Sealant terminology

[machurley22]

Can anyone help with the meanings of some of the terms used to describe sealants. EG there are acrylic, silicone and polyurethane (not to mention co-polymer) sealants and these can be high or low modulus. Then there's neutral cure.

I'm hoping to find a less expensive alternative to Sikaflex 291 (recommended by my local swindlery) to squirt up behind my rubbing strake to seal the hull-deck joint. Currently it is filled with a putty-like compond which appears to have dried, cracked and is falling out in lumps and it looks like I'm going to need 8 or 10 tubes to replace it, hence the desire for a cost-efffective goo. I do want to avoid "buy cheap, buy twice" syndrome though.

Thanks,

Dave

<hr width=100% size=1>

 

[starboard]

Try a product called Soudaflex 40, (made by a company called Soudal) a polyurathene sealant with the exact same specification as Sikaflex 291. I obtain mine from branches of Arco at about £3 per tube. I used it to stick down teak decking 4 years ago and as good as new today. Comes in Black, white and grey.

<hr width=100% size=1>

 

[Avocet]

"Polyurethane" "acrylic" and "silicone" are all materials. I think "Sikaflex 291" is a polyurethane. The "modulus" is just a measure of how "goopy" it is. The higher the modulus the thicker the stuff. Silicones come with a vast array of different properties (and prices) ranging from your cheap "B&Q type" bath sealants to expensive "marine" silicones like Dow Corning's stuff. Each is formulated to to a specific job. I don't think silicones make very good adhesives (you've probably seen bath sealant coming away from the side of the bath after a while) but some of the higher quality ones do stick better. None, (I think), are anything like as good as polyurethanes though. I don't know much about Acrylics at all but I think they form the basis of many door and window frame sealants for houses i.e. they form a skin on the outside but never really set under the skin. They can tolerate a lot of movement but have no strength. What you need depends on the job you want it to do. Is it going to form a structural bond or just fill a gap? If its the former, Sikaflex is almost certainly the only stuff I would trust. If you want to try other companies' equivalents, do a seach for "high modulus polyurethane" on the internet and see what comes up. There are loads on the market. Also, is the stuff going to be exposed to sunlight? If so, the cheaper ones can break down under ultraviolet light after a while.

<hr width=100% size=1>

 

[oldsaltoz]

G'day Dave,

Have you looked at the cost of Sikaflex in the 600 ml sausage form, much cheaper than the cartridges / tubes, you should have no problems borrowing a gun from someone.

Hope this helps

Avagoodweekend......



<hr width=100% size=1> Old Salt Oz /forums/images/icons/cool.gif Growing old is unavoidable. However, growing up is still optional.