UV Resistance

Question:

 

...As you know, we use  the PE flat film cuts as an intermediate layer in paving stone packages. It does happen, that less popular items are kept on our site for 1-2 years and so are subject to weathering. Here, we have discovered that the film disintegrates, is blown away by the wind and becomes damaging to the environment.

 

Answer

 

Along with other thermoplastics - e.g. polypropylene - polyethylene is a polyolefin. Ethylene, the basic component of polyethylene, is the olefin with the simplest structure:

 H    H

 |     | 

 C = C

 |     |

 H    H

 

In polymerisation, the ethylene molecules are bonded together. This results in the formation of long, chain-like macromolecules from equal components. The polyethylene molecules contain branches. Both the level of molecule chain branching and the length of the side chains have a significant effect on the properties of the polyethylene.

These molecule chains are "broken" under the influence of oxygen and light, the polyethylene disintegrates and dissolves into its base material - hydrogen and carbon. This process begins immediately, although it only becomes visible to our eyes after approx. 1 year, depending on solar intensity. Therefore, polyethylene is environmentally friendly, as no residues, gases, or other residues are generated.

However, this is precisely what you do not want in the current case. Making things more complex, is the fact that regenerate film is old film reconstituted. In the recycling process, old film is finely shredded, melted and extruded afresh into film. Yet this causes massive destruction of the mollecule chains, i.e. a regenerate film has relatively short molecule chains with little branching. Consequently, the film no longer has any high mechanical strength.

 

The following suggestions for improvement should be tested:

1. Use of new, transparent goods. As the film between the stones is in the dark and relatively dry, decomposition should be relatively slow, film simply protruding between the stones would disintegrate, as would cover sheets used.

2. Use of new goods, but fitted with UV protection. Disadvantage: relatively expensive (we enclose an offer) and this film would also be used for items with a far higher stock turnover.

3. Protection of your less popular items with a black cover layer. Black is the best protection against light and UV radiation. However, it does have the disadvantage that it is no longer possible to determine what is under the film without labelling.

 

Please discuss our suggestions internally in your company. We are, of course, available for any queries you may have.

 
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