Temperature minimum cure

Figure 2. Number of crosslinks formed (n) vs. time during cure" of coatings at various temperatures. For cure times, t, t, and t, the corresponding minimum cure temperatures are TuTt, and T,.

Figure 3. Arrhenius plots of cure time (t) vs. minimum cure temperature (T) for coatings at (a) pH 7.30 and (b) pH 3.52...

These squares of mortar with the glass cloth over each, are allowed to "cure" undisturbed for no less than seven days at a surface temperature of 70°F (14 days if the surface is at 60°F-the minimum cure temperature permissible). At the end of that period, the 2" wide open strips between the squares are mortared and cloth covered in the same manner, lapping the cloth 2" over the previously placed squares. (For this part of the work, 6" wide strips of glass cloth are used, and the mortar is extended from the 2" wide bare strip, 2" over the tapered edges of the squares.)... 

For spray-on applications, consult the manufacturer on minimum application temperature. Some materials do not flow through the pump or sprayer below 40°F to 50°F (4°C to 10°C) and some materials do not cure well below 30°Fto 40°F (-1°Cto4°C). 

Increase pressure. Check that clamps are seated properly Modify clamps or check for freedom of moving parts Use higher curing temperature. Check that temperature at the bond line is above die minimum specified throughout the curing cycle... 

Suppose now that the designer has developed a tentative design for the vessel, which includes the number of layers, material specifications for each layer, and the thickness of each layer, as well as the determination of the installation temperature, cure and operating conditions, and the maximum and minimum ambient temperatures that will be encountered both during operation and when idle. These operating and cure conditions to be specified are inside temperature and pressure, ambient temperature, and inside and outside heat transfer coefficient. 

The maximum cure temperature was limited to 140°C to ensure minimum homopolymerization of the epoxldlzed oils. Gel times were determined In separate experiments at 120°C by noting the time required for gelation to prevent stirring. 

In the case of epoxies using MD A or IPD hardeners, a minimum of 2-3 h at 120°C is required to achieve good corrosion, mechanical and heat resistant properties. For polyesters and bisphenol A epoxy vinyl esters, a minimum cure of 2-4 h at 70-80°C should be sufficient to ensure optimal corrosion properties. For novolac-based vinyl esters, 4h at 100°C will optimize the corrosion properties but to achieve a HDT of 150°C then a cure closer to this temperature is required. 

Adhesive flash can be softened by heating or wiping with solvent Adhesive not properly cured Use hi er curing temperature or extend curing time. Ibmperature and time must be above minimum specified. Check mixing... 

No appesirance of adhesive around edges of joiiit or adhesive bond line too thick Clamping pressure too low Starved joint Curing temperature too low Increase pressure. Check that damps are seating properly Apply more adhesive Use higher curing temperature. Check that temperature is above the minimum specified... 

---