Flexible CA Glue ?

[John Plater]

I have just read a comment about the brittle nature of a CA glue joint. I know this to be the case, especially when an accelerator has been used. I also read about using CA on a part of the joint to get an instant grab to hold it together whilst the regular wood glue on the rest of the joint cured. I have a memory from the dim and distant past of a CA glue which was flexible once cured, to enable the gluing of joints where dissimilar materials needed to be able to move against one another very slightly. As it was not relevant to me at the time I didn't follow it up so the detail has been lost. Has anyone out there heard of a similar product ?
ATB John

[Derwent Woodturning club]

Hi John,

As far as I am aware all CA glues cure very hard and brittle. My understanding is that the moisture in the air/materials causes the glue to polymerise, forming a solid block of acrylic resin almost instantly. The thinner the glue, the better it will make contact with the surfaces being glued. Once cured, you have a thin block of plastic that fills the gap between the surfaces, causing them to stick together. However, distortion of those surfaces can cause the bond between the surface and the plastic to fail. Further stress will crack the cured glue.

The only way I can see any flexibility would be to incorporate a flexible filler, but that would significantly weaken the joint, as with the thicker CA glue derivatives which are never as strong as pure CA, since the bond structure is broken up by the fillers.

Loctite do have such a derivative which incorporates rubber particles and provides a flexible bond.

My preference is for PU glues, which aren't brittle, and have the added benefit of being waterproof.

[Robin Goodman]

I have successfully used flexible CA glues in the past, mainly for acrylic sheet to wood joints or laminating wood where the pieces had to have grain in different directions.   As Paul says, they are usually toughened with rubber, but I have no evidence that this results in a significantly weaker glue; some talk about industrial strength.  I have used Clear N Tuff flexible CA from shop4glue. ( https://shop-4-glue.com)  Several other makes are available such as Loctite Superglue Power flex, Permabond 741 flexible CA or BSI Insta-flex - needs only a simple search on line.  Make sure you buy the clear version, some are in black; some are only available as thin rather than medium.