Lumiflon APCJ Journal |
| Posted on Jun 01 2003 at 12:00 AM |
| news >> Press Releases |
It could seem incredible, but repainting bridges could become a thing of the past. Fluoropolymerbased paints can last for more than 30 years without the need to repair the original surface . The benefits to cost and aesthetic value are obvious.
Asahi Glass developed "Lumiflon" in 1982 as the first solvent-soluble flouropolymer for coatings that can be cured under room temperature conditions, Lumiflonbased coatings maintain excellent appearances of buildings and other structures for over 20 years, Lumiflon can be applied in a variety of colours and protects substrate materials for years. It can ensure the longlasting beauty of their coloured surfaces. Therefore, Lumiflon based paints reduce the total maintenance cost, such as repainting or cleaning. In addition, because Lumiflonbased paints are long lasting with no need to repaint, the discharge of solvent in the air can be reduced dramatically. Recently, Asahi Glass has developed environmentally friendly Lumiflon grades, such as emulsion and powder grades.
FUNCTIONAL FLUOROPOLYMERS
Copolymerisation of fluorinated olefin and functional comonomers has often provided novel functional fluoropolymers and created a new market in various industries. However conventional fluoropolymers, such as PTEE, FEP, and PFA, and so on, were not necessarily suitable for coating applications because of drawbacks, such as their poor solubility in conventional organic solvents.
One of the major discoveries of fluoropolymer coatings was the development and the commercialisation of crosslinkable fluoropolymers. In 1982, Asahi Glass research and development developed soluble fluoroolefinvinyl ether copolymer, which was later called Lumiflon, for the first time.
This polymer comprises alternating sequences of fluoroolefin and several specific vinyl ether units, and is completely amorphous. The alternating sequences in the structure are responsible for the extremely high weather resistance of the resultant paint finish. The combination of several types of vinyl ether comonomers provides the polymer with various properties necessary for a paint, such as solubility, compatibility with pigments, cross linking reactivity and good adhesion, hardness and flexibility of the final finish (Figure 1 [omitted]).
DECADES OF PERFORMANCE
The appealing feature of this polymer as a paint material exists in its ease of handing and processing just like conventional paint resins, such as acrylic urechanes, and its excellent weather ability. The lifetime of Luminon coating is estimated nearly five times as long as that of acrylic urethane. Figure 2 [omitted] shows the result examined by an accelerated weathering test using sunshine weatherometer (SWOM). Lumiflon films are expected to protect undercoats from O2 permeation for long period of time. In this context, oxygen is classified as a potentially corrosive material, as are water and chlorine, and the oxygen permeation coefficient can provide information on how a system can resist corrosion.
The 02 permeation coefficient of Lumiflon remained unchanged after 5000 hours SWOM.
Dynamic visco-elastic properties of Lumiflon were unchanged after 3000 hours SWOM exposure. From this data, it is expected that Lumiflon will act as topcoat for heavy duty coating systems to maintain good appearance and the anticorrosive effect. The new system provides maintenance cost benefits for heavy duty coatings because a longer time is required before repainting. Figure 3 [omitted] indicates that life cycle cost or Lumiflon system is the cheapest compared to all other systems, such as alkyd, polyurethane and chlorinated rubber.
Lumiflon system shows smallest change before and after 2000 hours exposed with SWOM in all systems. Otherwise the alkyd system has a great tendency to decrease its impedance and surface resistance Chlorinated rubber and acrylic urethane systems show similar tendencies to alkyd systems. This means Lumiflon system is expected to have a big advantage for durable anticorrosive coatings.
An impedance measuring method can be used to predict the durability of each system. The change in impedance is plotted against exposure time and a straight line graph is obtained.The angle this line makes from the vertical,0, is obtained. High 0 values indicate good corrosion resistance.
The tan0 value for each system is calculated, as is the durable time ratio. These are shown in Table 1. This shows that life of Lumiflon film is about twice as long as that of acryfic uretbane (Figure 3 [omitted]).
HEAVY DUTY APPLICATIONS
The applications of Lumiflonbased coatings have been widely expanded to such architecture and heavy duty construction, such as bridges, and automobiles ships and airoplanes. Commercialisation started over 19 years ago, and now there are over 30,000 resultant applications.
In October last year, the bridge coating subcommittee of Japan's Society of Steel Construction evaluated that Lumifionbased paints could last 50 years on bridges inland and 30 years by the ocean.
Lumiflon offers a high gloss surface (more than 80% gloss at 60° specular gloss). It is the only fluoropolymer paint in the world to achieve this figure and therefore has proved to be most suitable for automobiles, ships and trains.
These applications require a sophisticated appearance and a wider range of colour choices, so Asahi Glass designed lower molecular weight polymers and paint makers for mulated special wetonwet clearcoat systems to obtain good leveling and a flat surface. Because, Lumiflon is able to transmit 90% of visible light, it also protects the surface with little affect on its original colour tone.
To add anti-mar and easy washable properties, higher Tg and higher OHvalue polymer were developed to make high crosslinking hard coatings.
Lumiflon is also suitable for aircraft coatings. Both molecular weight and OH value were controlled to achieve both good appearance and good jet oil resistance for airoplane coating. Furthermore, the polymer Tg was adjusted to meet the heat shock resistance in the range 50° C to 80°C. The airplane has been made fit for practical use for about eight years and within the time the coating keeps a good appearance and has properties that allow for easy washing.
Recently, global environmental viewpoints have raised concerns over acid rain, and in the paint industry, acid rain frequently creates watermarks.
Acid spotted areas of Lumiflon melamine films and acrylic melamine film were analysed by scanning electron micrograph (SEM) with 10% sulphuric add solution at 70°C for one hour. In the acrylic melamine film, big voids were observed, but in the Lumiflon melamine film, no significant changes were observed. Figure 4 [omitted] shows the section of the both films. Inside of spotted area of the film was shot and upside is surface. The acrylic melamine film was found to be porous, and thicker than the initial film, about 34pm. On the contrary, there were no significant changes as to section shape and film thickness in the Lumiflon melamine film.Therefore, the Lumiflon melamine film more difficult to erode by acid, and the add stains are easily cleaned up by water washing.
Finally, environmentally friendly coatings, such as emulsion and powder grades are now available with Lumiflon. To develop emulsion grades, the unit as hydrophilic parts has been introduced with fluoroethylene and other vinyl ethers. This emulsion grade has alternative sequence as solvent grade. Although OH units are introduced for good adhesiveness to substrates, both physical and chemical stability were excellent even at 50% bt weight polymer content. This emulsion is mainly used for one packed onsite repair coating.
The newest development on Luminon is the powder grade. It is the first fluoropolymer for the thermosetting powder coatings. High durable powder coating based on Luminon can be used on conventional powder coating facilities. Lumiflon takes one of the fluoropolymer's most advantageous features, such as its superior weather resistance. It can be applied in a variety of markets without special treatments. As a maintenancefree paint, Lumiflon is suitable for today's needs. It also offers an environmentally friendly solution with the introduction of longlasting emulsion and powder grades. APCJ