Casting and Curing of Bonded Prepolymer

The polyurethane mix must flow over the part that has been primed and fully wet it. The presence of air pockets will prevent adhesion. It is most important that the primed part of the molding reaches the full cure temperature so that proper bonding will take place. 

It is also very important to ensure that mold release does not come into contact with primer when the mold is being assembled. This will result in no bonding to all the contact areas. Care must be taken, especially of overspray, if the mold release is sprayed on. 

The strength of the bond will drop off as the temperature is raised. The strength decreases slowly until approximately 100°C, after which it declines rapidly. 

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