shelf life of fiberglass sizing

I bought a roll of triaxial knitted glass off of a craigslist ad a couple years ago. I'm wondering about the quality of laminates I lay up from this if I were to use it today.
It has a silane finish. Is there a well-accepted rule of thumb for the shelf life of the sizing/finish used on it?
If the shelf life has expired (probably, at this point) can I still use it with a reasonable expectation of successful end results? I'm not looking at a high-spec layup so it shouldn't be a huge issue, but I don't want to throw good money after bad, either. I plan on using this with an epoxy resin, most likely ProSet INF-114 over a Corecell core.
Any info/experiences would be appreciated.

 

The silane finish is compatible with epoxy. I don't know that it degrades. Do you know what brand it is?

 

Not sure of the brand- the label was in the end of the roll and went away with a prior project.

 

not likely it is an issue, but you might contact the manufacture, or at the very least one of their distributors and ask the question.

 

I've used 'glass that was quite "unfresh" and have had no issues at all.

 

Just one question for myself : would it be possible that a glass fiber fabric had the same degradation than glass in a window?

 

I've used CSM and some glass roving over 10 years old without a problem. The key is simple, as long as the stuff is DRY and not full of humidity (and never water saturated) it will be fine. I also use some carbon weave and tapes that are a few years old without any problems. Even better if stored in the dark so UV does not attack any surface treatment. The other thing that seems to last a long time are polyester pigments, not had any problems even with 15 yr old tints. Resins would be useless (esp hardeners), but the pigment itself seems to retain sufficient fluidity in the base to still be useable.

 

The material never saw water in the time I owned it and was wrapped in plastic and kept in an insulated garage. I'm thinking at this point I can probably use it and get acceptable results.

 

Glass in a window degrading ??

There was a long held belief that glass (especially in windows) "slumped" over many years.

This has been thoroughly refuted. I have never heard of any reason for glass to degrade. Of course there are many types of glass,

The formulation of Glass Fibre, however, has no direct correlation to sheet/moulded glass composition (see below) . Still, glass fibre longevity seems to be more based on the lifecycle of the product than the individual fibres.

Some boat hulls test have actually shown an improvement in some types of strength over time.
http://www.proglassinc.com/assets/boat.pdf





"Naming and use. Pure silica (silicon dioxide), when cooled as fused quartz into a glass with no true melting point, can be used as a glass fiber for fiberglass, but has the drawback that it must be worked at very high temperatures. In order to lower the necessary work temperature, other materials are introduced as "fluxing agents" (i.e., components to lower the melting point). Ordinary A-glass ("A" for "alkali-lime") or soda lime glass, crushed and ready to be remelted, as so-called cullet glass, was the first type of glass used for fiberglass. E-glass ("E" because of initial electrical application), is alkali free, and was the first glass formulation used for continuous filament formation. It now makes up most of the fiberglass production in the world, and also is the single largest consumer of boron minerals globally. It is susceptible to chloride ion attack and is a poor choice for marine applications. S-glass ("S" for "Strength") is used when high tensile strength (modulus) is important, and is thus an important building and aircraft epoxy composite. The same substance is known as R-glass ("R" for "reinforcement") in Europe). C-glass ("C" for "chemical resistance") and T-glass ("T" is for "thermal insulator" – a North American variant of C-glass) are resistant to chemical attack; both are often found in insulation-grades of blown fiberglass"
http://www.redorbit.com/reference/fiberglass/

 

Thanks for trying Rwatson. My question, put in another way, was: if the window glass is not degraded, why would do that same material in the form of fibers?
We are talking about degradation of a material, not a panel collapse due to fatigue.
Surprising that the GPR improve its mechanical properties over time but I speak of fiberglass, not GRP. It seems that my English is not good and you have not understood me.

 

My understanding is the fibers don't break down, but sizing and treatments can change with age. GRP products have shown to become stiffer with age, but this is a function of the resin system employed, not the fibers within the fabric.

To answer the previous notion that glass might be a liquid, an extremely viscous one, well it's not a liquid, but it's also not a true solid. It is an amorphous solid. In a nutshell and on a sub-molecular level, it's not "organized" enough to be considered a solid and there is enough movement to be considered liquid like, abet doing so very slowly. This all started when the wives tail of medieval glass being swollen at the bottom, suggested the glass had sagged in the sash. This isn't the case (over the given time frame), it's just lousy glass making. The short of it is, the molecules in glass actually flow, depending on several variables, but do so quite slowly. It would take billions of years for a pane of glass to sag in its sash, but it will given enough time.

 

My query was more about the finishing chemical used to help bond the resin to the fibers. I was under the impression that it degraded over time.

 

Sizing can beak down, but if stored properly, it'll last a very long time. UV, vibration, wide environmental swings, etc. all can conspire against you, but if kept, clean, dry, out of the sun and at reasonable temperatures, you'll be fine.