Polyvinylidene fluoride supported phase change material fibers fabricated via emulsion jet injection method

Abstract

The manufacture of fibers with thermoregulatory properties is generating increasing interest, given the ease with which these materials can be adapted to different geometries and applications such as the production of thermoregulating textiles, flexible sensors and human health care. In this sense, the encapsulation of phase change materials (PCMs) into microfibers is a promising option, given the high amount of energy that these materials can store/release at almost constant temperature. The predominant methods to produce microfibers with encapsulated PCMs lack a compromise between simplicity and final enthalpy, needing to use complex methods to obtain fibers with high PCM content. In this sense, this work presents a method that meets both simplicity and final enthalpy to produce polyvinylidene fluoride (PVDF) fibers with encapsulated PCMs. To achieve this, the emulsion jet injection method has been combined with the use of the polymer itself as an emulsion stabilizer, avoiding using surfactants. With this method fibers with up to 137 J/g of latent heat, which is the highest value obtained for polymeric fibers with encapsulated PCMs produced by microfluidic approaches, and a PCM content of 63 % have been produced. This has been favored by the polymer content in the precursors which, as shown by SEM and droplet size measurements, favors the stability of the emulsions, stabilizing the system during fiber production and increasing the final PCM content. Finally, thermal cycling tests of the fibers have shown a complete PCM retention capacity in DSC and 64 % of its enthalpy after being submitted to 1500 cycles sequentially in both air and water environments.