ISO 3451-1:2019 pdf free.Plastics – Determination of ash -General methods.
4 Principle
It is possible to determine the ash of an organic material by four main methods (methods A, B, C and D). a) Direct calcination, i.e. by burning the organic matter and heating the residue at high temperature until constant mass is reached, which may be carried out by two different procedures:
— burning with, for example, a Bunsen burner anti one or more calcining steps in a muffle furnace (method A);
— burning and calcining as one single step in a muffle furnace (method A — rapid ashing), if it can be demonstrated that the rapid ashing yields the same results as method A.
b) Calcination after sulfation, which may be carried out by two different procedures:
— with sulfuric acid treatment after burning, i.e. by burning the organic matter, transforming the inorganic residue into sulfates with concentrated sulfuric acid and heating the residue at high temperature until constant mass is reached. This is the common method of obtaining “sulfated ash” (method B);
— with sulfuric acid treatment before burning, i.e. by heating the organic matter together with concentrated sulfuric acid up to temperatures where fuming and subsequent burning of the organic matter occur, and finally heating the residue at high temperature until constant mass is reached (method C). This procedure may be used if volatile metal halides are liable to evaporate during burning of the organic matter. It is not applicable to silicones or fluorine-containing polymers.
c) Automated instrument method (method D).
In each case, the final step of the procedure is calcination at a pre-defined temperature (see 22).
NOTE The mass of the ash can vary with the temperature of calcination. For example, higher temperatures such as 850 °C convert calcium carbonate and other carbonates to their oxides and thus give lower values for the ash.
Use a fume cupboard or other suitable means for ventilation for the ashing procedure, if not required
otherwise by the furnace being used (e.g. for furnaces with an integrated exhaust system that shall not be operated in a fume cupboard).
For method A, if it can be conclusively demonstrated for a particular sample type that direct ashing
in a muffle furnace without preheating/igniting the sample over a Bunsen flame or equivalent gives
the same result, then this version of method A (rapid ashing) is permitted. The use of this rapid ashing method shall be included in the test report.
NOTE The precision and reproducibility of the ashing procedure depends on the temperature at which the burning and/or calcination process in the furnace (ohmic resistance heating or microwave heating) is performed. Efficient ventilation of the furnace is equally important, especially if the furnace is used for burning and calcination (rapid ashing method).
To ensure a constant quality of the ashing procedure, the lab shall verify the operation of the furnace at regular intervals. This verification shall include:
calibration of the furnace temperature using a reference traceable to a national standard according
to a validated calibration procedure;check of the efficiency of the furnace ventilation.
Especially for plastics containing fllers that decompose under elevated temperatures, such as calcium
carbonate, a precise and constant temperature in the furnace is important to ensure precise and
reproducible results.ISO 3451-1 pdf download.