(1 Scope
This standard specifies a method for the determination of mass loss during baking of powdered materials applied to substrates by electrostatic spraying.
The method described in this standard is a simple and practical test method. This method gives fairly accurate results for powder coatings with reported mass losses in the range of 2% (m/m) on baking. Beyond this range, the accuracy decreases with increasing mass loss.
Moisture in the product shall be included in the test results.
(2) Instrument
Flat-bottomed dish (pan): made of tinplate or aluminum, with a diameter of about 75mm.
The size requirements of the dish are not very strict, but the bottom surface should be very flat, so as to ensure good thermal contact, and it should be able to spread the powder coating sample into a thin layer with uniform parameter 1 (the thickness of the powder will have a certain influence on the test results. greater impact).
Blast constant temperature dry operation box: can maintain the temperature up to 250 ℃. The type of oven should be stated in the test report, because the type of oven can affect the test results.
Analytical balance: can weigh to 0. lmg.
Desiccator: Equipped with dry glue (mixed with cobalt chloride) desiccant.
(3) Sampling
Follow the provisions of 11 and 12 in ISO842: 1984 to take representative sample crystals produced in the test.
(4) Operation steps
① Sample
Put the flat-bottomed dish in an oven, and dry it for 15 minutes at the specified or agreed test temperature, then place it in a desiccator to cool to room temperature, and weigh the dish to an accuracy of 0.1 mg. Then with the same accuracy, weigh 0.50g ± 0.05g sample into the pan. Hold the pan with tweezers and shake it slowly so that the sample spreads evenly on the bottom of the pan.
A 0.5g sample can be spread into a thin layer about 60µm thick in a 75mm diameter dish.
② Determination
Avoid baking under the specified or agreed temperature and time requirements.
Place the pan containing the sample in an oven pre-adjusted to a specified or agreed temperature for a specified or agreed time. To promote rapid heat transfer, place the dish on a metal plate in the oven (at the oven thermometer).
Before the powder is fused, the powder may be expelled by the blast of the air circulation oven (with blast). Therefore, it is recommended to turn off the blower shortly after the start of the assay.
When a suitable heating time has been reached, move the flat bottom dish to a dry manipulator and allow it to cool to room temperature. Weigh the dish and the sample after baking, accurate to 0.1mg, and determine the mass of the powder after baking.
(5) Expression of results
According to the formula (6-5) to calculate the mass loss during drying, expressed as a mass percentage,
Calculate the average of two valid determinations and report the results to an accuracy of 0.01% (m/n)
