Can challenge glass fiber reinforced plastic! Prospects for new cellulose fibers

Wood pulp, hemp and linen are renewable raw materials that can be engineered into new properties with innovative technology. These fibers are environmentally friendly and help solve waste problems. DITF Denkendorf (German Textile and Fiber Research Institute) is developing these future fiber products and processes that will be suitable for the textile industry .

When it comes to biopolymers, we first need to determine what this means. Not all polymers are biodegradable, so not all polymers are biopolymers, says Dr. Frank Hermanutz, head of DITF biopolymers and wet spinning technology. “Biopolymers, like many biodegradable polyesters, don’t necessarily come from natural materials, they can also be made from petroleum, which does not change their biodegradability. We make creatures made from renewable raw materials,” he explains. Polymers are of particular interest. These natural polymers are as diverse as the products they make. In addition to the most common raw materials, wood and wood pulp, Hermanutz and his team also process chitin (chitin) and alginate fibers. Cellulose fibers are used in composites with hemp and linen.

Dr. Frank Hermanutz is the head of DITF Biopolymer and Wet Spinning Technology

Spinning environmentally friendly fibers with “green solvent”

DITF researchers have developed a special process involving “green solvents” for the production of cellulose fibers in a sustainable and environmentally friendly manner. In order to spun cellulose into fibers, the material must first be dissolved. However, since cellulose is insoluble in water, conventional methods involve the use of toxic solvents. Hermanutz and his colleagues have found an alternative, ionic liquid, which works simultaneously without producing toxic waste water. They use liquid organic salts with relatively large cations and are therefore liquid at room temperature. It dissolves the cellulose directly and can then be spun into fibers without the addition of a stabilizer. The solvent can be simply washed off with water, a process developed and established in DITF. “Ionic liquids also enable us to produce ultrafine fiber filaments that absorb large amounts of water and can be processed into medical and sanitary textiles,” adds Hermanutz.

Produces a wide range of products from cellulose IL fibers such as nonwovens and reinforced fabrics

The flagship use of DITF's innovative cellulosic fibers is the reinforcing fiber in "PURCELL", a composite made entirely of cellulose. “If we add cellulose fibers to the cellulose matrix, we get a composite with excellent fiber matrix adhesion. This is because both the fiber and the matrix are made of the same material,” says Hermanutz, PURCELL. A composite material that can be used in many ways, such as in the automotive industry. “We start with moldable semi-finished products, which are plates containing a certain amount of water. When the plates are heated to 160 degrees Celsius in a hot press, the water evaporates and is molded into the desired shape,” explains Hermanutz. In terms of surface modification, PURCELL composites are even superior to glass fiber reinforced plastics. Tests conducted at the German Textile and Fiber Research Institute Denkendorf (DITF) have shown that the surface can be painted or effectively dyed, while fiber reinforced plastics are impossible. of. “Because the material is not sticky, we can remove it from the mold after pressing without the release agent,” Hermanutz added.

Natural polymers are extremely versatile and fully recyclable

When the product made from it reaches its end of life, the greatest advantage of the sustainability of the new material will become apparent, that is, the cellulose composite is fully recyclable without waste. In DITF laboratories, PURCELL-based products can be recycled up to four times and processed into new composite materials. Product performance did not deteriorate under laboratory conditions. “We have simulated aging and found that quality has not declined. However, we still need to study the performance of materials in real-world conditions after ten years and fifteen years,” Hermanutz said. The recycled material can be reused or compost-degraded, thus being reintroduced into the material circulation. But there is another interesting possibility: cellulosic materials can be mechanically crushed and processed into fish food. Hermanutz said: “This material is guaranteed to be free of micro-plastics and the fish will be consumed in the same way as traditional plant residues.”

Cellulose composite PURCELL is especially useful as a lightweight structural component inside a vehicle

In the medium and long term, new materials can help offset the growing waste issues associated with composites. Currently, only about 250,000 tons of unrecoverable glass fiber reinforced plastic waste is produced annually in Germany. Currently, glass fiber reinforced plastic waste is simply burned and the glass fiber is used as a cement additive after combustion. “For example, the blades of wind turbines are made of fiberglass reinforced plastic. The service life of more and more wind turbines is due, which means that many wind turbines can no longer operate economically, they will be demolished, and a lot of wind The turbine will be dismantled. Fiberglass reinforced plastic waste will accumulate, further exacerbating the problem of non-recyclable waste," Hermanutz said. He hopes that PURCELL and the resulting materials will provide a technically comparable and sustainable alternative to fiberglass reinforced plastics.

Although the outlook is very good, the new material (still) still has some limitations. When high-strength structural components are required, pure cellulosic materials are not suitable, for example for the production of bodywork, "this is why we have developed a hybrid material with a carbon content of 30%. This has the required strength and stiffness. "Hermanutz. However, not all possible products require maximum strength. In this case, hemp and flax can be used as raw materials for composite materials. Cannabis and flax plants naturally have fibers of varying thickness and length. This is why hemp and linen cannot be used to produce high-strength products. However, this material can be pressed into a quality mat, for example, as a rear seat. But not all, in principle, any cellulose fiber has this potential.