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So Many Cenospheres, So Many Applications
Continue ReadingAlthough you may not know it, the modern world has many reasons to be grateful for cenospheres.
Few people know of their existence, even fewer people know where they are from. Although a quick glance at Wikipedia, the source of all sources, will inform the uninformed that, “A cenosphere is a lightweight, inert, hollow sphere made largely of silica and alumina and filled with air or inert gas, typically produced as a byproduct of coal combustion at thermal power plants. The color of cenospheres varies from gray to almost white and their density is about 0.4–0.8 g/cm3 (0.014–0.029 lb/cu in), which gives them great buoyancy.”
However, that does little to describe the true beauty of these tiny, yet powerful, balls of fly ash. For their real strength lies in the diversity of their use. As the French industry journal, Industrie & Technologies, states, “Because of their low density, small size, spherical shape, mechanical strength, high melting temperature, chemical inertia, insulating properties and low porosity, microspheres [also known as cenospheres] find a wide range of applications in industry. In particular, [they are ideal] for reinforcing materials or imparting properties of resistance to corrosion, or thermal and sound insulation to coatings or paints. They can be described as multifunctional fillers and integrate well in resins and binders such as thermoplastics and thermosetting.”
Cenospheres in Paints and Coatings
There are a great many uses for cenospheres in the paint and industrial coating industry, due to the additional qualities they provide. For example, cenospheres are often used in coatings to control infrared radiation, giving those coatings an advantage over ones that merely attempt to limit thermal conductivity.
Meanwhile, coating experts at Petra Buildcare Products, explain how cenospheres, “… improve the quality of the paint by improving the volume and density of the product. After application on the wall, the ceramic beads tend to shrink thereby creating a tightly packed film on the wall.”
Cenospheres in Syntactic Foams
Cenospheres are often used to make ‘syntactic foams’. These are specialized solids which use cenospheres as a filler to provide any number of advantages, from lower cost, to added strength, sound proofing, buoyancy and thermal protection.
Experts at Engineered Syntactic Systems describe syntactic foam as follows;
“The ‘syntactic’ portion refers to the ordered structure provided by the hollow spheres. The ‘foam’ term relates to the cellular nature of the material. Thanks to its unique properties of high strength at low density, syntactic foam has become widely used in subsea buoyancy applications. Syntactic materials are resistant to the combined effect of hydrostatic pressure and long-term exposure which make them ideal for oceaneering projects such as cable and hardball floats and instrumentation support. They also provide strength and structural integrity at a significantly lower weight per volume than most traditional materials which make them an attractive choice in many defence and civil engineering applications.”
Cenospheres in Petroleum Drilling
For proof of the unknown importance of cenospheres, you need look no further that the vital role they play in the petroleum industry. For while everyone knows of the importance of oil in the modern world, it is a little known fact that cenospheres have, as the French industry journal, Industrie & Technologies, states, “…been used for several years in the field of oil drilling to reduce the density of a petroleum cement paste without increasing the water content.”
Cenospheres in Plastics and Polymers
Cenospheres also have a use in the manufacture of plastics and polymers, as their re-formable shape or strength helps to avoid shrinkage in thermoplastics and thermosetting plastics.
They are also being used in modern composites in the automobile industry. For example, the 2016 Chevrolet Corvette contains a “sheet molding compound in which glass microspheres replace calcium carbonate filler and shave 20 pounds [9kg] off the sports car’s Stingray Coupe model weight.” The Vice President of the manufacturer, Continental Structural Plastics Inc., Probir Guha, explains the reason for the inclusion of cenospheres in the composite, in saying that, “the typical SMC formula for this type of vehicle application comprises 20% by volume of glass fiber reinforcement, 35% resin and 45% filler, usually calcium carbonate,” adding that, “This new SMC [sheet moulding compound] is cost competitive with aluminium.”
Cenospheres in Concrete
For years, cenospheres have been a useful additive to concrete, providing additional strength, and or sound insulation, whilst also lowering density. Jeff Girard, President at The Concrete Countertop Institute, explains these advantages, saying, “In theory, cenospheres can replace some of the normal-weight sand used in concrete. Cenospheres have a density that is less than water (averaging 0.7 vs. Water’s 1.0); quartz sand particles typically have a density of about 2.65. This means that 1 pound of cenospheres takes up the same absolute volume as about 3.8 lbs. of sand.”
Industrie & Technologies, also outlines the use of cenospheres as a means of lowering noise pollution, stating that, “[Cenospheres are used] in building materials to lighten concrete, while maintaining a compressive strength of 30 MPa at a density of 1.6 T / m3, improving their tightness and reducing their sound transmission. For example, the St. Petersburg Scientific and Technical Center of Applied Nanotechnologies (STCAN) is involved in building bridges with such concretes in Russia, [for a quieter road surface]. Cenospheres are also used to improve the thermal and sound insulation qualities of plasters, mortars and plasters, used for walls, floors and ceilings. An addition of 40% volume cenospheres halves the noise transmission coefficient.”
Cenospheres in Pharmaceuticals
Cenospheres have been used in the pharmaceutical industry for many years, as the small balls can act as a near-perfect transport device when coated with drugs. Additionally, as the French industry journal, Industrie & Technologies, notes, “Cenospheres covered with silver oxide may, for example, be integrated into dressings in order to accelerate wound healing.”
Cenospheres in Advanced Industries
A great deal of research is being conducted to discover new uses for this versatile by-product. For example, new catalysts for the methane oxidation process are being developed using magnetic cenospheres.
Cenospheres are also being used in the development of metal matrix composites (MMC), a variety of materials that attempts to combine the high energy absorption, impact resistance, and low density of the spheres with the qualities of other substances. Others, such as Paul Biju-Duval of the Georgia Institute of Technology based in Atlanta, have worked hard in the development of cementless building materials. His work continues, adding to a cenosphere mix, items such as bamboo and metallic tubing as a means to finding alternative, cheaper, stronger, and more environmentally-friendly construction methods.
Meanwhile, the Institute of Chemistry and Chemical Technology of the Russian Academy of Sciences in Krasnoyarsk, is studying ways that cenospheres could be used in catalytic transformations. While BAE systems is attempting to use cenospheres in paint as a means to support invisibility in the infrared spectrum, thus enabling military craft to have ‘invisibility cloaks’.
With such a wide range of uses, and an even wider range of potential uses, it is no wonder why interest in cenospheres is growing. As long as product developers are looking for light weight fillers, improved drug delivery systems, improved coatings, cement substitutes, and composite additives, then there will be a need for cenospheres. Plus with increased research into new uses for these versatile spheres, then only time will tell where the future of cenospheres lies.
Photo credit: dopcreator
Photo credit: syntactic foam suppliers, ESS
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A Process to Chemically and Mechanically Change 3D Printing Polymers, Even After Printing
Continue ReadingChemists from MiT have developed a process that potentially enables the polymers used in 3D printing to be altered, even after they have been printed.
Up to now, once polymers have been printed, they are considered ‘dead’ and no changes can be made to the polymer chains, but now, the door has been opened for monomers to be added that can amend the chemical and mechanical composition of printed plastics. This enables the researchers to adjust the size of printed objects, add water repellent properties, or even to fuse two printed objects together, simply by shining light on them, opening a world of far more complex 3D printed constructions.
Jeremiah Johnson, the Firmenich Career Development Associate Professor of Chemistry at MIT, explained the concept as, “The idea that you could print a material and subsequently take that material and, using light, morph the material into something else, or grow the material further.”
The story began in 2013, when, as the online journal Phys.org reports, “Johnson and his colleagues [former MIT postdoc Mao Chen and graduate student Yuwei Gu] set out to create adaptable 3-D-printed structures by taking advantage of a technique known as ‘living polymerization’, which yields materials whose growth can be halted and then restarted later on.” The journal continues by describing how the researchers found, “that they could use a type of polymerization stimulated by ultraviolet light to add new features to 3-D-printed materials. After printing an object, the researchers used ultraviolet light to break apart the polymers at certain points, creating very reactive molecules called free radicals. These radicals would then bind to new monomers from a solution surrounding the object, incorporating them into the original material.”
Johnson outlined the clear benefit of this at the time, saying, “The advantage is that you can turn the light on and the chains grow, and you turn the light off and they stop. [So that], in principle, you can repeat that indefinitely and they can continue growing and growing.”
Now the research team has taken their discovery to the next level, in a way that makes 3D printing a much less permanent result. The journal MiT News, notes how this latest breakthrough is an addition to their previous research, stating, “In their next effort, the researchers designed new polymers that are also reactivated by light, but in a slightly different way. Each of the polymers contains chemical groups that act like a folded up accordion. These chemical groups, known as TTCs, can be activated by organic catalysts that are turned on by light. When blue light from an LED shines on the catalyst, it attaches new monomers to the TTCs, making them stretch out. As these monomers are incorporated uniformly throughout the structure, they give the material new properties.”
“That’s the breakthrough in this paper: We really have a truly living method where we can take macroscopic materials and grow them in the way we want to,” said Johnson.
The researchers have published their results in the ACS journal Central Science, declaring that, “we have developed a first-generation living additive manufacturing process called ‘photoredox catalyzed growth‘ (PRCG) that enables the controlled insertion of monomers and cross-linkers into polymer networks to produce complex daughter objects from a single type of parent object. PRCG makes use of a newly developed photoredox catalyzed polymerization that avoids the undesired chain termination processes that are present in traditional free radical and iniferter polymerizations. Our approach enabled the fabrication of daughter gels with complex compositions and mechanical properties that would be difficult or impossible to achieve using traditional free radical polymerization methods.”
These monomers are able to adjust chemical and mechanical properties, such as stiffness or hydrophobicity (affinity for water), as well as swelling or contracting under temperature stimuli.
While the researchers acknowledge that the process still needs a lot of refining, stating that, “For practical applications, PRCG will require extensive development: the polymerization rate should be increased by at least an order of magnitude, the oxygen tolerance should be thoroughly investigated, and the expansion to bulk polymeric materials should be pursued.” Also, their work to date has also largely focused on gels, but they also make clear that their work is ongoing, and that numerous alternative catalysts are already being tested that are not affected by the presence of oxygen.
If these limitations are overcome, then 3D printing as a real-world production process may really begin to take-off. The idea that plastics can be printed and then amended, chemically or mechanically, by applying light is sure to attract the interest of polymer traders and plastics manufacturers worldwide.
Imagine, for example, how products could be improved if the consumer were able to fuse plastics parts together by shining a light at the joint. While other products could also be amended, for example, so that they travel flexible and can then be made rigid, or made hydrophobic, or made softer, or expand, or contract. Are these the 21st century polymers we’ve been waiting for?
Photo credit: Demin Liu and Jeremiah Johnson
Photo credit: American Chemical Society
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Microspheres Making Better Corks
Continue ReadingThe modern microsphere industry is helping to improve the ancient technology of preserving wine in bottles. By using AkzoNobel’s branded polymer microsphere Expancel, synthetic corks are able to make a seal that in many ways is superior to natural cork.
As the Expancel website boasts, “Synthetic cork can be a good solution in many applications. In theory, synthetic cork should avoid many of the inconsistencies associated with natural cork. But in practice, it’s not that simple. The foaming process is often the cause when there are issues. The key to the real-world performance of synthetic cork is the foaming process. Expancel [microspheres] in the mix ensures highly controlled foaming, giving very even and consistent results.”
Dominique Tourniex, CEO at Diam, a global leader in cork manufacturing, said, “We are purchasing little, tiny microspheres which expand during the process of mouldng the cork and so improve the performance of the closure.”
Better still, the microspheres help form a watertight seal that does not shrink or absorb moisture. It removes the chances of ‘cork taint’ in the wine, is European regulation 10/2011 compliant, and has recently been US FDA approved.
You can watch the presentation on how microspheres help improve cork manufacturing on YouTube here.
Given that, according to the Wall Street Journal, global wine consumption in 2014 was set at 38.4 billion bottles a year, then there is clearly a good market for cork manufacturers. While traditional wine markets in the US and Europe are currently stable, it is the booming demand for wine in the Far East that has packaging manufacturers whetting their lips. While the market is comparitively small at present, that is expected to change in the coming decade. For example, China alone, “saw a 69% growth in wine consumption from 2009 to 2013 and is forecast to grow by almost 25% from 2014 to 2018.”
With so many thirsty mouths and a desire for western lifestyles, the microsphere market could easily grow as wine consumption also takes off. With demand already growing through pressure from other chemical industry applications, raw material traders are beginning to wonder, “how high can microsphere prices reach, if new suppliers are slow to enter the market?”
Photo credit: AkzoNobel