The results of this study indicated that depolymerisation is a significant degradation mechanism in Baltic amber, since the thermally aged samples showed a progressive increase in the concentration of terminal unsaturated carbon–carbon bonds present at the surface. A degradation pathway that comprises depolymerisation and oxidation of the amber macromolecular structure was proposed. Yellowing and increase in roughness of the sample surfaces were shown to be correlated with the depolymerisation process. For that reason, discolouration and fragmentation of amber items in museum collections should be considered warning signs of ongoing polymer chain breakdown and suggest preventive conservation actions, such as exclusion of oxygen in the environment where amber objects are stored or displayed. For this purpose, the use of anoxic cases should be established as a recommended practice.
It is clear that the application of non-destructive colorimetric, profilometric and spectroscopic techniques has a significant potential for monitoring of degradation of Baltic amber during natural ageing. In particular, confocal profilometry could be successfully used for the characterisation of physical features as a consequence of chemical degradation, while, similarly to measurements on other polymer materials, e.g., dental resins [33], FT-Raman spectroscopy could pave the way towards quantitative determination of amber DP.
The results of this study indicated that depolymerisation is a significant degradation mechanism in Baltic amber, since the thermally aged samples showed a progressive increase in the concentration of terminal unsaturated carbon–carbon bonds present at the surface. A degradation pathway that comprises depolymerisation and oxidation of the amber macromolecular structure was proposed. Yellowing and increase in roughness of the sample surfaces were shown to be correlated with the depolymerisation process. For that reason, discolouration and fragmentation of amber items in museum collections should be considered warning signs of ongoing polymer chain breakdown and suggest preventive conservation actions, such as exclusion of oxygen in the environment where amber objects are stored or displayed. For this purpose, the use of anoxic cases should be established as a recommended practice.
It is clear that the application of non-destructive colorimetric, profilometric and spectroscopic techniques has a significant potential for monitoring of degradation of Baltic amber during natural ageing. In particular, confocal profilometry could be successfully used for the characterisation of physical features as a consequence of chemical degradation, while, similarly to measurements on other polymer materials, e.g., dental resins [33], FT-Raman spectroscopy could pave the way towards quantitative determination of amber DP.
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