Curing Behavior of Seven Segmented Polyurethane Adhesives.

摘要

The curing behavior of seven segmented polyurethane adhesives (Halthanes) was followed by dynamic viscosity measurements with time under isothermal conditions. Two types of adhesive systems were studied: (1) MDI/ BDO/ PTMG1 or 4,4' methylene bis (phenylisocyanate)/ butanediol/ poly(tetramethylene oxide) and (2) HMDI/ ADA/ PTMG2 or 4,4' methylene bis (cyclohexylisocyanate)/ aromatic diamine/ poly(tetramethylene oxide). Changing the hard segment former from MDI/BDO to HMDI/ADA significantly increased the cure rate. The accelerator, ferric acetoacetonate, used in combination with a tetrafunctional alcohol increased the cure rate of the MDI adhesive system to nearly that of the HMDI system. With increasing temperature, macroscopic phase separation of the excess MDI in the MDI terminated prepolymer is compatibilized by the curing agent. Thus MDI/BDO/PTMG1 systems are clear when cured at above 80 exp 0 C. This does not affect the hard-soft block structure which controls the adhesive properties. All components of the HMDI/ ADA/ PTMG2 systems can be compatibilized at 60 exp 0 C and will remain dissolved for several hours at room temperature. Therefore, these systems are dark but clear when cured. 4 figures. (ERA citation 07:059786)