Can I use glue sticks for exterior gluing? Are they waterproof / water resistant?
The problem with using a hot melt adhesive for exterior applications or applications involving direct water contact is that the adhesive is 100% thermoplastic with no added carriers, e.g. solvents. This means the adhesive sits on the surface of the materials being bonded rather than penetrating the surface with the help of the carrier (solvent).
If your substrates are porous (e.g. wood) or water can ingress/penetrate between the glue line and the substrate, this may cause the bond to fail, especially if there is a frost as this causes expansion.
Making a milk bottle igloo – if interior use Tecbond 261, if exterior and not required to be permanent again use Tecbond 261, but if you require a permanent waterproof bond use CT 1
Exterior applications should be avoided with standard hot melt adhesives as a general rule, unless specified by a member of the gluegunsdirect team and following your own application tests, as over the years we have found many applications, where in theory a hot melt adhesive would not be recommended, but in practice they have worked a treat !
On saying this, if the substrates were not porous you could try a polyurethane reactive hot melt adhesive (PUR) that dispenses and initially sets like a normal hot melt adhesive, but then over a period of several days cures to improve heat, water and chemical resistance.
Even with a PUR adhesive, if water can ingress between the glue line and the substrate, especially if it is liable to freezing temperatures, then adhesion failure may occur.