Bjorn:
    I spoke to the Raka people about using their "thin" epoxy, which is listed as being viscosity of 600 centipoise and has been used for infusions.   With their slow hardener one should get an actual flow time within the infusion of about 6 hours, with the time to a tacky set of about 12 hours, at which time the pump can be turned off, and after 18 hours the laminate should be set enough to peel off the membrane &C.   Pot life itself is far less than the actual flow time within the infusion naturally.   In the thin distributed state it is going to go off far more slowly than in the pot.   The question in my mind is how long does the first phase take, where the epoxy is being drawn into the laminate out of the pot, and how long does the resin go on distributing and equalizing after the taps are closed.  The latter phase should be critical to the resulting laminate, both in strength and weight.   12 hours is a long time to run a vacuum pump......... however there is no reason not to have a reservoir and a vacuum switch so it can be cycled.

                                                                                                                H.W.


On 08/24/2018 09:05 AM, Björn bjornmail@gmail.com [harryproa] wrote:

 

It seems like some terms (pot life, working life) are a bit fuzzy. I have been reading quite a few datasheets now, and some manufacturers have a large ratio been potlife and working life. Example: maybe 0.5hour potlife, 2 hours worklife, 3 hours geltime. Others have lets say 1,5 hours potlife, 2.5 hours worklife, and 3 hours geltime. I'm guessing that both epoxies might behave pretty much the same, it's just that they have different ways to define the first two stages. But that is just a guess.

Your epoxy looks very good!

I have this product, but I haven't tried an infusion with it:

http://www.nilsmalmgren...se/Datablad/TDS%20S%20NM%20Infusion%20665.pdf

The datasheet has a graph of how the viscosity changes with time.

I payed about 50 usd per litre for my 1.4 litres!

I've also been looking at this, which is cheaper:

https://shop1.r-g.de/en/art/104100AP

Regarding the "infusability comparison number" that I mentioned, it should of course be the ratio of potlife and viscosity. (not the product!)

Let's calculate the  "infusability comparison number"  for these products:

BAKELITE® EPR 04908

5 hours / 0.13 Pas = 40

NM Infusion 665

3 hours / 0.28 Pas = 10

R&G Epoxy Resin L + Hardener GL 2
3.5 hours / 0.25 Pas = 14

EP45 (The eBay stuff)

1 hour / 0.5 Pas (? no data) = 2

So if I try infusing again with NM Infusion 665, it seems like I have a 5x better chance to succeed, at least. =)

And it looks like the Swiss product is of exceptional quality, just like you would expect!

On Fri, Aug 24, 2018 at 2:37 PM, Fram henny@fram.nl [harryproa] <harryproa@yahoogroups.com.au> wrote:

 

A resin that starts to cure during the infusion is killing the composite part you are making. So for infusing you need a very slow hardener. As I've said in a previous post, in my case gelling starts only after about 8 hours or a bit sooner when temperature is more than 20 degr.C

Do not compare these resins with hand-lay-up resins. Total different animal...

> Op 24 aug. 2018 om 13:15 heeft Björn bjornmail@gmail.com [harryproa] <harryproa@yahoogroups.com.au> het volgende geschreven:
>
> Thanks, but I was looking for Mr. Fram's explanation/reasoning. Because as I per my message, my experience is that the viscosity gets too high to be usable (for hand layup) just slightly after passing potlife. So it seems to be an exponential process. Which I think most chemical reactions are.
>