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Hotmelt adhesives are thermoplastic and, as such, their performance alters with temperature. One of the more noticeable changes is the loss of bond strength with increasing temperature.
Heat resistance is a measure of bond strength for hotmelt adhesives, relating to the temperature (in ‘degrees Centigrade’) at which a standardised sample, when subjected to a constant load, fails. This test method complies with the requirements of BS 5350: Part H3.
To confuse matters further, 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.
Because bond strength can be influenced by several other factors (i.e. type of adhesive, the length of time exposed to elevated temperature, the magnitude and direction of the load imposed on the bond line, and the nature of the substrates being bonded), the quoted heat resistance figures of Tecbond hotmelts should only be used as a general guide when comparing different adhesives. It should not be assumed that the adhesives will be able to withstand the quoted temperatures in all cases.
The user should carry out their own tests to determine the suitability of an adhesive for a particular application.
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