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Posted: Thu May 02, 2019 8:08 pm
by Andy Meechan
Does SBR only work as a primer when it's mixed with cement or would it work if it was brushed on straight out the bottle?
Thanks in advance
Posted: Fri May 03, 2019 7:11 pm
by dig dug dan
Needs cement. I did an experiememt just last week. Three Offcuts of indian stone, one primed with sbr and cement, one primed with just sbr, one with nothing, all bedded down onto the same wet sharp sand mix.
Only the first one had stuck to the base!
Nuff said
Posted: Thu May 09, 2019 5:23 pm
by Tony McC
It all gets a bit complicated. SBR neat has diffferent properies to SBR mixed with a binder such as cement. On its own, it will 'stick', but it won't stick particularly well: mix it with cement, and it sticks like the proverbial to a blanket.
Many years ago, I was chatting with a chemist working at a company with a boss that was, at that time, a regular (and quite humorous) contributor to The Brew Cabin before his fall from grace. Anyway, this chemist went into incredible detail about just how SBR worked - it was the key ingredient in a specific brand-name product that had made that particular company a LOT of money, so there was hardly anyone that knew more than he did about SBR and its potential with mortars.
To give you an idea of how ineffective SBR can be, it was, at one time, supplied under a different name as a stabiliser for KDS. Dilute at something like 10:1, pour over freshly jointed block paving, and it loosely, that's the key word, loosely binds the KDS just enough to resist scour, but then not enough to make it in any way 'set' or go permanently hard.
The key is in the R of SBR - Styrene Butadiene Rubber....it's a glorified form of latex, and we all know that's not a particularly strong adhesive.