With the continuous development of science and technology, the military strength of various countries continues to increase. Nowadays, long-range over-the-horizon operations have become mainstream. Remote reconnaissance measurement technology and various stealth technologies are becoming more and more important. Among them, infrared stealth technology is a technology that makes the infrared radiation emitted by the object as similar as the surrounding background radiation as possible, so that the infrared detection sensor cannot distinguish the target object.
Materials used for infrared shielding coatings include metal powders, conductive polymers, organic / inorganic composite materials, and semiconductors. Taking into account the material weight, infrared shielding capability and mechanical properties, antimony tin oxide (ATO) nanoparticles synthesized by various technologies are widely used in infrared and thermal radiation shielding coatings. The currently unresolved problem is that when ATO nanoparticles are mixed with a polymer matrix, the mechanical properties of the fibers may decrease. Therefore, it is necessary to develop a wearable infrared (IR) and thermal radiation shielding material that can effectively increase the shielding efficiency without significantly increasing the weight of the fiber and maintaining the mechanical strength of the fiber.
Highlights
Researchers such as Sang-Mi Jeong of Gyeonggi University in South Korea successfully synthesized polyurethane-antimony tin oxide (PU-ATO) composite fibers. Compared with conventional polyester or PU fabrics, the PU-ATO composite fiber textiles developed in this research have Excellent IR and thermal radiation shielding performance, even after being exposed to ten cycles of repeated temperature changes of −20 ° C and + 80 ° C and long-term temperature changes of 30 days, the produced PU–ATO composite fiber still has a stable IR and thermal radiation shielding performance. The surface of the PU-ATO composite fiber is made hydrophobic to prevent IR and thermal radiation deformation due to the wetting of the PU-ATO composite fiber by the absorbed water.
When observing people under visible light and using an infrared camera, when covered with a commonly used polyester or polyurethane fabric, the infrared and thermal radiation emitted by the human body will also become visible through the fabric. On the contrary, when PU-ATO composite fiber clothing is used to cover a part of the human body, the infrared and thermal radiation emitted by the human body are shielded and the human IR contour cannot be recognized.
Hydrophobicity of PU-ATO composite fiber
Since the water absorption of the fiber will cause the IR image to be deformed, the hydrophobicity of the fiber is essential to maintain a certain level of infrared and thermal radiation shielding ability. The water wettability of the composite fiber was evaluated using a contact angle analyzer. As shown in Figure 4, the water contact angle of PU-ATO (1-4) composite fibers of different concentrations (0.5, 1.5, 3.0 and 4.0 mmol) are all ≥130 °, showing hydrophobicity. Therefore, the water droplets on the fabric surface Not absorbed, but easy to roll off.
Infrared and thermal radiation shielding properties of PU-ATO composite fibers in different environments
In order to be used as a practical wearable textile, the textile must maintain its infrared and thermal radiation shielding performance in different environments.
After repeated exposure to high (+ 80 ° C) and low (−20 ° C) temperatures, the surface temperature of PU-ATO (3) composite textiles remained stable. These results confirm that even if repeatedly exposed to high and low temperature conditions, the infrared and thermal radiation shielding properties of the composite textile can still be maintained.
Continuous infrared and thermal radiation shielding performance of PU-ATO (3) composite textiles. The temperature of the fabric surface was measured at a temperature of 40 ° C for 8 hours a day for 30 days. It was found that the surface temperature of the fabric remained around 25 ° C even for a long period of time.
According to the changes of temperature and time, the infrared and thermal radiation shielding performance of PU-ATO (3) composite textiles was repeatedly evaluated. A, After repeated heating (+ 80 ° C) and cooling (−20 ° C) cycle PU-ATO (3) surface temperature of composite textiles. B, After applying a temperature of 40 ° C for 8 hours (a total of 30 days) every day, the surface temperature of the PU–ATO (3) composite textile
In this article, the researchers made PU-ATO composite fibers and used them to weave wear-resistant textiles with IR and heat radiation shielding properties. At the same time, the fiber has excellent hydrophobicity, which can effectively avoid the IR image distortion caused by the fiber absorbing water. The reliability of PU-ATO composite fibers was confirmed by repeated exposure (ten times) to extreme temperatures of 80 ° C and −20 ° C and long-term exposure at 40 ° C for 30 days. With the continuous development of stealth technology for hiding infrared signals from objects, PU-ATO composite fibers are expected to drive new markets for wearable infrared stealth products.
Original link: https://doi.org/10.1038/s41427-020-0213-z