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Warren (Staff) - 11/3/2016 9:24:04 AM

Milky discolouration on exposure to water is a sign of moisture absorption.  EF80 is not naturally porous to water once fully cured, so it would indicate the resin part you have made is for some reason not fully cured.  Commonly this occurs quite recently after part manufacture when the resin seems cured and is safe to demould at room temperature, yet can still be sensitive to moisture absorption if exposed to water soon after demoulding. This would normally improve over several weeks as the resin finally fully cures over time. Other factors that could cause this include, poor mixing, inaccurate mixing ratio, low temperature curing or possibly the presence of some contaminants.

Initially I would get the milky parts into a very warm place for a period of time to see if they are still able to dry out. If you are lucky that may solve the problem.  We would suggest that a post cure of parts to be immediately used in water soon after build will help ensure the resin is as cured as it can be and lesson the chances of the resin going milky.

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Warren (Staff) - 3/7/2018 5:54:42 PM

Post cure is when, after the part has cured at room temperature, you put the part in an oven to further cure at an elevated temperature.

Epoxy resins initially cure at room temperature to an apparent cured state, but can take weeks or even months to fully cure inside and achieve its maximum strength.  A post cure in an oven can be used to speed this process up and will also achieve slightly better mechanical results.  A post cure is also very useful when you want to use the resin at a high temperature as the heat of the post cure ensures the resin won't soften when first exposed to heat - up to the heat distortion temperature limit the resin is designed to.

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Warren (Staff) - 3/8/2018 9:31:06 AM

60C for 6 hours would be a typical post cure for a resin like this.

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Warren (Staff) - 3/8/2018 4:22:23 PM

An elevated temperature cure will always help to an extent so if it is possible to do so then I would.  Even if you just leave it in the 30C room for a few days, you should certainly have a properly cured resin by the end of it.