Clothing and equipment for protection against heat — Test method for convective heat resistance using a hot air circulating oven
This test method allows the heat resistance of materials, clothing, and protective equipment to be evaluated when samples are suspended in a hot air circulation furnace for 5 minutes at the specified test temperature of 180°C or 260°C for 5 minutes. Any visible observations such as carbonization, deformation, degradation, delamination, brittleness, flaking, hole formation, ignition, melting, separation, or splitting of the sample are recorded and shrinkage measured.
Observations of degradation, brittleness, splitting, separation, or flaking may be considered subjective and should not be used as pass/fail criteria for a product standard.
-Forced air circulation furnace, capable of maintaining the test temperature for a period of 5 min and with sufficient internal volume to allow the suspension of the test sample with an air flow of 0.5 – 1.5 m/s at 20ºC 1 atm measured at the central point of the furnace.
The maximum temperature deviation from the specified temperature levels in:
-260 °C for each of the nine thermocouples shall not exceed 6.5 °C
-180 °C for each of the nine thermocouples shall not exceed 4.5 °C.
-Rigid and square 375 mm × 375 mm templates for sizing flat materials that are subject to shrinkage measurements. A 150 mm × 150 mm template can be used for flat materials that are not subject to shrinkage measurements.
-Graduated ruler, in mm.
-Stretch frame to measure the shrinkage of knitted materials.
Conditioning: minimum 1 m2 of sample or complete garment, for 24 h at 20 ± 2ºC and 65 ± 55 of relative humidity.
-Prepare the specimens as follows:
-If the sample is narrower than 375 mm, cut the sample in the direction of its length (375 mm) and rotate it so that this edge serves as the width.
-If the sample is less than 375 x375 mm, do the test with the complete element.
-In case the samples are not subject to shrinkage measurement, they can have a small size (150 x 150 mm).
-Calibrate the furnace before the test by verifying the uniformity of temperature, air velocity and check the thermocouple.
PROCEDURE FOR FLAT TEXTILES
-Mark and measure specimens according to ISO 3759 except for the distance between the two markings in each pair will be 275 mm.
-Heat the oven to the specified temperature and stabilize for 30 min.
-Suspend the sample using metal hooks at the top and centered in the oven so that it is within 50 mm of any surface of the oven or other sample for 5 min
-Do not open the door for more than 15 seconds. Turn off the air circulation while the door is open and turn it on again with the door closed. The total recovery time of the oven cannot exceed 30 seconds.
-Leave the sample in the oven for 5 min ± 15 s at the test temperature. The exposure time begins when the thermocouple returns to the test temperature.
-Immediately after exposure, remove the sample and examine it for evidence of carbonization, deformation, delamination, hole formation, ignition, fusion, separation, or splitting.
-5 minutes after exposure, if necessary, measure the marked dimensions of the sample to determine the % shrinkage in both directions. For knitted fabrics, use the stretch frame to return to the original dimensions for 10 minutes. Then, remove the samples from the frame and let the sample relax for 10 minutes and perform the measurement to assess whether the result is pass/fail.
-In the event that, when stretching the point samples, they break or do not reach the original dimension, this observation must be reported instead of the contraction measurement.
PROCEDURE FOR SMALL ITEMS AND CLOTHING ACCESSORIES
-Turn on the oven, heat it to the temperature of the test and let it stabilize for 30 min.
-For samples of less than 150 mm, samples with their normal width by 150 mm long should be used. Suspend these samples with their longitudinal axis in a vertical direction.
-If you need to measure their shrinkage, mark and measure the samples according to ISO 3759.
-prepare the samples according to one of two options:
-Attach the samples to the fabric with the same orientation and joining method used in the manufacture of the garment.
-Suspend the sample with metal hooks on top in the center of the furnace so that the entire sample is not less than 50 mm from any surface of the furnace or other specimen and the airflow is parallel to the plane of the material.
-Do not open the door for more than 15 seconds. Turn off the air circulation while the door is open and turn it on again with the door closed. The total recovery time of the oven cannot exceed 30 seconds.
-Leave the sample in the oven for 5 min ± 15 s at the test temperature. The exposure time begins when the thermocouple returns to the test temperature.
-Immediately after exposure, remove the sample and examine it for evidence of carbonization, deformation, delamination, hole formation, ignition, fusion, separation, or splitting.
-5 minutes after exposure, if necessary, measure the marked dimensions of the sample to determine the % shrinkage in both directions.
RESULTS:
-The test report must state
-All visual observations detected after the test on the sample
-Contraction in % of each direction of the tissue, when required
