Permanence of UV Absorbers in Plastics and Coatings

Abstract

Ultraviolet absorbers (UVA's) undergo photo-degradation with quantum yields on the order of 10 -6 even in glassy, unreactive matrices such as poly(methyl methacrylate) (PMMA). The kinetics of UVA loss in a film or coating can be described by the equation: A = log 10 [(1-T 0 )10 (A0-kt) + 1] where A is the absorbance at time t, T 0 is the initial transmission, A 0 is the initial absorbance, and k is a zero order rate constant. The rate constant can be found as the slope of log 10 (10 A -1) plotted vs. exposure. The derivation and implications of these equations and a general review of UVA degradation chemistry are discussed, including the effects of the matrix material, concentration, and hindered amine light stabilizers. The rate of UV absorber loss is of relatively minor consequence when the absorber is used as a bulk additive in a polymer, but is of critical importance in the service lifetime of coatings. The kinetics of photochemical UV absorber loss and use of loss rates in coating lifetime predictions are discussed in detail.

Photostabilization of Poly (Vinyl Chloride) by Some Schiff Base Derivedfrom 2-amino pyridine

“…[ This is also suggested for benzophenon [26][27], benzotriazole [28][29] and aromatic Schiff base photostabilizer [15]. These stabilizerstability and a provide very good long time stability and are usually offered to these mechanism.…”

Photostabilisation of Polymer Materials

“…The excited proton transferred product, loses its energy radiationless as thermal energy, by fluorescence or phosphorescence, to form the ground-state proton transferred product, followed by a proton shift, which forms the UVA in the ground-state back [8,9]. The excited proton transferred product, loses its energy radiationless as thermal energy, by fluorescence or phosphorescence, to form the ground-state proton transferred product, followed by a proton shift, which forms the UVA in the ground-state back [8,9].…”

Effect of Adding UV Absorbers Embedded in Carbonate Calcium Templates Covered with Light Responsive Polymer into a Clear Wood Coating

“…Organic UVAs are molecules with conjugated π electrons systems that are able to absorb the UV radiation and convert it into harmless heat [13]. Benzophenones type UVAs are commonly used with HALS (hindered amine light stabilizers), which show synergistic photoprotection [14].…”