Physical properties of wax?

I have been working with a mixture of oleic acid and paraffin wax as a
binder. The oleic acid is in the mix as a rheology modifier. I have
noticed something strange about the physical properties of the
material and I hope someone can explain it to me. I am not an organic
I use a low melting (around 50 deg C) paraffin wax which is a mixture
of C20 to C35 alkanes, mostly C23 - C26. I use lab grade (99.9%)
oleic acid.
I melt the wax at 100 deg C and mix in the oleic acid very thoroughly
then cool it to solidify.
I have tried 2 weight percent oleic acid and 5 weight percent oleic
The strange effect is that the physical properties of the resulting
solid material changes over time. Compared to the fresh mix, the low
oleic acid mix becomes more brittle in 2 - 5 days and the high oleic
acid mix becomes stronger and tougher in 2 - 5 days.
Why is this? Is there some sort of cross-linking reaction with the
double bond? Can the oleic acid oxidise a little after a few days
exposed to air?
Any comments?
Reply to
Alan Walker
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I agree that this may be a crystallization effect. Normally the paraffin would crystallize rapidly on cooling, accompanied by significant shrinkage. The oleic acid may be inhibiting the crystallization and spreading it over a longer time.
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Phase separation?
Reply to
Lasse Murtomäki
I can't fully explain what's happening but oleic acid and paraffin wax are probably not fully mutually soluble. You're getting a separation at some point which may lead to various hardening effects. Oleic acid will go rancid but I'm fairly sure it doesn't cross-link.
Barry Hunt
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