Isophthalic resin vs Vinyl Ester

Hi there.

I notice certain manufacturers don't offer a Vinyl Ester resin, but are selling isophthalic resin as their marine coat option. V/E comes up at nearly 2 times the price of the Iso. I wondered how much better the V/E is at preventing osmosis. And if used with a good g/coat how effective the Iso. resins are in this respect.

I guess it's a how long is a piece of string type question. But I would appreciate anyones opinion or experiences with this.

Many thanks

Dresca

 

Dresca,

There is a big difference between isophthalic polyesters and vinylesters, worth every penny of extra cost. In any polyester, ortho- or iso-, the monomer is styrene (45% to 48% by volume usually). The polyester molecule is dissolved in the styrene. A peroxide compound, usually methyl ethyl ketone peroxide (MEKP) is used to catalyze the resin, which cross-links with some of the styrene, but not all of it. What styrene is not used in the chemical reaction flashes off, giving that fiberglassy smell, leaving microscopic holes in the laminate. It is through these holes that water passes during osmotic blistering.

Vinylester resin also uses styrene as a monomer in about the same proportions. And it also uses peroxides like MEKP as a catalyst. What is different though is that practically all of the styrene is used in the chemical reaction. Most of the styrene catalyzes with the vinylester, and the remainder crosslinks with itself, which makes polystyrene molecules within the resin. This closes off the vast majority of the microscopic holes in the resin, and this is why vinylester is so impervious to osmotic blistering. This is why chemical storage tanks, such as underground gasoline tanks, are always made with vinylester resin.

I always specify vinylester resin for blister protection and repair if the client does not want to use epoxy resin. Epoxy, by the way, is 100% solid, and therefore is the best blister barrier material.

Eric

 

Thanks Eric

Appreciate the reply.

The tech. at the resin manufacturer said similar things concerning the styrene.

I've been told by 2 big resin manufacturer tech's that the Iso. resins have also excellent resistance to blister. Without getting into specific manufacturers - They sell this particular Iso. as a 'matched performance system' for use with their marine gelcoat for use in 'marine' and other similar industries. This particular iso. costs as much as my gelcoat, but the V/E is about 75% more expensive, it's a DCPD modified V/E specifically for skincoats. They describe the iso. resin that if used with their gelcoat it offers a 'superior blister resistance'. I guess I'm finding words like 'better' and 'superior' hard to quantify.

I worked out that with the pieces that I am building, these are 'in water' permanently, that I could make the whole piece from this Iso. resin for the same price as using a V/E skincoat and Ortho. backing. Hence the post.

I found this on the web
http://www.netcomposites.com/education.asp?sequence=24
bit on 'Blister Resistance'
Which covers some of what I asking, just how much better is the V/Ester over the Iso. in this respect? Will Iso. do the job as I seem to be suggested often?

Many thanks
Dresca

 

$ V benifits

Dresca, its a cost benifit v production decision, say on a solid layup where you gotta build up some thickness swap back to iso after the vinyle skin coat for thickness per $, if its sandwich with quite thin skins stick with vinyle or if you want & can afford the best stick with vinyle(better structural qualitys) or go to epoxy at higher per kg cost & higher labour/process cost again, but remember theres plenty of old boats well built with no or very few blisters that where layed up in iso/ortho. All the best from Jeff

 

That helps

Thanks Jeff,

I was wondering about older boats built using G/C+ Iso + Ortho.

->How much longer do the new boats last in comparison these days?

I need some more rigidity in the piece that I'm making, so I think then it will be G/C + V/E + ISO if the V/E has better structural properties as well. I'm all set up to spray open mould stuff and have no experience with Epoxies, so I reckon I'm set to run with the info. here.

Really appreciate the 2 replies. Having a forum of b/builders sure helps, as who would know more about B/Resistance than someone in the marine industry.

One other question if anyone can help. The V/E is an expensive material. Am I right in thinking most h/volume shops are spraying from 3 machines?
1. G/Coater +
2. then spraying in The V/E Skin +
3. spraying in the Ortho?
I know one of our competitors is set up this way, but I only have 2 reliable machines, and a third 'el-cheapo' spray machine which is hardly worth using. Question is
--> Anyone hand laying in skincoats on big objects?

Last question is - I was told by the resin manufacturer to use Powder bound CSM rather than Emulsion bound. -->Can anyone comment on this?

Many thanks
Dresca

 

Dresca, use the powder bournd say 300GSM choppy mat & lay it rich resin for skin coat, I only spray gel & hand lay or wet impregnate stitched fabrics. Regards from Jeff

 

Thanks Jeff

Cheers Jeff

 

That was my 13th post

So here's another just for luck!