Textile Insight

P hase Change Materials (PCMs) have the ability to absorb heat in hot conditions and release it when environmental temperatures become cooler. Paraffin is one PCM that has been used in textile materials. When temperatures surround- ing the paraffin become warm and reach the paraffin's melting point, its physical state shis from solid to liquid, and heat is absorbed. When the temperature surrounding the liquid paraffin cools, heat is discharged. Paraffin-based PCMs can also be microencapsulated to enhance the paraffin's packaging efficiency. However, challenges exist, including fabric rigidity and leakage, making the apparel un- comfortable to wear. Recognizing these potential shortcomings, Dr. Hideaki Morikawa and a team of advanced textile engineers at the Institute of Fiber Engineering at Shinshu University in Japan, began further research. Professor Morikawa notes, "Another problem is that the manufac- turing methods for producing paraffin-based, phase-change micro-capsules is complex and very costly. Worse still, this option offers in- sufficient flexibility for any realistic wearable application for workers experiencing extreme temperature shis." His approach involves the development of a novel woven fabric using ultra-fine nano-threads that responds to temperature changes as needed. Morikawa's team created a fabric utilizing coaxial electro-spinning of nano-scale threads containing PCMs in their core that can store-and-release heat as the PCMs change from liquid to solid. is manufacturing technique produces very fine fibers with diameters at the nanoscale. Morikawa explains, "A polymer solution held in a bulk reservoir (usually a syringe tipped with a needle), is linked to a high-voltage power source, which collects an electric charge on the surface of the liquid. A point is reached during the change where the electrostatic repulsion from the accumulated charge is greater than the surface tension, causing a very fine jet of the liquid. As the jet of the liquid evaporates in flight, it is elongated by the same electrostatic repulsion that created the jet, and the ensuing ultra-fine fiber is then gathered on a drum." Coaxial electrospinning is similar, but requires two or more polymer solutions fed from adjacent spinnerets, enabling the manufacture of hollow or coated nanofibers. "ese core-and-sheath fibers have a comparable structure to a very small coaxial cable," says Morikawa. "In this scenario, our scientists encased the PCM in the center of the electrospun nanofiber to resolve the issue of PCM leakage. e ultra-fine fibers allow very favorable flexibility that is suitable for wearing apparel." To spread the range of settings where the tex- tile would be suitable and accurate for thermal regulation, the Shinshu University scientists combined the PCM material with two other personal thermal regulation technologies. e team integrated photo-responsive materials (those that react when exposed to solar energy) with PCMs, providing the opportunity to improve the energy storage feature of the textile. Hideaki's team integrated the three options: carbon nanotube and polydopamine solar absorbers, PCMs, and electro-conductive polymers composed of poly 3-4 ethylenedioxythiophene and polystyrenesul- fonate (referred to as 'PEDOT:PSS') into a single "tri-mode" thermo-regulation wearable fabric. Morikawa notes, "is multi-core shell struc- ture allows for synergistic support between its many components, and offers instant thermal regulation that can adjust to a wide variety of environmental temperature variations." n Kathlyn Swantko is founder of FabricLink Network, www.fabriclink.com. Contact: kgswantko@fabriclink.com Enhancing Thermal Comfort Researchers Provide Advancement in Phase Change Materials Technology. Kathlyn Swantko Schematic illustrations of (a) fabrication process of the hierarchical core-sheath constructed fi- bers, (b) coaxial electrospinning, (c) reversible phase change process of core material, (d) solar heating effect, (e) Joule heating effect, and (f) various interfacial interactions. EDUCATION / SHINSHU UNIVERSITY FabricLink.com TheTechnicalCenter.com "Thank you for all the support you have provided to Concept III over the years. You know how much we value it. Keep up the good work!" David Parkes President Concept III Textiles Why clients are excited about the benefits of The FabricLink Network Partnership Opportunities: Kristi Rummel kristi@rummelmedia.com 608.435.6220 Editorial Opportunities: Kathy Swantko kgswantko@fabricklink.com 818.345.7501 How will they find you, if you're not there? The FabricLink Network THE Networking / Education Search Engine for ALL Things Textile Related! FL-TTC-TI-2016-2_Layout 1 9/19/19 11:54 AM Page 1 40 • Textile Insight ~ Winter 2023 textileinsight.com Image: AmericanChemical Society

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