Textination Newsline

Challa Kumar has developed methods to create novel plastic-like materials using proteins and fabric.

Every year, 400 million tons of plastic waste are generated worldwide. Between 19 and 23 million tons of that plastic waste makes its way into aquatic ecosystems, and the remaining goes into the ground. An additional 92 million tons of cloth waste is generated annually.

Challa Kumar, professor emeritus of chemistry, “fed up” with the tremendous amount of toxic waste people continually pump into the environment, felt compelled to do something. As a chemist, doing something meant using his expertise to develop new, sustainable materials.

“Everyone should think about replacing fossil fuel-based materials with natural materials anywhere they can to help our civilization to survive,” Kumar says. “The house is on fire, we can’t wait. If the house is on fire and you start digging a well – that is not going to work. It’s time to start pouring water on the house.”

Kumar has developed two technologies that use proteins and cloth, respectively, to create new materials. UConn’s Technology Commercialization Services (TCS) has filed provisional patents for both technologies.

Inspired by nature’s ability to construct a diverse array of functional materials, Kumar and his team developed a method to produce continuously tunable non-toxic materials.

“Chemistry is the only thing standing in our way,” Kumar says. “If we understand protein chemistry, we can make protein materials as strong as a diamond or as soft as a feather.”

The first innovation is a process to transform naturally occurring proteins into plastic-like materials. Kumar’s student, Ankarao Kalluri ’23 Ph.D., worked on this project.

Proteins have “reactor groups” on their surfaces which can react with substances with which they come into contact. Using his knowledge of how these groups work, Kumar and his team used a chemical link to bind protein molecules together.

This process creates a dimer – a molecule composed to two proteins. From there, the dimer is joined with another dimer to create tetramer, and so on until it becomes a large 3D molecule. This 3D aspect of the technology is unique, since most synthetic polymers are linear chains.

This novel 3D structure allows the new polymer to behave like a plastic. Just like the proteins of which it is made, the material can stretch, change shape, and fold. Thus, the material can be tailored via chemistry for a variety of specific applications.

Unlike synthetic polymers, because Kumar’s material is made of proteins and a bio-linking chemical, it can biodegrade, just like plant and animal proteins do naturally.

“Nature degrades proteins by ripping apart the amide bonds that are in them,” Kumar says. “It has enzymes to handle that sort of chemistry. We have the same amide linkages in our materials. So, the same enzymes that work in biology should also work on this material and biodegrade it naturally.”

In the lab, the team found that the material degrades within a few days in acidic solution. Now, they are investigating what happens if they bury this material in the ground, which is the fate of many post-consumer plastics.

They have demonstrated that the protein-based material can form a variety of plastic-like products, including coffee cup lids and thin transparent films. It could also be used to make fire-resistant roof tiles, or higher-end materials like, car doors, rocket cone tips, or heart valves.

The next steps for this technology are to continue testing their mechanical properties, like strength or flexibility, as well as toxicity.

“I think we need to have social consciousness that we cannot put out materials into the environment that are toxic,” Kumar says. “We just cannot. We have to stop doing that. And we cannot use materials derived from fossil fuels either.”

Kumar’s second technology uses a similar principle, but instead of just proteins, uses proteins reinforced with natural fibers, specifically cotton.

“We are creating a lot of textile waste each year due to the fast-changing fashion industry” Kumar says. “So why not use that waste to create useful materials – convert waste to wealth.”

Just like the plastic-like protein materials (called “Proteios,” derived from original Greek words), Kumar expects composite materials made from proteins and natural fibers will biodegrade without producing toxic waste.

In the lab, Kumar’s former student, doctoral candidate Adekeye Damilola, created many objects with protein-fabric composites, which include small shoes, desks, flowers, and chairs. This material contains textile fibers which serve as the linking agent with the proteins, rather than the cross-linking chemical Kumar uses for the protein-based plastics.

The crosslinking provides the novel material with the strength to withstand the weight that would be put on something like a chair or a table. The natural affinity between fibers and proteins is why it’s so hard to get food stains out of clothing. This same attraction makes strong protein-fabric materials.

While Kumar’s team has only worked with cotton so far, they expect other fiber materials, like hemp fibers or jute, would behave similarly due to their inherent but common chemical properties with cotton.

“The protein naturally adheres to the surface of the protein,” Kumar says. “We used that understanding to say ‘Hey, if it binds so tightly to cotton, why don’t we make a material out of it.’ And it works, it works amazingly.”

With the support of TCS, Professor Kumar is currently seeking industry partners to bring these technologies to market. For more information contact Michael Invernale at michael.invernale@uconn.edu.

Manufacture, wear, wash, incinerate: This typical life cycle of garments, which pollutes the environment, is to be changed in the future – towards principles of circular economy with recycling at its core. Using an outdoor jacket made from PET bottles and recycled materials, Empa researchers have investigated whether the product actually delivers what the idea promises.

At first glance, it's a normal rain jacket: three layers of polyester, a lining on the inside, a water vapor-permeable membrane on top and water-repellent fabric on the outside, with a hood. But the zipper makes you wonder. Instead of ending at collar height, it pulls up over the forehead ... – who would pull it that far?

The explanation is given by Annette Mark from textile manufacturer BTK Europe, who contributed to this product. The zipper is intended to be an eye-catcher – and is primarily for recycling: Sewn tight with a thread that dissolves in boiling water, it is easier to remove than two fasteners. "Pull once and you're done," says the expert on textiles and recycling. The light green color is also due to recycling: The raw material, a granule made from a mixture of different but single-variety textiles, is dark green – and melting and spinning out the material for new yarns lightens it.

Circular economy within textile industry
Magnetic buttons, seams, hems: Every detail of the jacket follows the Design2Recycle approach, as it says on the Wear2wear website. Six companies from Europe's textile industry have joined forces in this consortium to promote circular economy. After all, more than 70 percent of all textiles produced worldwide end up in landfills or incinerators without being recycled.

How can circular economy be acheived in this industry? A team from Empa's Technology and Society lab took a closer look at the jacket and its environmental impact using life cycle analyses over a four-year period of use; including washing it three times. The candidates: a jacket produced without circular economy methods, the "starter version" of the jacket available since 2019 in blue – with an outer layer made of polyester derived from used PET bottles – and the green version from the subsequent recycling process, in which unavoidable material losses are replaced by new polyester.

The researchers' analyses show that the recycled products perform better – in eleven environmental risk categories, including global warming, toxicity to ecosystems and water scarcity. There are strikingly large advantages in air pollution, for example, because fewer pollutants are released without incineration, as well as in water scarcity, especially for the green jacket after the first recycling "loop," for which PET bottles are no longer used.

Other insights from the analyses: In terms of greenhouse effect, the maximum benefit is a good 30 percent. And the use of PET bottles does not bring any major ecological benefits. What is decisive, on the other hand, is the number of recycling cycles to produce new jackets: The balance improves from jacket to jacket – provided the quality of the polyester remains high enough.

In practice, this is challenging, as Mark explains: "Depending on the origin, the raw material sometimes differs significantly." If the fibers have been coated with certain additives, the nozzles of the spinning machines can become clogged. And in general, the quality decreases with the number of recycling cycles: more irregular structures of the yarn and lower strength.

Annette Mark's conclusion on the Empa analyses: "very realistic" and useful for improvements. "The cooperation was very good," she says, "full transparency and no compromises." The researchers also found the collaboration fruitful. "Open collaboration between science and industry is enormously important," says former team member Gregor Braun, who has since left Empa and now works as a consultant for sustainability. "Sustainability and circular economy can work well together."

Will the jacket become a market success? "The textile industry is in a state of upheaval. A rethinking is taking place right now that we shouldn't miss," says Annette Mark. But large corporations that are already developing similar products "have completely different options." After all, talks are underway with a sportswear manufacturer – for a fleece jacket, for which the Empa findings could also be useful.

Microplastic fibers from textiles
Textiles made of polyester are making the headlines because of the release microplastic fibers – for instance, during washing – which is sometimes considered a threat to humans and the environment. Empa experts have studied the formation and release of microplastic fibers. Their results: Fibers are released primarily at the fabric's edges. Their formation and release depends, among other things, on the type of fiber, surface treatment and the type of cutting. Compared to other textiles, significantly fewer fibers are released from laser-cut textiles during washing. Empa is conducting studies with industrial partners to further reduce the formation of these fibers during textile production. In Swiss wastewater treatment plants, however, microfibers are largely removed from wastewater and incinerated with the sludge.

• Risk analyses for nanoparticles

In order to reduce the number of animal experiments in research, alternative methods are being sought. This is a particular challenge if the safety of substances that have hardly been studied is to be ensured, for instance, the completely new class of nanomaterials. To accomplish just that, Empa researchers are now combining test tube experiments with mathematical modelling.

They are already in use in, say, cosmetics and the textile industry: Nanoparticles in sun blockers protect us from sunburn, and clothing with silver nanoparticles slows down bacterial growth. But the use of these tiny ingredients is also linked to the responsibility of being able to exclude negative effects for health and the environment. Nanoparticles belong to the still poorly characterized class of nanomaterials, which are between one and 100 nanometers in size and have a wide range of applications, for example in exhaust gas catalytic converters, wall paints, plastics and in nanomedicine. As new and unusual as nanomaterials are, it is still not clear whether or not they pose any risks to humans or the environment.

This is where risk analyses and life cycle assessments (LCA) come into play, which used to rely strongly on animal experiments when it came to determining the harmful effects of a new substance, including toxicity. Today, research is required to reduce and replace animal experiments wherever possible. Over the past 30 years, this approach has led to a substantial drop in animal testing, particularly in toxicological tests. The experience gained with conventional chemicals cannot simply be transferred to novel substances such as nanoparticles, however. Empa scientists are now developing new approaches, which should allow another substantial reduction in animal testing while at the same time enabling the safe use of nanomaterials.

"We are currently developing a new, integrative approach to analyze the risks of nanoparticles and to perform life cycle assessments," says Beatrice Salieri from Empa's Technology and Society lab in St. Gallen. One new feature, and one which differs from conventional analyses, is that, in addition to the mode of action of the substance under investigation, further data is included, such as the exposure and fate of a particle in the human body, so that a more holistic view is incorporated into the risk assessment.

These risk analyses are based on the nanoparticles' biochemical properties in order to develop suitable laboratory experiments, for example with cell cultures. To make sure the results from the test tube ("in vitro") also apply to the conditions in the human body ("in vivo"), the researchers use mathematical models ("in silico"), which, for instance, rely on the harmfulness of a reference substance. "If two substances, such as silver nanoparticles and silver ions, act in the very same way, the potential hazard of the nanoparticles can be calculated from that," says Salieri.

But for laboratory studies on nanoparticles to be conclusive, a suitable model system must first be developed for each type of nanoparticle. "Substances that are inhaled are examined in experiments with human lung cells," explains Empa researcher Peter Wick who is heading the "Particles-Biology Interactions" lab in St. Gallen. On the other hand, intestinal or liver cells are used to simulate digestion in the body.

This not only determines the damaging dose of a nanoparticle in cell culture experiments, but also includes all biochemical properties in the risk analysis, such as shape, size, transport patterns and the binding – if any – to other molecules. For example, free silver ions in a cell culture medium are about 100 times more toxic than silver nanoparticles bound to proteins. Such comprehensive laboratory analyses are incorporated into so-called kinetic models, which, instead of a snapshot of a situation in the test tube, can depict the complete process of particle action.

Finally, with the aid of complex algorithms, the expected biological phenomena can be calculated from these data. "Instead of 'mixing in' an animal experiment every now and then, we can determine the potential risks of nanoparticles on the basis of parallelisms with well-known substances, new data from lab analyses and mathematical models," says Empa researcher Mathias Rösslein. In future, this might also enable us to realistically represent the interactions between different nanoparticles in the human body as well as the characteristics of certain patient groups, such as elderly people or patients with several diseases, the scientist adds.

As a result of these novel risk analyses for nanoparticles, the researchers also hope to accelerate the development and market approval of new nanomaterials. They are already being applied in the "Safegraph" project, one of the projects in the EU's "Graphene Flagship" initiative, in which Empa is involved as a partner. Risk analyses and LCA for the new "wonder material" graphene are still scarce. Empa researchers have recently been able to demonstrate initial safety analyses of graphene and graphene related materials in fundamental in vitro studies. In this way, projects such as Safegraph can now better identify potential health risks and environmental consequences of graphene, while at the same time reducing the number of animal experiments.