Typical Formulation Ingredients
Ingredient
Parts by weight
Crystalline polyester polyol (high crystallinity)
Amorphous polyester polyol (solid)
Thermoplastic polyurethane (Pearlbond TPU, Lubrizol)
Methylene diphenyl diisocyanate (MDI)
Amorphous polyester polyol (liquid)
Typical Properties
• OH / NCO ratio = 1:1.95
• Low application temperature
• Immediate green strength and rapid increase of the cohesive strength (crosslinking)
• The cross-linked adhesive has an excellent resistance to heat and ambient conditions
• Good adhesion to a variety of substrates
Resulting Properties
By being capable of curing to a thermosetting material, reactive hot melt adhesives eliminate or greatly reduce many of the performance problems associated with conventional hot melt adhesives. In addition, reactive hot melt adhesives have the ability to bond to many different substrates and, generally, have longer service life times.
Before the HMPUR adhesive reacts with ambient moisture, it must exhibit the properties of a conventional hot melt system. Typical application temperatures for HMPUR adhesives are in the range of 85°-140°C with melt viscosities from 2,000 to 80,000 cps. Application temperature and viscosity can be engineered by the balance of polyester and polyether components and the degree of amorphous structure in the polymer.