Green and environmentally friendly water-based PVDF fluorocarbon coating
With the rapid development of the national economy and the accelerated industrial modernization, the country has put forward higher requirements for the environmental protection of industrial development, especially under the concept of green and sustainable development, how to make chemical industrial products achieve safety and environmental protection, pollution-free, is an eternal theme that enterprises need to consider.
Since the solvent-based PVDF fluorocarbon coatings now widely used contain a large amount of organic volatile compounds (VOC), which can cause pollution to the environment, the more environmentally friendly water-based PVDF fluorocarbon coatings have been developed. Water-based PVDF fluorocarbon coatings use water as the carrier, which fundamentally reduces or eliminates the use of organic solvents. It not only has the inherent excellent performance of fluorocarbon coatings, but also reflects the characteristics of water-based coatings such as low VOC content, low toxicity and flame retardant. It not only reflects excellent characteristics in environmental protection, but also has a wider range of applications, such as thermoplastic polyolefin (TPO) roofing films, wood, stone and asphalt, concrete buildings, steel structures and other substrates.
Film formation mechanism
With the first stage of moisture dispersion moisture gradually reduced, the distance between particles and particles gradually become smaller, the system viscosity gradually increased, the particles contact each other and began to closely pile up; with the further evaporation of water between the particles, the particles due to mutual extrusion into polygonal particles, making the contact area between the particles increased, and finally in the appropriate temperature and airflow conditions, the particles spread each other, the boundary of the particles disappeared to form a continuous coating film.
Chemical film formation is generally a cross-linking reaction between film-forming substances and reactive groups in resins or cross-linking agents to form a net-like structure, resulting in a continuous and uniform coating film. In the process of film formation, there is not only one film-forming mechanism, but also a combination of several mechanisms, both physical and chemical film-forming processes, or both processes at the same time.
Lotion Type
The main component of PVDF waterborne coating is waterborne PVDF emulsion. Adding acrylic acid modification to PVDF polymer eliminates the adhesion hindrance of PVDF's chemical inertness to the substrate and makes the pigment dispersed evenly. The PVDF resin and acrylic resin in aqueous PVDF emulsion exist mainly in three forms: hybrid, core-shell and interpenetrating network.
In hybrid and core-shell coating films, PVDF particles are not uniformly dispersed in the continuous phase of the acrylic resin, and the coating film is susceptible to UV attack where the acrylic resin concentrates in the continuous phase. The interpenetrating network type is synthesized in such a way that PVDF and acrylic polymer form an interpenetrating network structure of the polymer so that the acrylic polymer can penetrate uniformly into the PVDF molecules. The resulting emulsion is a mixture of acrylic and PVDF polymers at the molecular level, without the presence of a continuous phase of acrylic resin, and the coating film exhibits excellent weathering resistance.
Preparation method
Water-based fluorocarbon resin preparation methods include physical mixing method and chemical polymerization method. Chemical polymerization method generally includes precipitation polymerization, suspension polymerization and emulsion polymerization method. Emulsion polymerization method is a relatively mature preparation method, based on emulsion polymerization process, using fluorinated vinyl monomer (or the introduction of non-fluorinated olefin monomer copolymerization), through the free radical reaction to obtain fluorinated polymer emulsion. Emulsion polymerization method occupies an important position in the production of waterborne fluorinated coatings, and can be divided into conventional emulsion polymerization method, seed emulsion polymerization method, in situ emulsion polymerization method, soap-free polymerization method, fine emulsion polymerization method, etc. according to the characteristics of implementation.
Market Applications
Mainly used in the construction industry, in the exterior wall surface decoration, the use of its coated decorative panels have now become an important material to replace tiles and glass curtain walls in the exterior decoration of high-rise buildings, can meet the requirements of green building codes and standards, so that the metal roof into a white cold roof, can effectively reflect the visible light and infrared light in the sun, while at the same time in the night outward radiation heat; in concrete facilities, the use of elastic PVDF water-based coatings, so that exterior wall coatings with good film elongation, to prevent the foundation due to subsidence, thermal expansion and contraction caused by the cracking of the exterior wall base; and for a variety of metal or other substrates surface decoration and protection.
In recent years, self-cleaning fluorocarbon coatings will become a new market favorite in the future by improving the hydrophilicity of the coating film surface, reducing the surface energy of the paint film or using photocatalytic technology to enhance the staining resistance of fluorocarbon coatings to achieve the self-cleaning effect.
