incompatibility glass and polyster resin ? 1

[niksmith]

I dont know whether this question is appropriate on this forum or in the polymer forum and so I will post this also there .
I am presently sticking glass( of 4 mm thickness ) using polyester resin onto fibre glass of around 2mm thickness . However the problem I have is that many of the pieces seem to break after some days .
My feeling is that there is an incompatibility in the coeffecient of expansions of the two materials namely glass and resin leading to this cracking during shipment by air .
I would like to know if someone has had a similar experience and the possible solution for this problem .

Thanks in advance

 

[cf10]

What is the mechanism of failure? Does the glass break in half, or (more likely) the fiberglass delaminates from the glass? Is there a glue used, or do you stick it on while the fiber or resin is "wet"?

They have different coefficients of expansion, but really, polyester is a poor adhesive if you are using it "wet". Polyester resin can shrink up to 5%, prestressing the brittle glass, and the brittle bond, a whole lot, priming it for a break. A flexible epoxy, as a glue or as the binder for the (cured) fiberglass, would work much better: its a better adhesive, and doesn't shrink.
I can help you with sourcing...

good luck,
CF

 

[niksmith]

Thank you CF10 for the reply . I stick the fibre glass resin onto the glass when it is still wet .I think you are right when you say that it may be better to use a flexible epoxy resin as a glue or binder once the fibre glas resin is cured . Can you let me have the names of some manufacturers of such elastic epoxy resins ?

Regards,

 

[cf10]

Resinservices has some very nice epoxies.

http://www.resinservices.com.

Their htr-212 with 386 Hardener is a good combo, very clear, high temperature resistant, and is flexible or 'toughened'.

For cheaper epoxies try douglas and sturges,

http://www.artstuf.com.

2001/7132 combo is also clear.

Also: you could make the fiberglass out of epoxy and fabric, instead of polyester and fabric, and avoid the gluing step.