Coatings exposure

Nitropropane is produced in low volume and occupational exposures occur primarily in its production and use as a solvent in inks, adhesives, paints and coatings. Exposures of the general population may occur in ambient air and water near industrial sites manufacturing or using 2-nitropropane, in cigarette smoke, and possibly from its solvent uses. 

Coatings were applied to flat sheet metal substrates (cold rolled steel) and cured with ultraviolet light. After application, the coated metal was placed onto a moving conveyer line and exposed to U.V. radiation from an Ashdee Unit source (2 lamps of 2,000 Watts each) placed 5 to 7 inches from the coating. Exposure time was 9 seconds. (Line speeds of 50 to 100 ft. per minute.) The coating compositions were also applied onto a metal sheet substrate... 

Fig. 1.15 Edge protection by various zinc coatings exposure in 6% NaCi solution. Unprotected edge 5 cm below surface. Note superior protection by galvanizing (Van Eijnsbergen, 1991 based on Swedish research work by Lindqvist, Meszaros, and Svensson).

TABLE 22.11 Four Typical Photodielectrics (Three Epoxy and One Polyimide) and the Processing Parameters for Coating, Exposure, Developing, Desmears, and Metallization... 

ISO 2810 [362] Paints and varnishes — Natural weathering of coatings — Exposure and assessment... 

Poly(vinyl cinnamate) Resists. Dichromated resists exhibit numerous shortcomings which include lot-to-lot variabiUty of the components, aging of the formulated resists in solution and in coated form, poor process stabiUty (due to a sensitivity to variations in temperature and humidity), and intrinsically low photosensitivity requiring long exposure times for adequate insolubilization. 

Unsaturated resias based on 1,4-cyclohexanedimethanol are useful ia gel coats and ia laminating and molding resias where advantage is taken of the properties of very low water absorption and resistance to boiling water (6). Thermal stabiHty is imparted to molding resias, both thermoplastic (71,72) and thermoset (73—76), enabling retention of physical and electrical properties at elevated temperatures (77). Additionally, resistance to chemical and environmental exposure is characteristic of products made from these resias (78). 

Membranes and Osmosis. Membranes based on PEI can be used for the dehydration of organic solvents such as 2-propanol, methyl ethyl ketone, and toluene (451), and for concentrating seawater (452—454). On exposure to ultrasound waves, aqueous PEI salt solutions and brominated poly(2,6-dimethylphenylene oxide) form stable emulsions from which it is possible to cast membranes in which submicrometer capsules of the salt solution ate embedded (455). The rate of release of the salt solution can be altered by surface—active substances. In membranes, PEI can act as a proton source in the generation of a photocurrent (456). The formation of a PEI coating on ion-exchange membranes modifies the transport properties and results in permanent selectivity of the membrane (457). The electrochemical testing of salts (458) is another possible appHcation of PEI. 

Whereas the eadiest fluorescent-dye pigments would last only 20 days outdoors in a screen-ink film, fade resistance has been improved to such an extent that some modem daylight-fluorescent coated panels stiU have useful color after nine months or mote in Florida sunlight in a 45° exposure tack facing south. The fluorescent layer is usually coated with an acrylic film containing a uv absorber. Indoor-accelerated exposure equipment is, of course, invaluable in the development of such systems. Better dyes and resins very likely will make possible fat mote stable coatings in the future. 

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