In the Lab
One Industry's Trash Is Another's Treasure
Fiber (cellulose) lost to scrap or waste when cotton is converted to fabric or garments may soon be used to produce a low-cost, high-value, high-strength fiber for air filtration, water filtration and agricultural nanotechnology, according to polymer scientists at Cornell University. The achievement is attributed to the recently perfected technique of electrospinning to spin nanofibers from cellulose.
"Cellulose is the most abundant renewable resource polymer on earth. It forms the structure of all plants," says Margaret Frey, an assistant professor of textiles and apparel at Cornell. "Although researchers have predicted that fibers with strength approaching Kevlar® could be made from this fiber, no one has yet achieved this."
Collaborating with assistant professor Yong Joo and graduate student Choo-won Kim, both in chemical engineering at Cornell, Frey has developed a new group of solvents for dissolving cellulose, allowing the production of fibers using the electrospinning technique.
Successfully used for the first time in early 2003, the technique of electrospinning cellulose on the nanoscale involves dissolving cellulose in a solvent, squeezing the liquid polymer solution through a tiny pinhole and applying a high voltage to the pinhole. The charge pulls the polymer solution through the air into a tiny fiber, which is collected on an electrical ground, Frey explains. The resulting fiber has a diameter of 100 nanometers, which is 1,000 times smaller than in conventional spinning.
"The technique relies on electrical rather than mechanical forces to form fibers," Frey says. "Thus, special properties are required of polymer solutions for electrospinning, including the ability to carry electrical charges." The researchers currently are using experimental solvents to find one that will produce fibers with superior properties.
While fiber or cellulose is currently lost to scrap or waste in the production of cotton products, Frey says that the possible production of a high-performance material from the fibers will increase motivation to recycle these materials and thus remove them from the waste stream.
Electrospinning typically produces nonwoven mats of nanofibers, which could provide nanoscale pores for industrial filters and more, according to Frey.
"Producing ultra-small diameter fibers from cellulose could have a wide variety of applications that would exploit the enormous surface area of nonwoven mats of nanofibers and the possibility of controlling the molecular orientation and crystalline structures of nanoscale fibers," says Frey.
If successful, possible applications might include air filtration, protective clothing, agricultural nanotechnology and biodegradeable nanocomposites.
Joo says the electrospun cellulose mats might also be used to absorb fertilizers, pesticides and other materials. "These materials would then release the materials at a desired time and location, allowing targeted application," says Joo.
The New York State College of Human Ecology at Cornell supports this research. For more information, visit www.human.cornell.edu.
Cease Fire in Ozone Attack?
Decreasing steadily since 1998, recent research indicates that total bromine, one of the most active destroyers of the ozone layer, in the lower atmosphere is now more than five percent below the peak reached that year.
In the August 15, 2003, issue of the journal Geophysical Research Letters, Stephen A. Montzka and colleagues from the National Oceanic and Atmospheric Administration?s (NOAA) Climate Monitoring and Diagnostics Laboratory in Boulder, Colo., attribute the decline primarily to international restrictions on industrial production of methyl bromide, a brominated gas that is regulated by the Montreal Protocol.
"This is welcome news for stratospheric ozone because it means that less bromine and chlorine have been entering the upper atmosphere, where the ozone layer resides, for a number of years now," said Montzka. Bromine is about 50 times more efficient than chlorine at destroying stratospheric ozone.
The NOAA scientists were able to discern the reversal in the long-term upward trend for bromine based on their ground-based measurements of methyl bromide and halons over the past eight years at 10 stations around the globe, including Cape Grim, Tasmania; the South Pole; Mauna Loa, Hawaii; and Barrow, Alaska.
Produced industrially for use as a fumigant in agriculture and in commercial shipping, methyl bromide is unique among ozone-depleting substances regulated by the Montreal Protocol because it also has substantial natural sources, including the oceans, wetlands, some plants and burning vegetation. Industrial production of methyl bromide has declined in recent years in response to restrictions outlined in the amended Protocol, researchers say. Originally signed by 23 nations in 1987, the Montreal Protocol limits the production of ozone-damaging compounds.
The large drop in atmospheric methyl bromide, about 13 percent since 1998, has more than offset the small increases still observed for bromine from fire-extinguishing agents known as halons. Methyl bromide and halons account for nearly all of the human-released bromine that reaches the stratosphere.
Based upon their results, the researchers say that overall ozone-depleting gases are declining faster than previously thought. But, caution the researchers, we're not out of the woods yet because bromine from halons is still increasing slowly.
While their results are encouraging, researchers note that the trends could change. "Decreases in ozone-depleting substances are a direct result of international limits on production," said Montzka. "Without continued worldwide adherence to the restrictions outlined in the protocol, these trends could slow and delay the recovery of stratospheric ozone."
For more information, visit www.agu.org.
Make-up with Local Flair?
If you're searching for the fountain of youth, you may have better luck in the country. Recent research confirms that high air pollution not only irritates your lungs, it also affects the way you look.
By using pollution maps provided by the European Space Agency (ESA) along with ultraviolet radiation data, cosmetics firm L'Oreal plans to investigate the future possibility of producing skincare products customized for local conditions.
The skin-aging effects of ultraviolet (UV) rays are well known, but the harmful consequences of air pollution on skin are less easily quantified outside of a laboratory. Working with the French Regional Centre for the Fight against Cancer and the Mexican National Institute of Public Health, in 1999 L'Oreal began a nine-month study in and around Mexico City -- one of the most polluted cities in the world.
To study the effects of ozone and nitric oxide on the skin, 96 people in a highly polluted district of the city were compared to 93 subjects living in a less exposed urban area 75 kilometers away.
"We saw many differences between the two groups," said Francois Christiaens of L'Oreal. "We observed increased oxidation of the sebum -- the oily secretion that lubricates and protects skin and hair -- and the very dry or very greasy skin features of our volunteers living in Mexico City."
According to Christiaens, the changes are cosmetic. Skin and hair smoothness and brightness change, and more seriously, as oxidation compromises the skin's natural defenses, it enhances irritation and allergic reactions.
Because differences were so pronounced between people living less than 100 kilometers apart, the researchers grew interested in acquiring more precise information on regional air pollution levels. This in turn increased the existing interest in satellite data, already used for UV forecasting.
"Today UV doses are either collected from ground sites or come from models, but coverage is sparse and there are limited data over time," said Christiaens. "But satellite data can give us global maps of UV levels, and we can use them to work out realistic doses, as well as fine-tune the doses simulated in laboratory tests."
Beginning in fall of this year, L'Oreal will receive regularly updated high-resolution maps of global UV doses and pollution levels, as part of a wide-ranging ESA Data User Program project called Tropospheric Emission Monitoring Internet Service (TEMIS). Using space-based atmospheric instruments such as SCIAMACHY, the project will chart global concentrations of trace gases, aerosols and UV for a wide range of end users.
For more information, visit
www.temis.nl/ or www.skin-science.com.
This news item originally appeared in the March 2004 issue Environmental Protection, Vol. 15, No.3.
This article originally appeared in the 03/01/2004 issue of Environmental Protection.