Intelligent barrier films are used in biochemical protective clothing: self-sensing, self-responsive, self-cleaning, and self-repairing!

Biochemical protective clothing usually needs to deal with very complex dangerous environments. In special cases, liquid-tight or air-tight protective clothing is required to protect against various toxic and harmful liquid, gas, smoke, solid chemical substances, biological poisons, and military gases. It plays a comprehensive protective role against nuclear pollution. This type of protective clothing must sacrifice comfort while ensuring protective performance. Therefore, in future research on biochemical protective clothing, how to achieve better protective performance is equally important as reducing weight and heat stress and improving the comfort of protective clothing.

Intelligent barrier film materials can enable the surface of biochemical protective clothing to have self-sensing (“sensor” function), self-response (“actuator” function), and adaptive capabilities to toxic and harmful substances, ensuring protective performance while adjusting according to the external environment. The breathability and moisture permeability of protective clothing, or the functions of self-disinfection or self-cleaning, can greatly improve the protective performance and comfort of biochemical protective clothing.

Barrier film material with “sensor” function

Smart materials that can sense chemical and biological stimuli (including chemical properties, pH value, ionic strength, reaction heat, moisture, surface tension, biological surface functionality, etc.) found in existing research include conductive polymers, thermosensitive aerogels, Chromium materials, active adsorbents and deformation materials, etc. Among them, conductive polymer is a biochemical smart protection sensor material with great application potential. For example, polymer-doped polypyrrole, polythiophene and polyaniline (PANI) can be used as sensors to detect volatile and liquid chemical substances. Its principle Yes: When these conductive polymers doped with special substances are exposed to substances with oxidation/reduction effects, a “doping-dedoping” reaction will occur, and the resistivity of the conductive polymers can be monitored to detect the presence of harmful substances. .

With MoO₃Films embedded with polyaniline in the matrix can detect formaldehyde and acetaldehyde at concentrations as low as 25mg/kg

In addition, enzymes can also be used to detect organophosphate chemicals. Developed by AgentaseA sensor that combines acetylcholine, acetylcholinesterase, urea, urease and a pH-sensitive dye that also responds quickly to temperature changes.

Barrier film material with “actuator” function

Shape memory polymer materials have the ability to maintain temporary shapes and can restore their original shape when subjected to appropriate external stimulation. They have many advantages such as low density, large recoverable deformation, easy processing and forming, and adjustable deformation temperature. As a ” The self-responsive barrier film material with “actuator” function has broad application prospects. At present, relevant research mainly focuses on thermally induced shape memory polymer materials. For example, shape memory polyurethane can use its thermal activation properties to provide warmth with low air permeability at low temperatures (Tg), thereby fully improving the wearing comfort of the fabric. Shape memory polyurethane has also been observed to have a moisture-sensitive effect, meaning that the breathability of shape memory polyurethane barrier films can also be modulated by changes in humidity.

Humidity and temperature stimulate shape changes of shape memory polyurethane materials

Currently, commercialized shape memory polyurethane materials include shape memory polyurethane heat-sensitive breathable membranes developed by Japan’s Mitsubishi Heavy Industries (SMP Technologies), and shape memory polyurethane-based membrane materials (made of temperature-sensitive membranes) developed by Finland’s Ahlstrom. , a breathable integral film sandwiched between two layers of microfiber spunbond polypropylene nonwoven), etc.

In addition, the electrobraking nanoporous polymer membrane prepared by grafting ion gel also shows great application potential in biochemical protective clothing. Under the action of applying and canceling the electric field, due to the ions located in the nanopores, The gel expands and contracts, allowing the pore size to be adjusted as needed to improve breathability.

Barrier principle of grafted ion gel polyester nanoporous membrane

Adaptive barrier film and its application in biochemical protective clothing

Adaptive smart materials can respond to external stimuli to provide wearers with instantFor example, it has a self-cleaning function or a self-healing function, which can promptly clean harmful chemicals on the surface, or repair defects on the surface of protective clothing to prevent the intrusion of harmful substances, achieving more intelligent protection.

Membrane material with carbon nanotube moisture-conducting pores developed by LLNL

Lawrence Livermore National Laboratory (LLNL) in the United States developed a membrane material called “second skin” in 2016. This material has neatly arranged carbon nanotube moisture-conducting pores with a size of less than 5nm and is breathable. Better than GORE-TEX membrane material. At the same time, since the size of biological viruses is usually larger than 10nm, it has good barrier properties against the invasion of biological viruses. In order to prevent the intrusion of smaller harmful chemicals, researchers are using chemically responsive functional groups to modify the surface of carbon nanotube films to achieve selective blocking of harmful chemicals. At the same time, researchers are also conducting research on another interesting “self-cleaning” defense method, that is, when reacting with harmful chemicals, the surface film material will automatically fall off to achieve self-cleaning purposes. It is reported that this research is funded by the US Defense Threat Reduction Agency (DTRA) and will be initially evaluated in early 2018 and is expected to be used in its future biochemical protective clothing systems.