News

Polyethylene in application

Total Petrochemicals last year launched a new generation of metallocene polyethylene resins for rotational moulding. Due to its high performances, one of them has been used in the production of tanks for agrochemicals products by Rotoplast for Hardi-Evrard.



Crop treatment and protection products are spread in the fields from tanks attached to tractors. These tanks must be completely resistant to the vibrations caused by transport, to temperature, to the density of agricultural fertiliser and to chemical alterations caused by contacts. Safety is an essential criterion for farmers, as is cost, because the purchase of this equipment entails a major investment.

To meet the justifiable expectations of these users, agricultural equipment specialist Hardi-Evrard has ordered polyethylene tanks based on rotational moulding. But not just any polyethylene. In this case, it is a metallocene resin developed last year by Total Petrochemicals (mPE M 3423 UV resin). It is one of the four innovative grades specially developed for rotational moulding by Total’s petrochemicals segment. Its performances make metallocene mPE M 3423 UV perfectly suited to chemical and agrochemical applications.

Close cooperation
For the tanks’ manufacture Hardi-Evrard commissioned Rotoplast, a specialised producer of rotomoulded polyethylene products in Beautor, France. From day one, Rotoplast worked closely with the Total Petrochemicals Feluy Research Centre. Several tests series were conducted to identify the optimal result during rotomoulding.
In rotomoulding, the polyethylene resin in powder form is placed in a mould of the shape of the final product. The mould is then sealed and placed in the oven, where it is rotated on two perpendicular axes. Under the combined effect of heat and rotation the powder melts and attaches itself to the mould’s interior surface. It is then removed from the oven and cooled in the cold air. The tank can subsequently be extracted from the mould. The entire cycle takes less than one hour.

Speed is one of the advantages of rotomoulding. A second is that it can be employed to manufacture high volumes of fairly technical pieces in complicated forms in a single operation, without assembly or soldering. It is especially economical for the manufacture of small series of a few hundred or thousand pieces, where an alternative process such as extrusion blow moulding would be ten times as expensive. The volume of the Hardi-Evrard tank is 4 cu m, but mPE M 3423 UV resin can be used to produce much larger pieces, up to 40 cu m. In all possible designs.

Numerous potential applications
The new metallocene polyethylene resins have become available at the same time as improvements to the process and to the rotomoulding equipment, bringing an increasingly wide array of applications within reach. Besides the chemicals and agrochemicals market, they are used a lot in water sports, in the manufacture of kayaks and buoys. A 5-metre boat was recently built from rotomoulded polyethylene, and consumers will soon be able to buy models 7 or 10 metres in length.



Rotomoulded polyethylene is also particularly suitable as underground tanks for degreasing and purification stations. Total Petrochemicals is able to predict the behaviour of polyethylene for several decades.

The automotive market, especially rotomoulded bodies for the new breed of lightweight, non-polluting cars, appears to be another interesting area. It’s a long way from the somewhat dowdy image of plastics. In a sign of the times, major Italian and French designers are now producing furniture and decorative objects in rotomoulded polyethylene.
Nowadays, polyethylene is synonymous with creativity!

>> click here to view the movie "Production of a rotomoulded tank" (.wmv 12 Mo)