On 7/16/2017 10:27 PM, Danny D. wrote:
On Sun, 16 Jul 2017 21:52:59 -0400, Ed Pawlowski wrote:

That would depends on where suburbia is. In the snowbelt, the roads
are salted and sanded and that can have an effect. Obviously that is
only a prtion of the problem but look at windshields after 60,000 miles.

Califonria suburbia. The environment doesn't get any easier than
California, except for the
full-time sun - there's almost no dirt, grit, salt, or cold to worry about.

I'd bet on UV. It is not kind to plastics.

I'd bet on the California UV also, as the plastic is "foggy".

There is always grit to worry about on the road.
I know the formula used for scratch resistant plastic but cannot divulge
it. It would basically be applied like a wax. That's why it may be in
a lens refinish kit but I do not know for sure. These finishes are also
used on plastic eyeglass lens which easily scratch. Composition I had
seen was for acrylic sheets.

Both acrylic and polycarbonate have good outdoor resistance but both are
much softer than glass and easily scratched and dulled. Years ago I had
a watch with plastic lens that I occasionally restored clarity with
tooth paste. Toothpaste contains particulate that will not scratch teeth
but is a mistake to use on plastic dentures as it could wear them. I
have an old dental bridge that once had a plastic coating. Now years
later after years of brushing it is gone and all metal.