A temperature-regulating fiber made of PEG-based smart copolymer

A poly(ethylene glycol) (PEG)-based thermoplastic shape memory polyurethane was synthesized via bulk polymerization. The corresponding fiber, as a temperature-regulating fiber, was fabricated via melt spinning. The prepared 100-dtex fiber had a tenacity of 0.7 cN/dtex and breaking elongation of about 488%. The fiber's phase change behaviors, crystalline morphology, dynamic mechanical properties, and temperature-resistant performance were investigated using polarizing optical microscopy, differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetry. The PEG soft segment phase transfer between crystalline and amorphous states resulted in heat storage and release. The hydrogen-bonded hard segment phase, serving as ‘physical cross-links,’ restricted the free movement of soft segments, hence at temperatures above the PEG phase melting transition, the fiber still possessed certain mechanical strength. The differential scanning calorimetry results indicated that the fiber had large latent heat-storage capacity of about 100 J/g with a crystallizing temperature of 20.9 °C and a melting temperature of 44.7 °C. The dynamic mechanical analysis results showed that the fiber has a plateau elastic modulus in the region above the PEG phase melting transition and below 160 °C. The thermogravimetry results suggested that the fiber had a much broader applicable temperature range compared to pure PEG. The thermo-mechanical cyclic tensile testing results showed that the fiber had good shape memory effect with the shape fixity ratio more than 85.8% and the recovery ratio above 95.4%.