[arunkumar]

wat makes the plastic/polythene non-degradable...?

[marquis]

I think you are referring to the TV commercials that claim plastic/polyethylene will never degrade.

I've wondered about that myself.  The claim doesn't seem reasonable.  How often do you see a plastic bottle by a road that has gone from it's original clear color to a yellow (degraded) color and brittle form?  This is a form of degradation and happens in a relatively short period of time.  Granted, this is photodegradation and land fill conditions would be different.  Still, I'd like to see the footnotes and special conditions that were used to generate that advertisement.

[Borek]

They degrade, albeit slowly.

Question is - which one is better, the one that degrades (and liberates chemicals) fast, or the one that degrades slowly, and is almost inert. I have not seen arguments that would make me think polyethylene is in general bad for environment. It is bad in some specific places - I recall reading or hearing about sea turtles dying of starvation after they got their oesophagus blocked. Or something close, I am not sure about details.

[typhoon2028]

PE & PP will degrade with sunlight (UV), but I don't think the chain lengths change much.  A very small amount of degradation can cause yellowing.  Obviously, the degradation had to be small or you would not have a bottle anymore.  A buried a PE in the ground will last a very long time.

[doc30]

Those plastics are far more degradable than glass. As others have mentioned, they are UV degradable. But they are not bio-degradable. No microbes metabolize PP or PE. There may be biochemists and biologosts trying to develop something than can metabolize it, but we aren't rhere yet. However, some bacteria have evolved through natural means to digest Nylon 6.