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PX resin and pigment pastes

http://www.talkcomposites.com/Topic28613.aspx

By Mikael_jo - 7/20/2018 10:35:56 AM

Hello

I have a question about mixing pigment pastes in our PX90 resin. In the TDS i read:
"In all cases, pigments should be added to Part A first, using the minimum amount of pigment required to achieve the desired strength of colour"
" The pastes are made from pigment powder that has been extensively milled into a small amount of base resin in order to produce a liquid paste thatcan be easily dispersed into the casting resin"
and it should be typically 2-6% by weight. ( add max 6% extra AB100g+P6g or 6% of the total AB94g+6g?)

So how should I count?
A: Same amount Part A and B and add max 6% pigment of total weight? (A100g + B100g + P12g)
B: Same amount Part A and B and add max 6% pigment of just Part A? (A100g + B100g + P6g)
C: Calculate together pigment and Part A and after that add Part B? (A100g + P6g +B106g) (6% of Part A)
D: Calculate together pigment and Part A and after that add Part B? (A100g + P12g +B112g) (6% of total resin?)
E: ...

I also see that different color have different density, So the amount of Base resin in the pastes is diffrent.

I want to mix the color pastes directly in the bottle with Part A, I think I can add max 60g pastes to 500g Part A.
And after this just calculate the colored Part A and Part B 1:1?

But how do I get the best performance?

I usually use epoxy and there is the mixing accuracy important!

Best Regards
Mikael Jonsson
By Warren (Staff) - 7/20/2018 4:12:01 PM

A simple rule with almost all pigments is to ignore the weight of the pigment when calculating the mix ratio of the main resin system.  This is because the amount of "base resin" used to make the dispersion is a small % of the overall pigment dispersion, so you end up adding only a tiny amount of resin from the pigment into the main mix so it is not realistic or needed to take it into account.

When  a pigment is quoted to say  "use  X  % of pigment" then the meaning is the total resin mix of part A AND part B.   So in your examples, the correct method to use is method  "A".