Researcher tells nonwovens industry: go fly a chitin.

Researcher Tells Nonwovens Industry: Go Fly A Chitin

nonwovens may be one of the beneficiaries of research into a novel, but not new, material called chitin (pronounced ki' tin) A new material that some experts have predicted may form the basis of a $2 billion industry by the end of the decade is targeting a variety of nonwoven products as some of its primary markets.

Chitin, a natural substance and the second most plentiful organic compound on earth, is a major component of the shells of crustaceans. It can be processed from shellfish waste that would otherwise be placed in landfills. It is also found in the cell walls of fungi, from which it can be extracted from fermentation.

Dr. Sam Hudson, a fiber scientist at North Carolina State University, Raleigh, NC, has been working on fundamental research on this material and its derivative chitosan since the early 1980s, when he was a chemist at Du Pont's research laboratories. Since then, he has moved to NC State, where chitosan remains his principal interest.

Chitin can be formulated in a variety of ways for a range of end uses. By heating chitin crystals with sodium hydroxide, the chemical structure of the chitin molecule can be altered to form chitosan, from which useful fibers and films can be made. Both chitin and chitosan molecules can bind metal ions, a quality that makes them excellent water purifiers. Both substances are also completely biodegradable and compatible with body tissues.

To date, chitin and chitosan have had limited use as ingredients in cosmetics and in such applications as wastewater purification and recovery of food processing by-products. But the characteristics of these two polymers have led many experts to predict that they will have important uses in soil treatments, sportswear, food packaging and preservatives, absorbable sutures, wound dressings, surgical implants, vehicles for drug delivery and separation of important proteins in biotechnology.

Major Research Still Needed

"The range of applications proposed for chitin and chitosan is so broad," said Dr. Hudson, "that people almost snicker when you talk about it." A great deal of fundamental research on the materials and their properties must pave the way before this becomes a reality, however, and this is the focus of Dr. Hudson's work.

A major goal of the research has been to counteract the propensity of chitosan fibers and films to lose strength in water, a common drawback among fiber and film forming materials based on natural polysaccharides.

Chitosan is a long, chainlike molecule and these molecules are laid out in an extended, linear fashion to form fibers. "The molecules in the fibers absorb water very readily because of their chemical structure and the water then acts as a kind of lubricant between the fibrillar structures, making them very weak and plastic and pliable," Dr. Hudson explained. "So by chemical crosslinking--that is, by adding another substance (epichlorohydrin) that creates a chemical bond between those long, chainlike molecules--we're adding stability to the structure when it's wet."

A study done in the Soviet Union gives chitosan fibers and films the ability to take up water repellent, water insoluble materials. This achievement has the potential for applications in the development of time-controlled delivery systems for medication, implanted under or delivered through the skin, using a completely biocompatible and bioabsorbable carrier.

Another possibility for chitosan is in filtration. The molecules of which the chitosan salts are composed combine a hydrophilic and a hydrophobic part, which means they naturally sort themselves out in solution so that the hydrophobic portions are clustered in groups. This behavior might shed light on ways large molecules might be chemically prodded to assemble themselves into membranes; the membranes could conceivably be used to filter out bacteria from liquid foods during processing or to extract desired proteins from the broth in which they are being mass-produced by genetically engineered bacteria.

Dr. Hudson has received seed money for his work from the North Carolina Textile Foundation through the College of Textiles and his research on cross linkage of chitosan has also been funded by the U.S. Army's Natick Research Center. Natick has been interested in chitosan films as a possible biodegradable packaging material for MREs (meals ready to eat).

The outlook for chitin and chitosan in the future is bright. "We're at the point now in our research," said Dr. Hudson, "where we can show some accomplishments and we're not talking about 'what if' we could do this or that.

"Whether chitin and chitosan will become something on a par with wood pulp and cellulose, which generated the rayon and paper and acetate industries, I don't know," said Dr. Hudson. "But chitosan is so much more versatile than cellulose and it has proven medical applications, in fiber or film form."