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News

Eastman introduces next generation biodegradable plastic

Eastman Chemical Company : 24 April, 2002  (Technical Article)
Eastman Chemical Company has announced the introduction of Eastar Bio Ultra copolyester, a new entry in its line of Eastar Bio biodegradable resins.
Eastar Bio Ultra copolyester features a higher melt viscosity than its sister product, Eastar Bio GP copolyester. 'Eastar Bio Ultra with its higher melt viscosity is engineered specifically for the rigorous demands of blown film processing, permitting higher throughputs and improved processability,' said Bert Heijne, Eastman's business market manager with responsibility for the biodegradable product line. 'Extrusion processing conditions will be similar to a high melt index low density polyethylene (LDPE).'

Engineered to be durable for its useful life, Eastar Bio Ultra completely biodegrades to carbon dioxide, water and biomass in 180 days in a commercial composting environment. It will become invisible to the naked eye in as little as twelve weeks, a time frame comparable to paper in the same environment.

Film made of this copolyester is strong, moisture-resistant, and durable outside a composting environment and provides good tear and puncture resistance, particularly at lower temperatures.

Applications for the product include agricultural films, lamination films for rigid food packaging, leaf and lawn waste bags and horticultural applications. Eastar Bio Ultra copolyester is approved for food contact in the European Union and the U.S.

When used as a laminate film on conventional biodegradable materials such as starch, Eastar Bio Ultra provides moisture protection and strengthens rigid packaging structures such as produce and meat trays, significantly increasing the volume of materials suitable for disposal in composting facilities.

The search for plastic material compatible with the environment has taken many paths over the last few decades. The goal was for a material that would last for the useful life of the product, biodegrade, process easily and be affordable. The need for a biodegradable product has evolved into a number of types of products.

Regulatory bodies, such as DIN (Germany), CEN (Europe), JAS (Japan), ASTM
(United States) and ISO (international), have published standards for biodegradability for these products. Although the definitions, test methods, and certification requirements differ in details, they have several features in common:

In a time frame comparable to kraft paper, a biodegradable polymer within an active composting environment must fragment and/or disintegrate sufficiently to completely pass through specifically sized sieving screens.

Within an active composting environment, the biodegradable polymer must be reduced to carbon dioxide, water, minerals and biomass in a time frame comparable to kraft paper, usually 6 months.

Toxic residues or toxic monomers cannot be produced by the composting process.

The compost containing the biodegraded polymers must support plant growth.

Eastman first introduced a biodegradable material, EASTAR BIO copolyester in the 1990s. A second generation of EASTAR BIO copolyester is now available, a material with substantial advantages over other forms of biodegradable and compostable materials.

EASTAR BIO copolyester is an aliphatic-aromatic copolyester that performs for the useful life of the manufactured article and then completely biodegrades in a composting environment in six months. Composed of terephtalic acid, adipic acid and butanediol.

This biodegradable thermoplastic resin is manufactured in Europe and is commercially available. It is a Eastman patented product, and the intellectual property surrounding its development covers a number of aliphatic monomers, a wide range of compositions and blends and articles made from the product, like films, fibers and non wovens.

It exhibits a balance of properties particularly of interest to processors and end users of nonwovens, food packaging and other forms of packaging. These properties include superior adhesion, mechanical properties, compatibility with other materials and the ability to blend with a range of fillers from starch to fiber, talc, and sawdust.

Blown film produced from Eastar Bio copolyester is a soft material, with modulus lower than low-density polyethylene but with superior dart impact strength, specifically at low temperatures. The strength properties may be altered by orientation/higher blow up ratios. Films of this material, although not clear, exhibit good contact clarity.

While the oxygen permeability of the copolyester is slightly lower than that of polyethylene, water vapor transmission rate is significantly faster. This property makes this copolyester a viable candidate for use in applications such as fresh food packaging and other applications that would benefit from moderately 'breathable' characteristics.

Eastar Bio copolyester offers excellent adhesion to a variety of substrates. Strong co extrusion structures can be produced with other polyesters and polylactic acid. Low melt viscosity allows excellent wetting of spun bond substrates to achieve significant mechanical adhesion at higher coat weights.

Additionally, the heat-seal initiation temperature when tested on a Theller unit is about 65C and ultimate heat-seal strength is in excess of 24 grams per mm. These characteristics allow lowering of the heat-sealing temperature of the structure by 10C compared to LDPE without sacrificing seal strength. Therefore Eastar Bio copolyester is an alternative resin for packages requiring the use of ethyl methacrylate (EMA) to lower the heat-sealing temperature or to decrease sealing time.

A film produced from Eastar Bio copolyester undergoes complete disintegration within 12 weeks, thereby complying with the specified time frame to meet DIN certification requirements. The film tested was 0.127 mm in thickness. Thickness does affect the time required to disintegrate the film. Thinner films will undergo disintegration in a shorter time frame, but both will completely biodegrade.

Eastar Bio copolyester may be processed over a wide temperature range dependent on the processing technique employed. Sufficient drying is recommended or process instabilities may occur because of decreased viscosity and melt strength.

It can be processed on standard polyethylene equipment for cast, blown and oriented film extrusion, injection molding, spun bond and melt blown nonwovens, extrusion coating and fiber spinning.

The development of environmentally sound materials has taken a number of paths. The growing infrastructure for handling biodegradable plastics and the efforts made to establish standards and certification protocols are rationalizing the marketplace for many of these materials. One important challenge is to ensure the reputation of man-made materials is not compromised by products which cannot degrade in the required timeframe or do not complete the biodegradation process to CO2, water, and biomass.

Eastar Bio copolyester has been extensively researched and exhaustively tested to ensure its ultimate benign effect on the environment. Its combination of processing characteristics, final film properties, and price/availability compared to other biodegradable plastic options make it a particularly viable candidate for a variety of film, fiber and coating applications. Applications for which its properties provide an advantage include refuse bags, drinking cups, disposable plates, food and non-food packaging, medical garments, agricultural film and nonwovens.

Eastar Bio copolyesters fully meet ASTM and DIN standards for biodegradation.
'There are a number of applications using Eastar Bio Ultra copolyester currently in development with customers,' said Heijne. 'These products will be hitting the markets in the coming months.'
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