Light Stabilizers for Coatings (eBook)

1Introduction 11
2Light and photo-oxidative degradation 13
2.1Light 13
2.1.1Photo-physical processes 15
2.2Photo-chemical degradation processes 16
3Stabilization options 21
3.1UV absorbent pigments 22
3.2UV absorbers 23
3.2.1UV absorber classes 24
3.2.2Mode of action of UV absorbers 27
3.2.2.1Phenolic UV absorbers 28
3.2.2.2Non-phenolic UV absorbers 30
3.2.3Examples of UV absorbers 30
3.3Free-radical scavengers 36
3.3.1Antioxidants 36
3.3.2Sterically hindered amines 38
3.3.2.1Mode of action of HALS 42
3.4Quenchers 45
3.5Peroxide decomposing agents 46
4Stabilization of coatings 49
4.1Automotive coatings 51
4.2Light stabilization of automotive coatings 52
4.2.1Two-coat systems 53
4.2.2Specific requirements of UV absorbers in coatings 55
4.2.2.1Solubility and compatibility of UV absorbers 56
4.2.2.2Volatility of UV absorbers 59
4.2.2.3Reactable UV absorbers 61
4.2.2.4Effect of UV absorbers on coating colour 63
4.2.2.5Unwelcome side reactions 64
4.2.2.6UV absorbers and photoinitiators 67
4.2.3Specific requirements on HALS in coatings 71
4.2.3.1Solubility and compatibility of HALS 71
4.2.3.2Volatility of HALS 74
4.2.3.3Reactable HALS 75
4.2.3.4Effect of HALS on coating colour 76
4.2.3.5Unwelcome side reactions 77
4.2.4Weathering results for two-coat systems 79
4.2.4.1Weathering tests 79
4.2.4.2Results for solvent-borne clear coats 86
4.2.4.3Results for water-borne clear coats 97
4.2.4.4Results for powder clear coats 100
4.2.4.5Results for UV-curable clear coats 103
4.2.4.6Coatings on plastic substrates 106
4.2.4.7UV protection of epoxy-based fibre reinforced plastics 111
4.2.4.8Effect of additional basecoat stabilization 114
4.2.4.9Exposure results for one-coat finishes 117
4.3Light stabilization of industrial coatings 121
4.3.1Stabilization of paints for metal substrates 122
4.3.2Stabilization of clear wood coatings 125
4.4Stability of light stabilizers 128
4.4.1Photo-chemical stability of UV absorbers 128
4.4.2Long-term stability of HALS 137
5Conclusions 141
6References 143
Authors 151
Index 153