Preparation And Performance Of Humidity Regulation And Humidity-sensitive Discoloration Fabrics

Humidity is closely related to people’s daily life.Humidity regulation and humidity-sensitive discoloration are widely used in intelligent humidity management textiles,respiratory monitoring,colorimetric sensing,message encryption and anti-counterfeiting,weather forecast and other fields.As people’s dress concepts change,the need for clothing is not only beautiful,but also hope that clothing has excellent comfort.In the hot season,especially the soldiers,delivery men,workers and other people working in the extreme heat environment need moisture wicking clothes.Improving the moisture conduction and sweat removal function of the moisture wicking fabric is of great significance to the development of intelligent moisture management textiles.A typical way of humidity monitoring is through the color change of humidity-sensitive discoloration materials.When interacting with humidity or water,humidity-sensitive discoloration materials can monitor the change of external humidity conditions and convey the phenomenon of color change to the observer.Hydrochromic materials have been extensively studied in the context of colorimetric humidity sensors,including cobalt chloride,graphene oxide,photonic crystals,cholesteric liquid crystals,aggregation induced photons,polymer electrolytes and covalent organic frameworks.Thus,it is significant to prepare convenient and practical humidity-sensitive discoloration materials,which can be used in bathing suits,observing moisture wicking effect of clothing and diapers,for promoting the development of fashionable clothing and humidity monitoring color indication.In order to solve the uncomfortable feeling of sticky and cold after sweating,a moisture wicking fabric with directional water transport function was designed.Discontinuous hydrophobic/hydrophilic Janus fabric resembling river branches is prepared by nano-ZnO pretreatment and screen printing for directional water transport and thermal conductivity properties.A river branch-like structure is constructed dexterously,and the effect is quantitatively adjusted by accurately regulating the gap width of hexagon water-transfer-channel.Fabrics based on these rivers branch-like hexagon structure possess enhanced moisture wicking performance,a desired water transport index of 147.26%,which are over seven times higher than conventional cotton fabrics.Meanwhile,nano-ZnO treatment improves the thermal conductivity of cotton fabric,which accelerates the evaporation of sweat on the surface of cotton fabric.Moreover,nano-ZnO cotton fabric shows an outstanding UV resistant property with 145 UPF value.The novel discontinuous hydrophobic/hydrophilic Janus fabric could provide a new strategy for the development of moisture management textiles.A humidity-sensitive discoloration polyester fabric induced by p H indicator cresol red/thymol blue is prepared via a facial screen printing.Boric acid can adjust the p H of the system as the humidity changes,thereby affecting the discoloration of cresol red/thymol blue.Silica gel and hydrophilic silica aerogel with porous structure are used as high-performance hygroscopic agent.The prepared humidity-sensitive discoloration cresol red/thymol blue polyester fabric（CRP/TBP）displays rapid response to relative humidity（RH）change and exhibits obvious color change.As humidity increases,the prepared discoloration polyester fabric shows multiple colors,and the absorption peaks of CRP and TBP shifted from 430 nm and 440 nm to 520 nm and 550 nm,respectively.The steady discoloration performance in the moisture absorption/drying process is observed after 25 cycles,pointing out good reversibility and repeatability of humidity-sensitive discoloration polyester fabric.Considering these excellent properties,humidity-sensitive discoloration polyester fabrics are promising as sensitive RH detector with widespread applications in discoloration materials,sensors and information storage encryption technology.Hydrochromic materials has been a novel topic in the research of stimuli-responsive sensors and anticounterfeiting encryption.A high-performance hydrochromic cotton fabric is fabricated with Co Cl₂/waterborne polyurethane via hot-press method.Moisture sensing metal salt cobalt chloride is introduced into waterborne polyurethane via physical doping to induce hydrochromic phenomenon.The hydrochromic cotton fabric possess superior fastness because of the hydrogen bonds composed of hydroxyl group on cotton fabric and carbonyl group,urethane bond,ether bond in waterborne polyurethane.Meanwhile,the hydroxyl group on cotton fabric and waterborne polyurethane endow hydrochromic cotton fabric with excellent hydrophilicity and high humidity sensitivity.Air humidity could be easily detected by hydrochromic cotton fabric.The absorption of humidity in rainy days led to pink color,resulting in a blue shift at 512 nm.In contrast,hydrochromic cotton fabric turn to blue color below RH59%in sunny days,leading to a red shift for up to 674 nm.Moreover,the hydrochromic cotton fabric exhibited eminent stability and cyclicity in response to either dry state or wet condition.Based on these excellent properties,hydrochromic cotton fabric fabricated with Co Cl₂/waterborne polyurethane are promising as smart sensors with potential application in sensitive RH detector,anti-counterfeiting technology and decorative coatings.