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Green additives could improve environmental profile of thermoplastic

By Joe Whitworth , 17-Oct-2012

Researchers have found green additives can improve the environmental profile of thermoplastic packaging materials and reduce oxygen transmission.

The green prodegradants, which are based on natural fatty acids and iron, turned conventional thermoplastic packaging materials into biodegradable materials.

Ferdinand Männle et al looked at thermoplastic packaging materials by using a mild oxidizing biobased additive.

Pro-degradant additives (PDA) have been used before to promote the degradation of polypropylene (PP) films and polyethylene terephthalate (PET).

Reduced oxygen transmission

In the first study, the addition of a green prodegradant to a 5-layer gas barrier laminate during processing provided it with significantly reduced oxygen transmission due to the resulting oxygen-consuming degradation process.

The results show that the oxygen transmission rate is significantly improved by addition of the prodegradant additive.

This can be explained by the oxygen consumption of a slow degradation process in the laminate which is induced by the prodegradant additive, said the researchers.

“Doubling of the amount of prodegradant additive does not induce significant degradation during processing and short storage.

“As a consequence, 5-layer laminates with reduced oxygen barrier layer thickness and retained gas barrier properties are feasible.”

Degradable properties

In the second part of the study a prodegradant additive was compounded into five different polypropylene qualities and their degradability was investigated.

The goal was to investigate changes in tensile properties and molecular weight during accelerated weathering due to oxidative degradation.

“The development of the mechanical properties also shows that all of the five PP qualities with prodegradant additive degrade rapidly when they are exposed to accelerated weathering.

"The typical mechanical properties of PP materials are lost after 72 hours of accelerated weathering.”

The researchers found several qualities of polypropylene which are used in packaging applications are degraded in accelerated weathering to an extent which makes digestion by microorganism feasible.

Degradable additives have caused controversy in the industry in the past with NAPCOR attacking their use in 2011, claiming they could be harmful to recycling systems.

Source: International Journal of Polymer Science

Published online ahead of print, doi: 10.1155/2012/297923

“Increased Performance of Thermoplastic Packaging Materials by Using a Mild Oxidizing Biobased Additive”

Authors: Ferdinand Männle, Jens Kjær Jørgensen, and Bjørn Steinar Tanem

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