Biodegradable/degradable polythene film
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Contents |
[edit] Introduction
Conventionally, plastics are made of fossil fuel. These conventional types of plastics are heavily used worldwide – mainly in packaging and household applications. The benefits of low production costs, light weight, strength, relative imperviousness to gas and water, clarity, and printability are highly regarded, but the final disposal of used flexible plastics causes problems. The ever increasing use of plastics, particularly in packaging, has become a significant source of environmental pollution (litter) and created problems in waste management. If disposed of by landfill, the plastics worsen the shortage of landfill sites. If the plastics are incinerated, they can emit poisonous gases such as dioxins. These problems motivate the public to take more care of the environment. Making plastic bags biodegradable is one way to try to ease the task of waste reduction.
[edit] What are my options for Polythene Film?
There are two main options for making normal polythene into a biodegradable film:
[edit] (1) Starch based or Biobased (Hydrodegradable)
It is made from corn (maize), potatoes, 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.
[edit] Examples of polymers with which starch is commonly used:
- Polycaprolactone (PCL)
- Polyvinyl alcohol (PVA)
- Polylactic acid (PLA)
These materials predominantly require a controlled microbial environment such as an industrial compost facility 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.
[edit] Pros & Cons of Starch based to Additive based film/bag
[edit] Pros:
- Degradable & Compostable
- No fossil fuel or very little fossil fuel (if % mixed with traditional polymer)
- Faster degradation
[edit] Cons:
- Poorer 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
- Can only be composted in a special composting facility.
[edit] Typical Application area
Industrial Compostable Facility, Please visit your local city government's website to see if you have an industrial composting facility that accepts residential compost.
[edit] (2)Additive based (Oxodegradable/Photodegradable)
These films are made by blending an additive to provide a UV / oxidative and/or biological mechanism to degrade them. This typically takes 6 months to 2 years in a landfill site and/or standard composting system. In these films, biodegradation is a two stage process; first the plastic is converted by reaction with oxygen (light, heat and/or stress) to molecular fragments that water can wet, and then these smaller oxidized molecules are biodegraded, i.e. converted into carbon dioxide, water and biomass by microorganisms.
[edit] Pros & Cons of Additive based to Starch based film/bag
[edit] Pros:
- Cheaper & Proven
- Controlled degradation
- These films look, act and perform just like their non-degradable counterparts, except they break down after being discarded.
[edit] Cons:
- Made using fossil fuel
- Degradation depends on conditions of heat, light, stress, air etc
- They do not comply with European Norms on compostable products
[edit] Typical Applications
Trash Bags, Garbage Bags, Compost Bags, Carrier bag, Agricultural Film, Mulch Film
[edit] News
BBC News: "All Tesco bags 'to be degradable dt. 10th May’06" http://news.bbc.co.uk/1/hi/uk/4758419.stm
BBC News: "Degradable carrier bags launched dt. 2nd Sep’02" http://news.bbc.co.uk/1/hi/uk/2229698.stm
