ASTM D1929-19 Standard Test Method for Determining Ignition Temperature of Plastics

The standard "ASTM D1929-19 Standard test method for determining the ignition temperature of plastics" published by the American Society for Testing and Materials (ASTM) describes a fire reaction test method for determining the flash ignition temperature and autoignition temperature of plastics in the laboratory using a hot air oven. The values ​​specified in the units are considered standard. No other measurement units are included in this standard. During combustion, gases or vapors or both that are potentially hazardous to personnel are released.

For the purposes of this standard, in addition to the terms and definitions given in ASTM D883, ASTM E456, and ASTM E176, the following definitions apply:

• The instantaneous ignition temperature refers to the minimum temperature at which, under specified test conditions, sufficient flammable gases are emitted to instantaneously ignite when a small external pilot flame is applied.
• Incandescent combustion refers to the combustion of a solid phase material without the occurrence of general ignition, without flame but with light emission from the combustion zone, due to slow decomposition and carbonization at various points in the sample.
• Autoignition temperature or self-ignition temperature refers to the minimum temperature at which the self-heating properties of the sample lead to ignition or at which ignition occurs spontaneously, in the absence of any additional flame ignition source, under specified test conditions.

Tests performed under the conditions specified in this standard can be of significant value in comparing the relative ignition characteristics of different materials. The values ​​obtained represent the lowest ambient air temperature that will cause the material to ignite under the conditions of this test. The test values ​​are expected to rank materials in terms of their ignition susceptibility under actual conditions of use.

This test is not intended to be the sole measure of fire hazard. In addition to ignition temperatures, this standard includes other factors such as fire hazards, burning rate or flame spread, combustion intensity, fuel content, combustion products, and others.

The equipment used in these tests includes:

• Hot air firing furnace: A furnace similar to that shown in the figure given in the Standard, consisting essentially of an electric heating unit and a sample holder.
• Furnace tube: A vertical tube made of ceramic that will withstand a temperature of at least 750 degrees, with an internal diameter of 100 mm plus/minus 5 mm and a length of 230 mm plus/minus 20 mm. The vertical tube rests on the furnace floor, fitted with a stopper for the removal of accumulated residue.
• Inner ceramic tube: A ceramic tube with a temperature resistance of at least 750 degrees, an inner diameter of 75 mm plus/minus 5 mm, a length of 230 mm plus/minus 20 mm and a thickness of approximately 3 mm is placed inside the furnace tube and placed on three small spacer blocks 20 mm plus/minus 2 mm above the furnace bottom. The top is covered with a disk of heat-resistant material with a 25 mm plus/minus 2 mm diameter opening in the middle, used for the observation and passage of smoke and gases. The pilot light is located immediately above the opening. Fire-resistant materials such as silica glass and stainless steel have also been found suitable for this application.
• Air source: An external air source used to supply fresh air through a copper tube at a constant and controllable rate from near the top of the annulus space between the ceramic tubes. The air shall be heated and circulated in the space between the two tubes and shall enter the inner furnace tube from the bottom. The air shall be measured with a rotameter or other suitable device.
• Electric heating unit consisting of 50 turns of 1,3 mm plus/minus 0,1 mm nichrome V alloy wire contained in a mineral fiber sheath and wrapped around the furnace tube and embedded in refractory cement. Other constructions such as finely wound wire embedded in molded ceramic fiber have also been found acceptable.
• Insulation consisting of a layer of mineral fibre approximately 60 mm thick and covered with a metal sheath
• Pilot igniter: Consisting of nominal 1,8 mm plus/minus 0,3 mm inside diameter copper tubing, connected to a source of 94 percent minimum purity propane gas and positioned horizontally 5 mm plus/minus 1 mm above the top surface of the disk cap. The pilot flame shall be set to a length of 20 mm plus/minus 2 mm and shall be located in the center of the opening in the disk cap.
• Sample support and holder: The sample tray consists of a metal container made of approximately 40 mm thick steel, 2 mm plus/minus 15 mm in diameter and 2 mm plus/minus 0,5 mm deep. It is held within a ring of stainless steel welding rod, approximately 2,0 mm in diameter. The ring is welded to a length of the same type of rod extending from the furnace door as shown. The base of the sample tray is located 185 mm plus/minus 5 mm below the top of the inner furnace tube.
• Thermocouples: 0,5 mm diameter, chrome-alumel (Type K) or iron-constantan (Type J) for temperature measurement. Thermocouples are connected to a calibrated recording device with a tolerance not exceeding plus/minus 2 degrees. The thermocouple tolerance shall be in accordance with standard IEC 584-2, Table 1, Class 2 or better.
• Heating control: A suitable variable transformer or automatic controller connected in series with the heating coils.
• Timing device: Must have an accuracy of at least 1 s.

The thermocouple measures the temperature of the sample. It is located as close as possible to the center of the top surface of the sample while it is in place in the oven. The thermocouple wire is connected to the sample support rod. Another thermocouple gives some indication of the temperature of the air passing near the sample. It is located 10 mm plus/minus 2 mm below the center of the sample pan. The thermocouple wire is connected to the sample support rod.

It is acceptable to use materials or products supplied in any form as test samples, some examples are pellets, powders and films. It is also acceptable to use composites as test samples. The test report should include full details of the form in which the test samples were tested. Samples containing high levels of inorganic fillers are difficult to evaluate. In some cases, the same material tested in different forms will give different results.

Our organization, which has been trying to support businesses from every sector with its testing, measurement, analysis and evaluation studies carried out in a wide range for years, has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. In this context, testing services in accordance with the "ASTM D1929-19 Standard test method for determining the ignition temperature of plastics" standard are also provided to businesses.