LIGHT AGEING

The commercial success of ABS polymers has led to the investigation of many other polyblend materials. In some cases properties are exhibited which are superior to those of ABS and some of the materials are commercially available. For example, the opacity of ABS has led to the development of blends in which the glassy phase is modified to give transparent polymers whilst the limited light aging has been countered by the use of rubbers other than polybutadiene. 

D. Scalarone, M. Lazzari and O. Chiantore, Thermally assisted hydrolysis and methylation pyrolysis gas chromatography mass spectrometry of light aged linseed oil, J. Anal. Appl. Pyrol., 58 59, 503 512 (2001). 

Different studies have been conducted by the same team of researchers for the analyses of tapestry fibres. The main aim was to study the surface evolution of these fibres, silk or wool, during light ageing or cleaning procedures. 

A term applied to a moulded product which has failed to fill out the pattern details, showing rounded edges and porosity, either surface and/or internal. It does not necessarily mean that insufficient weight of compound has been used. Light Ageing... 

This study was therefore undertaken to prepare and evaluate acrylonitrile—butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS) polymers under similar conditions to determine whether replacement of acrylonitrile by methyl methacrylate could improve color stability during ultraviolet light aging, without detracting seriously from the good mechanical and thermal-mechanical properties of conventional ABS plastics. For purposes of control, the study also included briefer evaluation of commercial ABS, MBS, and acrylonitrile-butyl acrylate-styrene plastics. 

Emulsion polymers and commercial controls were milled (Table III) and molded (Table IV) to produce test samples, and properties were evaluated following standard ASTM procedures (Tables V-VII). During accelerated ultraviolet light aging, the polymers were also examined by infrared spectroscopy of films cast from o-dichlorobenzene solution (Table VIII). 

Color stability the resistance of a petroleum product to change color due to light, aging, etc. 

Although none of the treated samples in Set B showed any improvement over the untreated silk after heating 4 days at 150°C, Cyasorb 531 again was the best of the lot (65.8 pmol/g silk). The best sample in Set B after artificial light aging for 8 days was Tinuvin 765, one of the HALS (14.2 pmol/g silk, a 31.4% reduction... 

Additional Differences Between Heat and Light Aging... 

Effect of dyes of different class on light ageing of PA is studied more detailed in the work [83]. It appeared that dyes, used by the authors, sensibilize PA photooxidation according to radical mechanism, however the total action of the dye may be stabilizing owing to shielding effect, and in some cases according to the mechanism of antioxidant action. 

Fig. 7. Stability of a sample of a-Si H under solar illumination, plotted according to the diffusion length method outlined in the text. The light-aged time (hours at one sun) is shown alongside each point.

Rubbers are used in a wide variety of service environments and share many of the requirements and features of other materials discussed in this book, although resistance to light aging is generally much less serious a problem than in plastics because of the extensive use of carbon black as a filler or pigment. Attention is therefore drawn to other chapters on environmental resistance and weathering. This section focuses on properties more closely identified with rubbers. 

Heat and light ageing Fair Very good Excellent... 

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