Powder coating and coating performance testing methods.

1 In the container status
open the bag for visual inspection. Observe whether there is a foreign object present in the sample, whether the color is uniform loose powder. (1) Qualified: uniform color, no foreign objects, loose powdered

.step
: Take about 100g (accurate to 0.1g) of the sample, place the sample in a test sieve with a chassis of 125 m (120 mesh), cover the sieve cover, by hand beat the vibration test sieve, until there is no drop of powder on the white paper under the test sieve. Carefully open the lid and visually see if the sample passes through the test sieve. Note (1) knock time is generally 15min to 30min. (2) If the sample fails to pass the test sieve in its entirety, gently transfer the residual sample to the weighing paper with a brush, weighing to obtain the residual mass, calculate the content of the sieve residue, expressed as a mass fraction (%). Qualified: All passed.2 glue time
product standards are specified in GB/T 16995-1997 "thermoso-solid powder coating at a given temperature of the determination of the gel time." Glue time refers to the amount of time it takes for a certain volume of powder coating to melt into a non-deformable object under specified conditions.
determination principle: a certain volume of powder coating samples in the heating block at the pit heated to the specified temperature, the molten material can not be measured into a wire time. The main materials and instruments include: verifications: for verifying the temperature of the heating block, known melting points. D-camphor can be used if checked at 180 degrees C. Heating blocks, thermometers, timers, agitators, measuring spoons, scrapers.
: Test temperature (180±1) degrees C, unless otherwise specified. (1) The heating block heats up to the specified temperature and stabilizes at least 10min. (2) Take 0.25mL sample placed in a heating block pit, the sample all melted immediately after the start of the timer. (3) Stir the molten sample with a blender, when the sample thickens, every 2 to 3s pull high melt, about 10mm height, until the wire becomes brittle or broken, can no longer pull the time to stop the timer, record the time that is the gel time of the sample. (4) Use a scraper to remove the sample from the heating block pit. Try again.
results indicate that the melt cannot be wired for a certain volume (approximately 0.25mL) after the powder coating sample is heated to a specified temperature (180 degrees C) in the pit of the heating block, in seconds (s), and the result is accurate to 1s. Two parallel measurements. The difference between the two results does not exceed 5% of the smaller value, and the results are averaged. Otherwise, the difference between the third measurement result and the other two results does not exceed 5% of the smaller value, and the result is the average of the three measurements. If the difference between the third test result and the other two results exceeds 5% of the smaller value, the fourth measurement is performed and the results of the four measurements are reported.
: the temperature of the heating block during the test process should be stable (select a suitable heating device, the environment is not ventilated).3 Liquidity
product standards are specified in the ISO 8130-5:1992 "Powder Coatings Part 5: Determination of The Fluidity of Powder Air Mixtures".
determination principle: in the air without air flow conditions, the specified quality of powder coatings placed in containers, under standard atmospheric pressure and temperature conditions, with clean dry air flow, to determine the flow of the medium and fluidized powder height and the rate at which the fluidized powder passes through a specific hole. The fluidization factor φ and powder flow rate (flow factor)R.
equipment: testing fluid equipment, timers (accurate to 1s), balances (maximum weighing 500g, precision up to 0.1g), height measuring tools (ruler).
the main points of operation: (1) use a stopper to block the flow powder mouth, said to take (250±10) g sample placed in the container. (2) The air is imported and the flow rate is based on the optimal fluidization effect of the powder, usually (200±10) L/h. Pay attention to observe the air flow rate. (3) Stir the powder during the fluidization process, avoid the groove or bubbles, until the fluidized bed height is constant (several consecutive measurements of the fluidized bed height). (4) Record the powder fluidization height h1 (constant post-height), accurate to 2mm. Turn off the air flow, make the powder stationary, measure the powder height h0 after rest, accurate to 2mm. (5) At the same flow rate again fluidized powder, stirring to the fluidized bed height constant, unplugged, while timing, let the powder flow out into the cup, collect (30±1) s inside the outflow of powder, weighing, accurate to 0.1g.
the results indicate: (1) the fluidization factor is h1/h0, (2) the powder flow rate (flow factor) R is m, in grams (g). Two parallel measurements. The difference between the two results does not exceed 5% of the lower value, and the results are averaged. Otherwise, the difference between the third measurement result and the other two results does not exceed 5% of the lower value, and the result is the average of the three measurements. If the difference between the third test result and the other two results exceeds 5% of the lower value, the fourth measurement is performed and the four measurements are reported.
: (1) The flow rate should be adjusted to ensure the optimal fluidization effect of the powder. (2) The correction of the flow meter.4 coating appearance
visual observation model in scattered daylight, if the coating film is flat or has a slight orange peel, the color meets the customer's requirements or is tested with an instrument in the agreed. Within the chromic range, it can be rated as "the appearance of the coating film is normal". Note: It can also be observed under the standard light source D65 and, if required, compare or measure the chromatric difference with the reference board.5 hardness
product standards in accordance with ISO 15184:1998 "color paint and varnish pencil method to determine hardness" provisions, pencil for the Chinese brand 101 drawing pencil.
test principle: the use of a known hardness mark of the pencil scraping coating film, with the pencil hardness mark to indicate the hardness of the coating film.
equipment: pencil tip applied load of (750±10)g; pencil 9B to 9H (soft to hard); This standard uses carbon steel plate (thickness 0.45mm to 0.55mm).
Operating points: (1) Prepare the pencil: first cut the pencil off the wood rod part, so that the lead core is cylindrical exposed about 5mm to 6mm, and then make the lead core vertical on the sandpaper to draw a circle grinding, until the lead tip grinds into a flat, sharp edge. (2) Test: fixed sample, pencil into the instrument and fixed, keep the instrument level, pencil tip on the surface of the paint film, immediately 0.5 to 1mm/s speed to push the instrument at least 7mm.
results indicate that the hardness of the pencil (scratch, scratch, or plastic deformation) of the coating is represented by the hardness of the pencil without scratching the coating by 3mm or more. Plastic deformation: permanent indentation of the surface of the lacquer film, no cohesion damage. Cohesive damage: scratching or scratching. This standard is expressed as a bruise result. Two parallel measurements, the results should be consistent.
: (1) when cutting pencils, the cut lead core should be cylindrical, without any damage, and exposed 5mm to 6mm long. (2) Each stroke, should be re-flattened with the prescribed water sandpaper at the end of the pencil core. (3) Scratches at least 7mm length, the results of the determination of the starting 3mm damage is not counted (did not make the coating appear 3mm and above scratches).6 Adhesion
product standards in accordance with GB/T 9286-1998 "color paint and varnish paint film scratch test" provisions.
test principle: according to the model substrate and paint film thickness selection of different spacing of the lacquer film grid shape cutting, so that it just penetrates to the substrate, according to the paint film from the substrate on the rowing area of the area to assess the number of grades, divided into 0 to 5 levels, 0 levels of the best, 5 of the worst. In this way, the performance of the paint film from the substrate is evaluated.
materials and instruments: single-knife (for any substrate), multi-knife (blade spacing of 1mm, 2mm, not suitable for paint film thickness greater than 120 m or hard coating or coating applied to soft substrate), transparent pressure-sensitive adhesive tape (25mm wide, bonding force 10± 1N/25mm or agreed), can use 3M tape 610 type or improved 600P type
operating points: (1) according to the substrate and paint film thickness to choose different cutting edge spacing tools; Cutters with blade spacing: (1) 0 to 60 m, hard substrate, spacing 1mm; (2) 0 to 60 m, soft substrate, spacing 2mm; (3) 61 to 120 m, hard or soft substrate, spacing 2mm; (4) 121 to 250 m, hard or soft substrate, pitch 3mm; (5) The substrate in this standard is a steel plate with a thickness of 0.45mm to 0.55mm, and a coating thickness of 60 to 80 m. Select a blade spacing of 2mm.
test: a model can be cut in three sets, the edge distance between each group should be greater than 5mm, and the edge of the model should be greater than 5mm. When cutting, the knife is perpendicular to the surface of the model, applying force evenly and cutting at a constant speed. All cuts should be cut through to the substrate, with 6 cuts in each direction.
results determine: (1) for soft substrate: cut, with a soft brush along the mesh graphics each diagonal gently swept back several times, and then swept forward a few times, to observe the paint film shedding phenomenon. (2) For hard substrates: (the substrate in this standard is steel plate): cut, with a soft brush along the mesh graphics each verse gently swept back a few times, and then swept forward a few times. Apply adhesive tape to the model of the hard substrate, remove the front section of the adhesive tape, then cut off the adhesive tape about 75mm long, flatten its center point above the mesh, and make full contact with the paint film. The adhesive tape length is at least 20mm longer than the mesh. Inside the adhesive tape 5min, hold the end of the tape suspended and tear it away at an angle as close as possible to 60 degrees (0.5 to 1.0)s. Observe the phenomenon of paint film shedding.
results show that: according to the standard division of 0 to 5 levels of the provisions of the paint film area shedding situation. The results were reported with consistent results from three sets of cuts.
: (1) Select the tool correctly and check that the blade is sharp. (2) The paste and peeling angle and time of the adhesive tape shall be stipulated according to the standard.7 impact
standards in accordance with GB/T 1732-1993 "paint film impact resistance measurement" provisions. The sample coating film is placed flat on the impacter's spade for impact test when punching, and the sample coating film is placed flat on the impacter's spade for impact testing when the reverse punch is flat on the impactor's spade.
test principle: a certain quality hammer dropped on the paint film test plate, so that the paint film with elongation deformation without causing damage to the maximum height of the paint film impact resistance, usually in centimeters (cm).
materials and equipment: (1) lacquer film impactor: QCJ type. The instrument hammer mass (1000±1)g; the depth at which the punch enters the groove is (2±0.1) mm; and the slider scale (50±0.1) cm, with a score of 1 cm. (2) Makou iron plate: size 50×120×0.3mm. (3) Thin steel plate: size 65×150× (0.45 to 0.55) mm (for putty film determination). (4) The substrate of this standard is a steel plate with a thickness of 0.45 to 0.55 mm, and a film thickness of 60 to 80 m.
operating points: the paint model flat on the lower part of the instrument iron drill, paint film face up or down, the hammer to the desired height, and then make the hammer freely drop impact sample, with a four-fold magnifying glass to observe the impact of the paint film cracks, wrinkles and peeling and other phenomena. Three impact tests were conducted on the same board. The results show that the impact resistance of the paint film is expressed at the maximum height that does not cause damage to the paint film.
: (1) when measuring, the model must be close to the surface of the iron drill, so as not to impact the sample beat and affect the test results. (2) The impact site of the model should be greater than 15mm from the edge, and the edge distance between the impact points should be greater than 15mm. (3) The surface of the impactor steel ball must be smooth, if there is rust, wear and tear phenomenon must be replaced.
results of the test factors: (1) the effect of temperature, humidity: after the preparation of the model and testing environment should be at constant temperature and humidity conditions, i.e. temperature (23±2) degrees C, relative humidity (50±5 percent). In general, high temperature and humidity will cause the paint film to soften, the impact-resistant results are high, and the opposite result is low. This standard requires the model to be baked and placed for a 24h test under constant temperature and humidity. (2) Impact depth: The impact depth of the impacter should be in the (2±0.1) mm range. If the depth of impact is too deep, the impact result will be low, on the other side, high. (3) The influence of substrate: different plates, such as makou iron plate and thin steel plate by the same surface treatment and paint film preparation, paint film impact-resistant results are often different. In general, the test results of the iron plate of the horse mouth are lower than that of the thin steel plate. The model substrate is required in this standard to be a steel plate. (4) The influence of the thickness of the paint film: the thickness of the paint film should be within the specified range when preparing the model. In general, the paint film is thick, which will make the impact result low and high. In this standard, the model film thickness is required at (60 to 80) sm. 8 bending test
the GB/T 6742 "color paint and varnish bending test (cylindrical shaft)" as stipulated in the product standard.
test principle: the paint film together with the substrate force deformation, check its rupture elongation, which also includes the interface between the coating film and the substrate.
equipment: (1) Type I tester: suitable for test plates with thicknesses not greater than 0.3mm, shaft rod diameters are 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 25mm and 32mm respectively. Type II tester (same as the GB/T 6742-1986 instrument) ;(2) Type II: suitable for test plates with thicknesses not greater than 1.0mm. The diameters of the shafts are 2mm, 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm, 20mm, 25mm and 32mm respectively. (3) Substrate: steel plate, horse mouth iron plate, soft aluminum plate, can use plastic substrate. In this standard, the bending test substrate is a horse-port iron plate with a thickness (0.2 to 0.3) mm.
test plate thickness should not be greater than 0.3mm for type I tester, and for type II tester, test plate thickness should not be greater than 1.0mm. If plastic plates are used, they can be up to 4.0mm thick.
operating points: (1) use I in the determination step of the specified single diameter shaft.