The Properties and Lifetime of Polymer UV Films
| Main Authors: | , , |
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| Format: | Article |
| Language: | English Slovak |
| Online Access: | http://www.viks.sk/chk/res_4_04_233_248.doc |
| Abstract: | SUMMARY. The use of UV filters is very important in the protection of archival and library collections against light. Basic information on the behaviour and the durability of a number of different UV filters is summarized. Study of the properties of UV filters provides information on the changes in the UV absorption characteristics during artificial ageing. A discussion is given of the optical and mechanical properties of UV filters CONCLUSION. It was found in the study of the optical, chemical and mechanical properties of UV films subjected to various ageing conditions that: The absorption of UV radiation by UV films is affected by accelerated ageing, where the greatest changes in all the tested films are caused by thermal ageing. The effect of the combined action of light and humid heat leads to lowered transmittance of the visible part of the spectrum in all the UV films. The changes in transmittance of UV radiation caused by light ageing are lower than for ageing by dry and combined ageing. Humid ageing has only a minimal effect on the transmittance of the UV and visible components of light. The UV films had high initial tensile strength and ductility (stretch at break); however, after 40-60 days of accelerated ageing, these values decreased considerably, especially tensile strength. This fact can probably be explained by the presence of an additive that had a detrimental effect on this quality. However, no such additive could be found using FTIR. The considerable increase in the brittleness of the film will have a detrimental effect particularly on removal of no-longer useful film from window glass. The behaviour of the adhesive layers was monitored during light ageing using FTIR. The results indicated that there was a change in the chemical structure in samples F and G. The polymer matrix remained unchanged. The colour stability of films A, B, C, D, E and F was very good. Only filter G became discernibly cloudy during all types of ageing, probably as a consequence of changes in the structure of the adhesive with the UV absorber. It follows from evaluating the monitored properties that only UV films B and D comply with the strict criteria required for the conservation of sensitive archive materials and can be recommended for use in practice. The rate of fading of a sensitive dye - methyl violet - through the action of light decreased to approximately one half after 140 hours of irradiation when using UV films. The lifetime of UV films is apparently limited and will depend on the specific climatic conditions during use. For example, film attached to window glass will be exposed to much more severe ageing conditions (heat, light, humidity) than film covering an exhibited object in a display case. It can be expected that window film on the south side of a building during the summertime will be exposed to similar conditions as were selected for accelerated ageing. It follows from the obtained information that periodic control of the spectral characteristics of UV films is essential |
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| ISSN: | 0034-5806 |
