Chementator: Sugar-beet pulp may cut the cost of biodegradable plastic    

Sugar-beet processors in the U.S. generate approximately 40 million tons of fiber-rich sugar-beet pulp every year as a byproduct of sucrose extraction. Most of it is used as livestock feed or in pet food. Researchers with the U.S. Agricultural Research Service (ARS; edlinks.chemengonline.com/7371-542) are working on a process to convert the pulp into a filler for polylactic-acid-based plastics (PLA), biodegradable plastics derived from fermented corn sugars. PLA’s physical properties are similar to those of polypropylene, but its production cost is higher, says Victoria Finkenstadt, a chemist with the ARS National Center for Agricultural Utilization Research (Peoria, Ill.). The inexpensive beet-pulp filler would reduce the cost. The researchers plasticize the pulp and reshape its particulate matter into tendrils by co-extruding it with glycerol at 75°C. The resultant material is co-extruded with PLA at about 170°C, then pelletized for injection molding. The goal is to have 40 – 50% filler in the plastic, but PLA’s tensile strength decreases in relation to the amount of filler, which does not adhere well to the plastic at high fill levels. Finkenstadt notes that sugar-beet pulp is hydrophilic, whereas PLA is…