Question: Should I use a cyanoacrylate superglue or one of those new one-part polyurethane glues for household repairs and assembly projects?
Answer: Both of these types of adhesives have the advantage of not containing solvents and being single component, so no measuring or mixing is involved. In addition, they both use moisture to initiate the curing. However, superglues use traces of atmospheric moisture on the surfaces to be bonded, while polyurethanes can cure from the outside of the bond or be speeded up by moistening the surface. Superglue products have been sold for many years and have the benefit of curing very rapidly (seconds to minutes) to give strong bonds on many surfaces (including fingers!).Surfaces need to be tight fitting, and bonds are not very tough from an impact point of view.
Polyurethanes cure slowly, requiring several hours to achieve strength, but can give tough flexible bonds. Although their gap filling ability is limited, they do give particularly good bonds on uneven surfaces like wood. Carbon dioxide is given off when polyurethanes cure, and the adhesives tend to foam a little to fill gaps.
Both adhesives will bond a range of materials, except for certain plastics like polyethylene or polypropylene. It should be pointed out that special versions of the adhesives, often involving primers, are available for industrial bonding of difficult plastics. Both adhesives have limited temperature resistance to about 200°F, and superglues have poor moisture resistance.
Although I have not seen long-term test data, polyurethanes are purported to have very good outdoor durability. I repaired a very badly damaged wooden cupola on top of my house 15 years ago, and it is still in one piece! I use both types of adhesives at home, and I recommend using superglue where a very fast repair is required. Polyurethanes are particularly effective for bonding wood for repair or assembly. Where very large gaps are present, you might consider using either a two-part polyurethane or an epoxy adhesive. ASI
Any views or opinions expressed in this column are those of the author and do not represent those of ASI, its staff, Editorial Advisory Board or BNP Media.