oxo-biodegradable additive family are well suited to a wide
range of processes and applications, have extensive food contact
status and have been used for many years to provide a reliable
and reproducible oxo-biodegradable profile around the world.
The key attribute of the Reverte®
technology is the degradation profile and how it compares with a
more conventional ‘oxo-biodegradable material.’
Wells Plastics laboratories measure the
first stage of degradation (oxidation) using carbonyl indexing
and embrittlement point determination, processes which have been
developed and exploited at Wells for many years and are now
adopted by the industry.
The growth of the carbonyl index relates to
the level of oxygen which has been incorporated into the polymer
and wherever a carbonyl group is introduced the polymer
undergoes a chain scission, i.e. a molecular weight reduction
and a change in its physical and chemical properties.
Graph showing direct relationship between
carbonyl index and molecular weight aged in accordance with ASTM
The more carbonyls introduced the further
removed it becomes from its polymeric nature. Once a critical
point has been achieved in carbonyl index the polymer loses its
flexibility and breaks apart under the minutest of stresses. At
this time it is considered to be at its ‘embrittlement point’.
What makes Reverte® stand out is the profile
of degradation, the curve plotted of carbonyl index versus time
starts off very flat with a period of no change in the carbonyl
index over time. This period is known as the ‘dwell time’
another phrase coined by Wells Plastics.
After the dwell time has been passed the
degradation then proceeds rapidly until the embrittlement point
is reached and beyond that the plastic falls apart.
The molecular weight is lowered and the
material available for biodigestion.
Biodegradability of a Reverte®
treated film occurs once the molecular weight is below 5000.
At this level the polymer no longer exists
and is a wide range of discrete oxidised species. Bacteria and
fungi find these species suitable for a source of carbon and can
be assimilated into the lifecycle resulting in the formation of
biomass and CO2 under aerobic conditions.
Biodegradation can only occur (whether this
is for Reverte® plastics or for
grass cuttings) in environments that have warmth, bacterial
activity and moisture. This fact is often overlooked when
marketing oxo-biodegradable or hydrobiodegradable materials.
an additive masterbatch in the production of plastic and provides
the most cost effective and safest method of dealing with
conventional plastic waste.