Abstract
A flexible hollow polypropylene (PP) fiber was filled with the phase change material (PCM) polyethylene glycol 1000 (PEG1000), using a micro-fluidic filling technology. The fiber’s latent heat storage and release, thermal reversibility, mechanical properties, and phase change behavior as a function of fiber drawing, were characterized. Differential scanning calorimetry (DSC) results showed that both enthalpies of melting and solidification of the PCM encased within the PP fiber were scarcely influenced by the constraint, compared to unconfined PEG1000. The maximum filling ratio of PEG1000 within the tubular PP filament was ~83 wt.%, and the encapsulation efficiencies and heat loss percentages were 96.7% and 7.65% for as-spun fibers and 93.7% and 1.53% for post-drawn fibers, respectively. Weak adherence of PEG on the inner surface of the PP fibers favored bubble formation and aggregating at the core–sheath interface, which led to different crystallization behavior of PEG1000 at the interface and in the PCM matrix. The thermal stability of PEG was unaffected by the PP encasing; only the decomposition temperature, corresponding to 50% weight loss of PEG1000 inside the PP fiber, was a little higher compared to that of pure PEG1000. Cycling heating and cooling tests proved the reversibility of latent heat release and storage properties, and the reliability of the PCM fiber.
Highlights
Clothing systems with adaptive thermoregulation and acclimatization properties are attracting a lot of attention [1]
phase change material (PCM) have been used for thermotherapy in medical and health care, thermal energy storage, heat pumps, solar engineering, electronic items, thermal triggers, microprocessors, and microclimate control [3,4]
The phase transition enthalpy of polyethylene glycol 1000 (PEG1000)-filled PP fibers strongly depends on the core-sheath ratio and thermal storage capacity of the PCM core of the bicomponent fiber
Summary
Clothing systems with adaptive thermoregulation and acclimatization properties are attracting a lot of attention [1]. A decade later, Vigo and Frost proposed filling hydrated inorganic salts and PEG into hollow rayon and polypropylene (PP) fibers to achieve temperaturecontrol textiles; they found that the heat capacity of PCM-filled fibers decreased with repeating heating–cooling cycles [23,24] In this context, the influence of adsorbed water molecules on a shortening of latent heat storage time during melting, on thermal stability, and on thermal behavior should be considered [25]. Polyethylene glycol 1000 (PEG1000) was injected into as-spun hollow PP filaments using a microfluidic setup, and latent heat storage and release, thermal stability, tensile properties, and phase change behavior as a function of fiber drawing were first studied. A similar technique was applied in an earlier study to fill a PP fiber with an ionic liquid containing copper decorated muscovite, producing a flexible phase change fiber [42]
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