Scientists Create Eco-friendly Adhesive System to Replace Harmful Glues

 A team of chemists at Purdue University led by Jonathan Wilker, professor of chemistry in the College of Science and of materials engineering, aims to develop a completely #sustainable #adhesive system.

“Our current adhesives create all sorts of environmental problems,” Wilker said. “Almost all glues are petroleum-based and do not degrade. The bonded materials in our products stay stuck together. Consequently, we cannot recycle many of the materials that we put into our recycling bins. Discarded products will sit in landfills for centuries and, sometimes, contribute to ocean microplastics.

Nature-Inspired Innovation

Wilker and his lab have spent years studying the science of sticky substances, analyzing marine animals that adhere, like mussels and oysters, and trying to create better, sustainable, affordable adhesives that work as well as any glue from the hardware store. He has a drawer of those commercial glues in his lab, which give off a strong and familiar smell.

“Those volatile petrochemicals in these glues can be toxic, which is a further problem with current technologies,Wilker said. One example is the common building material plywood, which is formed of wood pieces held together with formaldehyde-based adhesives. Newly built houses are off-gassing formaldehyde, exposing residents to this carcinogen.

Making Adhesives Safer and Stronger:

These substances are harmful both to the environment and to human health. However, people and companies are accustomed to using traditional adhesives; they’re strong, easy to produce and relatively inexpensive. Any new adhesive must work at least as well as traditional products, which is why Wilker keeps that drawer around: to test them, side by side against innovative substances.

“By studying how nature makes adhesives, we are learning how to design new technologies for our future society,” Wilker said. “Given all of the problems generated by current glues, we feel an obligation to create something better. Ideally, new adhesives will be bio-based and nontoxic. Strengths should be as high as current products. Then we would like to bond them strongly when needed and also be able to take the substrates apart when wanted. Further design constraints that we grapple with, in order to have impact, are costs needing to be low and having all starting compounds available at large scales.

After a series of experiments on a range of different biologically sourced and sustainable ingredients, the team settled on epoxidized soy oil for a main component. Epoxidized soy oil is already produced globally on a massive scale. For their work, the smallest container that they could purchase was a 55-gallon drum of the substance. Since each experiment uses just a little epoxidized soy oil, the level in their drum has dropped only a few inches after several years of testing.

Eco-Adhesives for a Sustainable Tomorrow

Wilker and his team added the epoxidized soy oil to malic acid, a compound most known for giving apples their tart flavor. Then they added tannic acid, to provide an aspect of the chemistry that mussels use for attaching themselves to rocks and each other. Tannic acid is a component of tannins, common in trees, red wine and black tea. Those three ingredients added up to an adhesive that is inexpensive, effective, scalable, practical to produce and completely sustainable.

“If you combine these components under the right conditions, adhesives can be made that are as strong as epoxies,” Wilker said. Epoxies are generally considered to be the highest performance class of adhesives. “All of the components are bio-based, safe and already available at train car scales. A bonus is that the adhesive is easy to make. Basically, you can mix and heat the components.” Other bio-based compounds can also be used with epoxidized soy oil, generating an entire family of new sustainable adhesives.

To test the adhesive’s performance, the scientists bonded together objects — wood, plastics or metals — and then used an instrument for breaking the bonds and measuring forces. In many cases, their new adhesives held up well, sometimes performing similarly to, or even better than, traditional toxic adhesives such as a superglue and an epoxy. Further research will refine the system and work to maximize societal and environmental impacts in areas ranging from medical innovations to industrial materials to packaging. Their team’s innovations may pave the way to a more sustainable system for holding the world together.

Wilker disclosed his adhesives to the Purdue Innovates Office of Technology Commercialization, which has applied for a patent to protect the intellectual property. This research was supported by the Office of Naval Research.

Source: Purdue University/specialchem

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Today's KNOWLEDGE Share:Warpage of a GF filled nylon

Today's KNOWLEDGE Share

Warpage of a GF filled nylon part is extremely dependent on temperature and moisture uptake.

Temperature increase is responsible for #matrix expansion (negligible for the fibers though), and moisture uptake produces matrix swell (again GF does not care much).So if a part is warped when dry as molded at room temperature (that is what simulation codes will predict for you !!) it will tend to "UNWARP" as you heat the part or let it uptake moisture.

This effect can perfectly be simulated, if you account properly for the anisotropic elastic properties and #fiberorientation and know the swell rate with water uptake.

For #temperature induced UNWARP you will need detailed CTE (T) in x, y and z though to get it right ! Those CTE's, with the needed level of detail, are not available directly from Flow Analysis codes for the moment, but e-Xstream engineering, part of Hexagon’s Manufacturing Intelligence division Digimat software can provide those.

Source:Vito Leo

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#polymers #plasticindustry #nylon #glassfiber #temperature #moisture

OCSiAl to Establish New Production Facility for Graphene Nanotubes in Serbia

OCSiAl has been granted a construction permit for a nanotube production facility near Belgrade, Serbia.The new nanotube synthesis plant will be launched in 2024 and will have a planned annual capacity of 120 tons per year.

Facilitate Logistics and Lower Supply Chain Costs:

In addition to synthesizing nanotubes, the facility will manufacture nanotube suspensions for lithium-ion battery manufacturers in Europe, the US, and Asia, enough to enhance the performance of more than 1 mln electric cars with an average battery capacity of 75 kWh per car.

“The project will facilitate logistics and lower supply chain costs. European-produced nanotubes and nanotube derivatives will be primarily supplied to our customers in central and western Europe, North America, and Asia,” said OCSiAl Group senior vice president Gregory Gurevich.

OCSiAl nanotubes create long and robust electrical networks between active material particles, improving key battery characteristics, including cycle life, lower DCR, C-rate performance, and cohesion between active battery material particles, making the battery electrodes more durable.

Graphene nanotubes unlock new #battery technologies, including high-#silicon content anodes, thick #LFP cathodes, fast-charging #graphite anodes, and more. They can be applied in both conventional and emerging battery tech, such as a dry battery electrode coating process, and solid-state batteries.

As well as synthesizing nanotubes and producing suspensions, OCSiAl project includes manufacturing of nanotube concentrates for high-performance polymers. The project has passed environmental impact assessment and it is 100% powered by green energy. It enjoys support from Serbian municipal and national governments. The plant is planned to be certified in accordance with ISO 9001, ISO 14001, and ISO 45001, and to be compliant with the IATF 16949 automotive industry standard. The project will create more than 200 job opportunities for engineers, scientists, managers, operators, and administrative staff.

Currently, OCSiAl has an extensive #manufacturing system of nanotube-based products in the regions of highest #marketdemand, such as China, Japan, Sri Lanka, Brazil, Malaysia, and other countries. The Serbia nanotube hub will operate in conjunction with the company’s operational R&D center and planned #graphenenanotube synthesis facility in Luxembourg together, the projects will significantly strengthen the stability of #OCSiAl’s supply chain and increase the cost-efficiency of #nanotube technologies for its customers.

Source:Source: OCSiAl/specialchem

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Today's KNOWLEDGE Share :Johann Friedrich Wilhelm Adolf von Baeyer

Today's KNOWLEDGE Share

Johann Friedrich Wilhelm Adolf von Baeyer-The Nobel Prize in 1905

The Discovery of Indigo:

In 1860,#AdolfvonBaeyer habilitated in Berlin and accepted a teaching position for organic chemistry at the Gewerbeinstitut in Berlin. In 1866, the University of Berlin, at the suggestion of A.W. Hofmann, conferred on him a senior lectureship, which, however, was unpaid. In this period however, Baeyer started his work on indigo, which soon led to the discovery of indole and to the partial synthesis of indigotin. Also in this period, Baeyer developed his theory of carbon-dioxide assimilation in formaldehyde. He was appointed chair at the University of Munich after Justus von Liebig had passed away and Baeyer was able to perform the synthesis of indigo.One year later, in 1881, the Royal Society of London awarded him the Davy Medal for his work with indigo. In 1883 Baeyer succeeded in correctly elucidating the structure of indigo. Although Baeyer patented the synthesis of indigo, it was not really economically feasible. The manufacturing costs were too high compared to the natural dye, so that this synthesis route had to be abandoned. Later, Baeyer and Viggo Beutner Drewsen developed an industrially insignificant indigo synthesis from nitrobenzaldehyde. Only in 1900 Karl Heumann developed an economical indigo synthesis.

The Synthesis of Alizarin:

Another economically important natural dye at the time was alizarin, which Baeyer’s assistants Carl Graebe and Liebermann reduced to #anthracene using zinc dust. They now developed a new #anthraquinone synthesis from anthracene with #potassiumdichromate and #sulfuricacid. By treating the anthraquinone with bromine at 100 °C and subsequent treatment with potassium hydroxide, the #alizarin could also be synthesized. Baeyer and Carl clarified the position of the hydroxy groups in alizarin. Baeyer also discovered the group of triphenylmethane dyes. To celebrate Baeyer’s 70th birthday, a collection of his scientific papers was published in 1905.

In 1905 he was awarded the #NobelPrize in #Chemistry for his services to “the development of organic chemistry and the #chemicalindustry through his work on #organicdyes and #hydroaromaticcompounds”.

Source:scihi.org

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An implantable device could enable injection-free control of diabetes

The device contains encapsulated cells that produce insulin, plus a tiny oxygen-producing factory that keeps the cells healthy.

One promising approach to treating Type 1 diabetes is implanting pancreatic islet cells that can produce insulin when needed, which can free patients from giving themselves frequent insulin injections. However, one major obstacle to this approach is that once the cells are implanted, they eventually run out of oxygen and stop producing insulin.

To overcome that hurdle, MIT engineers have designed a new implantable device that not only carries hundreds of thousands of insulin-producing islet cells, but also has its own on-board oxygen factory, which generates oxygen by splitting water vapor found in the body.

The researchers showed that when implanted into diabetic mice, this device could keep the mice’s blood glucose levels stable for at least a month. The researchers now hope to create a larger version of the device, about the size of a stick of chewing gum, that could eventually be tested in people with Type 1 diabetes.

“You can think of this as a living medical device that is made from human cells that secrete insulin, along with an electronic life support-system. We’re excited by the progress so far, and we really are optimistic that this technology could end up helping patients,” says Daniel Anderson, a professor in MIT’s Department of Chemical Engineering, a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES), and the senior author of the study.

While the researchers’ main focus is on diabetes treatment, they say that this kind of device could also be adapted to treat other diseases that require repeated delivery of therapeutic proteins.

MIT Research Scientist Siddharth Krishnan is the lead author of the paper, which appears today in the Proceedings of the National Academy of Sciences. The research team also includes several other researchers from MIT, including Robert Langer, the David H. Koch Institute Professor at MIT and a member of the Koch Institute, as well as researchers from Boston Children’s Hospital.

Replacing injections

Most patients with Type 1 diabetes have to monitor their blood glucose levels carefully and inject themselves with insulin at least once a day. However, this process doesn’t replicate the body’s natural ability to control blood glucose levels.

“The vast majority of diabetics that are insulin-dependent are injecting themselves with insulin, and doing their very best, but they do not have healthy blood sugar levels,” Anderson says. “If you look at their blood sugar levels, even for people that are very dedicated to being careful, they just can’t match what a living pancreas can do.”

A better alternative would be to transplant cells that produce insulin whenever they detect surges in the patient’s blood glucose levels. Some diabetes patients have received transplanted islet cells from human cadavers, which can achieve long-term control of diabetes; however, these patients have to take immunosuppressive drugs to prevent their body from rejecting the implanted cells.

More recently, researchers have shown similar success with islet cells derived from stem cells, but patients who receive those cells also need to take immunosuppressive drugs.

Another possibility, which could prevent the need for immunosuppressive drugs, is to encapsulate the transplanted cells within a flexible device that protects the cells from the immune system. However, finding a reliable oxygen supply for these encapsulated cells has proven challenging.

Some experimental devices, including one that has been tested in clinical trials, feature an oxygen chamber that can supply the cells, but this chamber needs to be reloaded periodically. Other researchers have developed implants that include chemical reagents that can generate oxygen, but these also run out eventually.

The MIT team took a different approach that could potentially generate oxygen indefinitely, by splitting water. This is done using a proton-exchange membrane — a technology originally deployed to generate hydrogen in fuel cells — located within the device. This membrane can split water vapor (found abundantly in the body) into hydrogen, which diffuses harmlessly away, and oxygen, which goes into a storage chamber that feeds the islet cells through a thin, oxygen-permeable membrane.

A significant advantage of this approach is that it does not require any wires or batteries. Splitting this water vapor requires a small voltage (about 2 volts), which is generated using a phenomenon known as resonant inductive coupling. A tuned magnetic coil located outside the body transmits power to a small, flexible antenna within the device, allowing for wireless power transfer. It does require an external coil, which the researchers anticipate could be worn as a patch on the patient’s skin.

Drugs on demand

After building their device, which is about the size of a U.S. quarter, the researchers tested it in diabetic mice. One group of mice received the device with the oxygen-generating, water-splitting membrane, while the other received a device that contained islet cells without any supplemental oxygen. The devices were implanted just under the skin, in mice with fully functional immune systems.

The researchers found that mice implanted with the oxygen-generating device were able to maintain normal blood glucose levels, comparable to healthy animals. However, mice that received the nonoxygenated device became hyperglycemic (with elevated blood sugar) within about two weeks.

Typically when any kind of medical device is implanted in the body, attack by the immune system leads to a buildup of scar tissue called fibrosis, which can reduce the devices’ effectiveness. This kind of scar tissue did form around the implants used in this study, but the device’s success in controlling blood glucose levels suggests that insulin was still able to diffuse out of the device, and glucose into it.

This approach could also be used to deliver cells that produce other types of therapeutic proteins that need to be given over long periods of time. In this study, the researchers showed that the device could also keep alive cells that produce erythropoietin, a protein that stimulates red blood cell production.

“We’re optimistic that it will be possible to make living medical devices that can reside in the body and produce drugs as needed,” Anderson says. “There are a variety of diseases where patients need to take proteins exogenously, sometimes very frequently. If we can replace the need for infusions every other week with a single implant that can act for a long time, I think that could really help a lot of patients.”

The researchers now plan to adapt the device for testing in larger animals and eventually humans. For human use, they hope to develop an implant that would be about the size of a stick of chewing gum. They also plan to test whether the device can remain in the body for longer periods of time.

“The materials we’ve used are inherently stable and long-lived, so I think that kind of long-term operation is within the realm of possibility, and that’s what we’re working on,” Krishnan says.

“We are very excited about these findings, which we believe could provide a whole new way of someday treating diabetes and possibly other diseases,” Langer adds.

The research was funded by JDRF, the Leona M. and Harry B. Helmsley Charitable Trust, and the National Institute of Biomedical Imaging and Bioengineering at the National Institutes of Health.

Source:MIT News

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Today's KNOWLEDGE Share:Acetals vs nylons

Today's KNOWLEDGE Share

Acetals vs nylons

Acetals – sometimes also known as polyoxymethylene (POM) – like nylons, are semi-crystalline thermoplastics, and some of their characteristics overlap, such as their fatigue resistance, chemical resistance, and wear resistance with a sharp melting point. Both are used for small components such as #washers, #discs, and #spacers.

One of the most popular properties of acetals is their ease of machining compared to various other engineering plastics, including nylon, as well as such as HDPE and UHMW. Acetals tend not to deflect away from or grab machining tools and they also chip nicely, making them ideal if an application requires the material to be machined.

There are distinct differences between nylons and acetals:

nylon offers superior tensile strength and bending stiffness

nylon can also handle higher loads and higher temperatures

nylon is susceptible to #UVradiation unless special additives are incorporated

nylon reacts poorly to changes in humidity, which cause it to swell and lose #tensilestrength

nylon is a #selflubricating material

acetal provides higher impact resistance and cold resistance

acetal is suitable for moderate loads.

acetal has much better wear resistance and #chemicalresistance

acetal has greater dimensional stability and resists moisture and humidity

acetal is shiny, while nylon appears dull in comparison

Like #nylon, #acetal comes in different formulations, though not so many, of which the main two are acetal copolymer (acetal-C) and acetal homopolymer (acetal-H).

The differences are slight: H has better mechanical properties than C, including higher strength and stiffness, better creep resistance and higher hardness rating. However, C has the better chemical properties, hydrolysis resistance, higher continuous allowable service temperature in air and less outgassing.

One of the biggest differences between C and H is centreline porosity, which is a characteristic of H but not C. Centreline porosity is caused by gasses trying to escape during the cooling process after extrusion or compression. It can appear as small bubbles in thicker rods or a white line down the middle of each cut edge of a sheet.

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