World's first 'green' linear polyethylene launched

Braskem, Brazil’s largest petrochemical firm, has developed the first internationally certified linear polyethylene - a flexible and transparent plastic widely used for food packaging - made from 100 per cent renewable raw materials. 

The new product is a co-polymer of ethene and butene. The butene co-monomer supplies some short lateral branches to the polymer chain - so that it resembles barbed wire - reducing the density of the polyethylene. 

Comprising about 10 per cent of the polymer chain, the butene is obtained by the dehydration of a biobased butanol produced through the fermentation of sugarcane. 

The process allows carbon dioxide to be captured and locked up in the plastic, Braskem says - helping to reduce the atmospheric levels of the greenhouse gas. 

The plastic is the latest product to come out of a two-year, $5 million (?2.52 million), Braskem programme to produce a family of ’green’ polyethylenes from sugarcane. 

In June 2007, the firm announced the world’s first internationally certified plastic obtained from 100 per cent renewable raw materials: a high-density polyethylene (0.96grams per cubic centimetre) widely used for rigid materials such as car fuel tanks, bottles and flasks. The linear polyethylene has a lower density of 0.92grams per cubic centimetre.

’We are not stopping with these two products. Actually, we are creating a new generation of biopolymers as part of our commitment to sustainable development,’ says Antonio Morschbacker, responsible for biopolymers at Braskem. 

The company has a single bio-ethylene pilot plant that can feed four different polyethylene pilot plans, allowing about one tonne of each polymer to be produced per month. Braskem’s goal is to produce about 200,000 tonnes of the green polymers per year in a commercial plant by 2010.

’The process used by Braskem is simple and easy to carry out,’ says Bluma Soares, professor at the Federal University of Rio de Janeiro. ’It’s possible that no-one has done this before because it’s easier to use petroleum than to use more land to grow sugarcane. However, the worldwide debate on the need to develop materials in ways that are less harmful to the environment has put factors other than the technical ease with which the plastic can be produced on the agenda.’ 

Meanwhile, Dow, the world’s largest producer of polyethylene, and Brazilian ethanol firm Crystalsev, expect to produce 350,000 tonnes of the plastic from sugarcane at their plant, which is expected to start production in 2011.

Luisa Massarani