Specular reflectance stability

For mesitylene and durene, the kinetics have been followed by specular reflectance spectroscopy [159]. The results indicated that mesitylene produces a fairly stable radical cation that dimerizes. That of durene, however, is less stable and loses a proton to form a benzyl radical, which subsequently leads to a diphenylmethane. The stability of the radical cation increases with increasing charge delocalization, blocking of... 

For mesitylene and durene, the kinetics have been followed by specular reflectance spectroscopy [17]. The results indicated that mesitylene produces a fairly stable radical cation that dimerizes. That of durene, however, is less stable and loses a proton to form a benzyl radical, which subsequently leads to a diphenylmethane. The stability of the radical cation increases with increasing charge delocalization, blocking of reactive sites, and stabilization by specific functional groups (phenyl, alkoxy, and amino) [18]. The complex reaction mechanisms of radical cations and methods of their investigation have been reviewed in detail [19a]. Fast-scan cyclovoltammetry gave kinetic evidence for the reversible dimerization of the radical cations of thianthrene and the tetramethoxy derivative of it. Rate constants and enthalpy values are reported for this dimerization [19b]. 

Listed in Table II are the reflective film materials undergoing outdoor exposure testing at DSET. Typical results for coupon testing of these materials are shown in Figures 9 and 10. Also shown are data from coupons cut from an uncoated aluminized polyester reflector supported in a Tedlar enclosure that was exposed in northeastern Oregon. Of the reflector material candidates studied, only the coated, silverized, stabilized polyester (OCLI) maintained its specular reflectivity for 18 months on EMMA (equivalent of 12 years). All reflective films showed severe reduction in mechanical properties. 

Zwinkels, J. C, Noel, M., and Dodd, C. X. (1994). Procedures and standards for accurate spectrophotoroetric measurements of specular reflectance. /4ppt Optics 33, 7933. Probably the best overview of measurement techniques, error aitalysis of measurement, and stability of specular standards. 

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