New Polyamides: Better Flame Resistance And Improved Physical Properties

A typical textile sample does not flare up suddenly as usual, but only hesitantly begins to melt. At first, the fabric only contracts and dark polymer droplets fall off very late ... An excellent result for flame retardancy, which was made possible by a new development by the "Deutschen Institute für Textil- und Faserforschung [German Institutes for Textile and Fibre Research]" (DITF). As the trade journal "Melliand Textilberichte" reports, it was possible to achieve a kind of intrinsic flame resistance for the first time, because the properties are directly part of the polymer chains of the material.

Flame retardant phosphorus compounds are usually added to the polymers as additives. However, large quantities of phosphorus compounds are required to achieve a good fire protection effect. And this is usually done at the expense of the physical and physiological properties of the textiles.

Contrary to the usual methods of adding flame-retardant properties to the polymer using phosphorus compounds as an additive, the researchers from Denkendorf with this new method were able to incorporate these directly into the polymer chains at low concentrations. This takes place directly during polycondensation, i.e. the synthesis of the plastic in reactor vessels.

In general, the aim here is to produce molecules with as long a chain as possible in order to guarantee good properties for later spin ability of the polymer granulate into textile fibres.

Fewer Phosphate Compounds With The Same Properties

One problem of traditional manufacturing processes is that when larger amounts of phosphorus compounds are added as additives, they prevent the formation of long molecular chains - they thus act as chain breakers. The resulting plastic is very difficult to process into fibres, and in addition, due to ageing and washing processes, the additive emerges from the fibre over time.

The new process allows compounds to be chemically coupled to the molecular chains and thus achieves a much stronger bond to the polymer - more than would be possible with additive blends.

The reduction of the required flame retardants makes it much easier to control the achievable molecular weight during synthesis, according to the journal. In this way, the viscosities can be precisely adjusted to guarantee the optimum spin ability of the polymer into fibres.

In addition, the chemical bonding of the flame retardants to the polymers prevents migration and leaking from the fibres due to ageing, which is common with the use of additives.

In their application, such textiles made of intrinsically flame-retardant polyamides show their advantages, especially where high flame-retardant requirements are placed on the materials. This is usually the case in home textiles like carpets, upholstery and seat covers or curtains.

Nonwovens And Nanofibers: New Manufacturing Processes For Reinforcement And Finishing

The production of smallest structures from micro- to nanofibers enables a highly efficient application in areas such as acoustics and filtration. Special emphasis is increasingly placed on promoting the development of environmentally friendly, solvent-free and ultimately cost-efficient manufacturing processes. The aim is to produce modern processes for nanofibers from polypropylene and other thermoplastics.

Harry Albus of JX Nippon, respectively of the JXTG Nippon Group, presents some current examples in his report in the trade journal "Technische Textilien" (3/18): Cross Laminated Airy Fabric (CLAF), Milife and nanofibers from multifilaments.

CLAF is used to reinforce nonwovens, foils, paper, etc. High tensile and tear strength, breathability, water and chemical resistance and dimensional stability in further processing are the "core competencies" of reinforcing fabrics. The aim is to increase the performance of the textile and reduce production costs. Bonding with other materials can be carried out thermally or by ultrasound, as well as by all other common laminating processes and by needle or water steel bonding.

High tensile and tear strength, good breathability, dyeability, printability and dimensional stability in further processing characterize the polyester nonwoven fabric "Milife". The molecular orientation of polyester melt-blown continuous filaments gives this melt-blown nonwoven high tensile strength combined with low basis weights and material thicknesses. During the process, a silk-like surface is created using a special process.

In addition to reinforcing other textiles, the aim of this development is particularly to optically and haptically refine the resulting final textile. Applications include interior design (e.g. pleats and wall coverings), packaging, medicine, adhesive tapes and other materials.

Nanofibers, Fanned Out By Vacuum And Melted By Laser

Solvent-free production of nanofibers from polypropylene is another focus of development at JXTG. The development of the laser-supersonic-stretching method makes it possible to produce nanofibers solvent-free, more homogeneous, more productive and, in addition to many other thermoplastics, also from polypropylene. The starting products from which the nanofibers are made are multifilaments that are drawn into a production chamber by means of a vacuum.

The vacuum causes the multifilaments to vibrate and they fan out. The individual filaments now released are melted - hit by a CO2 laser. The permanent vacuum draws the nanofibers from each individual filament, which are then homogeneously deposited on a freely selectable nonwoven carrier.


Sustainability: The industry change in the textile industry is unstoppable

Over the next few years, manufacturers and suppliers - from the chemical industry to the producer of the end products - will have to increasingly address the issue of sustainability. Start: Now. Because the environmental impacts of the textile industry are all too well known - from pesticide pollution and high water requirements during cultivation, to high C02 emissions during the production of synthetic fibers, to the unsafe handling of chemicals that are harmful to health and the environment during the manufacturing process, and the pollution of water bodies due to inadequate wastewater management. And consumers - the users - are increasingly demanding that this situation ist to be changed sustainably.
Criticism already starts at the conceptual level, so a reorientation must offer a clearly changed design approach for industrial and organisational problems - and is closely linked to a cradle-to-cradle design principle. This universal approach to sustainable design transforms linear production chains into closed material cycles and ultimately calls for the emergence of new business models.
The days when sustainability was more of a 'nice to have' are clearly over. Today it is a clear 'must have', a trend that is unavoidable all in all, and thus also a competitive advantage - which does not have to be a disadvantage on many levels, but on the contrary promises good turnovers and profits. In addition to the complete elimination of the waste problem through the cradle-to-cradle principle mentioned above, there are other approaches to raising recycling processes and products to a new quality standard.

Transparency And Identification As Characteristics

Nevertheless, further research and in-depth industrial restructuring are needed to make such technologies suitable for large-scale deployment. This does not only apply to the product as such, but also to all preliminary stages and resources. What is decisive for the quality of the novel recycling products is what takes place at the beginning of the textile value chain. And here the choice of fibres comes first. Some fibres or fibre blends are easier to transfer into a closed material cycle - because not all products can be produced from easily recyclable natural fibres.
The first promising approaches for clear and forgery-proof labelling and identification of fibres are chemical markings with pigments, identification via QR codes and the blockchain technology, which is becoming increasingly popular. In fact, traceability and transparency are becoming more and more important.

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.