Coating operations

Marine coatings can be applied by the use of spraying equipment, bmshes, or rollers. Coating operations at shipyards are typically conducted at two primary locations (1) outdoor work areas or (2) indoor spray booths. The outdoor work areas can include ship exteriors and interiors. Most shipyards report that typically only a small percentage (10%) of the coating operations are done indoors. However, in large constmction yards a larger propor- 

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A.dditives. Additives control coating behavior during appHcation or they can be used to alter the properties of the finished product. A single chemical additive may be used for several purposes. Some additives are essential to the production of a salable product, and others may be added only to obviate problems of the coating operation. 

Laminates. Laminate manufacture involves the impregnation of a web with a Hquid phenoHc resin in a dip-coating operation. Solvent type, resin concentration, and viscosity determine the degree of fiber penetration. The treated web is dried in an oven and the resin cures, sometimes to the B-stage (semicured). Final resin content is between 30 and 70%. The dry sheet is cut and stacked, ready for lamination. In the curing step, multilayers of laminate are stacked or laid up in a press and cured at 150—175°C for several hours. The resins are generally low molecular weight resoles, which have been neutralized with the salt removed. Common carrier solvents for the varnish include acetone, alcohol, and toluene. Alkylated phenols such as cresols improve flexibiUty and moisture resistance in the fused products. 

In addition to chemical and spectral sensitizers, several other classes of chemical compounds are added to emulsions before coating. Additives are used to facihtate coating operations, eg, surfactants (qv) and viscosity enhancers to reduce spontaneous development ia unexposed regions, eg, tetraazaiadenes and mercaptotetrazoles and to reduce abrasion and permit high temperature processing, eg, aldehydes (qv). 

In general, polycarbonate resins have fair chemical resistance to aqueous solutions of acids or bases, as well as to fats and oils. Chemical attack by amines or ammonium hydroxide occurs, however, and aUphatic and aromatic hydrocarbons promote crazing of stressed molded samples. Eor these reasons, care must be exercised in the choice of solvents for painting and coating operations. Eor sheet appHcations, polycarbonate is commonly coated with a sihcone—sihcate hardcoat which provides abrasion resistance as well as increased solvent resistance. Coated films are also available. 

Paper may also be colored by surface appHcation of dyestuff solutions after the paper has been formed and dried or partially dried by utilizing size-press addition, calendar staining, or coating operations on the paper machine. In addition, paper may be colored in off-machine processes by dip dyeings or absorption of dyestuff solution and subsequent drying, such as for decorative crepe papers. 

Surface Coating of Metal Furniture Stationary Gas Turbines Lime Manufacturing Plants Lead-Acid Battery Manufacturing Plants Metallic Mineral Processing Plants Automobile and Light-Duty Truck Surface Coating Operations... 

Pressure-Sensitive Tape and Label Surface Coating Operations... 

Each coating ojjeration Each coating operation Saturator Blowing still Storage and handling... 

Beverage can surface coating Bulk gasoline terminals Each coating operation All loading racks ... 

Thickening agents. When pseudoplasticity is necessary in NBR adhesives (spread coating operations, sprayed cements), carboxylic vinyl polymers can be added. 

The principal air pollutants are particulate matter (PM) and volatile organic compounds (VOCs). These are released from mixing and coating operations. Pollution prevention practices generally employed to reduce air emissions include ... 

The melting point of aluminium (660°C). The operating temperature usually reaches 750-850°C in pretreatment and 700°C in the bath, causing a loss in tensile properties of cold-drawn wire. On the other hand, if cold-worked material which is to be subsequently annealed is used in this process the annealing and coating operations may be combined, with obvious economic advantage. 

Improved processes and quality control have helped to establish these new coating materials but the care necessary for successful use has to be appreciated. Sections 11.1 and 11.2 have shown how necessary it is to remove millscale before coating and how scale-free surfaces may still retain seeds of further corrosion even when apparently cleaned well. The percentage of premature failures with sophisticated systems is still high, even on apparently well-prepared surfaces and there is a strong case for effective inspection at each stage of coating operations. 

Apart from his liaison, progressing and reporting duties, the inspector of protective-coating operations has three quite distinct areas of operation ... 

Formation of carbonyl groups which may occur when polyethylene is overheated, such as in an extrusion coating operation. Here a proper balance between extrudate temperature and exposure time to air is required. 

Particular attention should be paid to nonstandard production technologies including nonstandard methods of sterilization, sterile filtration and aseptic processing, lyophilization, microencapsulation, and certain critical mixing and coating operations. With such processes pilot-scale manufacture may not be predictive of industrial scale manufacture, and data on three full-scale production batches may be required in the application. 

Technical Terminologies of Coil Coating Operations and Pollution Control. 302... 

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