Special Features

Interesting facts about plastics and rubber

We come across plastics and rubber everywhere in our daily lives. Discover fascinating stories, surprising facts and interesting background information – from historical developments and well-known products to key figures and innovations in the industry.

Results (423)

  • Solar cells, phone displays and lighting could be transformed by nanocrystal assembly method

    A logo of the element 'Au' assembled by EPD method with gold nanoparticles. Image: Heyou Zhang Smart phones, tablets and laptop displays, camera lenses, biosensing devices, integrated chips and solar photovoltaic cells are among the applications that could stand to benefit from an innovative method of nanocrystal assembly pioneered by Australian scientists. Nanocrystals have a wide range of existing and potential uses, but they are often made with wet chemical methods that present challenges when seeking to incorporate them effectively into devices. However, researchers from the ARC Centre of Excellence in Exciton Science have demonstrated a highly efficient and controllable method to assemble single nanoparticles directly into a pre-patterned template. They have shared the details of this technique in an article published in the journal Advanced Materials that reviews the state of the field and summarises their novel approach. By applying an electric field at a certain level of strength, a technique called electrophoretic deposition (EPD), researchers at the University of Melbourne and Australia's national science agency, CSIRO, were able to create a nearly perfect single nanocrystal array using either gold nanospheres or gold nanorods. And by tweaking the potential applied to the materials as part of this field, the researchers even discovered they were able to dictate whether the nanocrystals assemble in vertical or horizontal configurations. Heyou Zhang working in the NanoScience Laboratory at The University of Melbourne's School of Chemistry. Image: Gavan Mitchell & Michelle Gough Lead author Mr Heyou Zhang, a PhD candidate, said: "Conventional nanofabrication methods normally produce 2D nanostructures. With the ability to assemble in both vertical and horizontal directions and with spatial control of the nanoparticles on the surface, this method provides far more opportunities to build and manufacture nanoscale structures." Although the manuscript focuses on assembly of gold nanocrystals, the technique has been applied to semiconductor quantum dots, magnetic nanoparticles and organic nanoparticles. The next goal for the research is the creation of a single quantum dot "on-off" switch, which can form part of a logic gate or memory pixel for high-density information storage. However, there is already interest from industry partners in other areas too. "We can use assembled gold nanocrystals arrays as a plasmonic pixel, which is a colour display unit with high purity and colour saturation," Heyou said. "It provides very distinct colour with angle or polarization-dependent properties, which has potential as a security feature or in medical imaging." Heyou feels the approach has great potential as a universal nanomaterial assembly method. He said: "We can use these particles to build up reconfigurable metal lenses, such as the lenses on your phone. "The thickness of the lens on your phone camera is limited by optical geometries, but with this method you might be able to shrink it down to micrometre size." The Centre is looking for partners to help scale-up the novel EPD process. Senior author Professor Paul Mulvaney, Director of the ARC Centre of Excellence in Exciton Science, said: "Heyou has found a novel approach to large scale fabrication for nanomaterials. This deposition method solves a fundamental roadblock for nanotechnology and creates a viable pathway for miniaturisation of both optical and electronic devices." Reference Heyou Zhang, Calum Kinnear and Paul Mulvaney,Single‐Nanocrystal Arrays: Fabrication of Single‐Nanocrystal Arrays, Advanced Materials 18 (2020), http://dx.doi.org/10.1002/adma.202070143

    Learn more

  • Bricks made from plastic, organic waste

    The unique chemical structure of the sulfur backbone in the novel rubber allows for multiple pieces of the rubber to bond together. Image: Flinders University Revolutionary 'green' types of bricks and construction materials could be made from recycled PVC, waste plant fibres or sand with the help of a remarkable new kind of rubber polymer discovered by Australian scientists. The rubber polymer, itself made from sulfur and canola oil, can be compressed and heated with fillers to create construction materials of the future, say researchers in the Young Chemist issue of Chemistry - A European Journal. "This method could produce materials that may one day replace non-recyclable construction materials, bricks and even concrete replacement," says Flinders University organic chemist Associate Professor Justin Chalker. The powdered rubber can potentially be used as tubing, rubber coatings or bumpers, or compressed, heated then mixed with other fillers to form entirely new composites, including more sustainable building blocks, concrete replacement or insulation. Cement is a finite resource and heavily polluting in its production, with concrete production estimated to contribute more than 8% of global greenhouse gases emissions, and the construction industry worldwide accounting for about 18%. "This is also important because there are currently few methods to recycle PVC or carbon fibre," says Associate Professor Chalker and collaborator Dr Louisa Esdaile, with support from other Flinders, Deakin University and University of Western Australia researchers. The unique chemical structure of the sulfur backbone in the novel rubber allows for multiple pieces of the rubber to bond together. Image: Flinders University "This new recycling method and new composites are an important step forward in making sustainable construction materials, and the rubber material can be repeatedly ground up and recycled," says lead author Flinders PhD Nic Lundquist. "The rubber particles also can be first used to purify water and then repurposed into a rubber mat or tubing." The new manufacturing and recycling technique, labelled 'reactive compression molding,' applies to rubber material that can be compressed and stretched, but one that doesn't melt. Image: Flinders University Co-author and research collaborator Dr Louisa Esdaile says the important research looks at ways to repurpose and recycle materials, so that these materials are multi-use by design. "Such technology is important in a circular economy," says Dr Esdaile, a special contributor to this month's Young Chemist issue of Chemistry - A European Journal (ChemEurJ). The new manufacturing and recycling technique, labelled 'reactive compression molding,' applies to rubber material that can be compressed and stretched, but one that doesn't melt. The unique chemical structure of the sulfur backbone in the novel rubber allows for multiple pieces of the rubber to bond together. The project started two years ago in the Flinders University Chalker Laboratory as a third-year project by Ryan Shapter, with Flinders University PhD candidates Nicholas Lundquist and Alfrets Tikoalu and others contributing to the paper in this month's special Young Chemist issue of ChemEurJ. Reference Lundquist et al., Reactive compression molding post‐inverse vulcanization: A method to assemble, recycle, and repurpose sulfur polymers and composites, Chemistry - A European Journal (2020), https://doi.org/10.1002/chem.202001841

    Learn more

  • High hopes for new-age rubber

    This is a diagram of the new rubber polymer. Image: Flinders University Imagine a self-repairing rubber, or super-adhesive made entirely from waste materials. It sounds like science fiction, but researchers have discovered a new kind of rubber and catalyst that together can be used with low energy consumption to make flexible, repairable, sustainable objects - including car tires. The new rubber material, made from cheap and plentiful industrial waste products sulfur, canola cooking oil and dicyclopentadiene (DCPD) from petroleum refining, can be completely repaired and returned to its original strength in minutes - even at room temperature - with an amine catalyst. The new type of rubber can be seamlessly repaired if damaged and can also be recycled, says research leader Flinders University Associate Professor Justin Chalker, whose team's breakthrough findings are described in leading international journal Chemical Science. The amine catalyst used to trigger the reaction that causes the rubber to self-repair occurs within minutes in some cases and it is all done at room temperature, scientists say. "This study reveals a new concept in the repair, adhesion and recycling of sustainable rubber," says Associate Professor Chalker, adding too many plastics, rubbers and ceramics are not recyclable. Each year in Australia, the equivalent of 48 million tires (tyres) reach the end of their life, only 16% of these are domestically recycled. Around two-thirds of used tires in Australia end up in landfill, are stockpiled, illegally dumped or have an unknown fate. This represents both a waste of resources and creates health and environmental issues. Each passenger car tire contains approximately 1.5kg of steel, 0.5kg of textiles and 7 kg of rubber. - Source: Planet Ark "It is exciting to see how the underlying chemistry of these materials has such wide potential in recycling, next-generation adhesives, and additive manufacturing." Researchers from the Chalker Lab at the Flinders University Institute for Nanoscale Science and Technology, with University of Liverpool and University of Western Australia colleagues, say the new rubber can be used as a "latent adhesive". "The rubber bonds to itself when the amine catalyst is applied to the surface. The adhesion is stronger than many commercial glues", says University of Liverpool researcher Dr Tom Hasell. "The polymer is also resistant to water and corrosion." Rubber bricks made out of this polymer can be chemically joined by applying the catalyst. "In some cases, the amine catalyst causes the rubber to bond in just minutes, and it can be done at room temperature", explains Flinders University lead author Sam Tonkin. "The rubber can also be used as a latent adhesive, where it bonds to the surface of another piece of rubber when the amine catalyst is applied. "Basically the rubber is not 'sticky' until the catalyst is applied." In addition to the highly useful practical applications, the new paper gives detailed fundamental studies on the mechanisms of the rubber repair. Reference Tonkin et al., Chemically induced repair, adhesion, and recycling of polymers made by inverse vulcanization, Chemical Science (2020), https://doi.org/10.1039/D0SC00855A

    Learn more

  • Team of Canadian and Italian researchers breaking new ground in materials science

    A study by a team of researchers from Canada and Italy recently published in Nature Materials could usher in a revolutionary development in materials science, leading to big changes in the way companies create modern electronics. The goal was to develop two-dimensional materials, which are a single atomic layer thick, with added functionality to extend the revolutionary developments in materials science that started with the discovery of graphene in 2004. In total, 19 authors worked on this paper from INRS, McGill, Lakehead, and Consiglio Nazionale delle Ricerche, the national research council in Italy. This work opens exciting new directions, both theoretical and experimental. The integration of this system into a device (e.g. transistors) may lead to outstanding performances. In addition, these results will foster more studies on a wide range of two-dimensional conjugated polymers with different lattice symmetries, thereby gaining further insights into the structure vs. properties of these systems. The Italian/Canadian team demonstrated the synthesis of large-scale two-dimensional conjugated polymers, also thoroughly characterizing their electronic properties. They achieved success by combining the complementary expertise of organic chemists and surface scientists. "This work represents an exciting development in the realization of functional two-dimensional materials beyond graphene," said Mark Gallagher, a Physics professor at Lakehead University. "I found it particularly rewarding to participate in this collaboration, which allowed us to combine our expertise in organic chemistry, condensed matter physics, and materials science to achieve our goals." Dmytro Perepichka, a professor and chair of Chemistry at McGill University, said they have been working on this research for a long time. "Structurally reconfigurable two-dimensional conjugated polymers can give a new breadth to applications of two-dimensional materials in electronics," Perepichka said. "We started dreaming of them more than 15 years ago. It's only through this four-way collaboration, across the country and between the continents, that this dream has become the reality." Federico Rosei, a professor at the Énergie Matériaux Télécommunications Research Centre of the Institut National de la Recherche Scientifique (INRS) in Varennes who holds the Canada Research Chair in Nanostructured Materials since 2016, said they are excited about the results of this collaboration. "These results provide new insights into mechanisms of surface reactions at a fundamental level and simultaneously yield a novel material with outstanding properties, whose existence had only been predicted theoretically until now," he said. Reference Galeotti et al., Synthesis of mesoscale ordered two-dimensional π-conjugated polymers with semiconducting properties, Nature Materials (2020), http://dx.doi.org/10.1038/s41563-020-0682-z

    Learn more

  • Stretch and flow: Research sheds light on unusual properties of well-known materials

    These are the results of the simulations matched the results of the experiments. Image: University of Patras Researchers from the Okinawa Institute of Science and Technology Graduate University and the University of Patras have taken a close look at the flow of materials that have both liquid-like and solid-like states, such as toothpaste, mayonnaise, and ketchup, using both simulations and experiments. Toothpaste, face creams, hair gel, mayonnaise, and ketchup are household items that most people don't think twice about but, in terms of their flow behavior, they have unusual properties. They're all elasto-visco-plastic (EVP) materials, which behave like solids when at rest but can yield to flow like liquids when placed under enough stress. Despite how common these materials are, our ability to model and predict their behavior relies on a theory that has only been shown to work under certain conditions. Scientists from the Micro/Bio/Nanofluidics Unit at the Okinawa Institute of Science and Technology Graduate University (OIST) and the Laboratory of Fluid Mechanics and Rheology at the University of Patras have revealed insights about these materials by combining experiments with simulations. Their research, published in PNAS, suggests that the materials' elasticity in its solid-like state is a key property that should be included in future models. "Over the last decade, advances in microfluidics experiments have revealed many unexpected phenomena in the flow of EVP materials," said Professor John Tsamopoulos, from the University of Patras. "Examples include the cusped shapes of bubbles in the gels and the loss of symmetry in the flow. These, and other observations, hinted that something was missing from the existing theory. Previous research in our lab suggested that elasticity, the ability of the material's microstructure to deform before yielding, was the missing part of the puzzle." The extensional flow was generated in the outbound channel. Image: OIST Professor Amy Shen, who leads the OIST Unit, emphasized the importance of this research. "Even when basic household items are set aside, having a fundamental understanding of how EVP materials flow is very useful, especially in biomedical science and geophysics." For example, she explained, blood is an EVP material - it behaves like a solid at rest but flows like a liquid in arteries. What's more, she added, some 3D-printed tissues and scaffolds can have EVP properties, and, on the geophysics side, volcanic lava behaves like an EVP material albeit on a much larger scale. Previous experimental research on EVP materials has measured their behavior under shear flow, obtained when layers of fluid slide past each other. But, when it comes to the industrial processing and uses of these materials, such as fiber-spinning and circuit-board printing, it's often the extensional flow - when the fluid is stretched - that's more important. The study of purely extensional flows is a great challenge in experimental fluid dynamics, and the extensional flow of EVP materials has never previously been successfully measured in experiments. To achieve this for the first time, Dr. Simon Haward, the group leader from the Micro/Bio/Nanofluidics Unit, used a novel microfluidic apparatus known as a cross-slot geometry. The apparatus comprised four channels that were all at right angles to each other. "Inside the cross-slot geometry, we used a Pluronic solution, a well-known EVP material," said Dr. Haward. "When we put pressure on the two inbound channels, which were located opposite to each other, the solution was pushed towards the center point and it came out of the other two channels. The resulting flow has a point at the center where the velocity goes to zero. In the two outbound channels, we generated an extensional flow where the fluid was stretched." Dr. Simon Haward holds up the apparatus for measuring the extensional flow of EVP materials. Image: OIST Meanwhile, Professor Yannis Dimakopoulos and researchers at the University of Patras created a theoretical model and simulated the flow of two EVP materials - the Pluronic solution and another material called Carbopol. They showed that complex patterns arose in the flow, which included the presence of solidified regions surrounded by the liquid-state. Their findings matched the experiments performed at OIST. "This model can describe simple EVP materials in shear, extensional and mixed flows. Although we only focused on two materials, it could be used on a wide variety with varying levels of elasticity, plasticity, viscosity, and other properties," said Stelios Varchanis, a Ph.D. candidate at the University of Patras and first author of the paper. "This makes the model appropriate for simulating flows during the design and optimization of various industrial processes." This research suggests that the existing theory needs to be overhauled to include the elasticity of the material. "Depending on the amount of deformation that the EVP material can sustain before yielding, it will either behave in a way close to what is predicted by the existing theory or will behave more like a flowing elastic-solid," said Stelios. "The experiments at OIST complimented the simulations," said Dr. Cameron Hopkins, from the OIST Micro/Bio/Nanofluidics Unit. "Even though the Pluronic solution that we studied only exhibits weak elastic effects, a small amount of asymmetry was observed in the flow indicating a deviation from purely fluid-like behavior, so the elasticity cannot be neglected. Our experiments provided strong support for the proposed modification of the theory." This research also involved Dr. Alexandros Syrakos from the University of Patras. Reference Varchanis et al., Transition between solid and liquid state of yield-stress fluids under purely extensional deformations, PNAS (2020), http://dx.doi.org/10.1073/pnas.1922242117

    Learn more

  • Next-generation solar cells pass strict international tests

    Australian scientists have for the first time produced a new generation of experimental solar energy cells that pass strict International Electrotechnical Commission testing standards for heat and humidity. The research findings, an important step towards commercial viability of perovskite solar cells, are published today in the journal Science. Solar energy systems are now widespread in both industry and domestic housing. Most current systems rely on silicon to convert sunlight into useful energy. However, the energy conversion rate of silicon in solar panels is close to reaching its natural limits. So, scientists have been exploring new materials that can be stacked on top of silicon in order to improve energy conversion rates. One of the most promising materials to date is a metal halide perovskite, which may even outperform silicon on its own. "Perovskites are a really promising prospect for solar energy systems," said Professor Anita Ho-Baillie, the inaugural John Hooke Chair of Nanoscience at the University of Sydney. "They are a very inexpensive, 500 times thinner than silicon and are therefore flexible and ultra-lightweight. They also have tremendous energy enabling properties and high solar conversion rates." In experimental form, the past 10 years has seen the performance of perovskites cells improve from low levels to being able to convert 25.2 percent of energy from the Sun into electricity, comparable to silicon-cell conversion rates, which took 40 years to achieve. However, unprotected perovskite cells do not have the durability of silicon-based cells, so they are not yet commercially viable. "Perovskite cells will need to stack up against the current commercial standards. That's what is so exciting about our research. We have shown that we can drastically improve their thermal stability," Professor Ho-Baillie said. The scientists did this by suppressing the decomposition of the perovskite cells using a simple, low-cost polymer-glass blanket. The work was led by Professor Ho-Baillie who joined the University of Sydney Nano Institute this. Lead author Dr Lei Shi conducted the experimental work in Ho-Baillie's research group in the School of Photovoltaic and Renewable Energy Engineering at the University of New South Wales, where Professor Ho-Baillie remains an adjunct professor. Under continual exposure to the Sun and other elements, solar panels experience extremes of heat and humidity. Experiments have shown that under such stress, unprotected perovskite cells become unstable, releasing gas from within their structures. "Understanding this process, called 'outgassing', is a central part of our work to develop this technology and to improve its durability," Professor Ho-Baillie said. "I have always been interested in exploring how perovskite solar cells could be incorporated into thermal insulated windows, such as vacuum glazing. So, we need to know the outgassing properties of these materials." Low-cost solution Professor Anita Ho-Baillie is the inaugural John Hooke Chair of Nanoscience at the University of Sydney Nano Institute. Image: UNSW For the first time, the research team used gas chromatography-mass spectrometry (GC-MS) to identify the signature volatile products and decomposition pathways of the thermally stressed hybrid perovskites commonly used in high-performance cells. Using this method, they found that a low-cost polymer-glass stack with a pressure-tight seal was effective in suppressing the perovskite 'outgassing', the process that leads to its decomposition. When put to strict international testing standards, the cells the team was working on outperformed expectations. "Another exciting outcome of our research is that we are able to stabilise perovskite cells under the harsh International Electrotechnical Commission standard environmental testing conditions. Not only did the cells pass the thermal cycling tests, they exceeded the demanding requirements of damp-heat and humidity-freeze tests as well," Professor Ho-Baillie said. These tests help determine if solar cell modules can withstand the effects of outdoor operating conditions by exposing them to repeated temperature cycling between -40 degrees and 85 degrees, as well as exposure to 85 percent relative humidity. Specifically, the perovskite solar cells survived more than 1800 hours of the IEC "Damp Heat" test and 75 cycles of "Humidity Freeze" test, exceeding the requirement of IEC61215:2016 standard for the first time. "We expect this work will contribute to advances for stabilising perovskite solar cells, increasing their commercialisation prospects," Professor Ho-Baillie said. Reference Shi et al., Gas chromatography–mass spectrometry analyses of encapsulated stable perovskite solar cells, Science 21 (2020), http://dx.doi.org/10.1126/science.aba2412

    Learn more

  • Plastic: lifeline for transporting water

    Topic of the Month Elimination of doubts about the suitability of epoxy resin in pipe and water storage systems By Guido Deussing Source: istock / Mumemories What would a town be like if it had no electricity? Dark at night, but still populated. A town without a water supply, on the other hand, would be a desolate, deserted place. The first people who left a life of hunting and collecting behind them made sure that there was a river near their settlement. They were quick to learn how to transport water over long distances – above ground, initially, then mainly underground later on and concealed in buildings. The problem here: mending leaks means, first of all, exposing hidden pipes on a large scale, so that the damaged section can be found and repaired. The CIPP (cured-in-place pipe) principle is an attractive alternative. What is involved here is simply the coating of entire sections of pipe with plastic or, more precisely, epoxy resin from the inside. The process is effective but not without its critics. For no good reason? Let us take a look at the details. The more people live in one place and the greater the level of urbanisation, the more important a sound water supply is. What is meant here is not merely general availability, i.e. the availability of sufficient quantities of high-quality water that does not represent a health risk. What is also meant is the installation of an intact storage and piping system, in order to be able to transport fresh water to the place where it is needed free of undesirable pollutants and odorants and to take waste water away again without any leakage loss. In the Roman Empire, aqueducts were a common sight both in towns and out in the country; some of these extremely impressive structures still exist today and testify to the architectural skills of the era in which they were built. Nowadays, most water pipes are installed underground and, in houses, concealed underneath plaster. When corrosion and leakage occur due to wear and tear, which can always be expected after a certain amount of time in systems that transport liquids, repairs are essential, in order to limit liquid loss as well as the extent of collateral damage. While it is comparatively easy to carry out maintenance work on pipe systems that are above ground, laborious excavation work can be expected if water pipes under streets or in-house walls have to be reached. The amount of work and expense needed can, however, be reduced if complete sections of piping are repaired rather than – quite literally – plugging individual holes, with the help of liner technology (relining) that does not require complex construction work. In this process, a liner impregnated with epoxy resin made, for example, of felt is pulled into the entire length of the corroded pipe. Experts are of the opinion that this CIPP principle is just as reliable as a completely new water pipe where imperviousness and load-bearing capacity are concerned, as soon as the epoxy resin has cured completely. Pipes can also be coated directly with epoxy resin, which is only advisable inside houses, however, due to the lack of additional stabilisation by an appropriate liner. More than just an attractive repair material Pont du Gard is an old Roman aqueduct near Nimes in Southern France. Source: istock / Bertl123 Let us take a look at epoxy resins, without getting too chemical about them: epoxy resins are synthetic resins that are used primarily as coating material due to their properties. Synthetic resins generally consist mainly of two free-flowing or viscous components that react with each other in different ways, become increasingly viscous in the course of time or under certain conditions and finally cure to become a thermosetting polymer. Chemically speaking, most epoxy resins in commercial use are manufactured by means of a reaction between a compound with a hydroxy group (R-OH) [this is the functional group of alcohols and phenols] and epichlorohydrin [a colourless liquid that smells like chloroform]. Epoxy resin was invented by the German chemist and inventor Paul Schlack, who obtained a German patent for it in 1939. The special feature of epoxy resins is: once they have cured, thermosetting polymers have good mechanical properties as well as high temperature and chemical resistance levels, so that they are considered to be high-quality plastics. They are used for such products as reaction varnishes, stove enamels, adhesives, laminates, mounting agents in metallography and moulding compounds for components in electrical and electronic engineering. Focus on thermosetting polymers Getting back to thermosetting polymers: they are plastics that are hardened by curing, a process that cannot be reversed by heat or any other means. Thermosetting polymers made from synthetic resins were, incidentally, among the first plastics to be produced industrially. “Bakelite, which was discovered in 1909, is the oldest example. Originally, they could only be manufactured from their source materials (e.g. phenoplastics made from phenolic resins) in moulds and were therefore known as moulding compounds too, in contrast to thermoplastics, which were known as injection moulding compounds. It was not until the mid-1960s that processes started to be developed that made it possible to manufacture thermosetting polymers by the injection moulding process. Thermosetting polymers are processed in numerous different ways today. The emphasis here is always on their high thermomechanical strength and their low specific component weight by comparison with metal.” [11]. Figure: Markomolecular structure of various types of plastic: A. Thermosets consist of closely-meshed polymers. Networks are shown in the figure as red dots. B. Elastomers consist of wide-meshed polymers. The wide mesh allows the material to be stretched under tensile load. C. Thermoplastics consist of uncrosslinked polymers, often with a partially crystalline structure (shown in red). They have a glass transition temperature and are meltable. (Source: wikipedia) Epoxy resin as coating Without mentioning specific figures, it can be said that the price of epoxy resin coating is relatively low, while the manpower for and expense of repair projects can be kept within reasonable limits. Estimates made in July 2015 indicate that about 80,000 tonnes of epoxy resin have been used to line the inside of water pipes in Europe since 1990: 60,000 tonnes in underground pipes and 20,000 tonnes in housing [1]. Most of the commercially used epoxy monomers are produced by the reaction of a compound with acidic hydroxy groups and epichlorohydrin: First the hydroxy group reacts in a coupling reaction with epichlorohydrin, followed by dehydrohalogenation. (Source: wikipedia) The figures suggest that a success story has been written here. The use of epoxy resins in water pipes raises critical questions too, however, which relate to the material itself and/or its source materials. This is because practically all the epoxy resins used in water pipes are the product of a two-stage reaction between bisphenol A (BPA) and epichlorohydrin (ECH), as the Epoxy Resin Committee (ERC) – an alliance of national and international epoxy resin manufacturers – explains. The result of the addition and subsequent condensation reaction is a thermosetting polymer, i.e. an irreversibly hardened plastic not affected by heat that has good mechanical properties and similarly high temperature and chemical resistance levels. Epoxy resin is used not only to coat water pipes but also to line the inside of food and beverage cans. Let us take another look now at the reactants separately and the warnings that have been issued about them: BPA is considered to be a “substance of very high concern” (SVHC) that has hormone-like and reprotoxic (CMR) properties [2-5]. ECH has a comparable profile and has also turned out to be carcinogenic in animal testing [6, 7]. Within permissible limits In view of potential harm to health and the environment, environmental associations are demanding a prompt end to the coating of water pipes with epoxy resin [5]. Epoxy resin manufacturers, on the other hand, claim that their products are highly beneficial in this application while representing no risk to health at the same time. They consider the probability that DBP will be released during the useful life of the epoxy resin coating due to improper installation or maintenance to be low. It is said that the material is not a significant source of potential human contact, so that it does not as a result represent a risk to health. The concentration of the reactants released during the coating process and in the course of useful life is, in turn, said to be uncritical too. There is apparently an estimated 200 kilograms of potentially free BDA in pipes above the ground and 600 kilograms in underground pipes – insignificant amounts in relation to the total volume of the overall amount of epoxy resin used. There is therefore no question of the limit at which a health risk arises being exceeded. However, what if water is transported through a pipe system coated with epoxy resin that has been treated beforehand with chlorine dioxide (ClO 2 ), a chemical that is approved for the disinfection of drinking water? Noyon et al. [8] have made an analysis of this process. They were prompted to do this by reports in which there was talk of water disinfected in this way that was transported through pipes repaired with epoxy resin and came out of the tap in a pinkish colour and smelling musty. The scientists explain that the discolouration indicated that the epoxy resins in the coating had been degraded and depolymerised to a large extent. In this context, Noyon et al. draw attention to reports according to which ClO2 is also made responsible for the accelerated degradation of polyethylene (PE) pipes. An initial GC/MS analysis had, finally, confirmed the presence of BPA in the discoloured water, while references had strengthened the assumption that degradation had taken place. Research needs to be carried out A similar GC/MS system was use to analyse bisphenols in water. Source: GERSTEL GmbH & Co. KG In the course of an in-depth examination of the matter, Noyon et al. asked themselves how a test needed to be configured in order to be able to reliably detect or rule out possible migration of BPA from an epoxy resin coating to water storage systems and water pipes. In 2018, incidentally, the German Environment Agency (UBA) reduced the maximum migration of BPA into drinking water from materials that come into contact with drinking water to 2.5 µg/l [9]. So far, there are no legal regulations about bisphenol F, bisphenol S and further bisphenols [10]. Noyon et al. finally developed a migration test in which they brought neutral water as well as water with added chlorine and chlorine dioxide (0.25 mg/l and 0.5 mg/l) into contact with various epoxy resins that are approved for use in water, tested them on an ongoing basis for a period of several months and determined the enriched analytes via solvent-free, “green” analytical procedures. [Details of these analytical procedures can be obtained from the author [ E-mail contact, keywort: BPA]. Insight into experimental details BPA migration continues to increase after five months: Noyon et al. come to the conclusion that the period during which epoxy resins that are used in water are evaluated should be lengthened considerably. Source: Noyon et al. Noyon et al. carried out different tests with a selection of epoxy resins, in water treated with chlorine and chlorine dioxide as well as in water that was not disinfected or treated. It was replaced several times a week. Specimens were tested that had been in contact with the epoxy resins for 24 hours in each case. The scientists report that the untreated water samples had relatively low BPA concentrations close to the detection limit of 10 ng/l in the course of the overall six-month monitoring process. One of the epoxy resins examined had, however, released up to 20 ng/l of BPA on an ad hoc basis at both the beginning and the end of the six-month monitoring period. Another epoxy resin had reached a maximum migration level of 180 ng/l shortly before the end of the period, before dropping to 40 ng/l. The analysis of water specimens from a test configuration in which epoxy resins were in constant contact with chlorine and/or chlorine dioxide for a period of four months produced different results: Noyon et al. write that neither BPA nor BPF were detected; what was detected instead, however, was 2,4,6-trichlorophenol (TCP) at a concentration level that decreased over time after chlorination was discontinued. This substance is linked to a pharmaceutical taste in drinking water. At the microbiological level, 2,4,6-TCP can be converted into 2,4,6-trichloroanisole (TCA), which in turn causes organoleptic problems due to the musty taste and/or smell associated with it. What remains to be said at the end Noyon et al. report that their tests have demonstrated that the current evaluation period of a few days or weeks for epoxy resins that are used in water applications is simply too short to provide meaningful data about the migration of, for example, BPA, and about the development of organoleptically relevant compounds. The research scientists stress that the periods should be lengthened in order to obtain objective results. With respect to the application of their method to real samples, Noyon et al. come to the conclusion that 2,4,6-TCP was detected sometimes, but not BPA or BPF. In addition to this, less BPA was detected in water storage systems than in repaired pipes, which is associated with various factors, including the surface volume ratio of water storage systems, the duration of the contact between the water and the epoxy resin, which may be longer in parts of the distribution network, and the quality of the epoxy resin used. To increase certainty, an obvious solution is to increase the length of time that these materials are evaluated experimentally. The scientists say that the analytical technology available is definitely highly suitable for the detection of BPA and chlorophenols and thus for evaluating the suitability of materials for water applications too. References [1] Epoxy resin in water pipes, evaluation of potential BPA emissions, Epoxy Resin Committee, July 2015, https://epoxy-europe.eu/wp-content/uploads/2019/07/Factsheet_Epoxidharz-In-Wasserleitungen-Bewertung-Potenzieller-BPA-Emissionen_FINAL.pdf [2] European Chemicals Agency (ECHA), https://echa.europa.eu/de/hot-topics/bisphenol-a [3] Bisphenol A – chemical used on a large scale that has undesirable side effects, German Environment Agency (2010), https://www.umweltbundesamt.de/sites/default/files/medien/publikation/long/3782.pdf [4] German Institute for Risk Assessment, questions and answers about bisphenol A, https://www.bfr.bund.de/de/fragen_und_antworten_zu_bisphenol_a_in_verbrauchernahen_produkten-7195.html [5] BUND press release (with an extensive appendix of source material): bisphenol A in drinking water pipes https://www.bund.net/fileadmin/user_upload_bund/publikationen/chemie/bpa_trinkwasser_hintergrund.pdf [6] Carcinogenic, mutagenic, reprotoxic (CMR) and other problematic substances in products, German Environment Agency (2011), https://www.bmu.de/fileadmin/bmu-import/files/pdfs/allgemein/application/pdf/3707_61_300_bf.pdf [7] Römpp Encyclopaedia, epichlorohydrin, https://roempp.thieme.de/B3NAV [8] Naïke Noyon, Nora Elyasmino and Auguste Bruchet, Les Risques sanitaires et organoleptiques liés au Bisphénol A relargués par les résines époxy, GERSTEL Solutions worldwide – SBSE Special (2015) 25-28 [9] Evaluation criteria and guidelines, German Environment Agency, 12. 09. 2019, https://www.umweltbundesamt.de/themen/wasser/trinkwasser/trinkwasser-verteilen/bewertungsgrundlagen-leitlinien#einfuhrung [10] Bisphenols, Bavarian Health and Food Safety Agency (LGL), https://www.lgl.bayern.de/lebensmittel/chemie/toxische_reaktionsprodukte/bpa/index.htm [11] Lexikon von Chemie.de, section about thermosetting polymers, https://www.chemie.de/lexikon/Duroplast.html

    Learn more

  • Antiviral and Antimicrobial Additive Developed for Face Masks

    Photo: istock / metamorworks Wearing a fase mask can significantly reduce the range of viruses that are coughed up. This is the conclusion reached by scientists from the university in Edinburgh, Scotland [1,2]. Nevertheless, the mask does not protect against infection per se. An Israeli company has now developed an additive wih an antiviral effect that can be applied to the mask. The emergence of the SARS CoV-2 virus, which causes COVID-19, has brought to the forefront another beneficial aspect of plastics — antimicrobial and antiviral additives that can help protect humans. Tosaf, a member of the Ravago Group, announced that it has developed an antimicrobial, antiviral additive for polyolefin nonwoven fabrics and films. The new additive will be used in the production of disposable face masks, protective apparel, and similar medical products. While it is recommended that many people, including healthcare workers and those vulnerable to the virus, wear face masks, the coverings do not fully protect individuals. Block viral particles that do not penetrate the mask’s barrier can remain on its surface and infect individuals upon contact and disposal, explained Tosaf. Most protective masks are made of several layers, and Tosaf recommends that manufacturers apply the additive when producing the outer layer of the mask for the most cost-effective and efficient result. This will destroy viral particles that land on the outside surface of the mask, eliminating danger to its user. If the mask user is already carrying the virus, the applied additive will kill viral particles that reach the outer layer from the inside, protecting others who may come in contact or be in proximity. The Antiviral, Antimicrobials Project was led by a three-person team in Tosaf’s R&D Division, based out of the company’s plant in Alon Tavor, Israel, one of the company’s 15 production sites located throughout the world. “Tosaf is one of 35 companies among 750 applicants that were chosen by the Israel Innovation Authority and granted funds to develop solutions for the global fight against COVID-19,” said Dr. Evgeni Zelikman, Chief Innovation Scientist for Tosaf. “Our extensive knowledge and experience in product innovation accumulated over decades of developing in-house solutions for thousands of clients worldwide, puts us in a prime position to tackle this challenge. We were able to respond quickly and come up with an effective and cost-efficient solution to further protect the global population from COVID-19. The opportunity to contribute is a great honor.” Tosaf serves the packaging, medical, agriculture, automotive, building and construction, home, sporting goods, and leisure markets. (Soure: PlasticsToday) Referencen [1] Viola et al., Face Coverings, Aerosol Dispersion and Mitigation of Virus Transmission Risk, 2005.10720.pdf [2] Youtube-Video: "Do face masks stop the spread of coronavirus? Scientists at Edinburgh University investigate, Do face masks stop the spread of coronavirus? Scientists at Edinburgh University investigate - YouTube

    Learn more

  • New Army 3-D printing study shows promise for predictive maintenance

    Army researchers study the performance of 3-D-printed metal parts and how they degrade as part of ongoing research in vehicle technology. The CCDC Army Research Laboratory at Aberdeen Proving Ground, Maryland, prints metal parts from powder. Image: Dave McNally Army researchers have discovered a way to monitor the performance of 3-D printed parts, which tend to have imperfections that affect performance in ways traditionally-machined parts do not. A new study published recently in the International Journal of Advanced Manufacturing Technology showed that the Army could detect and monitor the wear and tear of 3-D printed maraging steel through sensor measurement. These types of measurements help Soldiers maintain readiness because these indicators help predict when parts will degrade or fail, and need replacement. "3-D printed parts display certain attributes, due to the manufacturing process itself, which, unchecked, may cause these parts to degrade in manners not observed in traditionally-machined parts," said Dr. Jaret C. Riddick, director of the Vehicle Technology Directorate at the U.S. Army's Combat Capabilities Development Command's Army Research Laboratory. "Because of this, it's commonly understood that the use of these parts, in current cases, is meant to be a stop-gap to fill a critical need just as we have seen with 3-D printing during the COVID-19 response." He said the laboratory's study points to scientific discovery that ensures readiness in increasingly contested environments where the immediate need for replacement parts places constraints on the time it takes to deliver them from far away. In these cases, Soldiers would opt for a stop-gap to continue the mission rather having to abort the mission. This study was led by a team of researchers from the laboratory, the National Institute of Standards and Technology, CCDC Aviation and Missile Center and Johns Hopkins University, who likened cues from the material's performance to a vehicle odometer reading that signals a need for an oil change. "The strain or eddy current sensor would supply a measurement and let you know the part needs replaced," said Dr. Todd C. Henry, a mechanical engineer at the laboratory who co-authored the study. Henry wants to develop a tool for measuring the unique performance of each 3-D printed part acknowledging that each is different via sensor measurement. "If I took a batch of paper clips and started bending them back and forth they'll break from fatigue damage at different intervals depending on the internal imperfections associated with the steel," Henry said. "Every real-world material and structure has imperfections that make it unique in terms of performance so if the batch of paper clips take 21-30 cycles to break, what we would do today is after 15 cycles throw the batch of paperclips away to be safe." He said the imperfections in 3-D printed parts are typically attributed to voids and geometric variance between the computer model and the print. Sensor technology he's developing offers a way to track individual parts, predict failure points and replace them a few cycles before they break. "In order to create a high trust situation, you take little risk such as throwing the paper clip away after 15 cycles even though the lowest lifetime in your test batch was 21. If you try and take more risk and put the throw away limit at 22 cycles then the paperclip may break on someone sometime but you will save money." The research team conducted an experimental validation set for assessing the real-time fatigue behavior of metallic additively manufactured maraging steel structures. Army researchers are applying these findings to new studies to 3-D-printing of stainless steel parts and using machine-learning techniques, instead of sensors, to characterize the life of parts, Henry said. "With 3-D printing, you might not be able to replace a part with the exact same material," he said. "There is a cost and time benefit with 3-D printing that perhaps warrants using it anyway. Imagine a situation where you always chose the strongest material but there was another material that was cheaper and easier to get however you need to prove that this other material can be depended on." This study is as much about understanding the specific performance of a 3-D-printed material as it is about understanding our ability to monitor and detect performance and 3-D-printed material degradation, Henry said. Reference Henry et al., In situ fatigue monitoring investigation of additively manufactured maraging steel, The International Journal of Advanced Manufacturing Technology 107 (2020) 3499–3510, http://dx.doi.org/10.1007/s00170-020-05255-4

    Learn more

  • Better drinking water thanks to plastics

    Around 2.2 billion people do not have access to clean drinking water, although two thirds of the earth is covered with water. However, more than 97 percent of it is inedible salt water. So drinking water is a very rare commodity on earth. However, drinking water can be obtained from salt water. Polymers can help. Researchers in the College of Science have developed a material that is up to 40 times faster in desalinating small batches of water than other materials available today. Guoliang "Greg" Liu, an assistant professor in the Department of Chemistry, has been researching the design and synthesis of porous carbon fibers for the last several years. The material is composed of long, fibrous strands of carbon with uniform mesopores of approximately 10 nanometers. Liu sees the primary application of his porous carbon fibers in the automotive industry, where similar, but less efficient, materials are already used as the external shells of some luxury cars. Now, Liu reports a new application for this wonder material: capacitive desalination. "Because of the high surface area of the porous carbon fibers, we can store a lot of ions," said Liu, who is also an affiliated faculty member of the Macromolecules Innovation Institute. "Because of the interconnected porous network, the ion movement is very fast inside the pores." The most well-known method of desalination is reverse osmosis, in which seawater is forced through a semi-permeable membrane to separate salts from water. Liu said the materials and process in reverse osmosis are relatively mature now, and this energy-intensive process is efficient at treating large quantities of water. Capacitive desalination using porous carbon fibers, on the other hand, requires much less energy for treating water with low salinity. "The advantage of our process is that we can have much faster, much higher capacity, and more energy efficiency at this concentration range," Liu said. "Under our experimental conditions of around 500 milligrams (of salt) per liter, it's going to be way more expensive if you use other means because you're trying to get a little bit of salt out of the water." Tianyu Liu, a postdoctoral research associate in the Liu Lab, served as the first author in an article detailing this work published in Science Advances. He said the process was simple: he placed two pieces of porous carbon fibers into a saline solution, and then he applied a voltage through the fibers. This applied voltage created an electrostatic force that naturally attracted the salt ions out of the water. "Capacitive desalination treats the water using electrodes with high surface areas and electrical conductivity," Tianyu Liu said. "The potential you apply reduces the ion concentration in water, and then you discharge the ions to regenerate the electrodes. These processes are repeatable with negligible loss of desalination capacity." Tianyu Liu notes that while this material has shown great results, the research team has only shown a proof of concept for desalination. They are looking for engineering laboratories on campus and across the country to help scale up this research and design large-scale desalination cells. This work is conducted in collaboration with Prof. Zhen "Jason" He, a former faculty member of the Department of Civil and Environmental Engineering at Virginia Tech, and now a faculty member at McKelvey School of Engineering at Washington University in St. Louis. Greg Liu's porous carbon fibers are promising for end applications as diverse as batteries, cars, and desalination, and he's looking to see what else it can do. "We hit the jackpot," Greg Liu said. "We want to explore all of the advantages of this material. This material has many great properties, and there are so many things we can do." Reference Liu et al., Exceptional capacitive deionization rate and capacity by block copolymer–based porous carbon fibers, Science Advances 6 (2020), http://dx.doi.org/10.1126/sciadv.aaz0906

    Learn more

  • Wide bandgap semiconductor devices based on silicon carbide may revolutionize electronics

    Cubic silicon carbide. Image: Giuseppe Fisicaro Silicon plays a central role within the semiconductor industry for microelectronic and nanoelectronic devices, and silicon wafers of high purity single-crystalline material can be obtained via a combination of liquid growth methods. In Applied Physics Reviews, researchers describe the atomic mechanisms governing extended defect kinetics in cubic silicon carbide, which has a diamondlike zincblende crystal structure that manifests stacking and anti-phase instabilities. The study pinpoints the atomistic mechanisms responsible for extended defect generation and evolution. Growth of high-quality substrates for microelectronic applications is one of the key elements helping drive society toward a more sustainable green economy. Today, silicon plays a central role within the semiconductor industry for microelectronic and nanoelectronic devices. Silicon wafers of high purity (99.0% or higher) single-crystalline material can be obtained via a combination of liquid growth methods, such as pulling a seed crystal from the melt and by subsequent epitaxy. The catch is that the former process can't be used for the growth of silicon carbide (SiC), because it lacks a melting phase. In the journal Applied Physics Reviews, from AIP Publishing, Giuseppe Fisicaro and an international team of researchers, led by Antonio La Magna, describe a theoretical and experimental study of the atomic mechanisms governing extended defect kinetics in cubic SiC (3C-SiC), which has a diamondlike zincblende (ZnS) crystal structure that manifests both stacking and anti-phase instabilities. "Development of a technological framework for the control of crystalline imperfections within SiC for wide bandgap applications can be a game-changing strategy," said Fisicaro. The researchers' study pinpoints the atomistic mechanisms responsible for extended defect generation and evolution. "Anti-phase boundaries -- planar crystallographic defects representing the contact boundary between two crystal regions with switched bonds (C-Si instead of Si-C) -- are a critical source of other extended defects in a plethora of configurations," he said. Eventual reduction of these anti-phase boundaries "is particularly important to achieve good-quality crystals that can be used in electronic devices and enable viable commercial yields," said Fisicaro. So they developed an innovative simulation Monte Carlo code based on a superlattice, which is a spatial lattice that contains both the perfect SiC crystal and all crystal imperfections. It helped "shed light on the various mechanisms of defect-defect interactions and their impact on the electronic properties of this material," he said. Emerging wide bandgap semiconductor devices, such as the ones built with SiC, are significant because they have the potential to revolutionize the power electronics industry. They are capable of faster switching speeds, lower losses and higher blocking voltages, which are superior to those of standard silicon-based devices. Huge environmental benefits are also involved. "If the world's silicon power devices used within this range with were replaced by 3C-SiC devices, a reduction of 1.2x10^10 kilowatts per year could be obtained," Fisicaro said. "This corresponds to a reduction of 6 million tons of carbon dioxide emissions," he said. The researchers concluded that the low cost of the 3C-SiC hetero-epitaxial approach and the scalability of this process to 300-millimeter wafers and beyond make this technology extremely competitive for motor drives of electric or hybrid vehicles, air conditioning systems, refrigerators, and light-emitting diode lighting systems. Reference Fisicaro et al., Genesis and evolution of extended defects: The role of evolving interface instabilities in cubic SiC, Applied Physics Reviews 7 (2020), http://dx.doi.org/10.1063/1.5132300

    Learn more

  • A leap in using silicon for battery anodes

    Scientists have come up with a novel way to use silicon as an energy storage ingredient. They've developed a nanostructure incorporating carbon nanotubes to strengthen the material and modify the way silicon interacts with lithium, a key component in batteries used in electric cars and other devices. The same material you'll find at the tip of a pencil - graphite - has long been a key component in today's lithium-ion batteries. As our reliance on these batteries increases, however, graphite-based electrodes are due for an upgrade. For that, scientists are looking to the element at the heart of the digital revolution: silicon. Scientists at the U.S. Department of Energy's Pacific Northwest National Laboratory have come up with a novel way to use this promising but problematic energy storage ingredient. Silicon, used in computer chips and many other products, is appealing because it can hold 10 times the electrical charge per gram compared to graphite. The trouble is, silicon expands greatly when it encounters lithium, and it is too weak to withstand the pressure of electrode manufacturing. To tackle these issues, a team led by PNNL researchers Ji-Guang (Jason) Zhang and Xiaolin Li developed a unique nanostructure that limits silicon's expansion while fortifying it with carbon. Their work, which was recently published in the journal Nature Communications, could inform new electrode material designs for other types of batteries and eventually help increase the energy capacity of the lithium-ion batteries in electric cars, electronic devices, and other equipment. Image: Silicon microspheres have extraordinary mechanical strength due to the addition of carbon nanotubes which make the spheres resemble balls of yarn. In this representation, the image on the left illustrates a close-up of a portion of a microsphere made of silicon nano particles deposited on carbon nanotubes. (Illustration by Michael Perkins/PNNL) Taking the cons out of silicon A conductive and stable form of carbon, graphite is well suited to packing lithium ions into a battery's anode as it charges. Silicon can take on more lithium than graphite, but it tends to balloon about 300 percent in volume, causing the anode to break apart. The researchers created a porous form of silicon by aggregating small silicon particles into microspheres about 8 micrometers in diameter--roughly the size of one red blood cell. "A solid material like stone, for example, will break if it expands too much in volume," Zhang said. "What we created is more sponge-like, where there is space inside to absorb the expansion." The electrode with porous silicon structure exhibits a change in thickness of less than 20 percent while accommodating twice the charge of a typical graphite anode, the study found. However, unlike previous versions of porous silicon, the microspheres also exhibited extraordinary mechanical strength, thanks to carbon nanotubes that make the spheres resemble balls of yarn. Super-strong microspheres The researchers created the structure in several steps, starting by coating the carbon nanotubes with silicon oxide. Next, the nanotubes were put into an emulsion of oil and water. Then they were heated to boiling. "The coated carbon nanotubes condense into spheres when the water evaporates," said Li. "Then we used aluminum and higher heat to convert the silicon oxide into silicon, followed by immersion in water and acid to remove by-products." What emerges from the process is a powder composed of the tiny silicon particles on the surface of carbon nanotubes. The porous silicon spheres' strength was tested using the probe of an atomic force microscope. The authors found that one of the nanosized yarn balls "may yield slightly and lose some porosity under very high compressing force, but it will not break." This augurs well for commercialization, because anode materials must be able to handle high compression in rollers during manufacturing. The next step, Zhang said, is to develop more scalable and economical methods for making the silicon microspheres so that they can one day make their way into the next generation of high-performance lithium-ion batteries. Reference Jia et al., Hierarchical porous silicon structures with extraordinary mechanical strength as high-performance lithium-ion battery anodes, Nature Communications 11 (2020), http://dx.doi.org/10.1038/s41467-020-15217-9

    Learn more