Comparison

MS polymer vs Polyurethane adhesive: which should you use?

Two flexible, waterproof, one-part adhesives. The differences are foam, UV and what you can paint.

The short answer

MS polymer for anything visible, outdoors, or where foaming would be a problem. Polyurethane when you want a slightly stronger joint and none of that matters.

Side by side

	Polyurethane adhesive	MS polymer
Strength	High	High
Flexibility	Not established	Flexible
Gap filling	Low	High
Water resistance	Water resistant	Water resistant
UV resistance	Poor	Good
How it cures	Moisture cure	Moisture cure
Clarity	Varies	Varies
Typical working time	10 to 20 minutes	5 to 30 minutes
Typical full cure	24 hours	2 to 7 days
Maximum temperature	100C	90C
Needs clamping	Yes	No
Two part	No	No
Removable later	No	No

Highlighted rows are where the two genuinely differ. These describe the families in general, not any particular product, so check the datasheet of whatever you buy.

Choose Polyurethane adhesive when

It will see sunlight. It needs painting. Foaming out of the joint would ruin the look. You are working near skin, food areas or in poor ventilation, where the absence of isocyanates matters.

Choose MS polymer when

Hidden structural work where raw strength wins. You want the extra grip on timber and masonry. Cost matters and the joint is out of sight.

What actually separates them

Polyurethane cures on moisture and expands as it does, which fills gaps but pushes joints apart if unclamped, and it yellows in UV. MS polymer does not foam, does not yellow, takes paint, and has no isocyanate. Polyurethane still edges it on ultimate strength.

Polyurethane adhesive

The full guide: what it is for, where it fails, and which materials it suits.

MS polymer