By MohammadRiyaz - 4/5/2015 7:42:43 AM
Hi, I am using these compounds for my resin as these are the only ones available:Epoxy Resin - (Bisphenol – A – Epichlorohydrin)Hardener - (3 – Amino Methyl – 3, 5, 5 –trimethylcyclohexylamine)What ratio should I use so as to achieve a strong part and a glossy finish? I tried (10:1) and (5:1), the part still seems to be quite weak.I tested with the (5:1) ratio and the overall viscosity of the mixture seems low and I get air bubbles inside the part.The part is made up of 25 layers of glass fibres (Woven) so it's solid. Its a layering procedure only.The mixture also does not produce any heat when combined together.
The part also does not pop out of the mould and it takes a lot of hammering to get it out which damages the upper surface. I used a lot of Honey wax mould release for this as this was the only one available. The mould is just a hollow cavity of a part and I tried to layer the fibres using a stainless steel base below it. The resin still spreads on the whole stainless steel base when everything is cured but pops out well without effort due to wax release.I am quite new to this but I think with your advice I would be able to find a proper solution and share it with all of you. Thanks.
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By Dravis - 4/8/2015 11:00:29 AM
The hardener and resin are most often a "matched pair" so you will usually not get good results when "mixing" hardener and resin from different manufacturers or even different products from the same manufacturer.
Most "matched" Epoxy systems have a Hardener-to-Resin ratio of between 1:10 and 1:3, some specialist types may have 1:2 or 1:1, but that is usually coating types or "fillers"
Some Epoxy "systems" are very forgiving in terms of the mixing ratio, and do not require great accuracy in getting the ratio correct, others are very "delicate" and require precision weighing of both Resin and Hardener.
Also you really need to be sure of the ratio, is it by weight or volume??
Correctly cured epoxy resin will be very hard (normal laminating/infusion types) and quite brittle, when not being laminated or with added "filler" Some Coating types will be a bit "tough" or very slightly flexible.
If you can not get the correct ratio from the manufacturer, you can do a controlled test, by mixing up small batches (in disposable plastic cups) and leaving them to cure at the exact same temperature/moisture and for the same time. Then test them. The proper ratio will be the one that produces the hardest, slightly brittle sample. (I would test 1:3, 1:4 and 1:5 by weight first, they are the most likely)
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