Beyond general purpose PU sealants, there’s a range of more specialised products with slightly different formulations to hone them for specific purposes.
Chandlers often only have shelf space for a small range, so these specialist products often need to be specially ordered.
In the Sikaflex range, for instance, 292i is maritime construction adhesive with twice the strength of 291i. This gives it a high mechanical load capacity for structural bonding without mechanical fastenings.
Sikaflex 298 is a more fluid bedding compound that’s semi-self levelling for gluing down synthetic deck coverings and bedding in or sealing of teak that’s laid on a structural sub-deck.
Sikaflex 290DC Pro is for teak deck caulking and can be sanded. It’s quite a fluid formulation – don’t try using it on a vertical surface – so the bottom of the seam fills first without forming air pockets. It takes 5-7 days to cure, after which the excess can be chiselled off and then sanded.
Sikaflex 295uv and 296 are both optimised for bonding glazing, with the former formulated for organic glass that’s exposed to sunlight.
In the 3M range 4200FC is a medium strength polyurethane for bonding and sealing above and below the waterline that can be removed even after prolonged use.