Lots of ferment in biopolymers. (Close-Up).

* Someday we may dispose of old car parts by turning them into mulch. What may sound like an environmentalist's daydream is a potential outcome of R&D aimed at turning biodegradable polymers into engineering plastics capable of automotive use. These resins are derived from plant starch by bacterial fermentation and hence may be termed biopolymers.

Adding muscle to PLA 

In Japan, researchers are enhancing properties of polylactic acid (PLA) biopolymer in hopes of making it a viable option for automotive and other durable applications in a just few years. Until now, PLA has been targeted mainly at clear packaging. NEC Corp. in Tokyo reports that natural-fiber reinforcements derived from the kenaf plant can increase PLA's rigidity and heat resistance by 70% to 80%. NEC says PLA containing 20% kenaf fiber has a heat-distortion temperature of 248 F and is expected to find commercial use soon in housings for NEC computers.

In a parallel effort, Toyota Motor Corp., and Toyota Central R&D Labs, both in Tokyo, are investigating nanoclay particles as another reinforcement to boost the HDT of PLA. Researchers have identified a method for dispersing the ultra-fine particles in liquid lactic acid monomer. Toyota, which recently began producing its own PLA from sweet potatoes in Indonesia, has its eye .on auto interior parts.

New ways to 'grow' plastic

Metabolix Inc., in Cambridge, Mass., has received a federal grant to re-engineer the metabolism of E. coli bacteria to help it more efficiently convert sugar into engineered biopolymers. Metabolix is developing a Biopol resin family based on polyhydroxybutyrate valerate (PHBV). The goal is to reduce the cost of PHBV grades suitable for films, coatings, and molded durable goods.

In France, surplus production of wheat and sugar beets has prompted interest in using them to make biopolymers. Erstein Sugar Refinery in the Alsace region has fermented beets into a resin suitable for packaging. The feedstock is a waste liquid by-product of beet-sugar manufacturing.

Other French researchers are developing ways to make biopolymers from wheat. One group has a fermentation process for making a material suitable for extruded and molded fruit packaging. This resin works best in structural layers of a multi-layer package, combined with a biodegradable polyester film to protect it against moisture. Meanwhile, the Center for the Promotion of Carbohydrates (CVG) in Amiens has developed a mixing process for plasticizing wheat starch into a biopolymer said to have good mechanical properties.