Coatings application equipment requirements

Spray 0.1 ohm per square foot hard, dense coating. mechanical bonding to plastic special applications equipment required requires special applicator safety procedures for dust and fumes warps thermoplastics not suitable for thin-walled designs not field repairable. 

Selection by physical state. A resin s physical state can help determine the application equipment required. Solid materials can be applied by powder coating methods. Table 10.4 lists resins applied as powder coatings. Liquids can be applied by most of the other methods, which are discussed later. Many of the coating resins exist in several physical states. Table 10.5 lists the physical states of common coating resins. 

PIGMENTS, PAINTS, POLYMER COATINGS, LACQUERS, AND PRINTING INKS 1053 TABLE 27.4 Application Equipment Requirements of SCAQMD Clean Air Act ... 

Steel sheets are aluminized by a hot-dip process similar to galvanizing. The principal applications for such a product are furnaces and ovens, automobile mufflers, and other equipment requiring heat and corrosion resistance. When a sheet which has been coated with aluminum by a hot-dip process is exposed to a temperature over l,000°F (538aC). the aluminum forms an iron-aluminum alloy which is heat- and corrosion-resistant. 

Through the years, improved paints have been developed because of competition from environmental and consumer activists. The objective of improving overall quality and reducing emissions of VOCs has led to a wider selection of paint types. The user, therefore, must select a coating type that meets the cost of required application, equipment, energy costs for using, pollution and waste collection expenses, and application and cured performance requirements of the coating. 

The coating is more tolerant of water after application than organic coatings. However, it requires bulky equipment and cannot be applied in any other way. There are also the health and safety issues to be considered. 

Spray-on in situ technique is a very effective one for insulation and sealing in construction applications, which requires rather simple but special equipment to meter, mix and spray [7]. However, mainly due to the wasted overspray, this technique is also not very economical in addition to the fact that SPF applied usually needs a protective elastomeric coating to prevent and protect its surfaces from degradation caused by UV exposure [14]. 

Since these are two component materials, they must be mixed just prior to application. They require additional equipment and more expertise to apply than a single-packed product. Most epoxy finish coats will chalk, fade, and yellow when exposed to sunlight. 

Each system has its advantages and disadvantages. Typically, primer/cover-coat systems are more resistant to extreme environmental conditions such as hot oil or extended salt spray exposure. However, primer/cover coat systems are more expensive to apply because of the need to have two sets of application equipment, one for primer and another for cover-coat. One coat systems only require one set of application equipment and require only one application step instead of two, and hence, are less costly to process. Inventory issues are significantly simplified with the use of one coat adhesives. 

Parylene is a completely different class of coating. The p-xylylene monomer is stable as a gas at low pressure but polymerizes spontaneously on any surface on which it condenses. The polymer formed has excellent moisture, chemical, mechanical, and electrical properties, but expensive application equipment is required. 

Additional requirements for special dipping and coating applications Subpart I—Personal Protective Equipment (PPE)... 

Application of the adhesive Application must be performed - at the speed of the equipment - as an even coat, with the required coverage - Viscosity - Wetting of materials - Coverage, consumption - Stability of the adhesive in the tanks - Melting temperature of the hot melts... 

The polymers made from 1,1-difluoroethene (or vinylidene fluoride) are known as polyvinylidene fluoride (PVDF). They are resistant to oils and fats, water and steam, and gas and odors, making them of particular value for the food industry. PVDF is known for its exceptional chemical stability and excellent resistance to ultraviolet radiation. It is used chiefly in the production and coating of equipment used in aggressive environments, and where high levels of mechanical and thermal resistance are required. It has also been used in architectural applications as a coating on metal siding where it provides exceptional resistance to environmental exposure. The chemical structure of PVDF is shown in Fig. 11.40. Some products are copolymers. 

There are many claims about how much film weights can be reduced because of the uniformity of films deposited by electrocoat. Some of these claims appear to many to be over optimistic and some may even verge on being fanciful. Whether steel cans can only have a single coat is debatable, but it has been shown that one coat, when electrodeposited onto steel cans, will give acceptable performance, under laboratory and pilot scale conditions. What is for certain is that electrocoat can only be used for one coat of lacquer. Once the can is coated, no further coating can be deposited by electrodeposition. A second coat would need to be spray applied which could be considered counter productive. However, if a sufficiently thick and, more importantly, integral film free from defects coitld be uniformly deposited onto a steel can, then one coat application is feasible. This will require joint efforts from equipment manufacturers, lacquer suppliers and can makers. 

---