关键词: 温致变色, 氮化硼纳米片, 快速响应, 丝网印花, 智能纺织品, 涤纶/棉织物

Abstract:

Objective Thermochromic textiles based on fluorane dye microcapsules have many advantages, which are widely used in military camouflage, thermochromic clothing and smart windows, and so on. However, its application in the field of high sensitivity is limited because of its long discoloration time, wide discoloration range and hysteresis. Adhesives were necessary component in preparing the thermochromic textiles because of the lack of adhesion between the microcapsule and the surface of the fabric. However, most of the adhesives are polymer with poor thermal conductivity, which further reduced the thermochromic sensitivity of the fabric. Therefore, it is necessary to improve the color change sensitivity of thermochromic fabrics to broaden its application.

Method In this paper, fast response thermochromic fabrics were prepared by screen printing technology with a thermochromic slurry including Boron nitride nano sheets (BNNS), yellow thermochromic microcapsule, deionized water, adhesive and thickener. BNNS was adopted to improve the thermal conductivity of the thermochromic fabric, improving the temperature perception of the color chang core material.

Results BNNS were prepared by high-temperature oxidation and ultrasonic cell pulverization, whose properties were characterized by infrared spectroscopy, raman spectroscopy, X-ray spectroscopy and transmission electron microscope. The results showed that BNNS had a few layers structure with a mean particle size of 100-200 nm (Figs.1-3). A thermochromic printed fabric was prepared by screen printing technology with a thermochromic slurry including BNNS, deionized water, yellow thermochromic microcapsule (15%), adhesive (30%) and thickener (5%). The properties such as color performance and color change performance of thermochromic printed fabric were tested by colorimeter, digital camera and Adobe Photoshop CS software, and the influence of BNNS on these properties were investigated. The increase of BNNS content led to gradually decrease of the K/S value, reduction in the color change time, and narrowing of the color change range. When the content of BNNS was 2%, the performance of color performance and color change performance were generally the best, with the K/S value of 1.8 (Fig.5), the color change time of 8 s, the recoloration time of 13 s (Fig.7), the color change range of 31.4-37.2 ℃, and the recovery color range of 28.8-25.4 ℃ (Fig.8). Compared with the thermochromic fabric without BNNS, the color change time was shortened by 20%, the recoloration time shortened by 10.3%, the color change range reduced by 1.6 ℃, and the recoloration range reduced by 0.4 ℃ (Fig.8). In addition, BNNS content demonstrated little influence on the color fastness of thermochromic textiles. The color fastness to dry and wet rubbing and washing of the fast response color change fabric prepared are above grade 4 (Tab.1).

Conclusion The thermochromic printed fabric with fast response was prepared by screen printing technology with a thermochromic slurry including BNNS, yellow thermochromic microcapsule, adhesive and thickener. The relationship between the content of thermal conductive BNNS and the color property, color change property and fastness of thermochromic fabric were discussed. The results showed that when the content of BNNS is 2%, compared with the original thermochromic fabric, the fabric has shorter color change time (8 s), recoloration time (13 s), narrower color change range (5.8 ℃) and recoloration range (3.4 ℃). In addition, the doping of BNNS has little influence on the stability and color fastness of the thermochromic fabric, and the thermochromic fabric remains to have excellent color changeability after 200 cycles. However, BNNS is in a form of white powder, and its light scattering makes the fabric pale. Therefore, it is necessary to balance the relationship between discoloration performance and recoloration performance. In general, thermal conductive BNNS can effectively improve the color change sensitivity of thermochromic fabrics, and it also provides a new method of improving the color change sensitivity for other thermochromic materials.

Key words: thermochromism, boron nitride nanosheet, fast response, screen printing, intelligent textile, polyester/cotton fabric