There are mainly two options available to
make normal Polythene into Biodegradable film and these are as detailed
below:
Starch based or Biobased (Hydrodegradable)
It is made from
corn (maize), potatoes or wheat. This form of biodegradable films
meets the ASTM standard (American Standard for Testing materials)
and European
norm EN13432 for compostability as it degrades at least 60% within
180 days or less.
These materials predominantly require an active microbial environment
such as municipal compost before they will degrade. The heat, moisture
and aeration one gets in a compost pile are vital to this type of
biodegradable film working well.
Pros:
-Degradable & Compostable
-Normally No fossil fuel or very little fossil fuel (some grades have a % mixed
with traditional polymer)
-Faster degradation
Cons:
- Poor mechanical strength than additive based example – filling
a starch bag with wet leaves and placing curbside can result in the bottom
falling out when a hauler picks it up.
- Limited Shelf life and difficult to recycle
-Some argument over actual energy input as compared to oil based polymers when
you consider whole life cycle of growing crop through to raw material production.
-Relatively expensive polymer cost….but likely to fall in future as industry
develops
Typical Application area: Municipal/Local authority compost system
Additive based
Films made out of blending an additive
to provide UV/Oxidative and then Biological mechanism to degrade
plastics film typically in 6 months to 2 years in a landfill site
and/or standard composting system.
In this, biodegradation is a two stage process in which, first the
plastic is converted by reaction with oxygen (light, heat and/or
stress) to molecular fragments that are water wettable and second,
these smaller oxidized molecules are biodegraded. (converted into
carbon dioxide, water and biomass by microorganisms)
Pros: - Cheaper than starch based & Proven technology
- Controlled degradation
- Film made out using this look, act and perform just like their non-degradable
counterparts, except they break down after being discarded
- Easier to Recycle.
Cons: -Made using non-renewable fossil fuel
- Degradation depends on conditions of heat, light, stress, air etc
Typical Application area: Rubbish Bags, Compost Bags, Carrier bags,
Agricultural Film, Mulch Film
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