Styrene and Infusion...

General Composites Discussions Composites Talk
#1

To anyone that uses Polyester in the process of infusion…

Do you add styrene to your mix to thin out the resin to get better flow? I typically use epoxy but have had some recent customer interests in using Polyesters.

Maybe I’m just an absolute failure, but from what I’ve found is that the cure time with epoxy is longer, so it travels farther although slower as it has more time… Polyesters cure considerably quicker, so I would like to get as much flow as possible.

My test:
Epoxy from 3/8" feed on a controlled subject gets 30" from feed

Poly from 3/8" feed on same controlled subject gets 12" from feed

Current product in question:

PE Clear Surfboard 249. It is thicker than I am used to for Polyester resin and not sure how well / far it is going to infuse… I know I know, test test test. Just wondering what the general consensus was with using Styrene.

Thanks guys, I greatly appreciate it!

-C

#2

Don’t test test test. Do a search on viscosity, and more importantly, on rheology.

The rheology of a hand laminating polyester is totally wrong for infusion. It will infuse for a couple of inches, then suddenly halt.

Base polyesters are relatively thin, and need thickening (by adding amorphous silica, glycerene and other stuff) to turn it into a hand laminating polyester. Which does impregnate the fiber, but will not run out of the fiber on a vertical.

It does not make a lot of sense to first thicken a polyester, and modify the rheology, then thin it down again with styrene monomer, to make it into a (sort of) infusible resin.

Better find a source for infusible resin. Do a search for companies working with polyester resin, call them, and ask for their resin suppliers. These should be able to help you.

It is common to even thin out an unmodified resin with some styrene to thin it even more. Rheology is not changed however.

This will give a resin that has basicly the same characteristics as epoxy resins, with the major difference (during infusion) the curing speed. Epoxy cures slowly, polyester cures quite suddenly. There are peroxides (in USA: catalyst) which give longer geltimes, keep viscisity lower, and generate less exotherm. (Syrgis / Norac / Andos). Explore for instance the MCP and HCP75 peroxides.

edit: sorry to be a bit harsh, not my meaning. Just want to help.

#3

Herman,

No worries on “harshness”… I fully understand that being a bit abrasive is sometimes the best way to get a point across, I didn’t take it personally.

To be honest, I’ve never heard of Rheology until this very moment… did a quick search and wow, interesting stuff! I see where you’re coming from with regards to the reason the chemical is the way it is… it was engineered for a specific purpose and I am applying it to an application it was never intended for.

So from what I’m getting out of this (thus far):
Quick fix - wrongfully add styrene to change its rheology and get a bit more “flow” out of it.

Correct fix - get the right resin next time that was meant for infusion, haha.

I like the clarity of this 249 resin… its really clear, clearer than most every epoxy I’ve ever seen! Most PE’s that I’ve used in the past were so dark, so this stuff looks pretty sweet! Too bad its so thick. These parts are extremely cosmetic so clarity matters.

-C

#4

Suppliers should be able to sell you clear, infusible polyester. the only disadvantage of polyester is the added cobalt, which usually gives a purple hue, which turns green somewhat.

clear resins therefore are formulated from fast resins, that need only little cobalt. You will probably get the resin without cobalt, and have to add yourself. In that case use 6% or 10% concentration cobalt, this holds less diluents which can spoil things.

#5

Herman,

You my friend are a random book of knowledge and it’s awesome. Haha, it seems like I can ask about anything and you’ll be able to provide a solution, the history behind it, and how to approach it in different angles. Herman, you are an incredible individual!

-C

#6

Hehe, guess on the price that it has cost to reach that level…

The fun thing about my job is that I visit customers, who in general have a problem of some sort. At first you do not have enough experience to solve everything, but as you grow older, you encounter more and more similar problems, and by combining information you are able to solve everything.

This, combined with good contacts at about any supplier, is why I am what I am.

So only 2 tips:
-grab any opportunity to look into someone elses kitchen.
-keep good contact with your suppliers

#7

Using Silmar surfboard resin is your problem. In my experience catalyzing at 1%, (10 drops per ounce or 6 drops per ounce depending on who you ask) cures that resin in 5 seconds.

If you want to make a part using polyester resin I’d recommend using regular laminating resin at 1 - 1.5% or ISO tooling resin. When ever I have to make a part out of a polyester resin I’ll use an ISO tooling resin at 1 - 1.5%.

If you want to use something better than that, that isnt an epoxy, use a vinyl ester resin. I’ve infused everything from small 4" x 24" strips of carbon to entire jet ski hulls using ISO tooling and VE resin.