(1 Scope
This standard specifies the method for measuring the mass (expressed as a percentage) of the spray powder actually deposited on the standard target tube by spraying powder on the target tube with a Spray Gun under standard conditions.
This method is generally applicable to powders that are constructed by corona charging or tribocharging.
This method can be used to compare the deposition efficiency of different powders from the same Spray Gun or different bite guns of the same powder.
This method should only be used for comparisons in the continuous evaluation of powders or Spray Guns, since environmental and equipment influences vary significantly over time and geographical location to a large extent.
The result depends on the following properties of the powder: a. chemical composition; b. density; c particle size distribution; d. particle-f shape; e fluidity of its mixture in the air; f. moisture.
The results also depend on the test conditions, which include: a. The spray shape produced by the Spray Gun; b. The air pressure of the Spray Gun; c The voltage of the Spray Gun; d.
(2) Definition
The ratio of the mass of the deposited powder to the mass of the ejected powder, expressed as a percentage.
(3) Principle
This method stipulates that under known atmospheric temperature and humidity conditions, the charged powder is sprayed at a known flow rate on one of the five identical steel pipes covered by the method, and the mass of the powder deposited on the middle steel pipe is measured. Calculate the plot ratio from this.
This operation is done in an air extraction chamber.
(4) Instrument
①Steel pipe device consists of 5 steel pipes with an inner diameter of 25mm and a length of 500mm. A hole is drilled at one end of each pipe so that the pipe can hang white. Each steel pipe shall be properly grounded.
②Clean aluminum foil, industrial grade.
③ Suspension device, so that 5 steel pipes can be hung side by side at equal distances, and the center distance between the pipes is 95~105mm.
④ Vacuum cleaning bag.
⑤The oven can melt the powder.
⑥Balance, accurate to 0.1g.
⑦Timer, accurate to 0.ls.
⑧ powder spraying system consisting of a suitable electrically charged Spray Gun or a tribocharged Spray Gun installed together with a suitable powder collection device in an air extraction chamber.
⑨The insulating barrier shall be used as a powder collection device, which shall be large enough to prevent the powder sprayed from the Spray Gun from being shot on the steel pipe before and after the test, and shall be flexible enough to be removed during the test.
(5) Sampling
According to the provisions of IS08130-9, take a representative sample of the tested product, and it is recommended to take 2kg of companion crystals.
(6) Operation steps
① Under the conditions of temperature 23°C-12°C and relative humidity 20%-70%, conduct parallel tests of duplicate samples.
Due to the large volume of air passing through the air extraction chamber during the test, it was not possible to control the temperature and humidity within accurate ranges. In this case, the range of temperature and humidity shall be indicated in the test report.
② Wrap the 5 steel pipes with group foil so that the top and bottom edges are folded into the pipes to ensure good electrical contact. Weigh the aluminum foil used on the intermediate pipe with a balance, accurate to 0.lg.
③The method of measuring the powder flow rate is to use the powder injection system to inject the powder into a pre-weighed vacuum cleaning bag. When the timer is used to control the injection, l can be 60s, and then weigh the cleaning bag with the powder, which is accurate. to 0.lg. Calculate the powder flow rate in g/min.
When using a corona charged Spray Gun, adjust the injection gate of the powder injection device so that the powder flow rate reaches 150g/min+7.5g/min.
When using seat rubbing charge Spray Gun, the air pressure of the gangway to 300kPa (=3bar), and according to (6)
③ Measure the flow velocity of the powder as described in the first paragraph.
④ Put the Sihang device equipped with 5 cutting tubes into the spray chamber.
⑤ Install and level the Spray Gun in the extraction room, so that the Spray Gun can aim at the center of the middle steel pipe, and the distance between the Spray Gun and the steel pipe should be such that the sprayed powder can cover about 60% of the length of the center steel pipe. Record this distance. Ensure that the air flow through the extraction chamber channel is between 0.4m/s and 1.0m/s, and the flow direction of the air flow is parallel to the injection direction.
If a narrow tapered lance is used, it will be difficult to cover 60% of the pipe length, so any differences should be noted in the test report.
⑥Put the insulation block between the Spray Gun and the steel pipe.
⑦Open the switch to make the powder flow out. If you use an electric frog charging Spray Gun, you should adjust the voltage so that the solid display Spray Gun voltage (with proper polarity) is 60kV ± 1kV.
⑧Remove the insulating cover, so that the powder can be stabilized without crossing. Bite and shoot on the steel pipe for 60s10.5s. At the last moment of this stage, immediately place the insulating cover F and the sub-amplifier between the Spray Gun and the sample board, and close Spray Gun.
⑨Carefully remove the middle steel pipe from the suspension device, knock off any powder, and bake it in an oven adjusted to a certain temperature. The adjusted temperature should make the powder coating melt within 5 to 10 minutes. .
Do not subject powder coatings to the curing process as this can cause loss of hands.
⑩ Take out the steel pipe with aluminum foil from the baking and let it cool down, remove the molybdenum foil from the pipe and weigh it to the nearest 0.1g.
(7) Expression of results
ρ f - powder flow velocity, g/min.
② If the difference between the two results is not greater than 5% of the lowest value, calculate and report the arithmetic mean. If the results differ by more than 5%, perform a third test and report the arithmetic mean of all three results.
If the possible difference between the third measurement result and the average value of the first two measurements is also greater than 5n, explain this situation in the test report and report each result.
Indicates the result to one decimal place.
(8) Precision
Experience has shown that powder flow velocity can be determined with an accuracy of ±3%.
The deposition rate obtained with the most charged and tribo-charged Spray Guns is ±5% with a measurable accuracy.
