Surface Exposure Time SET

SET is the time elapsed between the surface preparation and actual bonding. After parts have been subjected to surface preparation, they must be protected from contamination during transportation and 

Process Flexo and Gravure Litho Offset, Letterpress Screen and Pad Laminating Coating  

Polymer name abbreviations PE = polyethylene, PP = polypropylene, PVC = polyvinyl chloride, PET = polyethylene terephthalate, PS = polystyrene, PVDC = polyvinylidene chloride, PU = pol)njrethane, ABS = acrylo butyl styrene, and PTFE = polytetrafluoroethylene. 

Landrock AH. Processing Handbook on Surface Preparation for Adhesive Bonding. Picatinny Arsenal Technical Report 4883. Dover, NJ Picatinny Arsenal December 1975. 

Snogren RC. Handbook on Surface Preparation. New York, NY Palmerton Publishing Co 1974. ISBN 0686482212. 

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In general, bond quality diminished with increased surface exposure time (SET). The best overall adhesive evaluated was epoxy film adhesive, which was found to be the least sensitive to the method of surface preparation used. In general, the best result was obtained when GRP laminates were bonded within 4 h after sanding. If absolutely necessary, bonding can be carried out after periods of time of up to 14 days SET, wifli only moderate strength loss. 

Experiments were conducted in a large (-26 m3) radon/thoron test facility (RTTF) designed for calibration purposes and simulation studies (Bigu, 1984). A number of different materials were exposed in the RTTF to a radon/radon progeny or thoron/thoron progeny atmosphere. Exposure of the materials was carried out under laboratory-controlled conditions of radiation level, aerosol concentration, air moisture content and temperature. The materials used were in the form of circular discs of the same thickness (-0.5 mm) and diameter (-25 mm), and they were placed at different locations on the walls of the RTTF at about 1.6 m above the floor. Other samples were placed on horizontal trays. Samples (discs) of different materials were arranged in sets of 3 to 4 they were placed very close to one another to ensure exposure under identical conditions. Exposure time was at least 24 hours to ensure surface activity equilibrium, or near equilibrium, conditions. 

T. Smith, J. Colloid Interface Set 75 (1980) 51 SD, UHV-evaporated gold film on glass (a) exposure time to air 0 min/surface clean at atomic level, (b) exposure time, 10 min. (c) exposure time, 90 min. 

A second set of experiments further supported the surface carbon route to methane. In these experiments a Ni(lOO) surface was precarbided by exposure to CO and then treated with hydrogen in the reaction chamber for various times. Steps (3) and (4) above were then followed to measure the carbide level This study showed that the rate of carbon removal in hydrogen compared favorably to the carbide formation rate in CO and to the overall methanation rate in H2/CO mixtures. Thus in a H2-CO atmosphere the reaction rate is determined by a delicate balance of the carbon formation and removal steps and neither of these is rate determining in the usual sense. 

Carbondioxide adsorption is another example of molecular adsorption which has been studied quite extensively in the past. While for some time is was generally accepted that CO2 forms carbonates with chromia surfaces very readily upon exposure, it was recently observed that carboxylate species may be formed. TDS spectra indicate [111, 112] that there are more weakly and less weakly bound CO2 species on the surfaces. We have studied the nature of those species by various techniques including infrared spectroscopy. Fig. 23 shows several sets of IR spectra. The pair of sharp bands around 2300 cm can easily be assigned to the more weakly bound CO2 with only slightly distorted structure... 

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