Bondo Glass With Expoxy Resin

[bguffer]

Hi all,

I have a bunch of Bondo type fiberglass mat and weave. Someone recently told me it was not intended to be wetted with epoxy resin. Is that true? What would happen if i used epoxy resin with the Bondo glass? Less strength, no strength, brittleness?

I am ordering some Aeropoxy/West Systems/Us Composites epoxy over the weekend. Both structural and laminating types. Should i purchase fiberglass meant to be used with epoxy resins as well? Or will the Bondo glass impregnated with epoxy resin still work for some/all purposes?

Bob

 

[quickburst]

Hi all,

I have a bunch of Bondo type fiberglass mat and weave. Someone recently told me it was not intended to be wetted with epoxy resin. Is that true? What would happen if i used epoxy resin with the Bondo glass? Less strength, no strength, brittleness?

I am ordering some Aeropoxy/West Systems/Us Composites epoxy over the weekend. Both structural and laminating types. Should i purchase fiberglass meant to be used with epoxy resins as well? Or will the Bondo glass impregnated with epoxy resin still work for some/all purposes?

Bob

Any fiberglass cloth, matt or whatever will work. While at US Composites get some 8oz cloth, good for most anything.

 

[rstaff3]

If I remember correctly, the weave of the bondo fabric I had was coarser and thus required more post-glassing filling than the glasses I got from, say Mr. Fiberglass.

 

[mkadams001]

The fiberglass cloth will work with epoxy.

 

[MarkII]

That's a good question about the Bondo fiberglass mat, the stuff that sort of resembles a Scotch-Brite pad. I'm not sure what that stuff is even meant for, and if you used it with epoxy, would you need to saturate the entire mat with it? That would be one heck of a lot of epoxy. :eyepop:

MarkII

 

[bguffer]

I think i heard something to the effect that the Bondo glass was meant to be used with polyester? resin. Not sure what happens when you exchange that with epoxy resin.

 

[mkadams001]

The fiberglass is the reinforcing agent for the epoxy or polyester resins. Either one will work fine with the glass cloth or mat. Polyester resins are much cheaper and weaker than epoxies. So, you have nothing to worry about using epoxy with glass cloths or mats.

 

[kramer714]

two different questions, mat and cloth

Mat: Fiberglass mats are designed for polyester resins because the binder that holds the glass fibers together dissolves in styrene (what makes the 'stink' in polyester resins), once the binder dissolves the fibers can be compacted down using a few specific tools including a roller that looks like a bunch of wheels and one that looks like a series of spikes. Making polyester parts usually involves putting down some wet resin, putting mat on top and then adding more resin working it down with the special rollers.

You can use epoxy with mat but it will be harder to get it in place as the fibers won't move as much, and can be more difficult to wet it. Having said that I have used fiberglass mat with epoxy many times, usually for making a fixture or mold.

Cloth: The issue with cloth is the sizing. Sizing is a treatment or coating that is applied to the glass cloth to help 'couple' the resin to the cloth, it also affect chemical resistance. There are various sizings around, Volan and silane are the most common. The sizing is what gives some fiberglass parts their color. Volan gives the 'green tint'. For rockets, fiberglass sold for polyester will work with epoxy, silane is typically used for surfboard fiberglass shouldn't be a problem for epoxy.

 

[stantonjtroy]

Actually cloth, that which has a weave ( cross weave, twill, unidirectional ect.) can be wetted out with either resin or epoxy. Matt, the stuff that looks like a scotchbrite, can only be used with resin. There is a light bonding agent added to matt (holds it together while dry) that will disolve in ester based resins (polyester or vinylester) allowing for a clean wet out. Epoxy, however, will not disolve this binder. People try and apear to succeed but the binder prevents actual surface bonding of the fibers at the micro level and delam/bond failure will eventually occure. Soaking the matt in acetone for about 10 min will remove the binder. Let it dry and epoxy can be used though the matt will become quite loose and a little messy to work with.
It also depends on the material. For example glass can use epoxy or resin; Carbon fiber can use both but epoxy is best. Quarts fiber and kevlar can only use epoxy. Then there are numerous different epoxies and resins. These are some good resources for info: https://www.fibreglast.com/contentpages-Learning-Center-286.html and https://www.acp-composites.com/home.php.

FWIW
Troy

 

[mkadams001]

Here is a link to an article about using West Systems Epoxy with chopped mat fiberglass.

https://www.westsystem.com/ss/chopped-strand-mat-epoxy/

 

[Rocket Al]

Actually cloth, that which has a weave ( cross weave, twill, unidirectional ect.) can be wetted out with either resin or epoxy. Matt, the stuff that looks like a scotchbrite, can only be used with resin. There is a light bonding agent added to matt (holds it together while dry) that will disolve in ester based resins (polyester or vinylester) allowing for a clean wet out. Epoxy, however, will not disolve this binder. People try and apear to succeed but the binder prevents actual surface bonding of the fibers at the micro level and delam/bond failure will eventually occure. Soaking the matt in acetone for about 10 min will remove the binder. Let it dry and epoxy can be used though the matt will become quite loose and a little messy to work with.
It also depends on the material. For example glass can use epoxy or resin; Carbon fiber can use both but epoxy is best. Quarts fiber and kevlar can only use epoxy. Then there are numerous different epoxies and resins. These are some good resources for info: https://www.fibreglast.com/contentpages-Learning-Center-286.html and https://www.acp-composites.com/home.php.

FWIW
Troy

I will second (or third) this info about the sizing in chopped strand mat. In discussions with the owner of Schiebly Chemical (from whom I buy big honkin' rolls of both mat and cloth) I asked about compatibility of both types of glass with polyester and epoxy resins, and was warned away from the use of mat with epoxy. Who am I to argue.


Al