO80 membranes, respectively. Thermal cycling tests were conducted for 150 cycles, showing a 5 % enthalpy reduction in TPU/OCTA80 due to crystalline phase degradation, while TPU/EICO80 exhibited a 2 % increase, likely due to PCM restructuring; however, long-term trends suggest a potential decline. This simple, cost-effective and environmentally friendly fabrication process highlights the potential of upcycling TPU waste and offers a scalable approach for developing TPU/PCM membranes with promising applications in textile thermal management systems.