| Fructose polymer film made of a polysaccharide called levan has been processed on a twin-screw lab extruder at the U.S. Army Natick Soldier Center in Natick, Mass. Levan is the scientific name for a polymer made naturally by bacteria in fast-flowing streams. It's under development by Montana Polysaccharides, a technology company in Rock Hill, S.C., for use in environmentally friendly adhesives and water-soluble films. Polysaccharides received EPA funding for the extrusion experiments because of levan's potential use as benign packaging in marine environments. The Natick Soldier Center produced 2-in.-wide tapes of 4-mil film. Levan polymer comes as a white powder with a Tg of 271 F, which makes it difficult to extrude without caramelizing. So the Natick lab mixes levan with glycerol plasticizer to lower the Tg to a range of 122 to 158 F. Levan currently costs $7/lb in ton batches, but as production volume increases, the price is expected to drop to around $2/lb, competitive with xanthan gum. Film data will be presented at Plastics Technology's Biopolymers Conference in Charlotte, N.C., in December (see p. 50). |
