Fluorine-free, ecologically water-repellent textiles with Bionic Systems
Stefan Thumm, RUDOLF (Germany)
Bionic is the future! By combining biology and technology RUDOLF develop new, promising, ecologically advantageous technologies in the field of hydrophobic properties:
RUDOLF developed an ecological possibility of imparting hydrophobic, forward-looking properties to textiles, in comparisation to conventional “nano”-products.
Products or finishes with nano particles for water and soil-repellent textile finishing were introduced as something completely new in the recent past. These products contain eg SiO2 nano particles, which are to create nano-scale surface structures on textiles. From a scientific point of view, nano particles are surely very interesting so that a transfer to the textile sector is obvious. However, the effect level of these “new“ products is not higher than of already known, conventional finishes. In addition, features such as fabric handle, resistance to washing and abrasion are very important when used in the clothing sector. If surface structures are created by means of particles, the handle and characteristics of textiles will distinctly deteriorate. Furthermore, slightest mechanical stress by abrasion (eg due to carrying a rucksack or washing) destroys the water and oil-repellent effects of these finishes.
The decisive effective components of these “nano“ products are still conventional fluorocarbon polymers. They have been used virtually unmodified for more than 30 years to obtain water, soil and oil-repellent textiles. However, for ecological reasons, the fluorocarbon polymer technology is increasingly under pressure.
“Nano“ thus seems to be only a marketing argument. The general public and finally consumers, by mistake, equate the term “nano“ with “modern and innovative“, which is even stressed by scientifically dubious certificates. There is no actual advantage, neither for consumers nor the environment.
Ecological security for your the textile chain
Recently, critical reports on PFTs (perfluorinated surfactants) have been frequently published. PFT is the generic term for all fluoro-organic compounds with a surfactant character. The best known representatives of this group are perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). These substances are watched because they are not degraded in the environment and, as far as toxicity is concerned, have not been thoroughly examined yet.
In media discussions about this very complex topic water, oil and soil repellents based on fluorocarbons, by mistake, have been often named as a source of these substances. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are not at all used for impregnating textiles, but are found at most in smallest quantities as byproducts when manufacturing fluorine-containing impregnating agents. A majority of PFTs reach nature by way of fire-extinguishing foams, galvanic processes and PTFE-coatings.
RUDOLF has made every effort to eliminate these byproducts and has succeeded in developing PFOS and PFOA-free fluorocarbon water repellents with the new so-called C6-generation. Despite these efforts, what is decisive for all parts of the textile chain, especially for brand manufacturers, is how public and consumers will in future react to this product optimisation.
The entirely fluorocarbon-free BIONIC-FINISH®ECO will open up new perspectives to the clothing sector. With this system RUDOLF have succeeded in developing water-repellent finishes that do not release fluoroorganic compounds.
BIONIC-FINISH®ECO offers the whole textile chain security for protecting their textiles and brands.
BIONIC-FINISH®ECO – Realising natural functions and implementing them effectively
Why do the feathers of birds not become wet? Why does this type of water repellency in nature work without perfluorinated compounds?
RUDOLF reply to these questions by means of the scientific branch Bionic. It is not the sense of Bionic to just imitate nature, but to realise the functional principles of natural systems and to transfer them to independent technical solutions. The basic idea of BIONIC-FINISH®ECO is the use of hyperbranched polymers, so-called dendrimers (Greek: dendron = tree); nature has served as a model for their ramified structure. Trees require the energy of light for photosynthesis, which they absorb from their leaves. The optimum surrounding, i.e. a large number of functional elements per volume in the treetop, enables high energy yield.
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Dendrimer structure and growth (graphic: Rudolf GmbH, Geretsried) |
This structure has been adopted for developing a water repellent, and a hyperbranched structure with a maximum density of hydrophobic functional elements per unit volume was synthetised.
Intelligent self-organisation for optimum water-repellent effects
Water-repellent effects of ®RUCO-DRY ECO on textiles (graphic: Rudolf GmbH, Geretsried)
Dendrimers can be produced step by step by combining multifunctional components. With each synthetic step of these hyperbranched polymers the number of reactive end groups grows exponentially. The specific control of reactions enables to functionalise end groups with hydrophobic residues at the end of a series of synthetic steps, which results in an extreme density of water-repellent groups. These hyperbranched, hydrophobic polymers are highly efficient and, due to their network structure, tend to self-organise and crystallise.
For optimum orientation and attaching to the fibre surface, ®RUCO-DRY ECO, the finishing product of BIONIC-FINISH®ECO, does not only use dendrimers but also specifically adjusted “comb“ polymers. The water-repellent effect level obtained in initial textile finishing has so far only been possible with fluorocarbon polymers.
Convincing versatility
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Highly water-repellent with a potential Laundry-Air-Dry behaviour
®RUCO-DRY ECO does not necessarily require a strong thermal treatment after home laundering, since the effects are often maintained even after line drying. This LAD-behaviour (Laundry-Air-Dry) is very important for end users. Preliminary tests for the LAD-potential on different fabrics are however recommended.
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Highly breathable membrane textiles
Due to the fact that ®RUCO-DRY ECO is free of paraffin, the breathability of finished textiles is not affected, which is important with regard to the wearability of sports and outdoor jackets etc. with membrane technology. This is confirmed by measuring the water vapour permeability according to ISO 11092. In contrast to conventional fluorine-free water repellents based on paraffin or formaldehyde-containing melamine, the application quantity of ®RUCO-DRY ECO is low with a simultaneously higher effect level.
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Soft handle, optimum sewability, raisable
Due to the fact that ®RUCO-DRY ECO is free of paraffin, the breathability of finished textiles is not affected, which is important with regard to the wearability of sports and outdoor jackets etc. with membrane technology. This is confirmed by measuring the water vapour permeability according to ISO 11092. In contrast to conventional fluorine-free water repellents based on paraffin or formaldehyde-containing melamine, the application quantity of ®RUCO-DRY ECO is low with a simultaneously higher effect level.
