Ash content of plastic samples (plastics, plastic composites) is accessible as mass or mass fraction after direct annealing of the sample following DIN EN ISO 3451.
The sample is burnt at high temperatures (usually at 950 °C, the exact temperature depends on the respective plastic system). Subsequent annealing ensures that the combustion residue has been completely converted into ash that cannot be burnt further. The progress of the annealing is monitored by weighing (continuously for sample weights of up to 5 g).
The sample mass is selected according to the ash content to be expected – thus, with a sample weight of 100 g, ash contents of up to >0.01% can be determined in accordance with the standard.
For sample weights of up to 5 g (expected ash content 1%), ash determination can be ideally combined with thermogravimetric analysis (TGA). For investigations on unknown plastic samples, an IR analysis (vibrational spectroscopic investigation) of the sample is recommended in advance.