Frequently Asked Questions
- With what level of certainty can the timing of degradation be controlled?
- Do the additives or finished products need to be stored or handled in any special way?
- Is biodegradation the end result of degradation?
- Is the plastic material in a flexible packaging product (e.g. a shopping bag) after degradation reduced to zero?
- How can microbes consume a plastic material?
- Will d2w™ degradable plastics create methane in a landfill?
- Is feedstock recycling a better solution?
- Is incineration a better method of disposal of plastic waste?
With what level of certainty can the timing of degradation be controlled?
As indicated elsewhere, the speed of degradability can largely be controlled by the additive package used for any particular application. The actual speed of degradation, however, is affected by the levels of uncontrollable variables - particularly heat, light and stress - to which the plastic is exposed. Higher than planned levels of these will speed up the process and lower levels will slow it down (but not stop it). For this reason, manufacturers typically build a significant safety margin into the planned degradation time so as to ensure that the properties of the plastic remain intact for the full useful life of the product in question.
Do the additives or finished products need to be stored or handled in any special way?
As indicated in the answer above, a degree of care is sensible so as to ensure that the products are not exposed to excessive heat, light or stress. For example, degradable plastics should be stored in a cool/shaded place rather than in the open air or in a hot, sunny place. Beyond this sort of 'common sense', no special requirements apply.
Is biodegradation the end result of degradation?
For d2w™ film, the answer is yes. Oxidative degradation of d2w™ polyethylene and polypropylene causes a breakdown of the molecular backbone of these plastics. The molecular chains become shorter and water 'wettable' permitting the formation of a bio-film on the surface of the plastics which allows microbial deterioration to take over.
Is the plastic material in a flexible packaging product (e.g. a shopping bag) after degradation reduced to zero?
Flexible plastic packaging, by its nature, has properties that are essential to provide effective packaging products. These properties include water resistance, flexibility and strength. The long entangled molecular chains within a polymer determine these properties. With the oxidative action of d2w™ the molecular 'backbone' collapses. The initial result is embrittlement and disintegration - the material can no longer be considered as a plastic. Ultimately, after microbial deterioration has completed, the overall degradation process will have resulted in the creation of some H2O, some CO2, and a small amount of biomass.
How can microbes consume a plastic material?
Normally the microbes can not access the carbon or hydrogen in a plastic material because the chains are too long - indicated by the huge molecular mass of plastics, e.g. 300,000u However, it is now widely recognized that when a plastic material descends to below 40,000 molecular weight - due to oxidative degradation - the material becomes water wettable and can sustain a bio-film on its surface. This bio-film supports numerous micro-organisms that will feed off the carbon and hydrogen elements of the oxidizing plastic.
Will d2w™ degradable plastics create methane in a landfill?
No, methane occurs in anaerobic conditions when carbon can only combine with hydrogen. The d2w™ degradation process is an oxidizing system - if no oxygen is present the carbon and hydrogen remains locked in the remnants of the plastic and methane will not be emitted.
Is feedstock recycling a better solution?
(Feedstock recycling refers to the concept of returning waste plastic fully upstream to the petrochemical refinery. The waste material re-enters the manufacturing process.)
No, economics do not favour this scheme. The resultant feedstock is as expensive as virgin material, notwithstanding the extra indirect costs of collection, transportation and sorting.
Is incineration a better method of disposal of plastic waste?
Polyethylene, like all plastics, is actually a very refined form of oil. It therefore has a very high calorific value. However, in practical terms efficient disposal by incineration is difficult. Given the problems associated with emissions, the need to move waste plastics sometimes over long distances to incinerators and the negative public attitude towards building new incinerators, insufficient capacity is available - or likely to be available for the foreseeable future - in most countries and parts of the world.