North America is finally beginning to acknowledge the potential of biodegradable polyesters in packaging. The continent is lagging behind Europe and Asia in finding packaging applications for these synthetic resins, which break down rapidly after disposal. In fact, global suppliers have been commercializing a wide range of these biodegradable polyesters for the past five years. Demand is increasing at a reported rate of 30% per year—although from a comparatively small base. In addition, its continued growth faces some stumbling blocks in North America.

One obstacle that this 'green' packaging must overcome is its high cost. Synthetic biodegradable polyesters range from $1.50-$2.00/lb—making them more expensive than paper and plastics such as LDPE, PP, PS, and PET. Suppliers had expected the resin's viability to be boosted by the rise of composting, its low cost of disposal and its marketability as an environmentally friendly material. However, North America has been much slower than expected in building infrastructure for sorting and composting organic waste. In addition, higher cost has often outweighed 'green' value. For example, last year Bayer AG stopped making the synthetic polyester products that the company had introduced in 1995 because of "no sound economic justification" from regulatory organizations.

Nevertheless, synthetic biodegradable polyesters are increasingly being utilized in flexible and rigid packaging. These polyesters are classified into two categories—highly amorphous polyesters, which are flexible and clear, and semicrystalline polyesters, which are more rigid. These resins are produced in modified PET polymerization plants from petrochemical feedstocks. While other petrochemical-based polymers take centuries to break down after disposal, these polyesters take approximately 12 weeks to disintegrate under aerobic conditions—meaning water and microbes are present. They decompose into CO2 and water rapidly and thus comply with U.S., European and Japanese composting standards.

These 'green' polyesters are now being used primarily for paper coating, fibers and garbage bags, says Julian Jensen, business market manager at supplier Eastman Chemical. The company offers Eastar Bio, which comes in general-purpose and blown-film grades. "We plan to stay ahead of fast-rising demand," says Jensen. Another market for biodegradable polyesters is thermoformed packaging, where they add functional features—such as moisture resistance—to cheaper biodegradable materials. A third use for these resins is in blends with PLA, starch, organic wastes and natural-fiber reinforcements such as flax. Blends account for a substantial part of the material's market because they mitigate its high cost.

Many global suppliers now offer products in the U.S. For example, BASF sells Ecoflex copolyesters, which only recently arrived in the country. Ecoflex films are clear, strong and cling well—making them suitable replacements for vinyl in vegetable, fruit and meat wraps. In comparison, polyesters from Eastman Chemical are well suited for rigorous environments. They block moisture and grease—making them ideal for lawn-and-garden bags, agricultural films, netting and paper coatings. Two other global suppliers with U.S. offerings are Korea's SK Chemicals and Japan's Showa Highpolymer, part of the Showa Denko group. SK Chemicals' products are utilized in films, disposable cutlery, food trays, hairbrush handles and paper coatings, while Showa's resins can be found in commodity bags, traffic cones and industrial trays.

Blends represent a thriving market for biodegradable polyesters, not only because of their high cost, but also because they work well in combination with each other and with organic materials such as PLA and thermoplastic starch. For example, Eastar Bio and Cargill Dow's PLA are combined because of complementary properties—the former is tough and adheres well, but has low stiffness, while the latter is brittle and possesses poor adhesion properties. A combination of the two produces a material that exhibits their individual strengths. Japan's Dainippon Ink and Chemicals (DIC), meanwhile, combines polyester and PLA properties in a biodegradable copolymer, which is based on a copolyester and lactic acid. The copolyester imparts flexibility while lactic acid imparts stiffness. Indeed, blends offer a way to optimize material strengths and compensate for weaknesses.

Synthetic biodegradable polyesters are making strides in food packaging. They are now utilized in thermoformed trays for fresh produce and meat, as well as in disposable plates, bowls and cups. Apack AG, Germany, sells polyester food trays, which have already replaced EPS foam trays for organic produce in two leading U.K. supermarket chains. They are 3 times the price of EPS counterparts but their 'green' appeal is highly valued for natural foods. Along with produce trays, Apack also makes meat trays, which are said to improve shelf life by 50% to 6-9 days. An Apack subsidiary is also pushing biodegradable polyesters for use in hot- and cold-drink disposable cups. Seeking to replace EPS, these 'green' cups reportedly provide good insulation and protection from moisture penetration. Meanwhile, Earthshell Corp., CA, and DuPont have joined forces in targeting the disposable food-service market, which includes plates, hinged clamshells, hot and cold cups, etc. DuPont is offering a new flexible sandwich wrap for fast-food chains.

Indeed, the market for synthetic biodegradable polyesters is showing steady growth. Suppliers are working on cost-effective production methods to get prices down. In the next few years, expect suppliers to come to market with polyesters produced by bacteria fed with glucose.

Source: Biodegradable Polyesters: Packaging Goes Green
Robert Leaversuch, Executive Editor
Plastics Technology, Sept. 2002
http://www.plasticstechnology.com/articles/200209fa3.html