Polymer Surfaces photodegradation

B. Ranby and J. F. Rabek, "Photodegradation, Photo-Oxidation and Photo-Stabilization of Polymers", J. Wiley Sons, New York, 1975 also, B. Ranby, "Polymer Surfaces", D. T. Clark and W. J. Feast, Editors, Chap. 18, J. Wiley Sons, New York, 1978, see also B. J. Bulkin, C. S. Chen and E. M. Fierce,... 

Photodegradation of polyethylene waste can be markedly accelerated via its grafting with acrylamide [98], In contrast, photostabilization of polyethylene and polypropylene can be achieved as a result of the grafting of 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone using gamma radiation [ 147], In this case, the grafted compound acting as a U V stabilizer is chemically bound to the backbone chain of the polymer and its evaporation from the surface can be avoided. 

Alternatively because of the degree to which it both reflects white light and absorbs in the ultraviolet, it may inhibit photodegradation. Which of these two possibilities predominates depends on a variety of factors including the concentration of the TiOj pigment used, the nature of any surface treatments, and the extent to which the polymer itself is able to resist photodegradation. 

The surface oxidation products dete ted by the decrease in contact angle upon photolysis of PVCa films may dominate the photoconductivity of t. is polymer. Work is underway to confirm this relatio. ship and measure surface conductivity simultaneously with bulk conductivity as a function of photodegradation. 

Fundamental questions related to the electronic configuration of the open or colored forms and the number and structures of the photomerocyanine isomers are considered on the basis of the results of continuous-wave (stationary) and time-resolved (picosecond, nanosecond, and millisecond) Raman experiments. For spironaphthoxazine photochromic compounds, the Raman spectra may be attributed to the TTC (trans-trans-cis) isomer having a dominant quinoidal electronic configuration. Surface-enhanced resonance Raman spectroscopy (SERRS) is demonstrated as a new analytical method for the study of the photodegradation process in solution for nitro-BIPS derivatives. The development of this method could lead to the identification of the photoproducts in thin polymer films or sol-gel matrices and ultimately to control of degradation. 

When many polymers are exposed to UV levels similar to those on a sunny day near to the equator, photodegradation reactions proceed very rapidly and the rate of oxygen consumption is very high. With some polymers, oxygen diffusing into the material from the exposed surface is consumed by reaction before it can penetrate very far. Therefore, under a period of sustained UV exposure, any oxygen that had... 

Inspection of fracture surfaces of photodegraded polymers often reveals the presence of a smooth brittle zone near to the surface and a much more ductile fracture in the interior. The brittle zone depth often corresponds to that of the highly degraded depth obtained by FTIR or molecular mass measurements. 

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