ASTM D5630-22 Standard Test Method for Ash Content in Plastics

The American Society for Testing and Materials (ASTM) standard, “ASTM D5630-22 Standard test method for ash content in plastics,” describes a test method developed to determine the inorganic content of plastics by destructive ashing procedures. Ash levels of 0,01 percent or greater are covered by this test method. These ashing procedures are used only to measure residual solids in the polymer and cannot be used to qualitatively identify individual chemical components of the ash.

This test method is limited to materials (including glass) that are stable to 900 degrees. “ASTM D2584-18 Standard test method for loss on ignition of toughened reinforced resins” is recommended for unknown samples and when fusion of inorganic moieties may be a concern.

Fluorinated polymers and polymers containing halogenated components are not included in these procedures.

This standard includes two procedures for determining inorganic residues in plastics:

• Procedure A Muffle furnace technique: This technique is used for samples weighing 5 to 50 grams. The samples are flared over a burner before being reduced to ash in a muffle furnace.
• Procedure B Rapid ashing furnace technique: This technique is used for samples of 2-10 grams. The samples are burned and reduced to ashes in a muffle furnace.

For more efficient ashing, the plastic sample should be in powder or pellet form. This test method provides consistent filler content results for a given filler in a given resin. However, this method may not provide absolute filler content in all cases. This includes polymers filled with calcium carbonate, nano clays, and carbon black. Procedure B, “ISO 3451/1 It is equivalent to Method A described in the standard “Plastics - Determination of ash - Part 1: General methods”.

For the purposes of this standard, the terms and definitions given in “ASTM D883-22 Standard terminology for plastics” and “ASTM D1600-18 Standard terminology for abbreviated terms for plastics” are valid.

This test method is based on the weight loss of a plastic sample by burning it to oxidize all organic matter. Inorganic residues from plastic ashing can be anti-block, fillers, reinforcements, catalyst residues, colorants, etc. The quantitative amounts of each are important variables in the manufacturing process.

During the tests, a flame height of more than 2,5 cm from the burner is likely to cause fine particle loss. Also, large sample sizes may cause the evolution of pyrolysis products that may affect ash recovery. To prevent the sample from oxidizing and burning too quickly, the furnace doors must be in the closed position during the firing period. In the meantime, it is necessary to ensure that all crucibles have cooled to ambient temperature before weighing.

The main equipment used in these tests includes:

• A balance capable of weighing the sample to the nearest 0,0001 g. The balance should be checked periodically to ensure accuracy.
• Porcelain, platinum or quartz fiber crucibles of sufficient size and inert to the material being tested. Quartz fiber crucibles are used only in Procedure B.
• Electric resistance heating or microwave heating muffle furnace capable of maintaining a temperature of 900 degrees plus/minus 25 degrees. If an electric muffle furnace is used, it should be placed in a well-ventilated hood. If a microwave oven is used, it should be placed in or next to the hood and the exhaust pipe should be vented to the hood or atmosphere through duct work to prevent inhalation of combustion by-products. A microwave oven capable of providing 2,8 m3/min of air flow to be moved through the microwave cavity is recommended.
• Chiller: A nichrome triangle (nichrome is an alloy of nickel and chromium with small amounts of silicon, manganese and iron) is placed on a polypropylene funnel connected to a dry compressed air source or equivalent. Calibrate the air flow with a wet test meter or bubble meter to obtain a flow rate of approximately 30 L/min.
• Burner.
• Desiccator.

For nylon and similar hygroscopic materials, samples are dried to constant weight before testing.

When preparing the crucible, porcelain or platinum crucibles are cleaned with tap water and an abrasive detergent. It is necessary to ensure that the baked-on residues are completely removed from the crucibles. Quartz fiber crucibles are disposable products and do not require cleaning. Clean crucibles are baked in a muffle furnace for 5 minutes at the set operating temperature to burn off residues in the crucibles. After baking the crucibles, they are placed in a desiccator to cool for 20 to 30 minutes (porcelain or platinum crucibles) or 2 minutes (quartz fiber crucibles).

The ash and mass percentage in the analysis sample are calculated according to the formula given in the standard.

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