Advantages & Disadvantages Of Acrylic

The term “acrylic” is used for products that contain a substance derived from acrylic acid or a related compound. Most often, it is used to describe a clear, glass-like plastic known as poly(methyl) methacrylate (PMMA). PMMA, also called acrylic glass, has properties that make it a better choice for many products that might otherwise be made of glass. There are two basic types: extruded and cast.

Advantages
Many different products are made from acrylic, including shower doors, bath enclosures, windows, and skylights. It is many times stronger than glass, making it much more impact resistant and therefore safer. Falling against an shower door will not likely break it, for example, and baseballs that crash through glass windows will, in most cases, bounce off acrylic windows. It also insulates better than glass, potentially saving on heating bills.

Acrylic glass is also very clear, allowing 92% of visible light to pass through it. Very thick glass will have a green tint, while acrylic remains clear. It also weathers well, keeping its clarity over the years without turning yellow or breaking down when exposed to sunlight over a long period of time.

Another advantage of acrylic is that it is only half as heavy as glass. This makes this material easier to work with, and makes it a better choice for projects where weight is an issue. It can also be sawed, whereas glass must be scored.

Virtually all major public aquariums now build display tanks out of this thermoplastic, and it is often used in many other buildings. When this material is just over 1 inch thick (about 25 mm), it is bullet resistant; the presidential motorcade, the pope’s booth-vehicle, teller enclosures, and drive-through window enclosures all feature bullet-resistant acrylic. It is used for airplane windows as well.

Misconceptions and Disadvantages
There are some misconceptions about acrylic acid (CAS No. 79-10-7), namely that it yellows, turns brittle, and cracks over time. Though this might be true of cheap forms of plastic, it is not so with acrylic. If taken care of, this material can remain new looking for several decades, regardless of age or exposure to sun. Some people worry that it scratches too easily, but unlike glass, scratches may be buffed out.

For all of its advantages, there are two disadvantages of acrylic: It is more expensive than glass, and if exposed to a direct flame, it will melt and eventually burn. Burning releases toxic fumes, so safety precautions should always be taken when it is being cut with power tools or bent using heat. When it is not cared for properly, or when inferior acrylic is used, it can scratch, and improperly made joints can be very visible.

Smart Filter Can Strain Oil Out of Water

A smart filter with a shape-shifting surface can separate oil and water using gravity alone, an advancement that could be useful in cleaning up environmental oil spills, among other applications, say its University of Michigan developers.

The system could provide a more efficient way to remove crude oil from waterways without using additional chemical detergents, or even after detergents have been added, said Anish Tuteja, an assistant professor of materials science and engineering. Tuteja is the corresponding author of a paper on the research published in the Aug. 28 issue of Nature Communications.

The new coating is a blend of a rubbery, commercially-available polymer and a novel nanoparticle. The polymer can readily form hydrogen bonds with water. The nanoparticle, developed by project collaborators at the Air Force Research Laboratory, is very low in surface energy and does not get wet by oil.

The coating creates a smart filter that lets only the water through. It accomplishes this by taking advantage of both gravity and the capillary action phenomenon that enables liquids to defy gravity in narrow enough spaces. It uniquely exploits differences in the capillary action behaviors of oil and water, the researchers said.

In their experiments, the researchers dipped postage-stamp-size pieces of stainless steel window screen and polyester fabric into their solution. Then they cured the coated snippets under ultraviolet light. Meanwhile, they made four different types of oil/water mixtures, including emulsions with various ratios of water and canolaoil (CAS No:120962-03-0). Emulsions, like mayonnaise, are mixtures of liquids that can be difficult to separate.

They were able to use their coated filters for more than 100 hours without clogging—-a vast improvement over today’s technology. In addition to oil-spill clean-up, the technology could be used in wastewater treatment, oil purification for fuel applications, and in the cosmetics industry.

The work is funded by the Air Force Office of Scientific Research. The university is pursuing patent protection for the intellectual property, and is seeking commercialization partners to help bring the technology to market.

Meets Acetone

Acetone (the CAS number is 67-64-1) is a colorless and highly flammable liquid, most commonly associated with nail polish remover. This substance is a ketone, a group of materials that all have similar molecular makeup consisting of a carbonyl group bound to two other atoms or molecules of any kind. Ketones are a very diverse group and contain a large number of disconnected substances like sugars, pheromones, polymers and solvents. Acetone is a very simple ketone, consisting of a carbonyl and two CH3 molecules.

The chemistry of acetone seems a lot more complex than it actually is. The center of the substance is a carbonyl group; this is simply a carbon and oxygen atom that are double joined with one another. Next, the carbonyl group is bonded to two CH3 molecules, which means a molecule comprised of one carbon and three hydrogen atoms. This simple construction gives acetone a wide range of properties and makes it easy to transform into other materials.

The material has a wide range of different properties. It is a colorless liquid that both evaporates and auto-combusts at relatively low temperatures. It is heavier than air, so the vapor will move along surfaces rather than float. This makes it especially dangerous as the vapor can move to an ignition source and travel back to the liquid. In addition, it is a solvent, which means is can dissolve other materials, and miscible with water, meaning it will easily mix in any quantity.

Most of the acetone used in the world today is produced artificially, but it is a natural substance. Most mammals and some other animals naturally produce acetone within their bodies. Some studies have also found that diets rich in ketones will increase acetone levels and reduce the likelihood of seizures in children. The amounts produced inside a person’s body pale in comparison to the over 6.5 million tons produced annually around the world.

While many processes use acetone as is, many others require further processing in order to turn it into a different substance. The most common end product is bisphenol A (BPA) a substance found in a huge number of products. BPA is used to create polymers and artificial resins and can be found in everything from plastic water bottles to metal can liners to thermal paper.

Most Americans recognize acetone as fingernail polish remover. This capitalizes on its abilities as a solvent, it is harmless in low quantities to human skin but it rapidly dissolves the polymer-based polish used in modern cosmetics. Even so, acetone is a dangerous substance and prolonged bodily contact should be avoided.

Switchgrass Bait and Switch

Newshound Joe Sullivan digs into what ever became of $70 million that the state of Tennessee spent in the flush days of 2007 to start up a switchgrass and cellulosic ethanol (also known as Ethyl Alcohol , the CAS number is 64-17-5) industry in the state.

The good news on the project is that the promised 250,000 gal per year cellulosic ethanol plant did open, in Vonore, Tennessee. The bad news is that it has not been using any of the switchgrass grown on 5,000 surrounding acres. The switchgrass part of the project involved the University of Tennessee Institute of Agriculture. The state figured switchgrass would grow great there. And it seems to have been correct.

Sullivan reports that more than half of the $70 million project money went to build the pilot plant. But corporate partner DuPont (now DuPont Cellulosic Ethanol) has used the pilot plant to test and demonstrate its ability to make ethanol from corn stover. Corn stover is a feedstock that is available in huge quantities…. in Iowa. As it happens, DuPont’s first commercial-scale cellulosic ethanol plant is in Nevada, Iowa, and is set to come online soon.

C&EN has mentioned the Vonore plant a half dozen times (including in a previous post on this blog). The move away from switchgrass escaped our attention, but it is an important development for the UT folks and the farmers they have been working with.

Researchers develop superior fuel cell material

               Researchers develop superior fuel cell material
Fuel cells are a promising technology for use as a source of electricity to power electronic devices, vehicles, military aircraft and equipment. A fuel cell converts the chemical energy from hydrogen (fuel) into electricity through a chemical reaction with oxygen.  A fuel cell can produce electricity continuously as long as there is a fuel supply.

Using a mixture of gold, copper and platinum nanoparticles, IBN researchers have developed a more powerful and longer lasting fuel cell material. This breakthrough was published recently in leading journal, Energy and Environmental Science.

Current commercially available fuel cells use platinum nanoparticles as the catalyst to speed up the chemical reaction because platinum is the only metal that can resist the highly acidic conditions inside such a cell. However, the widespread use of fuel cells has been impeded by the high cost of platinum and its low stability.

To overcome this limitation, a team of researchers led by IBN Executive Director Professor Jackie Y. Ying has discovered that by replacing the central part of the catalyst with gold and copper alloy and leaving just the outer layer in platinum, the new hybrid material can provide five times higher activity and much greater stability than the commercial platinum catalyst. With further optimization, it would be possible to further increase the material’s catalytic properties.

IBN’s new nanocomposite material can produce at least 0.571 amperes of electric current per milligram of platinum, compared to 0.109 amperes per milligram of platinum for commercial platinum catalysts. This is also the first time that a catalyst has been shown to enhance both the stability and activity for the fuel cell reaction with a significantly reduced platinum content.

To make this catalyst more active than the commercial platinum catalyst, the researchers have designed the core of the nanocrsytalline material to be a gold-copper alloy, which has slightly smaller lattice spacing than the platinum coating on the nanocrystal’s surface. This creates a compressive strain on the surface platinum atoms, making the platinum more active in the rate-limiting step of oxygen reduction reaction for the fuel cell. Replacing the core of the nanoparticle with the less expensive gold-copper alloy cuts down the usage of platinum, a highly expensive noble metal.

Professor Ying said, “A key research focus at IBN is to develop green energy technologies that can lead to greater efficiency and environmental sustainability. More active and less costly than conventional platinum catalysts, our new nanocomposite system has enabled us to significantly advance fuel cell development and make the technology more practical for industrial applications.”

Setback for Pyrite Photovoltaics

Extensive tests by US researchers on nanocrystals of the pyrite phase of iron sulfide – also known as fool’s gold – suggest that the material is unlikely to be a good candidate for photovoltaic (PV) applications, contrary to some predictions. Not all experts agree, however, and believe that there could yet be some genuine sparkle in the material.

‘There were early data in the 1980s and 90s looking at pyrite photovoltaics which found that this was possible since pyrite was a semiconductor,’ says Brian Korgel of the University of Texas at Austin, who led the research. ‘But the devices performed poorly and in a sense it was dropped.’ However, interest has been revived recently, given the relatively low cost of preparing Fe2S. ‘It is made of Earth-abundant materials and is not toxic and, because it is dark, it is a really strong light-absorber,’ Korgel notes.

The team used an established technique to create nanocrystals of pyrite and incorporated the crystals into four different types of photovoltaic device. ‘The pyrite nanocrystals simply did not work,’ Korgel says. ‘There was no PV activity. When we measured the electrical properties we found they were very electrically conductive, like a metal. You can’t make a PV with a metal as an absorber layer.’

The conductivity is a result of high doping of the crystals, Korgel says. ‘Theory has shown that surfaces of pyrite (the chemical formula is FeS2 and its CAS No. is 1309-36-0) can sustain defects that give rise to doping like this. Therefore it might be possible make pyrite PVs if someone figures out how to passivate the surfaces, but I’m convinced, based on our studies, that it won’t be easy. Someone must do something quite special for it to work. I think it is a dead-end.’

However, not everyone is as pessimistic. Cyrus Wadia, of the Lawrence Berkeley National Laboratory in the US and currently assistant director of Clean Energy and Materials R&D in the US government Office of Science and Technology Policy, says: ‘In general, I think the work is an important step in our understanding of pyrite.’ Wadia adds: ‘To balance my optimism for future pyrite work, I will be the first to state that pyrite has great promise but we are just beginning to learn about the many practical challenges of using pyrite in a photoelectrical device. So any results, good or bad, feed our understanding and we must keep expanding that knowledge base. That said, I wouldn’t jump to conclusions based on these results alone. Korgel’s work draws on existing best practices for growing pyrite nanocrystals which we already believe to be problematic. I think we are still a long way from knowing the true potential of pyrite in a photovoltaic application.’

Coal-bed Methane Exacerbates Global Warming

Methane (natural gas), while perhaps most closely related in our minds with petroleum, also occurs in association with coal, the Nation’s most abundant fossil fuel resource. From poisonous methane gas in mines and sewers to increasing the greenhouse effect, not everyone is laughing about methane gas. Long a dangerous byproduct of coal mining, methane gas stored in coal beds is now being put to good use.

Natural Gas and Coal Based Methane Gas
Methane, CH4 (the CAS number is 74-82-8), is a molecule that is created predominantly by bacteria that feed on organic material. In wet areas, where there isn’t a lot of oxygen, methane is created by anaerobic bacteria. Some of the methane is trapped as a gas or a solid, or is dissolved or eaten. The process of coalification, in which plant material is processed into coal over a period of thousands of years, generates large amounts of methane gas, the primary component of natural gas. Coal beds and coal seams are saturated with varying amounts methane gas that’s held in place by water and water pressure.

Uses
Methane can be burned to generate electricity. Many pig, cow and poultry farms in several countries are helping control methane emissions by converting methane to a power source. Controlling methane emissions can significantly slow global warming, according to NASA. Home test kits are available to detect methane gas.

Where CBM is Found
Commercial production of coal-based methane (CBM) started in the United States in the 1980s and is being undertaken in other countries—most notably China—that need new sources of clean energy. The coal-rich Appalachian Mountains are a prime source of CBM, but there are also massive beds in the Western United States. The largest potential source is the Powder River Basin. The Wyoming Oil and Gas Conservation Commission estimates there are 31.8 trillion cubic feet of CBM in the Wyoming section alone.

Environmental Effects
The water is often loaded with salt that can pollute water supplies and damage soil and plant life. CBM operations store most of the pumped water in massive holding ponds that allow the water to aerate, helping evaporation to separate salt from water. Tapping into new sources of natural gas is considered a more eco-friendly alternative to coal burning, but extracting gas from coal creates problems. The main obstacle is disposing of water pumped from coal seams, according to a report from Montana State University. 

Nitrogen-Sulfur Polymers Break New Ground

In a set of chemical firsts, University of Iowa researchers have created three polymers that incorporate nitrogen-sulfur groups: sulfenamides (–R2NSR–), diaminosulfides (–R2NSNR2–), and diaminodisulfides (–R2NSSNR2–). The members of this new family of polymers, described at the American Chemical Society national meeting in Philadelphia on Monday, fall apart in aqueous solution and appear to be nontoxic—ideal properties for using them as biodegradable drug-delivery materials.

The three nitrogen-sulfur functional groups are found in a modest number of small organic molecules, but they haven’t appeared in macromolecules until now, noted Iowa’s Ned B. Bowden, whose group carried out the research in collaboration with the group of Iowa colleague Aliasger K. Salem. Bowden’s team prepared the polymers by reacting secondary amines with sulfur reagents (Macromolecules, DOI: 10.1021/ma300190b and DOI: 10.1021/ma2023167). For example, the researchers made poly(diaminosulfides) by reacting secondary amines with bis(N-dialkyl) sulfides.

They made microparticles out of the polymers and showed in lab tests that, similar to polyester drug-delivery materials, the particles are absorbed by human embryonic cells and exhibit no measurable toxicity. Once they enter cells’ mildly acidic environment, the polymers degrade rapidly, Bowden explained. He is intrigued by the degradation products, which include sulfur monoxide, hydrogen sulfide, and allicin (the CAS number is 539-86-6 and itd formula is C6H10OS2)—a sulfur antioxidant compound found in garlic. The release of these by-products could possibly be controlled for additional therapeutic effects beyond those of a delivered drug, he suggested. Besides drug delivery, the functional groups might also be incorporated into conducting polymers for electronics applications, Bowden added.

“The ability to incorporate N–S linkages into a polymer backbone brings a wealth of opportunities ranging from biomaterials to microelectronics,” commented polymer expert Craig J. Hawker, a former IBM researcher now at the University of California, Santa Barbara. “It’s not often that a new class of polymers is developed that bears little resemblance to current materials—these polymers are really something unique.”

Understanding Cut Apples

You start eating an apple, and just then you friend calls you up about homework, and you’re speaking for hours together. When you come back to your apple, it’s gone brown all over. What happened?

Rusting In Apples
The brown colour is because your apple has rusted! That’s because apples are rich in iron, which is present in all their cells. When you cut an apple, the knife damages the cells. Oxygen from the air reacts with the iron in the apple cells, forming iron oxides. This is just like rust that forms on the surface of iron objects. An enzyme called polyphenol oxidase (that’s present in these cells) helps make this reaction go faster.

If you cut a browned apple into two again, you’ll notice that the insides are still white. That’s because the cells inside were intact, and did not let oxygen enter right inside. Lots of other fruits and vegetables also turn brown when cut. These include bananas, pears and even potatoes.

How To Prevent?
There’s no harm in eating an apple that has turned brown, for the iron oxide will not affect you. But when you’re making a fruit salad or apple pie, the browning may make it look unattractive. Here are some things you can do to stop or slow the browning:

Cut and keep the apples under water. This prevents air from reaching the iron. But it may cause some vitamins to leach into the water. Rub the cut apples with lemon juice. The acid in the lemon juice stops the polyphenol (also known as Grape, red, ext) oxidase from working. If you’re making apple pie, you can dip the apples in boiling water for a few seconds and take them out. This is called blanching, and it stops the browning enzyme.

Keep the apple pieces in an airtight jar, or wrap them in cling wrap very tightly. This also stops air from getting to them. And finally, the method we like the most. Turn your apple into apple juice. The iron oxide gives it the special golden-brown colour, and it’s a tastier way to consume an apple!

U.S. Vitamin C Antitrust Lawsuit Was Rejected

A Chinese company has agreed to pay $10.5 million to U.S. purchasers of vitamin C who accused it of conspiring to raise prices by limiting exports, a proposed settlement showed.

The proposed settlement, filed in U.S. District Court in Brooklyn on Monday, is the first in a long-running legal battle brought by commercial buyers of vitamin C against four Chinese companies.

Under the settlement, the company, formerly known as Jiangsu Jiangshuan and now called Aland (Jiangsu) Nutraceutical Co., will pay $9.5 million to direct purchasers of the vitamin C and an additional $1 million to indirect purchasers. The two groups of purchasers were certified as separate classes by judge Brian Cogan in January.

If it is approved by the judge overseeing the case, it would be the first civil settlement reached with a Chinese company under U.S. antitrust cartel law, lawyers for the purchasers said.

“As such, the settlement is an important step in private enforcement of U.S. antitrust laws,” a court document said.

In September, Cogan rejected the defendants’ key defense: that they were required under Chinese law to coordinate production and prices of their exports. The defendants had argued that they should be shielded from the U.S. lawsuit under a doctrine which protects foreign companies ompelled by their own governments to go against U.S. law.

Jim Southwick, a lawyer who represents a class of purchasers who buy directly from the Chinese companies, said the settlement belies that defense.

“If the Chinese government truly forces them to fix the price, how is it that one defendant settles the case separately?” Southwick said.

Richard Goldstein, an attorney for Aland, did not immediately return a call seeking comment on the proposed settlement.

The purchasers sued Aland and three other Chinese vitamin C (also called as L(+)-Ascorbic acid)makers in 2005 after their alleged price-fixing deal in 2001 sent vitamin C prices sky-rocketing. The other three Chinese defendants are Hebei Welcome Pharmaceutical Ltd, Northeast Pharmaceutical Co Ltd and Weisheng Pharmaceutical Co Ltd.