Fluorocarbon powder coating

Comparison of solvent-based fluoropolymer and fluorocarbon powder coating developed in Japan shows that elimination of solvent is not only good for environment but also improves performance (UV stability especially is improved). The study was carried out with a very well designed testing program to evaluate the weathering performance of the material. 

ABHERENT. Any substance that prevents adhesion of a material to itself or to another material. It may be in the form of a dry powder (a silicate such as talc, mica, or diatomaceous earth) a suspension (bentonite-water) a solution (soap-water) or a soft solid (stearic acid, tallow waxes). Abherents are used as dusting agents and mold washes in the adhesives, rubber, and plastics industries. Fats and oils are used as abherents in the baking industry. Fluorocarbon resin coatings on metals are widely used on cooking utensils. 

Other support materials of minor importance include various fluorocarbon powders, glass beads, carbon, and dendrite salts. Fluorocarbon powders are used primarily for the separation of reactive compounds that would destroy or be destroyed by other materials. A low surface energy and electrostatic properties make fluorocarbon powders difficult to coat and pack into columns. Because of their controlled shape, glass beads are used mainly for theoretical studies but have a low loading capacity and an active surface. 

Acrylate polymers and certain polyvinyl butyrals, sihcone fluids, tita-nate esters and fluorocarbon compounds are used as flow control agents in powder coatings to modify the surface tension of the film in the melt stage, preventing crate formation and improving substrate wetting. 

If solid polymer objects are fluorinated or polymer particles much larger than 100 mesh are used, only surface conversion to fluoropolymer results. Penetration of fluorine and conversion of the hydrocarbon to fluoropolymers to depths of at least 0.1 mm is a result routinely obtained and this assures nearly complete conversion of finely powdered polymers. These fluorocarbon coatings appear to... 

If solid polymer objects are fluorinated or polymer particles much larger than 100 mesh are used, only surface conversion to fluorocarbon results. Penetration of fluorine and conversion of the hydrocarbon to fluorocarbon to depths of at least 0.1 mm is a result routinely obtained and this assures nearly complete conversion of finely powdered polymers. These fluorocarbon coatings appear to have a number of potentially useful applications ranging from increasing the thermal stability of the surface and increasing the resistance of polymer surfaces to solvents and corrosive chemicals, to improving friction and wear properties of polymer surfaces. It is also possible to fluorinate polymers and polymer surfaces partially to produce a number of unusual surface effects. The fluorination process can be used for the fluorination of natural rubber and other elastomeric surfaces to improve frictional characteristics and increase resistance to chemical attack. 

FLUOROCARBON 11 (75-69-4) Reacts violently with barium, alkali amides, alkali metals, metal powders, sodium, and potassium, molten aluminum or magnesium. Undergoes thermal decomposition when exposed to red-hot surfaces or fire, forming chlorine, hydrogen fluoride or chloride, phosgene, and carbonyl fluoride. Contact with water causes slow decomposition. Attacks some plastics, rubber, and coatings. Attacks aluminum, copper, magnesium, tin, zinc. 

Volatile metal halides, usually chlorides and fluorides, also form the heart of several processes used to produce surface layers, rich in aluminium, chromium, or silicon, or combinations of these. In these processes, the workpiece to be coated is buried in a powder bed and heated to reaction temperature. The bed consists of a mixture of inert alumina filler, a master alloy powder that contains the aluminium, etc., and an activator such as ammonium chloride. Basically, at about 630°C, the activator volatilizes and the aluminium chloride vapour reacts with the master alloy to produce a volatile aluminium chloride, which then reacts with the workpiece surface to deposit aluminium. The deposited aluminium proceeds to diffuse into the surface layers of the workpiece to produce a diffusion coating. The process is driven basically by the difference in aluminium activity between the master alloy and the worlqtiece. These processes are well documented in principle, but their execution to provide reproducible and reliable results still involves considerable experience, or rule of thumb. These processes will be described in detail in Chapter 10. Finally, a chlorination treatment is used to remove tin from tin-plated steel. This uses a normally deleterious reaction to advantage and profit in the recovery of both tin and steel for recycling. Fluorination is used in the manufacture of polymers and fluorocarbon consequently, materials suitable for construction of these plants must be resistant to fluorine attack. 

Some mold release agents are sprayed directly onto the tool steel of the mold. These include among others some silicone and some fluorocarbon-based materials. Other mold release agents are coated or sprayed onto the surface of the molding powder. This is done in batch blenders just before pack out to avoid passage through an extruder. Most release agents that are melt blended with polymer can be applied in this alternative fashion. 

---