US scientists are hailing sugar beet pulp as a potential source of biodegradable thermoplastic packaging.
According to a study published in Agricultural Research magazine (January 2013), to make the plastic, Agricultural Research Service (ARS) scientists incorporated sugar beet pulp with polylactic acid (PLA) using a twin screw extruder.
With the assistance of water and/or glycerol, this resulted in thermoplastic composites that retain mechanical properties similar to polystyrene and polypropylene, which are used for food packaging.
This material can be subsequently processed by extrusion or injection moulding to produce neat sugar beet pulp products.
The new thermoplastic is cost competitive with commonly used petrochemical plastics, according to the researchers.
Professor Jinwen Zhang of Washington State University, and ARS chemist LinShu Liu and plant physiologist Arland Hotchkiss, both at the ARS Eastern Regional Research Centre in Wyndmoor, Pennsylvania, collaborated on the project.
“The technology is promising and provides a ‘green’ material for food packaging,” said Hotchkiss.
Properties similar to low-density polyethylene
The group claims the material possesses mechanical properties that are similar to those of low-density polyethylene, which is used for opaque plastic containers, bags and film coverings. It can also be blended with PLA and other biodegradable polymers for enhanced water resistance.
The composite could function as a light weight-bearing material comprising up to 98% sugar beet pulp, the scientists state.
This continued development of sugar beet pulp plastic – for example, as yoghurt cups, cottage cheese tubs or other thin, opaque plastic containers – could benefit sugar beet growers and beet sugar processors, they claim.
PLA is commonly derived from sugars in corn, sugar beet, sugar cane, switchgrass and other plants. Building on initial work done published in Industrial & Engineering Chemistry Research in 2008, the scientists showed up to 50% sugar beet pulp can be incorporated with PLA.