Silicone sealant

Sitting in the Handyvan today, enjoying a well earned cuppa, reading a Toolsatan catalogue.

Looking at silicone sealants I noticed they do High modulus and low modulus and there are Acetoxy and neutral cure ones. Never known what that means, so I e-mailed Evo Stick from my smartphone to ask. Got the following reply, which might be informative.

----------------------------------------------------------------- Essentially there are four different terms, commonly used in the description of silicone sealants, for DIY/building applications.

High modulus and low modulus refer to the modulus of elasticity. A high modulus rubber is a harder tougher material, suited to low movement joints such as around baths and washbasins. Low modulus rubbers are softer, deform more easily, and are better suited to use in movement joints, such as in external applications.

Acetoxy and neutral cure refer to the different chemistry of the curing (setting) reaction.

Acetoxy silicones have a strong smell of vinegar, which is acetic acid, and are generally high modulus. These sealants bond extremely well to glass and glazed tiles, but the acid may attack some surfaces such as metals and some plastics.

Neutral cure products have a different smell, contain no acid, and bond extremely well to concrete, brick, most metals and most plastics. They are generally low modulus. (Neither of them bond to polyethylene or polypropylene.)

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Reply to
The Medway Handyman
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Neutral cure is handy if you need to seal upto some corrodable metal, eg aluminium.

And for some applications, there are other products. Have you come across GeoCell TheWorks (either SF or TS sell it)? It's not silicone:

Pros: very sticky - and claims to stick to damp surfaces.

Cons: very sticky! (use masking tape rather than trying to wipe it off) Also not as shiny as silicone.

I used some to fill the joints in my wooden windows and it has held fast even against measureable expansion and contraction of the gap.

I have not tried it underwater - it's claimed to be useful for certain plumbing related leak fixes.

I did use some to bond a patch over a hole (over the inside) in my electric meter box outside, then bonded another disc cut from scrap GRP slightly smaller than the hole, in the hole to get a flush finish. It certainly seems to stick things together well too.

Reply to
Tim Watts

Its also been in the wiki since Methuselah was a boy ;-)

wiki.diyfaq.org.uk/index.php?title=Silicone

Reply to
John Rumm

Which explains why I had to get a tube of Urethane bond to fix a prolyprop cold frame skeleton some years back. Brian

Reply to
Brian Gaff

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