Abstract: This article provides a brief analysis of the influence of polyester resin on the weather resistance, salt spray resistance, water resistance, and other main properties of powder coatings for aluminum profiles in practical applications. Actual test results are also cited for reference.

1. Preface:

Powder coatings, which are completely solvent-free and can be completely converted into coatings, have gained widespread attention worldwide due to their high coating efficiency, good comprehensive protection and decoration performance, and rapid development.

In recent years, with the implementation of stricter policies by the government to replace and eliminate paint products, water-based coatings and powder coatings have become the preferred choice. Therefore, their application in metal building materials and other fields has become inevitable. Powder coatings are widely used in various aspects of buildings due to their excellent durability, decorative properties, and processing formability.

Aluminum profiles account for over 80% of metal building materials due to their excellent processing performance and lightweight characteristics. Since the emergence of powder coatings in the early 1970s, their application in aluminum profiles has grown rapidly. At present, the application of powder coatings in aluminum profiles has expanded from Europe to the Americas, Australia, the Far East, the Middle East, and Africa.

In the coating of aluminum profiles, representative types of powder coatings include epoxy resin, polyester resin, acrylic resin, and fluorocarbon resin powder coatings. As an application, most highly corrosion-resistant aluminum profiles such as aluminum frames, doors and windows, balconies, corridors, and partition panels are coated with polyester and acrylic powder coatings.

In addition, due to the excellent adhesion and corrosion resistance of epoxy resin powder coatings, but slightly poor weather resistance, they are generally used indoors or as primers.

Since powder coatings are widely used on aluminum profiles, they should meet the requirements of aluminum profile spraying and application. As the most important component of powder coatings, polyester resin is closely related to the quality of various properties of powder coatings, such as weather resistance, water resistance, mechanical properties, etc. Anhui Shenjian New Materials Co., Ltd., as the first listed enterprise in the powder coating industry and a leading polyester manufacturer, contributes to the application of powder coatings in aluminum profiles.

The following text will briefly describe the main aspects in which resin should be selected for powder coating of aluminum profiles, and verify them with some experimental data of polyester resin.

2. Selection of resin weather resistance

2.1 Testing methods for weather resistance

Most applications of aluminum profiles are outdoors, so the first consideration for powder coatings for outdoor aluminum profiles should be the weather resistance of the coating. According to the standard GB5237.4-2008 "Aluminum Alloy Building Profile Part 4 Powder Spray Coating Profile", the weather resistance of aluminum alloy profile coatings is determined by xenon lamp artificial accelerated aging test, and divided into the following two levels (see Table 1).

2.2 Factors affecting resin weather resistance

Polyester resin is the most important component in powder coatings, and its weather resistance directly determines the weather resistance of the coating. Due to differences in raw materials and process conditions, the weather resistance of resins from different manufacturers and brands also varies to some extent.

Polyester resin is actually synthesized by esterification and condensation reactions of polyacids and polyols. Therefore, the use of raw materials and the rationalization of processes directly determine the weather resistance level of polyester resin. Generally, the more weather resistant raw materials are selected for the synthesis of polyester resin (such as IPA, CHDA, NPG, CHDM, etc.), the higher the weather resistance level of polyester resin. However, in actual production of polyester resin, other performance and process factors need to be comprehensively considered.

Source of this article: Aluminum Processing

The above is all the content shared by Yongji Industrial, a manufacturer of aluminum alloy powder coatings.