ISO 3451-5-2002 pdf free download.Plastics — Determination of ash — Part 5: Poly(vinyl chloride).
7.2 Method A (determination of unsulfated ash)
7.2.1 Heat the clean crucible and lid (5.1 ) in the muffle furnace (5.3) at for and cool in the desiccator (5.5) to room temperature. Weigh the crucible with lid to the nearest .
7.2.2 Introduce into the crucible a suitable quantity of sample (see Table 1 ) (finished product samples should preferably be cut into small pieces). Weigh the crucible with lid and test portion to the nearest and calculate the mass of the test portion ( ).
7.2.3 Heat the crucible directly on the heating device (5.2) so that the test portion burns slowly and loss of ash is avoided. Continue this operation until no more smoke is evolved. In the event of violent burning, the test portion may be added in successive portions.
7.2.4 Partially close the crucible with the lid so that the volatile matter evolved does not carry away particles of ash. Place the crucible at the entrance of the muffle furnace maintained at (the temperature in the entrance zone is about to ), then advance the crucible slowly into the furnace. Calcinate for at . It is recommended that the design of the lid be such that, when placed on the crucible, the lid fits well but does not close the crucible completely.
7.2.5 Remove the crucible with lid from the furnace, place it in the desiccator, allow to cool to room temperature and weigh to the nearest ( ).
7.2.6 Calcinate again, under the same conditions, until constant mass is reached; i.e. until the results of two consecutive weighings do not differ by more than . The total duration of heating in the furnace shall however not exceed . If constant mass is not attained after this time, the mass after shall be used for calculating the test results.
7.3 Method B (determination of sulfated ash)
7.3.1 Proceed as detailed in 7.2.1 .
7.3.2 Proceed as detailed in 7.2.2.
7.3.3 Proceed as detailed in 7.2.3.
7.3.4 After allowing the crucible and contents to cool, add concentrated sulfuric acid (4.1 ) dropwise by means of a pipette (5.4) of suitable capacity until the residue is soaked completely. Heat carefully on a suitable heating device (5.2) until the evolution of smoke ceases, taking care to avoid spattering of the contents of the crucible.
7.3.5 If, after allowing the crucible to cool, carbon is still evident, add 1 to 5 drops of sulfuric acid and reheat until evolution of white fumes has ceased.
7.3.6 Place the crucible at the entrance of the muffle furnace (5.3) maintained at and proceed as detailed in 7.2.4, 7.2.5 and 7.2.6. The residue after calcination shall be grey or white, but not black.ISO 3451-5 pdf download.