Coatings continued exposure

In an unpublished study at the U.S. Forest Products Laboratory, the moisture content of wood treated with two commercial formulations reached 48 to 58 percent (based on ovendry weight of treated sample) in 4 weeks1 exposure at 27°C and 90 percent relative humidity. Continuous exposure of wood treated with water-soluble salts to conditions above 80 percent relative humidity can result in loss of chemicals and in adverse effects on dimensional stability and paint coatings. Corrosion of some metals in contact with the wood will also occur. 

Continuous exposure to temperature conditions in excess of 300°F can be detrimental to many of the formulations. Excessive temperature will normally result in cracking of the coating system. 

Ultraviolet radiation is required only for the first step. The second step, while independent of UV radiation, is influenced by heat. Continuous exposure to a mercury arc to determine tack-free time can influence the course of the polymerization because of an increase in temperature of coating and substrate caused by the intense heat of the mercury arc. To avoid this complication and to maintain control of the temperature of the coating during cure, exposure to the mercury arc was generally limited to two seconds. This proved adequate to give a tack-free condition within one second following exposure for the most reactive epoxides. 

The oxidation of Co(II)EDTA to Co(III)EDTA by pyrolusite-coated silica under dynamic flow conditions exhibited breakthrough characteristics (Figure 1) that were consistent with earlier research (Jardine and Taylor, 1995). The oxidation was initially rapid and slowed with continual exposure of Co(II)EDTA to the Mn-oxide. Jardine and Taylor (12) showed that the loss of oxidative potential was not caused by the accumulation of Mn on the surface and postulated that an intermediate Mn(III)-oxide solid phase, Mn203, was formed that impeded the redox reaction. XANES spectroscopy was used to determine the speciation of the solid-phase as a function of reaction time in order to identify the inhibition mechanism. 

Uses Hard coating for optical thermoplastics (PC, polyacrylates) for glazing, windscreen, computer screens, ophthalmic applies, and for laminated structures (heat-resist, impregnants for continuous exposure to 360 C)... 

The choice of conducting substrate becomes more difficult when postdeposition high-temperature treatments are necessary. This is often the case for complex oxides, such as perovskites or oxynitrides [9], which may require firing at temperatures above 600°C in order to obtain the desired crystalline phase. This prohibits the use of float glass, which softens above 550°C. Certain types of borosilicate glass can be used up to 650 C, while fused silica or sapphire can withstand continuous exposure to temperatures up to 950°C. Unfortunately, the conductivity of ITO films quickly decreases above 350°C. FTO and ITO/FTO coatings are stable up to 600-700 C [2,10], and may still have acceptable conductivities at higher temperatures provided... 

Corrosion inhibitors in paints protect metallic surfaces from oxidation. Coating primers are used when there is continuous exposure to corrosive elements, e.g., in marine applications. Examples are coal-tar derivatives, epoxy resins and coal-tar modified epoxies. Primers that inhibit corrosion by anodic or cathodic polarization contain inorganic metallic pigments such as chromates or leads or both. Composite pigments containing calcium oxide, zinc, silica, and oxides of phosphorus and boron can also be used (Mathias 1984). Nowadays, powder paints such as polyester and epoxy powder paints can also be used for corrosion inhibition (Rose and Vance 1997). 

Continuous Exposure Tests Several tests are used to evaluate the performance of coated steel substrates that involve continuous exposure to... 

In earlier applications of SIMS and FABMS the sample was deposited as a thin film on the probe resulting often in cationization by the surface metal to form [M + cation]. Latterly, solutions in a liquid matrix coated on the probe surface have been customarily used, a method which allows continuous exposure to the ion or atom beam of fresh solute molecules. 

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