The testing methods for insulated boards using impregnating varnish are strictly conducted in accordance with the national standards规定的 test methods, as detailed below.
GB/T 1981.2—2009 "Paint for electrical insulation — Part 2: Test methods" for epoxy board manufacturers
GB/T 15022.2—2007 "Resin-Based Active Composite for Electrical Insulation - Part 2: Test Methods"
GB/T 1408.1-2006 "Test Methods for Electrical Strength of Insulating Materials — Part 1: Tests under Power Frequency"
GB/T 1410—2006 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials"
JB/T 1544—1999 "Method for Rapid Thermal Aging Test of Electrical Insulating Varnishes and Varnished Cambrics — Thermal Point Slope Method"
GB/T 27749-2011 "Test Code for Thermal Resistance of Insulating Paints - Electric Strength Method"
Appearance. Test tube method: Pour the paint into a clean, colorless, transparent glass tube with a diameter of 15mm, and let it stand at (23±2)℃ until the bubbles disappear. Then, observe the color of the paint under daylight diffused light to determine if it is transparent, and check for any mechanical impurities and non-soluble particles.
② Viscosity. The viscosity was measured using a rotational viscometer at (23±1)℃ in accordance with ISO 2555:1989. Two measurements were taken and the average viscosity was reported.
③ Solid Volatile Content. Add 10g of paint sample to a specimen with a base area of 45mm×45mm and a thickness of approximately 0.2mm, and place it horizontally in an oven for baking. The baking temperature and time are the same as the paint cake preparation, and the average value is obtained by three measurements. Additionally, add 2g of the sample to an aluminum foil with a base area of φ75mm and a thickness of approximately 0.2mm, place it horizontally in the oven for baking, and the baking temperature and time are the same as the paint cake preparation. The average value is obtained by three measurements.
④ Gel Setting Time. Conduct two measurements and report the average gel time using a gel time tester, in compliance with GB/T 15022.2—2007.
⑤ Thick Coating Curing Capability. Using a 45mm x 45mm aluminum dish, clean with xylene and anhydrous ethanol. Calculate the amount of paint required for a 4mm thickness of the sample based on the volatile content during curing. Add the sample to the aluminum dish, place it horizontally in an oven for curing, with the baking temperature and time matching the paint cake production. Test two samples.
Density. Determined using a hydrometer in accordance with the methods specified in ISO 2811, with two measurements reported to provide the average density. Epoxy Board Manufacturer
Storage stability: Take approximately 150g of paint sample and weigh it in a 250mL sealed container to an accuracy of 0.5g; place the container in an oven at (60±2)℃ for 96 hours, then remove it from the oven and cool it to 23℃ before re-weighing. The weight should remain unchanged, within an allowable 0.5g weighing error, and viscosity should be measured.
The reaction between lacquer and copper. A bundle of 36 copper wires, each with a diameter of 0.5mm and a length of 120mm, was wrapped with cotton cloth at three points to form a bundle. The bundle was cooled to room temperature in an oven at 105°C, soaked in the test lacquer for 10 minutes, then dripped lacquer for 5 minutes before drying according to the product standard or supplier's specifications. After cooling, the bundle was re-soaked in lacquer and the aforementioned operation was repeated. After cooling, the cotton cloth was removed, the copper wires were inspected, and the color changes were recorded.
⑨ Adhesive Strength. Spiral coil method: The φ1mm aluminum wire is wound around a φ6.3mm mandrel, with a tensile force of 10N applied to the wire, with no gap between adjacent turns. The spiral section is 75mm long, bent into a ring at both ends. The coil is cleaned in a toluene-ethanol mixture, followed by 1-2 rinses in acetone, then dried. It is vertically immersed in insulating varnish for 5 minutes, withdrawn at a speed of 10cm/min, and allowed to drip dry vertically for 30 minutes before being flipped 180° to repeat the immersion and curing process.
On the tensile testing machine bracket, the fulcrum distance is 44mm, the upper pressure head is aligned with the center of the specimen, bending force is applied to the specimen at a speed of 50mm/min, and the force at the moment of specimen cracking is recorded. The test is conducted at (23±2)℃ with a preheating period of not less than 5 minutes at high temperature, using the middle value of 5 specimens as the result.
Flexural Strength. Insulating varnish is injected into a cylindrical mold that has been de-molded, with a length of 90mm and an inner diameter of (8±0.1)mm as provided by the epoxy board manufacturer. The mold is then baked and cured at a specific temperature and time, followed by de-molding, pressing, and cooling. The cross-sectional diameter D of each sample is measured with an accuracy of ≤0.02mm, and then tested. The pressure head radius r1 is (5±0.1)mm, the fulcrum radius r2 is (2±0.2)mm, with a fulcrum spacing of 60mm and a displacement rate of 5mm/min. Place the sample on the testing equipment, adjust the stop recording instrument, and apply continuous pressure for the bending test until the sample breaks. Record the load at the moment of breakage. If the break occurs outside the central 1/3 segment of the test bar, the test results are invalid.