[China Aluminum Industry Network] The non-isothermal curing reaction of powder coating for polyester/TGIC aluminum profiles was studied by differential scanning calorimetry (DSC). The curing reaction process of powder coating was analyzed using the temperature-rate heating rate chart. The characteristic parameters of gelling temperature (TO), curing temperature (TP) and post-treating temperature (TF) were 122 °C, 150 °C and 206 °C, respectively. The DSC test analysis confirmed the system powder coating. The lower curing temperature is about 120°C, and the preferred curing process parameter of electrostatic spraying is 200°C/20min, which provides an important reference for the determination of the process control of electrostatic spray curing of aluminum profile powder coatings. Powder coating is a solvent-free solid powder environment-friendly paint, with good decorative, protective and high coating efficiency. It is widely used in the coating of metal surfaces, especially aluminum profiles. Compared with conventional surface treatment methods for aluminum profiles such as anodization and electrophoretic coating, powder coatings are rich in color, environmental pollution and energy consumption are significantly reduced, and mechanical properties of coating films are greatly improved. Therefore, electrostatic spraying of powder coatings has become the main surface treatment of aluminum profiles. One of the methods. The solidification process of powder coating refers to the powder coating powder layer that is adsorbed on the surface of the workpiece under the effect of electrostatic attraction, and the process of coating film with certain mechanical properties and appearance quality requirements through high-temperature curing treatment is the quality control of electrostatic spraying product of aluminum profiles. One of the key production processes, the curing process conditions will directly affect the appearance and mechanical properties of aluminum spray products. If the coating does not cure well, the cracking of the coating will occur during the extrusion of the coated profile, and the use value of the powder coating cannot be achieved. This study used differential scanning calorimetry to analyze the curing process of polyester/TGIC powder coatings commonly used in aluminum profiles. The curing temperature, isothermal curing temperature, and lower curing of commonly used aluminum/TGIC powder coatings for aluminum profiles were discussed. The influence of temperature on the curing process of aluminum profiles provides an important reference for the control of the electrostatic spraying and curing process of aluminum profiles, and the accuracy is verified by the use of a furnace temperature tracker during the actual production process. 1 Curing process analysis 1.1 curing process Differential scanning calorimetry (DSC) is widely used in the study of the curing process of thermosetting powder coatings. Using the aluminum profile special polyester/TGIC ((mass ratio of polyester to TGIC) 0.93:0.07) powder coating system, the DSC test was conducted at a constant temperature of 10°C/min, and the results are shown in FIG. 1 . As can be seen from Figure 1, the solidification process of the powder coating goes through the following stages: 2 peaks appear in Zone A and Zone B. They are the glass transition and melting process of polyester resin and TGIC respectively. The peak temperatures of peaks 1 and 2 are 62.97°C and 98.8°C, respectively. The area C is the solidification process of powder coating, with obvious exothermic peaks. The temperature range is 120- At 200°C, the temperature at the bottom of the peak 3 is approximately 180°C, which is the preferred curing temperature of the powder coating. Considering the addition of the pigment filler in the production formula, the curing temperature in the spraying production is preferably increased to 200°C to ensure the curing cross-linking reaction is complete. In the melt extrusion production process of powder coating, the extrusion temperature cannot exceed 120°C, so as to avoid the occurrence of curing reaction and cause the powder coating to have "dross". 1.2 Prediction of Curing Characteristic Temperature Using the aluminum special polyester/TGIC powder coating system, the DSC test was conducted at 5°C/min, 10°C/min, 15°C/min, and 20°C/min heating rate respectively. The DSC curve is shown in FIG. 2 . From Figure 2, we can see that as the heating rate increases, the curing peak of the heat flux-temperature curve drifts upward, and the initial curing temperature T0, the curing temperature Tp, and the post-processing temperature Tf all shift to the high temperature direction as the heating rate increases. The heating rate was plotted against the curing response eigenvalues ​​T0, Tp, Tf and linearly fitted. The curve obtained by extrapolating to a heating rate of 0 is shown in Fig. 3. Curing characteristic temperature The initial curing temperature (TO), curing temperature (TP) and post-treating temperature (TF) are 122°C, 150°C, 206°C, respectively. The TO, TP characteristic values ​​obtained by the dynamic heating method cannot be directly used for spray curing. Process control temperature, because in the powder coating formulation also added a lot of pigment filler, the actual control of the curing temperature in industrial production is much higher, but it provides a theoretical basis for the determination of the curing process conditions. 1.3 Lower curing temperature In order to verify the initial temperature of the aluminum electrostatic spray curing process, the DSC test was performed under the following conditions: using a polyester/TGIC powder coating system for aluminum profiles, the curing temperature was selected to be 100°C, 110°C, and 120°C, respectively. After 30 minutes at their respective temperatures, the temperature was lowered to 30°C, and then the temperature was raised to 250°C at a heating rate of 10°C/min. The curve of the heat flow rate-time variation is shown in FIG. 4 . As evident from Figure 4, the DSC curve at 100°C and 110°C has a solidification peak, while there is no solidification peak at 120°C for 30 minutes after melting and holding, indicating that the powder coating sample has taken place at 120°C for 30 minutes. Cross-linking curing reaction, so in the process of electrostatic spraying of aluminum powder powder, in order to ensure the surface effect of the profile, the melting, leveling process temperature is maintained at the curing temperature for as long as possible, and the melt extrusion temperature must be Below 120°C, it is possible to avoid "slagging". 1.4 Determination of the curing process temperature Aluminum powder coating electrostatic spraying industrial production mostly adopts the isothermal curing continuous process, and selects the polyester/TGIC powder coating system for aluminum profiles to perform DSC testing on the isothermal curing process under the conditions of 160°C, 180°C, and 200°C, respectively. The time is 30 minutes. The measured heat flow rate-time curve is shown in Figure 5. As can be seen from Figure 5, with the same curing time, the heat flow rate of the polyester/TGIC system gradually increases as the temperature rises, and the heat flow rate tends to be stable after a certain curing time, and the heat flow rate hardly changes with time after 20 minutes. In order to ensure that the curing reaction is complete, a certain curing time must be maintained; under different isothermal conditions, the heat flow rate becomes narrower as the temperature increases, and the shorter the time required for the increase in temperature to reach the same heat flow rate, the more constant it needs to be maintained. Curing time, to shorten the curing reaction time; but the high temperature curing easy to make additives in coating formulations (such as benzoin degassing agent) caused by poor heat resistance coating yellowing, low temperature curing time, low production efficiency, aluminum electrostatic spraying In industrial production, the curing temperature and time are determined to be 200°C/20min. 1.5 Production Process Temperature Control Aluminum powder electrostatic spraying curing process can be divided into three stages of heating, heat preservation and cooling. The temperature rising stage is the melting and leveling process of the powder coating to obtain good surface effect; the curing cross-linking reaction of the powder coating mainly occurs in the heat preservation stage, and the certain temperature and time ensure that the cross-linking curing reaction of the coating is complete and reaches the aluminum profile product Required mechanical properties. Fig. 6 shows the production temperature control curve of an aluminum profile spraying manufacturer. It uses the special powder coating of aluminum HT8043SF50 aluminum profile, and is detected by Data furnace temperature tracker. The profile is preheated for 8 minutes to reach the curing temperature (200°C) and the holding section is 200. °C, 20 minutes to ensure solidification, after 27min cooling out, the entire curing process is 30min, practice has proved that the appearance of aluminum spray coating products and mechanical properties to meet the production process requirements. 2 Conclusion The non-isothermal curing DSC method was used to analyze the curing reaction of the polyester/TGIC system powder coating. The characteristic parameters such as gel temperature (TO), curing temperature (TP) and post-treatment temperature were determined by temperature-rate heating rate plot extrapolation method. (TF) were 122°C, 150°C, 206°C, respectively. Isothermal curing process DSC test, the actual lower curing temperature of about 120 °C, aluminum electrostatic spraying industrial production in the curing temperature and time control at 200 °C, 20 min is more appropriate. The industrial production practice proves that: using Data furnace temperature tracker to detect the solidification process of powder coating, the profile preheating and melting phase is heated for 8 minutes, the curing and insulation section is 200°C, and the furnace is cooled after 20 minutes. The appearance and mechanical properties of the aluminum spray coating product meet the production process. Claim. Flat Slings,Polyester Flat Webbing Sling,Flat Polyester Woven Webbing Sling,Flat Woven Webbing Sling Guangdong Gongyou Lift Slings Machinery CO.,LTD , https://www.wmpallettruck.com