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I'm researching the degradation of polyethylene (PE) plastic films such as in plastic bags, and am trying to figure if they degrade chemically. If so: under what conditions, and into what byproducts. Most sources for PE say that it is inert, but it seems to be referring to the pellets used in manufacturing rather than the film/end product. I don't know if surface area has a significant effect here.

I know they mechanically break down (fragment) due to heat, sunlight (UV), physical stress, etc. Does anyone know how small these fragments can get and if they can be moved through water (possibly a separate question).

My question is about either high- or low-density PE.

For more context, see: Removing agricultural plastic film waste after 10+ years degradation

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Unless polyethylene has been pretreated during its manufacturing process it is a very obdurate material, being susceptible to degradation by oxidation and UV light. Degradation can occur with chlorine, particularly of polyethylene water pipe that convey chlorinated water.

Concerning minute fragments of polyethylene results from degradation, these like the parent material they derive from are very obdurate. They can be moved by surface waters to end up in oceans to be constituents of ocean plastic garbage dumps.

Some researchers have found that polyethylene can be susceptible to accelerated degradation via microbes. If polyethylene is pretreated/conditioned with steam, heat or UV exposure the affect of microbial colonization and attach is enhanced.

Oxo-biodegradable carbon backbone polymers - Oxidative degradation of polyethylene under accelerated test conditions

Microbial Degradation of Polyethylene

Degradation of Polyethylene by Fungus

Biodegradation of low density polyethylene (LDPE) by fungi
isolated from municipal landfill area

Biodegradation of Polyethylene by Bacillus cereus

  • by "obdurate" do you mean that it persists as a compound (ie does not break down chemically)? I am unfamiliar with the word in terms of science and dictionaries define it in relation to people, meaning "stubborn" – ElizabethEnviro Aug 24 '15 at 13:23
  • One of the challenges is that we do not know who left this material out (and when), so we have no way of knowing whether it was pre-treated. The assumption is that it was not – ElizabethEnviro Aug 24 '15 at 13:25
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    @ElizabethEnviro: Yes. Geologists use the word for rocks or parts of rocks that persist while other rocks or parts of rocks weather or erode – Fred Aug 24 '15 at 13:26
  • @ElizabethEnviro: I agree, best to assume it is untreated. PE sheets have been around for decade. During the late 1970s it was the latest thing as a means to control weeds. It was a spectacular failure. That type of PE was untreated. I'm assuming your PE sheets would be the same. Also, as far as I am aware, degradable PE bags first became available maybe 5 to 10 years ago. – Fred Aug 24 '15 at 13:29

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