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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Page 40
... decrease approximately linearly with crosslink density or the reciprocal of the molecular weight between crosslinks at low to moderate degrees of crosslinking . At higher densities the decrease is nonlinear . The solubility is ...
... decrease approximately linearly with crosslink density or the reciprocal of the molecular weight between crosslinks at low to moderate degrees of crosslinking . At higher densities the decrease is nonlinear . The solubility is ...
Page 57
... decreases as the density of a polymer matrix and content of the crystalline phase increases . ( vi ) Factors which decrease the segmental mobility ( crystallization , chain stiffness , and crosslinking ) decrease the diffusion rate ...
... decreases as the density of a polymer matrix and content of the crystalline phase increases . ( vi ) Factors which decrease the segmental mobility ( crystallization , chain stiffness , and crosslinking ) decrease the diffusion rate ...
Page 416
... decrease in tensile strength Time in Xenotest ( h ) ( type 1200 ) required for 50 % decrease in tensile strength Control ( nonstabilized ) 0-6 800 Tinuvin 770 DF Chimassorb 944 LD LD } 0.05 6-4 4 000 0.05 Tinuvin 770 DF 0.1 13.0 9 750 ...
... decrease in tensile strength Time in Xenotest ( h ) ( type 1200 ) required for 50 % decrease in tensile strength Control ( nonstabilized ) 0-6 800 Tinuvin 770 DF Chimassorb 944 LD LD } 0.05 6-4 4 000 0.05 Tinuvin 770 DF 0.1 13.0 9 750 ...
Contents
Preface | 1 |
Antioxidants | 19 |
Introduction to the Oxidative and Photo | 42 |
Copyright | |
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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 chain chelates Chem Chemical Chimassorb 944 Ciba-Geigy coatings compounds concentration copolymers crystalline Cyanamid Cyanox Cyasorb UV decrease Degrad Developments in Polymer effect embrittlement EPDM free radicals Goodrite HALS hindered amines hydroperoxide Irganox kinetics LDPE light stabilizers low-density polyethylene LDPE mechanism Melting metal molecules monomers nickel(II nitroxy radicals Nondiscolouring nonstaining O₂ OH OH permission from Ref peroxy radicals phenolic phosphite photo-oxidation 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 он