Photochemical degradation of polyvinylchloride

Depth Profiling of the Optical Absorption Coefficient in Ultraviolet-Degraded Poly(Vinylchloride) Films by Dual Beam Light Profile Microscopy

“…In practical degradation problems, their concentrations are distance dependent on the scale of micrometers because the chain growth kinetics are governed by the local availability of oxygen, radicals, and/or other initiating species. [2][3][4][5][6][7][8][9] In an industrial problem, polyene concentration profiles may be highly diagnostic of the location of an initiating source of degradation in a complex structure. 8,9 In the course of photolysis under broadband UV wavelengths, [4][5][6][7] initially the native PVC is transparent over the optical bandwidth of the photolysis radiation.…”

“…2a and 2b show several effects supported by known features in the photo-degradation of thin film PVC. [2][3][4][5][6][7] In forward irradiation, luminescence peaks at a short distance inside the photolysis entry surface. In the photolysis regime used by the present work, photoproduct absorption is high enough to cause visible depth attenuation in the source beam within approximately 30 m of the front entry surface.…”

“…This dependence often derives from restrictions on the transport of reagents to within short distances from a surface or interface in a material. A classic effect is the yellowing of many polymers [2][3][4][5][6][7][8][9][10][11][12][13] under exposure to UV radiation. This process occurs efficiently in zones of a material in which oxygen concentrations are low or negligible, at depths of tens or hundreds of micrometers below the surface.…”

“…In poly(vinyl chloride) (PVC) [2][3][4][5][6][7][8][9] and related polymers such as poly(vinyl alcohol) (PVA) [10][11][12] and poly(vinyl acetate) (PVAc), 13 when thin films are subjected to thermal or UV photo-degradation, yellowing arises from the for-mation of poly(ene) chains of structure -(CHϭCH) n -. As degradation proceeds, the chain length n increases from 2-4 through 12 units or greater, 7,12 producing increased visible wavelength absorption in sub-surface zones.…”

“…This classic process in polymer science has been studied by a number of groups using destructive analytical techniques. [2][3][4][5][6][7][8][9]14 Recently, we introduced laser light profile microscopy (LPM) 15,16 as a method for directly observing luminescent and scattering structures in inhomogeneous thin films on a scale of sub-100 m. While a number of methods (as recently reviewed in Ref. 17) have been reported in past works for depth profiling the optical properties of materials, LPM has the distinct advantage of achieving this on a direct basis.…”