Milky Vinylester

[mikereed100]

I just laid up a fairly thick (3 layers each mat/roving, about 4mm) cylinder. As the layup kicked it turned a milky white and so it remains. There was no runout, the fibers were well saturated, the piece cured fully, no tackiness, there was no moisture in the resin and it was not a humid day. The piece was fairly exothermic but not overly so as far as I could tell. The manufacturer is stymied, never heard of this before. Any ideas?

Mike

[ondarvr]

What did the left over resin in the container look like, milky or clean?

[mikereed100]

Originally Posted by ondarvr

What did the left over resin in the container look like, milky or clean?

Good point, it was clear.

[ondarvr]

Sounds like damp glass, sometimes you don't notice it at first, but after it sits there for a while it starts to get milky.

[mikereed100]

Originally Posted by ondarvr

Sounds like damp glass, sometimes you don't notice it at first, but after it sits there for a while it starts to get milky.

Ahhhh, I'll bet that's it. I'll spend some time drying the glass on the next one and see how that goes. Thanks!

[tunnels]

Originally Posted by mikereed100

I just laid up a fairly thick (3 layers each mat/roving, about 4mm) cylinder. As the layup kicked it turned a milky white and so it remains. There was no runout, the fibers were well saturated, the piece cured fully, no tackiness, there was no moisture in the resin and it was not a humid day. The piece was fairly exothermic but not overly so as far as I could tell. The manufacturer is stymied, never heard of this before. Any ideas?

Mike

Milky resin . Water , gel coat or some other contaminant . Damp glass , damp surface , damp container ,
Did the resin still go hard in the usual gel time ? or is it slow and not properly hard ??
Some thing that no one ever takes into consideration is humidity !! The presents of moisture is ever present as it surrounds us everywhere we go work and live . Its a killer !!

[mikereed100]

Originally Posted by tunnels

Milky resin . Water , gel coat or some other contaminant . Damp glass , damp surface , damp container ,
Did the resin still go hard in the usual gel time ? or is it slow and not properly hard ??
Some thing that no one ever takes into consideration is humidity !! The presents of moisture is ever present as it surrounds us everywhere we go work and live . Its a killer !!

It gelled normally and seems to have cured well but I will redo the piece as it is part of a rudder drum and will spend it's life submerged. The glass had been stored outside and, although it was boxed, I am sure it picked up some condensation. I will sun-dry it before trying again. Amazing how such a small amount of moisture can have such an effect. The part looks like I added white pigment and is opaque!

[tunnels]

Originally Posted by mikereed100

It gelled normally and seems to have cured well but I will redo the piece as it is part of a rudder drum and will spend it's life submerged. The glass had been stored outside and, although it was boxed, I am sure it picked up some condensation. I will sun-dry it before trying again. Amazing how such a small amount of moisture can have such an effect. The part looks like I added white pigment and is opaque!

The dryer the glass the better ,sun dry is ok but make sure you get it inside and undercover before the evening condensation starts to decend !!!

[legendinownmind]

If the whole laminate looked normal until it started to cure then you are OK. It is just the resin. I have laid up parts using vinyl ester that did the same thing. They turned out fine. It could be something with the catalyst causing the color change.

[tunnels]

Originally Posted by legendinownmind

If the whole laminate looked normal until it started to cure then you are OK. It is just the resin. I have laid up parts using vinyl ester that did the same thing. They turned out fine. It could be something with the catalyst causing the color change.

I just had a flash from the past !
Was it chopped strand matt you were using or a fabric material stiched , woven or what ever ??? ?
Chopped strand matt comes in two forms of binder for holding the strands together !!

[legendinownmind]

tunnels,
we used chop on the part. So, yeh it could have been the binder.

[ondarvr]

Do you mean chop from a chopper gun (gun roving), or chop strand mat?

Gun roving doesn't use binder and there are a couple of types of binder for CSM, but they shouldn't create issues and cause the resin to become milky.

If what cured in the bucket stayed clear, but the laminate was milky, it leaves some type of contaminate in the glass, water or ?.

You did say this didn't look like it was from heat, correct, just a white milky look, was it even through out the resin?

[tunnels]

Originally Posted by legendinownmind

tunnels,
we used chop on the part. So, yeh it could have been the binder.

Yes the binder could have contibuted to the milky look
E matt has a emoltion binder and is the most common . The binder picks up moisture and during wintery or times of high humidity gets damp .
P matt has a differant binder and is not prone to the same problem .

[ondarvr]

Yes there are binders applied in an aqueous solution, both polymer and PVAC types can be used in this way. These binders can be made more or less hydrophobic as needed for the use in mind. They are then heated to remove any residual moisture. Re-absorption of moisture may, or may not affect the binder to a great extent, it depends on the type and the specific formulation. Another method is to apply the binder in powder form and then heat it until it melts onto the fiber, these types would have varying degrees of water resistance and absorption also. What it comes down to is not so much which type of binder is used, but if there was enough moisture in the storage area for it to cling to the glass in the first place, absorbed or not.

[tunnels]

Originally Posted by ondarvr

Yes there are binders applied in an aqueous solution, both polymer and PVAC types can be used in this way. These binders can be made more or less hydrophobic as needed for the use in mind. They are then heated to remove any residual moisture. Re-absorption of moisture may, or may not affect the binder to a great extent, it depends on the type and the specific formulation. Another method is to apply the binder in powder form and then heat it until it melts onto the fiber, these types would have varying degrees of water resistance and absorption also. What it comes down to is not so much which type of binder is used, but if there was enough moisture in the storage area for it to cling to the glass in the first place, absorbed or not.

Did you know also that p matt is slightly stronger than e matt !
Pmatt wets out better and the resin completely surrounds the strands where as ematt has a small percentage of bundles of strands that never get completely encapsulated with resin .