Adhesive should be applied in horizontal or vertical straight lines. “S” beads are always a ‘No No’ as they can act as a water trap. Two beads that flatten out to around 20mm wide each, with a space in between, are better than dispensing a large mass of adhesive.
Open time is the timespan from when the adhesive is applied, to when it no longer bonds to another substrate – normally quoted in minutes. It is important to understand open time as it can mean the difference between two substrates bonding or not. A product’s open time is always stated on its technical data sheet.
A quick way of testing if a product is ‘still open’ is as follows:
Wearing disposable gloves, press your index finger into the adhesive and squash down to a 2-3mm bond line. Alternatively, use a clean stainless steel spoon or a spatula. If you get a good transfer of adhesive to your finger, the adhesive is still ‘open’ and an acceptable bond will be achieved.
If the transfer is reduced, the adhesive has started to skin over and the ultimate tensile strength and peel forces will be reduced.
If there is no transfer of adhesive to your finger, the adhesive has skinned over and an acceptable bond will not be achieved.
If you have any questions on how best to apply adhesive to ensure maximum performance, give us a call, or follow us on LinkedIn where we will keep you updated with Application Best Practice.