Tag Archives: #plastic

Researchers Create Eco-friendly Plastic From Cellulose And Water (Material Science)

Göttingen University researchers create new kind of environmentally friendly bioplastic with hydroplastic polymers

Plastics offer many benefits to society and are widely used in our daily life: they are lightweight, cheap and adaptable. However, the production, processing and disposal of plastics are simply not sustainable, and pose a major global threat to the environment and human health. Eco-friendly processing of reusable and recyclable plastics derived from plant-based raw materials would be an ideal solution. So far, the technological challenges have proved too great. However, researchers at the University of Göttingen have now found a sustainable method – “hydrosetting”, which uses water at normal conditions – to process and reshape a new type of hydroplastic polymer called cellulose cinnamate (CCi). The research was published in Nature Sustainability.

Plastics are polymers, meaning that their molecular structure is built up from a large number of similar units bonded together. Currently, most plastics are manufactured using petrochemicals as raw materials, which is damaging to our environment to both extract and dispose of. In contrast, cellulose, which is the main constituent of plant cell walls, is the most abundant natural polymer on earth, constituting an almost inexhaustible source of raw material. By slightly modifying a very small portion of the chemistry of cellulose by introducing a “cinnamoyl” group, the researchers succeeded in making a specific CCi that is suitable for the formation of a new type of bioplastic with hydroplastic (ie soft and mouldable on contact with water) polymers.

Bioplastics like this could be useful in many different situations, such as biology, electronics and medicine. Photo: K Zhang

This means that it can be moulded using little more than water at everyday temperature and pressure. This unique method – known as hydrosetting – enabled the researchers to produce a variety of shapes simply by immersing the bioplastic in water and leaving it to dry in the air. The moulded shapes kept their stability in the long-term and could be reshaped over and over again into a variety of 2D and 3D shapes. Although the plastic should not be used for direct contact with water – because it will lose its shape – it can hold water and be used in humid conditions. The CCi bioplastics showed high quality mechanical properties when compared with plastics that are currently widely used.

“Our research provides a feasible method to design other eco-friendly hydroplastics from renewable resources,” explains Professor Kai Zhang from the University of Göttingen. “This should open up new avenues of research, stimulating further exploration of other sustainable bioplastics with superior mechanical properties and new features.”

The hydrosetting process avoids expensive and complex machinery and harsh processing conditions. Photo: K Zhang

The hydrosetting process avoids expensive and complex machinery and harsh processing conditions. This eco-friendly method highly simplifies plastics manufacture, making their processing and recycling more economical and sustainable. “This research offers tremendous potential for bioplastics like this to be applied in many different situations, such as biology, electronics and medicine,” says Zhang before adding: “In particular, the detrimental effects of plastics on the environment, which is damaging to all forms of life on earth, would be minimized by reusing hydroplastics with their unique features.”

Featured image: The newly produced bioplastic consists of “hydroplastic polymers”, which become soft and malleable on contact with water. Photo: K Zhang


Original publication: Jiaxiu Wang, Lukas Emmerich, Jianfeng Wu, Philipp Vana and Kai Zhang, “Hydroplastic polymers as eco-friendly hydrosetting plastics” 2021, Nature Sustainability, DOI: 10.1038/s41893-021-00743-1.


Provided by University of Göttingen

Microbes In Cow Stomachs Can Break Down Plastic (Chemistry)

Bacteria found in the rumen, one of the compartments that make up the cow stomach, can break down plastics, representing an eco-friendly way to reduce litter

Plastic is notoriously hard to break down, but researchers in Austria have found that bacteria from a cow’s rumen – one of the four compartments of its stomach – can digest certain types of the ubiquitous material, representing a sustainable way to reduce plastic litter.

The scientists suspected such bacteria might be useful since cow diets already contain natural plant polyesters. “A huge microbial community lives in the rumen reticulum and is responsible for the digestion of food in the animals,” said Dr Doris Ribitsch, of the University of Natural Resources and Life Sciences in Vienna, “so we suspected that some biological activities could also be used for polyester hydrolysis,” a type of chemical reaction that results in decomposition. In other words, these microorganisms can already break down similar materials, so the study authors thought they might be able to break down plastics as well.

Ribitsch and her colleagues looked at three kinds of polyesters. One, polyethylene terephthalate, commonly known as PET, is a synthetic polymer commonly used in textiles and packaging. The other two consisted of a biodegradable plastic often used in compostable plastic bags (polybutylene adipate terephthalate, PBAT), and a biobased material (Polyethylene furanoate, PEF) made from renewable resources.

They obtained rumen liquid from a slaughterhouse in Austria to get the microorganisms they were testing. They then incubated that liquid with the three types of plastics they were testing (which were tested in both powder and film form) in order to understand how effectively the plastic would break down.

According to their results, which were recently published in Frontiers in Bioengineering and Biotechnology, all three plastics could be broken down by the microorganisms from cow stomachs, with the plastic powders breaking down quicker than plastic film. Compared to similar research that has been done on investigating single microorganisms, Ribitsch and her colleagues found that the rumen liquid was more effective, which might indicate that its microbial community could have a synergistic advantage – that the combination of enzymes, rather than any one particular enzyme, is what makes the difference.

While their work has only been done at a lab scale, Ribitsch says, “Due to the large amount of rumen that accumulates every day in slaughterhouses, upscaling would be easy to imagine.” However, she cautions that such research can be cost-prohibitive, as the lab equipment is expensive, and such studies require pre-studies to examine microorganisms.

Nevertheless, Ribitsch is looking forward to further research on the topic, saying that microbial communities have been underexplored as a potential eco-friendly resource.

The study, “Together Is Better: The Rumen Microbial Community as Biological Toolbox for Degradation of Synthetic Polyesters”, Front. Bioeng. Biotechnol., 02 July 2021 | https://doi.org/10.3389/fbioe.2021.684459


Provided by Frontiers

Turning Plastic into Foam to Combat Pollution (Physics)

RESEARCHERS DEVELOP A METHOD TO REUSE PREVIOUSLY NONRECYCLABLE PLASTIC.

Biodegradable plastics are supposed to be good for the environment. But because they are specifically made to degrade quickly, they cannot be recycled.

In Physics of Fluids, by AIP Publishing, researchers from the University of Canterbury in New Zealand have developed a method to turn biodegradable plastic knives, spoons, and forks into a foam that can be used as insulation in walls or in flotation devices.

The investigators placed the cutlery, which was previously thought to be “nonfoamable” plastic, into a chamber filled with carbon dioxide. As pressure increased, the gas dissolved into the plastic.

When they suddenly released the pressure in the chamber, the carbon dioxide expanded within the plastic, creating foaming. Author Heon Park said the process is like opening a can of soda and releasing the carbonation.

“Tweaking temperature and pressure, there is a window where we can make good foams,” said Park. “It’s not that every temperature or every pressure works. We found what temperature or what pressure is the best to make those nonfoamable plastics into foams.”

Each time plastic is recycled, it loses a bit of its strength. Foams are an ideal new material, because they are not required to be strong in many applications.

“Whenever we recycle, each time, we degrade the plastics,” said Park. “Let’s say we have a biodegradable spoon. We use it once, and we recycle it back into another spoon. It may break in your mouth.”

The ideal structure of a foam depends on its final use. Bulky foams, which have large or plentiful air pockets, are good for buoys. The researchers found, contrary to what was previously thought, lower chamber pressures led to bulky foams.

Making biodegradable plastics recyclable could alleviate some of the global pollution problem. While biodegradable material eventually breaks down in nature, it is even better for the environment if plastics can be repurposed.

Biodegradable and recyclable plastics can be used more than once but are also less of an environmental threat if they end up in oceans or landfills. The team believes this process could be implemented on a large scale.

“We can expand foaming applications to a lot of plastics, not just this plastic,” said Park.

The article “Recycling and rheology of poly(lactic acid) (PLA) to make foams using supercritical fluid” is authored by Heon E. Park, Lilian Lin, and Young Lee. The article will appear in Physics of Fluids on June 29, 2021 (DOI: 10.1063/5.0050649). After that date, it can be accessed at https://aip.scitation.org/doi/10.1063/5.0050649.

Featured image: Foam structure for various temperatures and pressures. The bulkiest foams have the largest air pockets and are good for flotation devices. CREDIT: Heon Park


Provided by AIP Publishing

Researchers Turn Wood Into Plastic (Engineering)

Plastics are one of the world’s largest polluters, taking hundreds of years to degrade in nature. A research team, led by YSE professor Yuan Yao and Liangbing Hu from the University of Maryland, has created a high-quality bioplastic from wood byproducts that they hope can solve one of the world’s most pressing environmental issues.

Efforts to shift from petrochemical plastics to renewable and biodegradable plastics have proven tricky — the production process can require toxic chemicals and is expensive, and the mechanical strength and water stability is often insufficient. But researchers have made a breakthrough, using wood byproducts, that shows promise for producing more durable and sustainable bioplastics. 

A study published in Nature Sustainability, co-authored by Yuan Yao, assistant professor of industrial ecology and sustainable systems at Yale School of the Environment (YSE), outlines the process of deconstructing the porous matrix of natural wood into a slurry. The researchers say the resulting material shows a high mechanical strength, stability when holding liquids, and UV-light resistance. It can also be recycled or safely biodegraded in the natural environment, and has a lower life-cycle environmental impact when compared with petroleum-based plastics and other biodegradable plastics. 

“There are many people who have tried to develop these kinds of polymers in plastic, but the mechanical strands are not good enough to replace the plastics we currently use, which are made mostly from fossil fuels,” says Yao. “We’ve developed a straightforward and simple manufacturing process that generates biomass-based plastics from wood, but also plastic that delivers good mechanical properties as well.”

To create the slurry mixture, the researchers used a wood powder — a processing residue usually discarded as waste in lumber mills — and deconstructed the loose, porous structure of the powder with a biodegradable and recyclable deep eutectic solvent (DES). The resulting mixture, which features nanoscale entanglement and hydrogen bonding between the regenerated lignin and cellulose micro/nanofibrils, has a high solid content and high viscosity, which can be casted and rolled without breaking.

“We’ve developed a straightforward and simple manufacturing process that generates biomass-based plastics from wood, but also plastic that delivers good mechanical properties as well.”

— Yuan Yao, assistant professor of industrial ecology and sustainable systems.

Yao then led a comprehensive life cycle assessment to test the environmental impacts of the bioplastic against commons plastics. Sheets of the bioplastic were buried in soil, fracturing after two weeks and completely degrading after three months; additionally, researchers say the bioplastic can be broken back down into the slurry by mechanical stirring, which also allows for the DES to be recovered and reused. 

“That, to me, is what really makes this plastic good: It can all be recycled or biodegraded,” says Yao. “We’ve minimized all of the materials and the waste going into nature.”

The bioplastic has numerous applications, says Liangbing Hu, a professor at the Center for Materials Innovation at the University of Maryland and co-author of the paper. It can be molded into a film that can be used in plastic bags and packaging — one of the major uses of plastic and causes of waste production. Hu also says that because the bioplastic can be molded into different shapes, it has potential for use in automobile manufacturing, as well.

One area the research team continues to investigate is the potential impact on forests if the manufacturing of this bioplastic is scaled up. While the process currently uses wood byproducts in manufacturing, the researchers say they are keenly aware that large-scale production could require usage of massive amounts of wood, which could have far-reaching implications on forests, land management, ecosystems and climate change, to name a few.

Yao says the research team has already begun working with a forest ecologist to create forest simulation models, linking the growth cycle of forests with the manufacturing process. She also sees an opportunity to collaborate with people who work in forest-related fields at YSE — an uncommon convenience.

“It’s not often an engineer can walk down the hall and talk to a forester,” says Yao.

Yao, an emerging scholar in the field of industrial ecology, joined the YSE faculty last year. Her research examines the environmental and economic impacts of emerging technologies and industrial processes., integrating interdisciplinary approaches from the fields of industrial ecology, sustainable engineering, and systems modeling to develop techniques that promote more sustainable engineering approaches and policies.


Reference: Xia, Q., Chen, C., Yao, Y. et al. A strong, biodegradable and recyclable lignocellulosic bioplastic. Nat Sustain (2021). https://www.nature.com/articles/s41893-021-00702-w https://doi.org/10.1038/s41893-021-00702-w


Provided by Yale School of Environment

TPU Chemists Convert Plastic Bottle Waste into Insecticide Sorbent (Chemistry)

Scientists of Tomsk Polytechnic University proposed a method to create a sorbent for imidacloprid insecticide removal from water. The sorbent belongs to metal-organic frameworks, a class of non-conventional materials. The TPU chemists grew such a framework right on polyethylene terephthalate (PET) used to produce regular plastic bottles. The method is quite simple and allows converting used materials into a useful product. The research findings are published in Applied Materials Today academic journal (IF: 8,352; Q1).

©TPU

Metal-organic frameworks are substances with a three-dimensional structure, where clusters or metal ions are bridged by organic ligands. The result is a porous material with the properties of both metals and organic compounds.

“Due to their porous structure and a number of other properties, metal-organic frameworks have a high potential as sorbents. We are particularly interested in the problem of insecticide sorption, which are extensively used in modern agriculture and accumulated in soil and water.

We have proposed a new method to synthesize a metal-organic framework named UiO-66 with zirconium ions. The source material is what interests us first of all,” Pavel Postnikov, the research supervisor and Associate Professor of TPU Research School of Chemistry and Applied Biomedical Sciences, says.

©TMU

The researchers experimented with imidacloprid. This is one of the most widespread insecticides used in agriculture, including against Colorado potato beetles.

“Imidacloprid accumulates in natural water bodies penetrating from soil. According to Canadian researchers, imidacloprid was detected in waters around the world at concentrations ranging from 0.001 to 320 micrograms per litre. UiO-66 is usually derived at high temperatures and pressure using commercial terephthalic acid. However, we used PET consisting of ethylene glycol with terephthalic acid. This acid is a structural material for organic linkers in frameworks and plastic bottle material already contains it,” Oleg Semyonov, one of the article authors and Junior Research Fellow at TPU Research School of Chemistry and Applied Biomedical Sciences, explains.

To create a framework, the chemists cut the plastic into small squares and partially destroyed them in an acidic solution. Then, zirconium salts were added to the solution.

“Terephthalic acid is partially released from PET forming small “anchors” on the surface of the plastic pieces while a part of the acid remains in the solution. Zirconium ions attach to the “anchors” and then, the process of self-assembly inherent to metal-organic frameworks occurs and further results in a framework formed on the plastic surface. This framework is sensitive to imidacloprid and due to its porosity and physicochemical properties, it attracts insecticide molecules removing them from water,” the researcher says.

“During the experiments, we ran the insecticide solution through the sorbent. The effective water purification took 15 grams of sorbent per 1 liter, which is a very good indicator. Besides, the sorbent may be reused several times. We reached up to five cycles during our experiments. However, we expect that the sorbent will retain its properties much longer,” the scientist says.

In the long run, in practice, this sorbent can be used in filtration systems, for instance, at agricultural enterprises.

“Our sorbent also has one more advantage. Usually, metal-organic frameworks are powder-like. They choke filters so that filtration systems should be designed considering this feature. The particles of our sorbent are larger and they do not choke a filter.

In addition, due to larger particles, the throughput of the sorbent is higher and liquids penetrate easier. According to our calculations, in this case water passage requires one hundred times less pressure as compared to powders. Ultimately, it is important for the technology development and use of this sorbent in a real technological process,” Oleg Semyonov adds.

The scientists are currently conducting experiments using other metal-organic frameworks derived from PET.

The research work is supported by the grant of the Russian Foundation for Basic Research.

References: Oleg Semyonov, Somboon Chaemchuen, Alexey Ivanov, Francis Verpoort, Zdenka Kolska, Maxim Syrtanov, Vaclav Svorcik, Mekhman S. Yusubov, Oleksiy Lyutakov, Olga Guselnikova, Pavel S. Postnikov, “Smart recycling of PET to sorbents for insecticides through in situ MOF growth”, Applied Materials Today, Volume 22, 2021, 100910, ISSN 2352-9407,
https://doi.org/10.1016/j.apmt.2020.100910.
http://www.sciencedirect.com/science/article/pii/S2352940720303589

Provided by Tomsk Polytechnic University

There Are Microplastics Near the Top of Mount Everest Too (Earth Science)

Researchers analyzing snow and stream samples from the National Geographic and Rolex Perpetual Planet Everest Expedition have found evidence of microplastic pollution on Mount Everest. While the highest concentrations of microplastics were around Base Camp where hikers and trekkers spend the most time, the team also found microplastics as high up as 8,440 meters above sea level, just below the summit. The findings appear November 20 in the journal One Earth.

This image shows a view of the National Geographic and Rolex Perpetual Planet Everest Expedition climbers’ tents, made from waterproof acrylic material, at Camp IV/South Col. In the background, climbers make their way to the summit wearing plastic-based waterproof outdoor gear. http://www.NatGeo.com/Everest. ©Mariusz Potocki/National Geographic

“Mount Everest has been described as ‘the world’s highest junkyard,'” says first author Imogen Napper (@Imogennapper), a National Geographic Explorer and scientist based at the University of Plymouth who is described by her colleagues as a “plastic detective.” “Microplastics haven’t been studied on the mountain before, but they’re generally just as persistent and typically more difficult to remove than larger items of debris.”

Microplastics–tiny particles of plastic that come from the slow breakdown of larger litter–pose a huge ecological threat because they are easily consumed by animals and are so small that they are difficult to clean up. Microplastics are common in the ocean, but are not as carefully studied on land, especially remote mountaintops.

This image shows a selection of microfibers found in snow samples from Mt. Everest Balcony (8,440 m), collected during the National Geographic and Rolex Perpetual Planet Everest Expedition, which are consistent with fibers from outdoor clothing. http://www.NatGeo.com/Everest ©Imogen Napper/National Geographic.

“I didn’t know what to expect in terms of results, but it really surprised me to find microplastics in every single snow sample I analyzed. Mount Everest is somewhere I have always considered remote and pristine. To know we are polluting near the top of the tallest mountain is a real eye-opener.”

While some members of the research team climbed the mountain collecting samples during the Everest expedition in the spring of 2019, much of the work was done in a lab many miles away, where Napper and her team analyzed the samples. “The closest I got to Mount Everest was in my lab at University of Plymouth in the UK,” Napper jokes. She wanted to determine not only whether there was plastic on the mountain, but what type of plastic was there. This is an important step in figuring out where the pollution originated.

“The samples showed significant quantities of polyester, acrylic, nylon, and polypropylene fibers,” says Napper. “Those materials are increasingly being used to make the high-performance outdoor clothing climbers use as well as tents and climbing ropes, so we highly suspect that these types of items are the major source of pollution rather than things like food and drink containers.”

While this study clearly demonstrated the presence of microplastics on Mount Everest, the best way to clean this pollution remains to be seen.

“Currently, environmental efforts tend to focus on reducing, reusing, and recycling larger items of waste. This is important, but we also need to start focusing on deeper technological solutions that focus on microplastics, like changing fabric design and incorporating natural fibers instead of plastic when possible,” she says.

The researchers also hope that their work will help clarify the extent to which plastic pollution jeopardizes all environments, not just the ocean.

“These are the highest microplastics discovered so far,” says Napper. “While it sounds exciting, it means that microplastics have been discovered from the depths of the ocean all the way to the highest mountain on Earth. With microplastics so ubiquitous in our environment, it’s time to focus on informing appropriate environmental solutions. We need to protect and care for our planet.”

References: Bede F.R. Davies, Imogen E. Napper, Heather Clifford, et al., “Reaching New Heights in Plastic Pollution—Preliminary Findings of Microplastics on Mount Everest”, one Earth, VOLUME 3, ISSUE 5, P621-630, NOVEMBER 20, 2020. https://www.cell.com/one-earth/fulltext/S2590-3322(20)30550-9?utm_source=EA https://doi.org/10.1016/j.oneear.2020.10.020

Provided by Cell Press

The Highest Heat-resistant Plastic Ever Is Developed From Biomass (Material Science)

The use of biomass-derived plastics is one of the prime concerns to establish a sustainable society, which is incorporated as one of the Sustainable Development Goals. However, the use of most of the biomass-derived plastics is limited due to their low heat resistance. Collaborative research between JAIST and U-Tokyo has successfully developed the white-biotechnological conversion from cellulosic biomass into the aromatic polymers having the highest thermodegradation of all the plastics reported ever.

Development strategy for cellulose-derived PBI and PBI/PA film having ultra-high thermoresistance and frame retardance. ©JAIST

Developing novel energy-efficient materials using biomass is frontiers to establish a sustainable environment. Plastics lightweight in nature produced from renewable biomass are prerequisites for developing a circular economy. However, currently available bioplastics are mostly aliphatic (e.g.; PLA, PHA, PA11, etc.) and thus consists of poor thermostability, which restricts their further applications. Aromatic backbone-based polymers are widely considered for their high heat-resistance (e.g; Zylon®, Celazole®, Kapton®, etc.) but developing aromatic heterocyclic monomers from biomass are rare due to difficulty in controlling their structure.

Two specific aromatic molecules, 3-amino-4-hydroxybenzoic acid (AHBA) and 4-aminobenzoic acid (ABA) were produced from kraft pulp, an inedible cellulosic feedstock by Prof. Ohnishi and his research team in U-Tokyo. Recombinant microorganisms enhanced the productivity of the aromatic monomers selectively and inhibited the formation of the side products. Prof. Kaneko and his research team in JAIST have chemically converted AHBA into 3,4-diaminobenzoic acid (DABA); which was subsequently polymerized into poly(2, 5-benzimidazole) (ABPBI) via polycondensation and processed into thermoresistant film. Also, incorporating a very small amount of ABA with DABA dramatically increases the heat-resistance of the resulting copolymer and processed film attributes to the highest thermostable plastic on record (Figure 1). Density functional theory (DFT) calculations confirmed the small ABA incorporation strengthened the interchain hydrogen bonding between imidazoles although π-conjugated benzene/heterocycle repeats have been considered as the most ideal thermoresistant plastics for around 40 years.

Organic plastic superior in thermostability (over 740 °C), was developed from inedible biomass feedstocks without using heavy inorganic fillers and thus lightweight in nature. Such an innovative molecular design of ultra-high thermoresistance polymers by controlling π-conjugation can contribute to establishing a sustainable carbon negative society, and energy conservation by weight saving.

References: Nag, A., Ali, M. A., Kawaguchi, H., Saito, S., Kawasaki, Y., Miyazaki, S., Kawamoto, H., Adi, D. T. N., Yoshihara, K., Masuo, S., Katsuyama, Y., Kondo, A., Ogino, C., Takaya, N., Kaneko, T., Ohnishi, Y., Ultrahigh Thermoresistant Lightweight Bioplastics Developed from Fermentation Products of Cellulosic Feedstock. Adv. Sustainable Syst. 2020, 2000193. https://doi.org/10.1002/adsu.202000193 link: https://onlinelibrary.wiley.com/doi/10.1002/adsu.202000193

Provided by Japan Advanced Institute Of Science And Technology

Energy-Harvesting Plastics Pass The Acid Test (Material Science)

A polymer previously used to protect solar cells may find new applications in consumer electronics, reveals a KAUST team studying thin films capable of converting thermal energy into electricity.

Diego Rosas-Villalva explained that the team was surprised that such an extremely thin polymer was so effective in improving the lifetime of the device. © 2020 KAUST

When two sides of a semiconductor are at different temperatures, electron migration from hot to cool areas can generate a current. This phenomenon, known as the thermoelectric effect, typically requires semiconductors with rigid ceramic structures to maintain the heat difference between the two sides. But the recent discovery that polymers also exhibit thermoelectric behavior has prompted a rethink of how to exploit this method for improved energy harvesting, including incorporation into wearable devices.

Derya Baran and her team at KAUST are helping to engineer self-powered devices using a conducting polymer containing a blend of poly(3,4-ethylenedioxythiophene) and polystyrenesulfonate (PEDOT:PSS) chains. Relatively inexpensive and easy to process for applications, including inkjet printing, PEDOT:PSS is one of the top-performing thermoelectric polymers thanks to its ability to take in efficiency-boosting additives known as dopants.

Diego Rosas-Villalva, a researcher in Baran’s group, explains that thermoelectric PEDOT:PSS thin films are often exposed to dopants in the form of strong acids. This process washes away loose PSS chains to improve polymer crystallinity and leaves behind particles that oxidize PEDOT chains to boost electrical conductivity.

A polymer-based thin film developed at KAUST can perform thermoelectric power conversions with less chance of premature failure. © 2020 Diego Villalva

“We use nitric acid because it’s one of the best dopants for PEDOT,” says Rosas-Villalva. “However, it evaporates rather easily, and this decreases the performance of the thermoelectric over time.”

After the doping step is completed, the PEDOT:PSS film has to undergo a reverse procedure to neutralize or “dedope” some conductive particles to improve thermoelectric power generation.

Typical dedopants include short hydrocarbons containing positively charged amine groups. The KAUST researchers were studying a polymerized version of these amine chains, known as ethoxylated polyethylenimine, when they noticed a remarkable effect–PEDOT:PSS films dedoped with polyethylenimine retained twice as much thermoelectric power after one week compared with untreated specimens.

The team’s investigations revealed that polyethylenimine was effective at encapsulating PEDOT:PSS films to prevent nitric acid escape. In addition, this coating modified the electronic properties of the thermoelectric polymer to make it easier to harvest energy from sources, including body heat.

“We were not expecting that this polymer would improve the lifetime of the device, especially because it’s such a thin film–less than 5 nanometers,” says Villalva. “It’s been incorporated into other organic electronics before, but barely explored for thermoelectrics.”

References: Diego Rosas Villalva, Md Azimul Haque, Mohamad Insan Nugraha, and Derya Baran, “Enhanced Thermoelectric Performance and Lifetime in Acid-Doped PEDOT:PSS Films Via Work Function Modification”, ACS Appl. Energy Mater. 2020, 3, 9, 9126–9132, 2020 doi:
https://doi.org/10.1021/acsaem.0c01511

Provided by King Abdullah University Of Science And Technology

New Type Of Plastic Made From Reclaimed Waste (Material Science)

A new type of plastic made of reclaimed waste readily degrades in less than a year. The substance that will soon serve to manufacture and break down mainly disposable products in an ecofriendly way goes by the name of polyhydroxybutyrate. This innovative material can be produced on an industrial scale in a new process developed by the Fraunhofer Institute for Production Systems and Design Technology IPK and its partners.

Compounded and granulated polyhydroxybutyrate (PHB). © Fraunhofer IPK/Andy King

Everyday life devoid of plastics – that would be hard to imagine. They figure prominently in packaging and consumer goods, and are indispensable to industry applications such as automotive and medical engineering. Reuse and recycling of plastics from fossil resources is hardly common practice. On top of that, they degrade at a glacial pace and pollute the environment for a long time to come. The great patches of plastic waste floating on our oceans attest to their power to pollute. Plastic bottles and bags despoil beaches and, in many places, entire stretches of land.

The Fraunhofer IPK team developed this injection molding tool to replicate prototype components made of polyhydroxybutyrate. © Fraunhofer IPK/Andy King

The Bioeconomy International research initiative

The need for global recycling strategies is urgent, given plastics’ heavy use all over the world. More and more governments are resorting to bans to curb the swelling tide of plastic waste. A viable option to replace fossil-based plastics on a large scale has yet to be found. This is why the German Federal Ministry of Education and Research (BMBF) launched the “Bioökonomie International” (Bioeconomy International) research initiative in close cooperation with Fraunhofer IPK, the Department of Bioprocess Technology of the Technical University of Berlin, regional industrial partners and international research partners from Malaysia, Columbia and the USA. These researchers are developing a method of manufacturing polymers without drawing on premium resources such as mineral, palm and rapeseed oils, the production of which is very detrimental to the environment.

A new plastic much like polypropylene

This new process turn industrial leftovers such as waste fats that contain a lot of mineral residue into polyhydroxybutyrate (PHB). Microorganisms can metabolize these residues in special fermentation processes. They deposit the PHB in their cells to store energy. “Once the plastic has been dissolved from the cell, it is still not ready for industrial use, because the hardening process takes far too long,“ says Christoph Hein, head of the Microproduction Technology department at Fraunhofer IPK. The raw material has to be mixed with chemical additives downstream in post-production stages. For example, the research team adjusted the plasticizing and processing parameters to trim the recrystallization time to fit the timing of industrial processing. The resultung biopolymer’s properties resemble those of polypropylene. But unlike PP, this plastic degrades fully in six to twelve months.

In this method of producing plastic, microorganisms synthesize the entire polymer in a biotechnical process. “To this end, we convert biogenic residues such as waste fats into polyesters that can be put to technical use,” says Hein. The researcher and his team opted for microorganisms, genetically modified with molecular methods, to serve as biocatalysts. With the help of chemical purification processes and an extensively optimized material, they have been able to develop a novel family of materials that satisfy the demands of technical plastics.

No petroleum-based synthetic components needed

The new process not only dispenses with petroleum-based synthetic components altogether; it also enables green plastic alternatives. Naturally occurring microorganisms can break down these newly developed plastics, so they need not be subjected to the special conditions that serve to degrade matter in industrial composting plants. They offer an ecofriendly alternative to making and degrading single-use products and other disposable items.

The process also lends itself to producing high-quality plastic parts for certain technical applications and periods of use. The specifications for this sort of product are more demanding. They may have to exhibit specific geometric tolerances and surface qualities or be reproducible with great precision. The researchers developed highly specialized replication processes to meet these requirements.

Provided by Fraunhofer