Stach, P., Martinkutė, G., Šinkūnas, P., Natkaniec-Nowak, L., Drzewicz, P., Naglik, B. & Bogdasarov, M. (2019). 
An attempt to correlate the physical properties of fossil and subfossil resins with their age and geographic location. 
Journal of Polymer Engineering, 39(8), 716-728.

https://doi.org/10.1515/polyeng-2019-0159

Abstract
Testing of the correlation between physical properties of natural resins such as microhardness, density and UV-excited 
fluorescence emission with their age, geological conditions, botanical and geographical origin and chemical structure was performed.
These physical parameters, especially microhardness, are the result of resins fossilization processes like cross-linking 
and polymerizations of compounds present in the fossils. In addition, hardening of the resins may be also an effect of miscellaneous
chemical processes induced by various environmental, biological and geological conditions. The principal component analysis
found that the correlation of microhardness, density and fluorescence intensity with the resin age is quite low. 
The results suggest that variability of physical properties is caused by geographic location and locally occurring geological conditions. 
The physical properties of natural resins are most strongly correlated with chemical structure and geographic location. 
The resins with higher microhardness values come from marine environment depositions. The same trend was observed for resins affected 
by volcanic activity. Moreover, high fluorescence intensity was also observed for resins affected by above mentioned geological conditions. 
However, the density values of tested resins revealed the lowest correlation with their age, botanical source and geological history.

Keywords: microhardness; natural polymer; principal component analysis (PCA); resins