In article ,
Ian Stirling wrote:

Don Bruder wrote:
In article ,
"Ge
offrey W. Schultz" wrote:
snip I know nothing of Acetal or UHMW (until reading this message, not even
the fact that they existed) but I can tell you with certainty that the
UV resistance of PE (Either HD or LD "flavors") is pretty much
nonexistent. They'll both "brittle up" and start to crumble in short
order. Depending on the thickness, coloring (if any), exact amount of
exposure, intensity of the UV source, and so on, they may start showing
signs of problems in just a few hours, or they may stand up for a few
days, but they *WILL* disintegrate into a worthless scattering of
plastic dust in far less time that what you're likely to call
"acceptable" for your application.

It depends on the additives.
I've got an around 10 year old poly-tunnel, which is ~0.5mm polythene sheet
covering aluminium hoops.

"Polythene"? (Tries to figure out why that rings a bell... And fails...
I've heard of the stuff before, but I can't remember where or in what
context)

Idunno what you've actually got, but if it has survived 10 years in
sunlight, I'm certain beyond any possibility of doubt that it's
something other than Polyethylene.

Whether high or low density, polyethylene is notorious for
disintegrating in sunlight - 6 months, tops, is all the longer a piece,
especially a thin sheet, of it can be reasonably expected to last when
directly exposed to sunlight. If it lasts beyond that, it's a safe bet
that, whatever it is, it ain't PE.

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