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Performance Study and Analysis of White Pure Polyester Powder Coatings
With the increasingly strict environmental requirements, powder coatings have developed rapidly due to their many advantages such as low pollution, high decorative properties, 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.
Carboxyl polyester resin is cured with triglyceride isocyanurate (TGIC) and hydroxyalkylamide; Hydroxyl polyester resin can be cured with amino resin and polyurethane. Chinese experts started with the formulation design of pure polyester powder coatings based on carboxyl polyester resin TGIC system, and studied the effects of base materials, fillers, and additives on the physical and mechanical properties of their coatings (impact resistance, flexibility, inclined flowability, hardness, adhesion, UV aging resistance, etc.). They also provided the comprehensive performance raw material ratio of the coatings, demonstrating the results of research on the properties of white pure polyester powder coatings.
The effect of changes in the dosage of curing agent TGIC on the coating film
TGIC is a white powder with a melting point of about 95 ℃ and an epoxy value of 0.92 or higher. According to experts, the difference between it and bisphenol A epoxy resin is that it does not contain benzene rings and ether bonds. Therefore, the cured product has excellent UV resistance and good light and color retention properties. The experiment shows that the amount of TGIC used is 4% of the resin content, which cannot fully cure the polyester resin, resulting in poor impact resistance; At 6%, the impact strength of the coating film is good. Further experiments have shown that a dosage of 6% to 8% of TGIC 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 effect of additive dosage
The experiment shows that the dosage of resin is 600g, and the dosage of brightener 931 is about 8g, which is better; The dosage of leveling agent FC-100 is about 10g. According to experts, benzoin molecules have two benzene rings and one hydroxyl group, making it a multipolar defoamer with low surface tension. Its disadvantage is that when used too much, it can cause the coating to turn yellow at high temperatures, usually maintained at around 0.5% of the resin dosage.
conclusion
⑴ Polyester resin selection CC450
Among the three polyester resins 6700, 6600, and CC450, according to experts, CC450 has low melt viscosity, narrow molecular weight distribution, good compatibility and dispersion with fillers, and the resulting powder coating film has good overall performance.
⑵ Selection of fillers
When combined with CC450, BaSO4 and 90 # CaCO3 have better overall performance and can be considered for use together. According to experts, the use of DuPont's product CR-828 for titanium dioxide has excellent 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 brightener 931 is 8g, the leveling agent FC-100 is 10g, and the defoamer benzoin is 3g. The comprehensive performance of the coating film is good.
Carboxyl polyester resin is cured with triglyceride isocyanurate (TGIC) and hydroxyalkylamide; Hydroxyl polyester resin can be cured with amino resin and polyurethane. Chinese experts started with the formulation design of pure polyester powder coatings based on carboxyl polyester resin TGIC system, and studied the effects of base materials, fillers, and additives on the physical and mechanical properties of their coatings (impact resistance, flexibility, inclined flowability, hardness, adhesion, UV aging resistance, etc.). They also provided the comprehensive performance raw material ratio of the coatings, demonstrating the results of research on the properties of white pure polyester powder coatings.
The effect of changes in the dosage of curing agent TGIC on the coating film
TGIC is a white powder with a melting point of about 95 ℃ and an epoxy value of 0.92 or higher. According to experts, the difference between it and bisphenol A epoxy resin is that it does not contain benzene rings and ether bonds. Therefore, the cured product has excellent UV resistance and good light and color retention properties. The experiment shows that the amount of TGIC used is 4% of the resin content, which cannot fully cure the polyester resin, resulting in poor impact resistance; At 6%, the impact strength of the coating film is good. Further experiments have shown that a dosage of 6% to 8% of TGIC 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 effect of additive dosage
The experiment shows that the dosage of resin is 600g, and the dosage of brightener 931 is about 8g, which is better; The dosage of leveling agent FC-100 is about 10g. According to experts, benzoin molecules have two benzene rings and one hydroxyl group, making it a multipolar defoamer with low surface tension. Its disadvantage is that when used too much, it can cause the coating to turn yellow at high temperatures, usually maintained at around 0.5% of the resin dosage.
conclusion
⑴ Polyester resin selection CC450
Among the three polyester resins 6700, 6600, and CC450, according to experts, CC450 has low melt viscosity, narrow molecular weight distribution, good compatibility and dispersion with fillers, and the resulting powder coating film has good overall performance.
⑵ Selection of fillers
When combined with CC450, BaSO4 and 90 # CaCO3 have better overall performance and can be considered for use together. According to experts, the use of DuPont's product CR-828 for titanium dioxide has excellent 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 brightener 931 is 8g, the leveling agent FC-100 is 10g, and the defoamer benzoin is 3g. The comprehensive performance of the coating film is good.