Scope:

ASTM D1929 measures the self-ignition temperature and flash ignition temperature of plastics. Self-ignition temperature is the lowest temperature at which the sample self-ignites and Flash Ignition Temperature is the lowest temperature at which the sample releases combustible gases. 

The test results can be used to compare the relative ignition characteristics of different materials, and to rank materials based on ignition susceptibility. The test results are not used to assess the potential fire hazards of a plastic sample.

Test Procedure:

In ASTM D1929, theASTM D1929 involves a hot air furnace with an adjustable movement of hot air rising through it. The furnace is tuned to a fixed temperature. The test specimen is lowered to the center of the furnace with a specimen holder. A cover with a hole is positioned on the furnace for gases to escape.

When testing for flash ignition, a small pilot flame is placed over the hole. The pilot flame will burn if the plastic sample is discharging any ignitable gases. The temperature at which the plastic self ignites is the spontaneous-ignition temperature. A thermocouple monitors the test.

specimen:

A specimen of 3 grams is required for plastics with a density of more than 100 kilograms per cubic meter. For plastics in sheet form, stacked sheets of 3 grams and dimensions of 20 mm x 20 mm are needed.  

For cellular plastics with a density lower than 100 kg/m³, a block of 20 mm × 20 mm × 50 mm is needed with its outer skin removed.

Results:

ASTM D1929 is used to determine two temperatures that are vital to understanding a particular plastic’s safety levels:

Spontaneous Ignition Temperature or Self-Ignition Temperature: It is the lowest temperature at which the test piece self-ignites without an added flame or external source of ignition.

Flash Ignition Temperature: It is the lowest temperature at which sufficient gases are produced that are ignitable with an external ignition source such as a small pilot light.