Plastics study claims trace amounts of PLA ruin recycled PET

Jane Ellis, packagingnews.co.uk, 19 February 2008

 

Polylactic acid (PLA), even when found in very small quantities in plastics collected for recycling, could make recycled PET resin "unsuitable for most applications", a study has claimed.

 

The study was carried out for trade association PET Containers Recycling Europe (PETcore) by Switzerland-based PTI Europe, which specialises in PET package development and research but is not a member of PETcore.

 

PETcore said PTI Europe was "completely independent and has no finance or support from any PET company". 

 

PTI Europe's initial start samples showed a higher yellowness for the PLA bottles in the neck and other unstretched areas, compared with standard PET bottles. The haze value also increased significantly for bottles made from PLA, which is derived from cornstarch.

 

When drying PLA flakes, PTI Europe noticed that PLA tended to stick to the metal surfaces of the dryer or to form agglomerates.

 

The firm said: "It seems that standard PET drying conditions are too high for PLA, which could have an effect on production efficiency."

 

In addition, the extrusion process "badly affected" the colour/haze of the pellets, making them "very hazy" after extrusion.

 

The presence of 1% of PLA resulted in opaque extruded pellets.

 

PETcore said the findings contradicted the views of PLA manufacturers, who had said that 0.1% of PLA in collected PET could be processed successfully.

 

Around 40 billion PET bottles (one million tonnes) are currently collected across the EU, but PETcore said "input purity, sorting and recycling technologies and high-quality market outlets" were vital if this was to increase.

 

Last November, Innocent Drinks decided to stop using PLA  for its fruit Smoothie bottles because the material did not use any recycled content and commercial composting was not yet a "mainstream option" in the UK.