Flexible conductive coating helps smart nonwovens

Smart nonwovens combine the advantages of nonwovens with the functional characteristics of smart coatings and laminates。Compared to traditional textiles, non-woven fabrics have high strength and durability as well as relatively low manufacturing costs, making them a very attractive alternative for many applications。These characteristics make it the preferred choice for a wide range of products, including materials used in the medical, personal care, transportation, household goods and construction industries。

Nonwovens themselves can be made from a variety of base materials, including natural or synthetic materials, which are bonded in various ways to form a network of fibers。Some nonwovens can be manufactured using a mixture of base materials, including microfibers or nanofibers。Some non-woven fabrics can be leather-core structures, and different non-woven fabrics are made of different base material mixtures。Depending on the material and manufacturing process used, non-wovens can be given specific performance characteristics, such as absorption, liquid repellency, flame retardancy, stretchability, softness, insulation or filtration ability。

Adding functional coatings to non-woven materials can add some new functions while retaining some or all of the initial performance characteristics of non-woven materials。Smart coatings can be created using resins, polymers, and high-tech materials such as carbon nanotubes to provide unique functionality。The resulting coated non-woven fabric will have combined properties that neither component alone can provide。The non-woven fabric as the base material gives the composite tear and tensile strength, elongation and dimensional stability, and provides support for the coating applied to it。Coatings control chemical properties and characteristics, such as wear resistance and resistance to liquid and gas penetration。

By carefully choosing the combination of base fabric and functional coating, manufacturers can produce smart fabrics that combine many different possible performance characteristics。In general, properties that can be changed with coatings include general fabric properties, appearance and aesthetics, and barrier properties。Smart coatings offer a wider range of performance characteristics, including electrical conductivity, bacterial resistance or susceptibility。

Smart coated non-woven materials have created new market opportunities in several markets。For example, antibacterial properties can be added to disposable surgical gowns and other medical and personal care products。Non-woven materials with humidity sensing ability can play a potential role in building materials as well as agriculture and the environment。

The combination of two or more layers of materials into composite materials to form a coated fabric is defined as "a material consisting of two or more layers, at least one of which is a fabric, and at least one of which is a polymer layer."。Although non-woven fabrics are not considered textiles, they can be similarly coated or laminated to form a composite material。

Coated or laminated non-woven fabrics can be manufactured using a variety of methods, including scraping, transfer, spraying, etc。All of these methods have the same basic steps: the textile material is fed from the tension roller to the coated area, the coated fabric is heated to solidify the coating or create a gel, the solvent is volatilized, and the coated fabric is cooled。

For smart coated fabrics, the quality of the substrate is critical。When manufacturing high-performance non-woven coated fabrics, the purity and physical properties of the materials used in the coating and the process steps of the coating technology are also important factors to consider。The method used to deposit and bond the coating to the non-woven material must be carefully considered to ensure that the final product has the desired performance characteristics。

Battelle has created a smart conductive coating that can be used on non-wovens and other flexible or irregular substrates。Battelle's HeatCoat technology enables a unique combination of performance features that produce uniform, gentle warming without negatively affecting the performance of the fabric itself。

While there are many potential applications for heated or conductive fabrics, most conductive coatings are not suitable for soft, irregular, or flexible substrates。Most existing technologies cannot be used to bend flexible substrates (such as non-woven fabrics), or to lose electrical conductivity when bending, or to change surface properties to make the substrate harder, or both。

Most heated fabric technologies increase the weight and volume of the fabric, affect the drape of the material, and are prone to breakage。A gentler, more uniform heating can be achieved by pumping heated air between layers of fabric, a method sometimes used for heating patients during surgery。This solves hot spot problems and provides consistent warmth retention, but increases volume and reduces fabric flexibility and drape。Ventilation systems also require considerable power and have to be connected to fans, which limits their practical environments。

Other products, such as home health products or consumer goods, can be heated in an oven or microwave using a layer of gel between layers of fabric。These products provide even heat, but are very heavy and bulky。The gel layer is also prone to cooling quickly, often becoming too hot when initially heated, but rapidly losing heat once the product is removed from the heating source。Some products use chemicals that generate heat when the barrier between them is breached。These products hold heat longer, but are limited to single use, and have the same drawbacks in terms of weight and volume, and pose additional risks to consumers due to the use of chemicals involved。

Battelle's HeatCoat technology takes a completely different approach。The coating consists of dispersed single-walled carbon nanotubes (CNT)。When applied to non-woven fabrics, it forms a thin conductive layer that generates heat when a power supply is applied。The CNT coating is very thin, does not change the flexibility or drape of the fabric it is applied to, and does not add weight or volume to the final product。HeatCoat technology maintains electrical conductivity even when bent and delivers uniform, predictable heat to soft, pliable and irregular substrates。It offers several advantages over traditional heating coating solutions:

• HeatCoat technology can be applied directly to the substrate。Combined with closed-loop temperature control and low-resistance electrical interfaces, it delivers the required heat exactly and minimizes the required power。

• HeatCoat technology is flexible and maintains electrical conductivity during bending。When applied to the softest substrates such as memory sponges or fabrics, it does not affect hardness and will move with the substrate。

• HeatCoat technology can be applied to non-woven fabrics using a variety of methods, including scraping, transfer, Zimmer coating, spraying, etc。Good thermal contacts are provided even on soft or irregular surfaces, thus preventing hot spots。

• HeatCoat technology precisely controls the temperature curve to prevent unexpected overheating of the substrate or underlying material。This makes it safe to use in fabrics that come into contact with people and other temperature-sensitive applications。

• HeatCoat technology also enables transparent conductors that have no impact on RF communications。

Battelle has conducted in-depth research in the field of CNT coatings, optimizing the performance, stability, manufacturing, integration and maintenance of CNT coatings and their products。HeatCoat technology, when combined with good design, enhances thermal uniformity, reduces wasted power, and enables control of individual heated areas through closed-loop feedback。These elements can be added as needed, from low-cost, flexible consumer applications to complex, engineering-specific aerospace or industrial applications。The technology has already been demonstrated in several non-woven applications, including fabric heating systems for thermoregulation therapy and durable fiberglass MATS for anti-icing or de-icing of wind turbines or propellers。

HeatCoat technology is an integrated heating coating system based on CNT coatings that creates resistive heating by passing an electric current through a conductor。At a fixed voltage, the amount of heat generated depends on the applied voltage and heating resistance。The high conductivity and low resistivity of the CNT coating means that heat can be generated from extremely thin films, which can be flexible or even transparent。

The CNT coating is very thin and adheres to the shape of the product, usually no more than 3μm thick, which allows the coating surface to adhere closely to the surface of the substrate。The coating can be easily sprayed or printed onto any substrate, including heat stable and/or sensitive substrates。

The HeatCoat system has passed rigorous durability tests throughout its development。This extensive testing provides a high degree of confidence in HeatCoat's use in a variety of applications。These tests include resistance to humidity, solvents and water;Corrosion resistance;Cyclic bending;Cycle heat load;High strain test。

Non-woven heating products manufactured using CNT coating technology can be used in a wide range of commercial and industrial applications。Lighter, thinner and more flexible than existing fabric heating technologies on the market, these heating materials offer significant advantages and open up new possibilities in areas where weight, thickness or heating is difficult。Potential applications for HeatCoat technology include:

• 医疗：Heating fabrics for surgical sheets and patients, gowns for medical staff, or wraps for thermoregulation treatments。

• 汽车：Heated seat cover。

• 建筑：Heating pads for roof deicing, concrete laying and other building applications。

• 农业：For greenhouses and seed impregnation。

• 能源：It is used for anti-icing or de-icing of wind turbines and heating insulation materials。

The optimized HeatCoat not only provides heat to the substrate for its application, but the conductive CNT coating has many other potential applications, including supporting wearable technology or integrated sensors。We are only now beginning to explore the potential opportunities for non-wovens with integrated conductive CNT coatings and sensors。In the coming years, integrated conductive CNT coatings will bring many new opportunities for non-wovens。