polyester resin infusion logistics questions...

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#1

Hey everybody

we are making composite skateboards (mostly skateboards) using a VARTM process. Its going pretty well now.

BUT

we are doing some research into cheaper resin systems to lower the bottom line (SURPRISE!!!) and so we are looking into polyester and vinylester infusion resin systems, and i have some questions about those. My background with polyester resin systems is the surfboard industry, so im pretty familiar doing wet layups with it. Ive only infused a handfull of test samples with a polyester system before using our VARTM method that we use successfully with our skateboards. so here are the questions:

should i be nervous about damaging our vacuum pumps? i know styrene is pretty agressive stuff, is there a danger of short or long-term damage to the pumps or to the vacuum manifold?

does anyone know of a clear vinylester or polyester resin system? the samples we have are very dark in color, like brownish. our parts are all very bright neons and rich colors, and the tint has not been able to overpower the resins natural color.

thanks for any help

-david

#2

No worries with styrene… it’s not an issue and actually if you vacuum bag you’re eliminating the VOCs from going into the air. The pump oil catches the styrene and should be disposed of properly as it’s hazardous waste. It doesn’t effect the pump itself.

Ultimately you’re sacrificing in strength and durability by using a vinyl/polyester resin. You’ll probably need more material for the same strength as with epoxy, so that may or may not make it cheaper. Though there are many forms of resins now. I’ve worked with vinylester for infusion and the parts came out good though, epoxy is superior.

I don’t remember the brand of resin we had used but it also had a bit of a color to it as well.

have you considered prepregs? They’re very easy to lay up and make excellent quality parts. WIth out of autoclave stuff, you can cure at lower temps and get good properties. You can pre cut kits, and make the workflow more streamlined.

There is a bit more investment in some ways but, setup on infusion can be a pain and one mistake and you ruin a part. Pre preg is also not as bad in price because you only buy one material, no mixing… the advantages go on. You might want to price it out and figure in labor savings as well as savings in waste. If you used reusable bags you could eliminate much of the need for consumables.

I’ve been messing around with making some boards… just in design phase. I have a ton of unidirectional that I plan on using to make the lightest strongest part possible. Seems like it could be a fun project.

#3

yea i know about the strength issues… but the boads are verywell built and we could add additional reinforcements. of course thorough tesing will be done before we go to sell them if we get that far. honesty i dont really want to use polyester or vinylester just due to the health hazards and the strong smell. it doesnt bother me much (its the smell of my childhood lol my dad made surfboards for a living) but the general workforce doesnt seem to tolerate it well, even with masks…

the molds are 2 part closed molds, no vacuum bags.

as for the prepreg option - we use a 10mm thick PET core called 3d core and it consumes quite a bit of resin to fill the channels. so much so that a prepreg fabric wouldnt be able to provide enough resin to fully saturate the core. we could do a combination of prepreg and infusion but at that point its the same amount of preparation and materials but with the same resin injection necessity. i was thinking last year about curing the skins of the boads first, then bonding in a core… but they wouldnt look nearly as cool

thanks

-david

#4

heres a link to our website, you can see some pics of the boards there.

http://hydroflexskateboards.com/portfolio-item/skateboard-models/

also, heres a link to a quick video of our infusion process.

http://vimeo.com/74988073

-david

#5

That’s pretty sick.
Mind if I ask what resin you’re currently using?

#6

That looks really awesome, great job!
Polyster infusion doesn’t harm a good rotaryvane pump. Make sure you keep an eye on your oil and change it on time.
A clear polyester or vinyl are hard to find and if there are there they probably are expensive.

#7

thanks for the kind words guys. we are currently using Gurit Prime 20LV infusion resin. really good results with this stuff. very low viscosity, pretty minimal shrinkage, nice cured properties

we decided not to go the polyester / vinylester route yet… but we will still continue to research slowly.

the best candidate we found for a polyester resin is a surfboard resin. very clear, nice looking light blue - green tint. but it is expensive (though not as much as epoxy, but almost) and we need to make sure everything on the production line is polyester freindly… were not there yet. PLUS, the epoxy seems to have better properties anyways.

thanks for the vacuum pump info, that puts my mind at ease a bit :slight_smile:

thanks

-david

#8

great boards! Really like the colors of the resin!

#9

Try to use urethan resin , its cheaper than epoxy but still has good specification
it is used for many types of carbon fiber profiles and tubes

#10

If you like the Prime20LV, I would suggest you try the Prime20ULV. This has a lower viscosity. They use the same base resin, but the hardener is different. I personally prefer ULV over the LV version, but both are good.

#11

yea i asked about it but they told me the shrinkage is a bit higher… unfortunately we are so resin rich at the moment that a higher shrinkage rate would be pretty bad.

we are working on a new mold design that may be able to improve that, but it will take time to reconfigure the whole production line if we decide to go that route. i think ts definitely where we should be headed, but i dont make the final decisions.

there is another resin type in the same lineup as the 20LV and the 20ULV, called 27LV. it apparently has a slightly lower viscosity than 20LV but lower shrinkage as well, we are excited to try it.

i am curious to try the ULV AND urethane at some point, if i can get samples.

thanks

-david