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Aalto University Uses Palm Wax For Water Resistance

Amidst concerns over use of c to make textiles waterproof, scientists from Aalto University have used an ecological method to make garments water-resistant with wax obtained from Brazilian palm tree leaves. The treatment is non-toxic and doesn’t impair breathability.

Aalto researchers have developed an ecological and water repellent wax particle coating suitable for wood cellulose fibres, which also retains the breathability and natural feel of the textile. The coating uses carnauba wax, which is also used in such things as medicines, foodstuffs, as well as the surface treatment of fruits and car waxes. The new coating is suitable not only for textiles but also for other cellulose-based materials.

During the processing, the wax is thawed and decomposed in water into wax particles that are anionic (negatively charged) just like cellulose. For the wax particles to adhere well to the cellulose surface, something cationic (positively charged) is needed as a buffer, since the oppositely charged particles attract one another. In previous studies, a natural protein called polylysine was used for this.

However, as Aalto University PhD student Nina Forsman points out, “Polylysine is very expensive so in our current study, it’s been substituted with a much cheaper, cationic starch that’s already commercially available.” Though cationic starch is not quite as effective as polylysine, two layers of the starch mixed with two wax particles are sufficient to make the textile waterproof.

The researchers compared the breathability of textiles treated with natural wax with textiles that had been treated with commercial products. Ecological wax particles made the textiles waterproof and also retained their breathability, while textiles treated with commercial controls had reduced breathability.

The multidisciplinary research team also included designer Matilda Tuure from the Aalto University School of Arts, Design and Architecture and as part of her master’s thesis, she designed and manufactured three coats for which the wax coatings were put through their paces.

The wax coating can be applied to the textile by dipping, spraying or brushing onto the surface of the textile, and all three methods were tested. They found that dipping is suitable for smaller items of clothing and spraying or brushing is better for larger ones. In industrial-scale production, wax treatment could be part of the textile finishing process along with the colour pigmentation of the wax, which makes dyeing and waterproofing possible at the same time.

The team found that the wax coating is not resistant to detergent washing, so the product is best suited for less frequently washed outer garments such as jackets. For the sake of simplicity of use, the consumer could potentially apply the coating themselves to the textile after each wash, and this requires more research and development though.

The effect of the drying temperature after wax treatment on waterproofing was also observed, and it was concluded that the best water resistance is obtained when the drying temperature is lower than the melting temperature of the wax.

“We tested the coating on different textile materials: viscose, tencel, cotton, hemp and cotton knitwear. We found that the surface roughness of textiles affects how well it repels water – the rougher the surface, the better. This is because, on a rough surface, water droplets contact the textile surface in a smaller area,” says Forsman.

Researchers Produced Materials to Replace Plastic

Aalto University and VTT (Technical Research Centre of Finland) scientists have produced a new bio-based material by uniting wood cellulose fibres and the silk protein found in spider web threads.

The material – very firm and resilient – may be used in the future to replace plastic, as part of bio-based composites and in medical applications, surgical fibres, the textile industry and packaging.

Achieving strength and extensibility at the same time has so far been a great challenge in material engineering. Increasing strength has meant losing extensibility and vice versa. The new material overcomes this challenge.

According to Aalto University Professor Markus Linder, nature offers great ingredients for developing new materials, such as firm and easily available cellulose and tough and flexible silk as used in this research. The advantage with both of these materials is that, unlike plastic, they are biodegradable and do not damage nature the same way micro-plastics do.

“Our researchers just need to be able to reproduce the natural properties,” adds Linder, who led the research.

“We used birch tree pulp, broke it down to cellulose nanofibrils and aligned them into a stiff scaffold. At the same time, we infiltrated the cellulosic network with a soft and energy dissipating spider silk adhesive matrix,” said research scientist Pezhman Mohammadi from VTT.

Silk is a natural protein which is excreted by animals like silkworms and also found in spider web threads. The spider web silk used by Aalto University researchers, however, is not actually taken from spider webs but is instead produced by the researchers using bacteria with synthetic DNA.

“Because we know the structure of the DNA, we can copy it and use this to manufacture silk protein molecules which are chemically similar to those found in spider web threads. The DNA has all this information contained in it,” Linder explains.

“Our work illustrates the new and versatile possibilities for protein engineering. In the future, we could manufacture similar composites with slightly different building blocks and achieve a different set of characteristics for other applications. Currently, we are working on making new composite materials as implants, impact resistance objects and other products,” says Mohammadi.

The research project is part of the work of the Centre of Excellence in Molecular Engineering of Biosynthetic Hybrid Materials (HYBER). The research has been published in Science Advances.