using old fiberglass

[jpolenek]

I've read that fiberglass deteriorates with time and may eventually have reduced adhesion to epoxy. Is there any data to support this?

I have a bunch of RA7715 UNI that's about 5 years old which I want to use on my new Cozy MK IV project. It has been stored in a garage so it was protected from direct exposure to the elements but in terms of temperature and humidity, it has gone through several summers and winters. Should I use it or would I be better off scrapping it just to be safe?

 

Joe

[Wayne Hicks]

Only 5 year old? Use it in confidence.

 

This is my opinion: short of doing a microscopic analysis, there isn't much of a way for layman builders quantify the quality of older cloth other than to use it and see how it wets out. If it wet outs well, that tells me that the chemicals they put into the cloth to help wet it out are still in good shape. If the cloth doesn't wet out well, then that's a sign that the chemicals are breaking down.

 

Again, my opinion, cloth has to be really, really old or have been abused significantly before throwing it away. "Abused" meaning exposed to sunlight, dust, dirt, debris, etc.

[jpolenek]

I ran across an article in Cozy Newsletter #83 entitled "Care of Glass Cloth" by fiberglass expert Gary Hunter.

 

The age of the fiberglass doesn't seem to matter. If the glass has gotten wet then it's no good because the adhesion-promoting "sizing" (a water soluble coating) has likely washed away. High humidity is not a problem as long as it hasn't caused mildew.

If in doubt, test a piece and if the epoxy wets out properly, the glass is OK to use.

 

Joe Polenek