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Re: UV

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Based on work with other "plastics" IMO the problem is with direct sunlight, indirect sunlight delivers energy at orders of magnitude less.'s hard to get a suntan indoors :)

For example,  PEX (cross linked polyethylene tubing) is only rated for 30 days direct sunlight exposure but has no problem with indirect (bounced, reflected) sunlight it might see in a crawlspace.

FRP retrofit of columns need UV protection when the columns are exposed to sunlight,  unprotected epoxy  deteriorates rather quickly in direct sunlight.

I would say FRP that is in "fully shaded" location & never sees direct sunlight would be fine the cost savings worth any potential risk & what are the consequences of failure?

Also, are there other environmental  factors that  protective additives or coatings  give protection against?

I have chunk of 20 year old epoxy sitting on my work bench in the garage....indirect sunlight for 20 years, looks like new.  The same piece would go chalky in a few months in the sun.

To add to Jordan's comment........I think water or snow would probably be your only problematic surfaces.  Bare earth & vegetation doesn't reflect much.


On 3/1/07, M. David Finley, P.E., P.A. <davidfinley(--nospam--at)> wrote:
Do UV rays "bounce" and/or reflect?
My reason for asking is that exposed structural fiberglass (and other materials such as PVC) normally need to have UV inhibitors or a protective coating if they are used in exposed (outdoor) conditions.
But what about something placed under a bridge deck for example.  It would not get direct UV radiation, but could there be long term deterioration due to reflected UV?

David Finley
M. David Finley, P.E., P.A.
2086 SW Main Boulevard - Suite 111
Lake City, FL  32025