With the increasingly strict environmental requirements, powder coatings have developed rapidly due to their many advantages such as low pollution, high decorative value, and good comprehensive performance. According to experts, there are currently three widely used powder coatings, namely: epoxy type, epoxy polyester type, and pure polyester type. Due to the absence of unsaturated groups and hydroxyl groups in epoxy resin, polyester resin has significant advantages in weather resistance. Therefore, it is mainly used for various outdoor appliances such as highway guardrails, isolation piers, street lamps, outdoor transformers, and cabinets on telecommunications lines. There are many types of polyester powder coatings, and a series of curing agents can be used for the curing of polyester powder.

Carboxylated polyester resin is cured with tri glycidyl isocyanurate (TGIC) and hydroxyalkylamide; Hydroxypolyester resin is cured with amino resin and polyurethane. Chinese experts started with the formulation design of carboxyl polyester resin TGIC system pure polyester powder coating, studied the effects of base materials, fillers, and additives on the physical and mechanical properties of the coating film (impact resistance, flexibility, inclined flowability, hardness, adhesion, UV aging resistance, etc.), and provided the raw material ratio for the comprehensive performance of the coating film - showcasing the results of research on the performance of white pure polyester powder coating.

The influence of changes in the dosage of curing agent TGIC on the coating film

TGIC is a white powder with a melting point of approximately 95 ℃ and an epoxy value of 0.92 or higher. According to experts, the difference between it and bisphenol A-type epoxy resin is that it does not contain benzene rings and ether bonds, so the cured product has excellent UV resistance and good light and color retention. Experiments have shown that a TGIC dosage of 4% of the resin content cannot fully cure polyester resin, resulting in poor impact resistance; At 6%, the impact strength of the coating is better. Further experiments have shown that a TGIC dosage of 6% to 8% is sufficient to fully crosslink CC450; As the dosage continues to increase, the compatibility of TGIC in CC450 deteriorates, leading to a decrease in coating performance.

The impact of additive dosage

The experiment shows that a resin dosage of 600g and an enhancer dosage of 931 of around 8g are better; The dosage of leveling agent FC-100 is about 10g. According to experts, the molecule of benzoin contains two benzene rings and one hydroxyl group, making it a multipole defoamer with low surface tension. Its disadvantage is that when used excessively, it can cause the coating to turn yellow at high temperatures. Generally, it can be maintained at around 0.5% of the resin dosage.

Conclusion

⑴ Polyester resin selection CC450

According to experts, among the three polyester resins 6700, 6600, and CC450, CC450 has low melt viscosity, narrow molecular weight distribution, good compatibility and dispersibility with fillers, and the resulting powder coating film has good comprehensive performance.

⑵ Selection of fillers

When combined with CC450, BaSO4 has better comprehensive performance with 90 # CaCO3 and can be considered for use in combination. According to experts, the titanium dioxide used is DuPont's product CR-828, which has good comprehensive performance.

⑶ Curing agent dosage and additives

According to experts, the curing agent TGIC is about 6-8% of the base material (resin), the brightening agent 931 is 8g, the leveling agent FC-100 is 10g, and the defoamer Benzoin is 3g. The resulting coating has good comprehensive performance.