Judging from the history of the automobile industry, the quality of domestically produced automobile brands will soon catch up with or exceed the international level. There are many varieties of automobile-specific powders and large amounts of powders used, which will soon open up new application areas for powder coatings. Follow the management specifications of the automobile industry and be familiar with PPAP documents to build a bridge for the comprehensive application of powder coatings in the automotive field.
The development of China's automobile industry has attracted worldwide attention. Cars are no longer a symbol of noble status, but a consumer product for daily life. Automobile-specific powders are another expansion space for the application of powder coatings industry.
There are many varieties of powders used in automobiles, which can be divided into two categories: special requirements powders and conventional requirements powders. Special categories include: automobile body special powders, automobile wheel special powders, automobile fuel tank special powders, automobile engine special powders, etc.; conventional categories include: automobile wiper special powders, automobile filter special powders, automobile seats and accessories special powders, etc.
Powder coating for automobile body
Traditional liquid paint body coating is divided into three coating knife characters: primer, midcoat and topcoat. Later, it developed to use powder spraying to replace liquid paint primer and midcoat (first two-in-one special primer), and then spray topcoat. The first two-in-one special primer has a wide selection of powder systems, such as pure polyester, polyurethane, acrylic, etc.
However, under the influence of environmental protection trends, body coating has gradually adopted a full powder coating spraying scheme. General Motors, Ford, and Chrysler, the three major automobile companies, first entered the research and development of powder topcoat for automobile bodies in 19%. Now the coating of body powder coating has two-in-one primer spraying, and then directly using powder topcoat glazing; or after electrophoretic primer, directly using mid-top powder coating.
A certain automobile company took the lead in commercializing powder topcoat in May 1997. becoming the first automobile manufacturer in Europe to apply powder topcoat. Powder replaces paint to reduce the painting process, and there is no solvent at all, which is more efficient, energy-saving and environmentally friendly.
The reference scheme for the body spraying process is as follows: pretreatment → drying → weld sealing → two-in-one base powder spraying → pre-baking (160-180℃/8-10min) → inspection and mid-coat grinding → dust removal → powder powder glazing spraying → curing (2Omin@180-200℃) → inspection and finishing → offline
Body-specific powder is typical of automotive powder, which represents the decorative and weather resistance requirements of most automotive powder varieties. In order to match the fullness of paint, automotive body glazing powder (or mid-surface glazing powder) usually adopts acrylic acid/DDDA powder system. Body-specific powder has high gloss (20° probe gloss greater than 90%), excellent leveling and vividness (DOI value 85%). Moreover, it has excellent weather resistance, and the natural exposure life in Florida, USA is 40-60 months. The range of powder particle size distribution should be narrow, D50 is between 32μm-42μm, Dl0>15μm, and D90<55μm. Fine powder below 10μm is less than 5%, and acrylic/DDDA powder is suitable for high-end car body coating requirements.
Acrylic/DDA car body powder has the following advantages:
(1) The coating film is transparent and clear, not yellowing, not fogging, and has high vividness;
(2) The coating has good flow and leveling properties, and the coating film has good fullness;
(3) Good solvent resistance;
(4) Excellent scratch resistance;
(5) Environmentally friendly products, do not contain heavy metals.
