Thermoplastic hotmelt adhesives
They are coPA, coPES, PSA, EVA, with:
l typical working temperatures 150-230 ¡ãC
l viscosity range 3¡¯000-150¡¯000 cps
Thermoplastic hotmelt adhesives are in plasticized form whenever they are heated, and solid when cooled. The process is therefore fully repeatable and reversible. Under higher tempera-tures, the bonding strength will be decreased. However, there are thermoplastic hotmelt adhesives that can withstand temperatures above 200 ¡ãC, and they are well accepted even in the automotive industry.
Thermoset (duroplastic) hotmelt adhesives
They are one-component, moisture curing / crosslinking reactive polyurethanes, with:
l typical working temperatures 90-130 ¡ãC
l viscosity range 3¡¯000-35¡¯000 cps
Thermoset hotmelt adhesives are applied hot, in plasticized state, same as the thermoplastic adhesives, but they are not cross-linked at the time of application. The adhesives cross-link with humidity over a time period of some hours to 2 days, depending on the polymers. Contrary to thermo-plastics, these adhesives are not plasticized again when they are reheated. The process is not reversible.