3-D Textiles Protect Against Extreme Heat Loads

The ideal complement to conventional protective clothing are functionalized, so-called three-dimensional undergarments. This newly developed protective clothing consists of a multi-layer structure in which the different layers assume different functions. The central role is played by a spacer fabric.

The protective effect of this spacer knit is based on the one hand on the avoidance of skin contact with the layers of protective clothing above, in order to prevent scalding caused by one's own body sweat, and on the other hand on a cooling effect produced by moisture removal. The knitted fabric works particularly well by producing locally different stiffnesses. The stiffness can be adjusted precisely on the machine side via the pile yarn and changed flexibly during the process.

In Germany, around 10 percent of the workforce are exposed to high temperatures at their workplaces, write the authors Lukas Lechthaler, Kristina Simonis, Marie-Isabel Popzyk, Christoph Peiner, Thomas Gries from the Institute of Textile Technology at RWTH Aachen University (ITA), Aachen and Markus Tutsch from STS Textiles GmbH & Co. KG, Grunbach, in their article in Technical Textiles. And complement them: In addition to intense physical exertion, an increased ambient temperature can lead to an increase in body temperature and thus to life-threatening heat shocks (from 40° C body temperature). This danger can and must be countered with the use of suitable protective clothing. It also shows the need to develop new materials.

A New Approach To Heat Protection

Within the framework of the research project "Development of heat-exposed occupational safety textiles", the focus is on the deeper layers of clothing. As a rule, conventional cotton underwear is used to absorb moisture, while the outer layers protect against heat radiation and burns. The cottonis in direct contact with the skin and can absorb and store large amounts of moisture due to its good absorption properties. The problem with this is that the stored moisture leads to a strong warming due to heating from the outside, which is not absorbed by protective clothing. This can actually lead to scalding and overheating due to the body's own perspiration.

The share of this heat damage in all accidents at work is about 50 percent for heat-exposed workplaces in Germany. The aim is to reduce this proportion to 10 percent by using 3D underwear.

Pressure-loaded areas in particular are reinforced locally in order to reliably prevent contact between the skin and the layer of protective clothing above it. In highly stressed areas such as knees, elbows or shoulders, local reinforcements must therefore be provided via stiffer pile threads that keep the needed distance. According to the current state of research, however, there is no possibility of changing the stiffness of the pile yarn during the production process.



Lower Pollutant Load Due to the Use of Thermoplastic Elastomers in Vehicle Interiors

For most people, the most conspicuous type of emission from a car is usually found in the interior - the smell. The substances in the air can come from a wide variety of interior components. In the past, plastic parts, in particular, have often attracted attention due to an unpleasant odour. It is interesting to note that in Europe and America a 'new car smell' is predominantly rated as pleasant, whilst in Asia it is often perceived as disturbing. The use of new types of elastomers is intended to significantly reduce the load in the future.

Air quality is generally a major issue in the automotive industry, but in addition to CO2 and nitrogen emissions to the environment, indoor air quality is now also of great importance – ultimately for both manufacturers and customers. In some countries, such as China, Japan and Korea, legal standards have even been introduced in recent years that clearly regulate the maximum concentration of some pollutants in the interior. It is therefore very likely that such or similar standards will also be applied in Europe and America in the same way in the future.

Emission values are among the most important material properties for automotive interiors, as they also make a significant contribution to driving comfort. For this reason, components must not release any substances into the air over a long period of time that could attract attention through unpleasant odours or impair the health of the occupants, write Florian Dresel and Dr.-lng. Thomas Köppl of Hexpol TPE in Lichtenfels in an article for the magazine ‘Plastverarbeiter’.

Emission And Solution Approaches

High-quality thermoplastic elastomers (TPE) are actually perceived positively by people with four of the five classic senses and are therefore increasingly being used in automotive interiors. This makes it particularly clear how important it is to select the right solutions. Mixtures and raw materials must be chosen carefully and with great effort.

In addition to the technical properties of materials, great importance is now also attached to the origin and sustainability of the raw materials. For this reason, the production of plastics from fossil raw materials is increasingly criticized. As an environmentally friendly alternative, products are therefore being developed that contain large amounts of plant-based raw materials. Moreover, these renewable raw materials, such as sugar cane, often originate from certified sustainable cultivation (e.g. ISCC+) and thus contribute to reducing the CO2 footprint. Depending on the hardness of the material, even a bio-based content of up to 90 per cent is possible.

New Water-Based Latex Dispersion For Abrasive Carrier Textiles

Abrasives such as abrasive belts, fibre discs, flap discs, abrasive sleeves and polishing tools are available in a wide variety of designs, sizes and formats. They are not only used for sharpening, but also for smoothing and polishing objects and for dimensional stability. Textile-based industrial abrasives are one of the key segments of abrasives.

For decades, aqueous polymer dispersions have increasingly been used to manufacture such products – to improve mechanical and thermal resistance as well as adhesion between layers as muchas extending the service life of the material.

Aqueous latex dispersions give industrial abrasives on textile substrates important properties such as flexibility, heat resistance and durability during the actual grinding process. Typically, the abrasive consists of an impregnated fabric made of cotton, polyester or a blend as carrier. The backing is lacquered on the back and the abrasive particles sit on the backing, fixed with phenolic resin.

The use of aqueous polymer dispersions to impregnate and coat the backing allows modifications to the stiffness of the fabric. It improves the mechanical properties and adhesion between the abrasive particle layer and the backing. It also improves heat resistance and durability to coolants. And it also acts as a barrier to prevent the phenolic resin from damaging the backing through the top layer, write Michael Karnop and Sören Butz of Synthomer Deutschland GmbH in the trade journal Melliand International.

Optimisation And Quality

Newer products have better peel strength and higher thermal resistance and are clearly more environmentally friendly.
 The parameters of the polymerization process are optimized to ensure a clean, low VOC product with low CO2 emissions.

One of the key functions of such a polymer dispersion in textile-based abrasives is to improve the mechanical bond between the abrasive particles and the backing, regardless of the fibre type. This contributes directly to the durability and life of the abrasive.

Grinding and polishing is usually carried out at a very high speed. Thermal resistance is therefore a decisive property that must be taken into account when developing a high-performance dispersion for industrial abrasives. The composition of this polymer dispersion, in particular the monomers and crosslinker components, has a significant influence on the thermal resistance.

New products also have good compatibility with phenolic resin, which is often used to grind the sand fixation on the surface. By mixing a small amount of these products with the resin, a change in flexibility is achieved so that the final product can withstand the bending process towards the end of production. This involves stretching and bending abrasives at different angles to better match the abrasives and substrates.

By optimizing process parameters and modern quality control, current products can be developed that contain ten percent more solids with a constant particle size distribution than their predecessors.

Fibre-Plastic Composites As High-Performance Products And Smart Materials

Technical textiles are assigned more and more properties. Fibre-plastic composites (FKV) are already being used as promising smart materials. These belong to a special type of functional materials that perceive environmental stimuli, react to them and can return to their original state once the stimulus has subsided.

For 20 years now, FKV have enjoyed increasing popularity in the field of resource-efficient mobility. Due to their high stiffness and low weight compared to traditional materials such as aluminium, steel or magnesium, FKVs are used as load-bearing structures in aircraft, automotive, rail and marine traffic.

By integrating functional materials into layered structures, they are provided with structure-integrated functions, such as lighting, de-lcing or continuous structure monitoring, as well as guidance and activation functions. They thus become said smart materials.

Particularly promising smart materials are shape memory alloys (FGL), which are characterized by a high energy density, a high force generation potential and enormous formability and stability in the high-temperature phase. The integration of the FGL during the manufacturing process of reinforcing fabrics guarantees long-term stability, reproducibility and cost reduction with regard to adaptive FKV (AFKV for short), according to the report by Moniruddoza Ashir, Jan Hindahl, Andreas Nocke and Chokri Cherif (Technical University of Dresden) in the technical journal Technische Textilien.

The research of the Dresden scientists shows promising approaches in lightweight structures with morphing capabilities - thanks to the development of AFKV based on FGL actuators. A structural integration of FGL wires in reinforcing fabrics was implemented fully automatically in a single process step and with the aid of weaving (textile) technology.

Further research activities of the Dresden researchers from the "Institut für Textilmaschinen und Textile Hochleistungswerkstofftechnik" (Institute for Textile Machinery and High-Performance Textile Technology) will in future aim to promote the development of adaptive, tapered FKV with locally adjustable bending stiffness in order to ultimately achieve an even greater degree of deformation. Exemplary applications for the developed AFKV include aerodynamic flaps or rudders, for example, but also medical applications for humanoid kinematics and various technical applications for clamping and gripping devices.