Photostabilization of Polymers: Priciples and ApplicationDuring the last two decades, the production of polymers and plastics has been increasing rapidly. In spite of developing new polymers and polymeric materials, only 40-60 are used commercially on a large scale. It has been estimated that half of the annual production of polymers is employed outdoors. Increasing the stability of polymers and plastics towards heat, light, atmospheric oxygen and other environmental agents and weathering conditions has always been a very important problem. The photochemical instability of most of polymers limits them to outdoor application, where they are photo degraded fast over periods ranging from months to a few years. To the despair of technologists and consumers alike, photodegrada tion and environmental ageing of polymers occur much faster than can be expected from knowledge collected in laboratories. In many cases, improved methods of preparation and purification of both monomers and polymers yield products of better quality and higher resistance to heat and light. However, without stabilization of polymers by applica tion of antioxidants (to decrease thermal oxidative degradation) and photostabilizers (to decrease photo-oxidative degradation) it would be impossible to employ polymers and plastics in everyday use. |
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Absorbance absorption acetate acid additives Amer anatase antioxidants Appl Applied Science Publishers benzophenone carbon black carbonyl carbonyl groups Carbonyl index CH₂ CH3 CH3 CH3 chelates Chem Chemical Chimassorb 944 Ciba-Geigy coatings colour compounds concentration copolymers Cyanamid Cyanox Cyasorb UV Developments in Polymer diffusion effect embrittlement EPDM free radicals Goodrite HALS hindered amine hydroperoxide Irganox kinetics LDPE light stabilizers low-density polyethylene LDPE mechanism metal molecular monomers nickel(II nitroxy radicals Nondiscolouring nonstaining O₂ OH OH permission from Ref peroxy radicals phenolic phosphite Photochem photodegradation photostabilizers pigment piperidine plastics poly(vinyl chloride polyethylene polymer polymer matrix polymeric polyolefins polypropylene polypropylene films polyurethane powder processing R₁ R₂ react reaction Reprinted with permission ROOH rubber rutile salicylate sample Scott singlet oxygen solubility spectra spectroscopy structure surface Symp synergistic Table temperature thermal oxidation Tinuvin 770 TiO2 Topanol UV irradiation Wavelength nm yellow