Hotmelt adhesives are thermoplastic and, therfore, their performance changes with temperature. One of the more prominent changes is the reduction of bond strength with increasing temperature.
Heat resistance is a measure of bond strength for hotmelt adhesives, relating to the temperature (in ‘degrees C’) at which a standardised sample fails (when subjected to a constant load).
A Ring and Ball Softening Point (the point at which the adhesive becomes liquid – usually a higher value than the heat resistance figure for any given adhesive) is often quoted for hotmelt adhesives, and this is sometimes misinterpreted as a measure of heat resistance.
Adhesive bond strength can be influenced by various other factors (such as type of adhesive, length of time exposed to higher temperature, the amount and direction of the load imposed on the bond line, and the nature of the substrates being bonded). Therefore, the quoted heat resistance figures of FOSPAT hotmelts should only be used as an approximate guide when comparing different adhesives. It shouldn’t be assumed that the adhesives will be able to withstand the quoted temperatures in all cases.
The user should conduct their own tests to determine the suitability of an adhesive for a particular application.