Synthetic material

Description

Plastics are not subject in archaeology. However, methods used in archaeometry can be used to examine them. The main question here is the type of carbon source from which a plastic was made off – biogenic or petrochemical (from natural gas or petroleum).

Plastic consists of long-chain molecules that give plastics the desired properties (strength, formability, durability). Plastics can be made from petrochemical or natural raw materials or a mixture of these. Natural plastics are also known as “biogenic” plastics, whose precursor materials are produced from the fermentation of starch or sugar. Using ¹⁴C analysis, we can distinguish biogenic from petrochemical material. Due to its age (the age of the oil from which the raw material is derived is several million years old), petrochemical material contains carbon that does not contain ¹⁴C. Biogenic material has the ¹⁴C carbon signature of the corresponding growth year of the sugar or starch. In our ¹⁴C laboratory the biogenic fraction is determined according to ASTM-D 6866 and EN 16640:2017, respectively.

Sample properties

For the determination of the biogenic portion:

Solids: approx. 10 mg

Liquids: 0.1 ml (typically sample quantities of a few ml are sent to us due to easier handling)

Gases: 0.5 – 1 L

If the material to be tested consists of a mixture of biogenic and petrochemical starting materials, it must be ensured that the sample is representative of the material to be tested. It may need to be homogenised.