| d2w Inside Program |  |
|
Question : What are oxo-biodegradable plastics?
Answer :
Oxo-biodegradable Plastic
D2W® Oxo-biodegradable plastic passes the tests prescribed by "American Standard for Plastic that Degrade in the Environment by a Combination of Oxidation and Biodegradation"
Degradation reactions will start soon after the product is made, but the fact that the formulation contains a stabilizing package moderates these reactions so that outward signs of degradation such as loss ofmechanical integrity should not be evident. This leads to the conceptof an induction period for break down and thus a useful shelf life. Additive works to break down the carbon-carbon bonds in the plastic leading to a lowering of the molecular weight and eventually to a loss of strength and other properties. The plastic does not just fragment, but is consumed by micro-organisms after the additive has reduced the molecular weight to sub 40,000 Daltons, and it is therefore "biodegradable." This process continues until the material has biodegraded to nothing more than CO2, water, humus, and trace elements.
d2w® Oxo-biodegradable = Oxidation + Biodegradation
Step 1: Oxo-degradation is an abiotic/chemical stage which begins with the cleavage of carbon chain backbone in PE and PP into shorter chain molecules and the incorporation of oxygen into these molecules as organic functional groups (i.e.: carboxylic orhydro-carboxilic acids, esters as well as aldehydes and alcohols). The hydrocarbon polymers change their behaviour from hydrophobic to hydrophilic thereby allowing the fragmented polymer to absorb water.
Step 2: Bio-degradation is a microbiological stage in which biodegradation of the fragmented polymer takes place. The molecular weight of the polymer is reduced during the first step to levels that will allow bacteria, fungi and algae to consume the carbon backbone fragments into their trophic process. The end chemical products of the biodegradation step are CO2, H2O, a small quantity of minerals and biomass with no toxic or harmful residues to soil, plants ormacro-organisms.
Degradation and biodegradation of an oxo-biodegradable polyethylene specimen consistent with changes expected by Tiers 1 and 2 of ASTM D 6954-04 has been found by RAPRA. Oxo-biodegradable plastic also passes the eco-toxicity tests prescribed by Tier 3 of ASTM d 6954-04, including seed germination, plant growth and organism survival (daphnia, earthworms).
|
|
