A method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish

Abstract

The present invention discloses a method for rapidly testing the moisture absorption and caking properties of polyamide-imide insulating varnish, comprising the following steps: S1: preparing a testing liquid; the testing liquid comprises water and a testing agent, wherein the testing agent is one or more solvents in the polyamide-imide insulating varnish; S2: adding the testing liquid dropwise to the polyamide-imide insulating varnish under stirring conditions, wherein when the testing liquid is added dropwise to the polyamide-imide insulating varnish, the insulating varnish resin precipitates, and stirring is performed to redissolve the insulating varnish resin; S3: repeating step S2 until the insulating varnish resin precipitates and cannot be dissolved under stirring after the testing liquid is added dropwise; S4: calculating the volume ratio of water in the added testing liquid to the solvent in the polyamide-imide insulating varnish to determine the moisture absorption and caking properties of the polyamide-imide insulating varnish. By adding a fixed amount of water-containing testing liquid, the present invention replaces the slow moisture absorption process in the natural environment, significantly shortening the testing cycle.

Description

Technical Field

[0001] The invention relates to the field of polyamide-imide insulating varnish performance testing, in particular to a method for quickly detecting the moisture absorption and agglomeration performance of polyamide-imide insulating varnish. Background Art

[0002] Polyamide-imide insulating varnish is a wire enamel with excellent overall performance and is a heat-resistant wire insulation material with a grade of up to 220. Its main raw materials are aromatic anhydrides, aromatic diamines, or diisocyanates; its solvents are N-methylpyrrolidone (NMP), dimethylacetamide (DMac), and dimethylformamide (DMF); and its diluents are xylene and trimethylbenzene.

[0003] While polyamide-imide varnish offers excellent overall performance, it does have drawbacks. For example, its shelf life is only one year, and for self-lubricating polyamide-imide, only 0.5 years. This is primarily due to the fact that the solvent components (NMP, DMAC, and DMF) in the insulating varnish are highly hygroscopic, causing caking and precipitation after absorbing a certain amount of moisture. This caking during use requires replacing the insulating varnish and cleaning the paint box and pipelines, significantly impacting the normal operation of downstream enameled wire factories, compromising both quality and production.

[0004] The current common testing method involves taking a certain weight of paint sample and placing it in a fume hood, simulating the temperature and humidity of a workshop environment. The method then observes the time it takes for the insulating paint to absorb moisture and form lumps, thereby inferring the stable lifespan of the coating line. This method is time-sensitive, typically requiring one to three days to fully reflect the differences in moisture absorption and lumps in polyamide-imide insulating paint. Summary of the Invention

[0005] The present invention aims to address, at least to some extent, one of the problems in the related art. To this end, the present invention provides a method for rapidly detecting the moisture absorption and agglomeration properties of polyamide-imide insulating varnishes. By adding a quantitative aqueous testing solution, the method replaces the slow moisture absorption process in the natural environment, significantly shortening the testing cycle.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solution: a method for rapidly detecting the moisture absorption and agglomeration properties of polyamide-imide insulating varnish, comprising the following steps:

[0007] S1: preparing a detection liquid; the detection liquid includes water and a detection agent, and the detection agent is one or more solvents in the polyamide-imide insulating varnish;

[0008] S2: Add the test liquid dropwise to the polyamide-imide insulating varnish under stirring conditions. When the test liquid contacts the polyamide-imide insulating varnish, the insulating varnish resin precipitates. The insulating varnish resin is then redissolved by stirring.

[0009] S3: Repeat step S2 until the insulating paint resin precipitates and cannot be dissolved under stirring after the test liquid is added, and then stop adding the test liquid;

[0010] S4: Calculate the volume ratio of water in the added test solution to the solvent in the polyamide-imide insulating varnish to determine the moisture absorption and agglomeration properties of the polyamide-imide insulating varnish.

[0011] Furthermore, the polyamide-imide insulating varnish includes a solvent and an insulating varnish resin, wherein the solvent includes one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone, and the insulating varnish resin is dissolved in the solvent.

[0012] Furthermore, the solid content of the insulating varnish resin in the polyamide-imide insulating varnish is 25%-35%.

[0013] Furthermore, the detection agent is one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone.

[0014] Furthermore, the detection agent is N-methylpyrrolidone.

[0015] Furthermore, the volume ratio of N-methylpyrrolidone to water in the detection solution is between 1:3 and 1:5.

[0016] Furthermore, in steps S2 and S3, magnetic stirring is used when the detection liquid is added dropwise.

[0017] Furthermore, in steps S2 and S3, when the detection liquid is added dropwise, the polyamide-imide insulating varnish is heated to maintain the temperature at 40-60°C.

[0018] Furthermore, when the detection liquid is added drop by drop in steps S2 and S3, the polyamide-imide insulating varnish is in a sealed container, and the sealed container is provided with a dropping port.

[0019] The above-mentioned technical solution provided by the embodiment of the present application has the following advantages over the prior art: the polyamide-imide insulating varnish in the present application contains a solvent and an insulating varnish resin, and the insulating varnish resin is dissolved in the solvent and appears clear and transparent as a whole; the detection liquid contains water and a detection agent, and the detection agent is one or more solvents in the polyamide-imide insulating varnish. When the detection liquid contacts the polyamide-imide insulating varnish, the water in the detection liquid affects the solubility of the solvent, causing the insulating varnish to precipitate and agglomerate. If the water content is small, the water can be dispersed by stirring, so that the agglomerated insulating varnish resin is redissolved. If the added water exceeds the allowable value, the precipitated agglomerated insulating varnish resin cannot be dissolved again. At this time, the water absorption capacity of the polyamide-imide insulating varnish reaches the maximum value. The water absorption capacity can reflect the moisture absorption and agglomeration performance of the polyamide-imide insulating varnish; in addition to water, the detection liquid of the present application also includes a detection agent. The detection agent is of the same type as the solvent in the polyamide-imide insulating varnish, so that the effect of the detection liquid on the solvent in the polyamide-imide insulating varnish is relatively mild, making the precipitated insulating varnish resin easy to dissolve under stirring conditions. The present application abandons the existing method of observing moisture absorption and agglomeration performance under natural conditions, and replaces the slow moisture absorption process in the natural environment by adding a quantitative water-containing detection liquid, thereby greatly shortening the detection cycle. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described in detail with reference to the examples. The following examples are used to illustrate the present invention, but are not used to limit the scope of the present invention. Without departing from the spirit and essence of the present invention, modifications or replacements made to the methods, steps or conditions of the present invention are within the scope of protection of the present invention. Unless otherwise specified, the experimental materials, reagents, instruments, etc. used in the examples of this invention are all commercially available; unless otherwise specified, all technical means in the examples of the present invention are conventional means well known to those skilled in the art.

[0021] The present application provides a method for rapidly detecting the moisture absorption and agglomeration properties of polyamide-imide insulating varnish, comprising the following steps:

[0022] S1: Prepare a testing solution; the testing solution includes water and a testing agent, and the testing agent is one or more solvents in the polyamide-imide insulating varnish;

[0023] S2: Add the test liquid dropwise to the polyamide-imide insulating varnish under stirring conditions. When the test liquid contacts the polyamide-imide insulating varnish, the insulating varnish resin precipitates. The insulating varnish resin is then redissolved by stirring.

[0024] S3: Repeat step S2 until the insulating paint resin precipitates and cannot be dissolved under stirring after the test liquid is added, and then stop adding the test liquid;

[0025] S4: Calculate the volume ratio of water in the added test solution to the solvent in the polyamide-imide insulating varnish to determine the moisture absorption and agglomeration properties of the polyamide-imide insulating varnish.

[0026] In the present application, the polyamide-imide insulating varnish contains a solvent and an insulating varnish resin, and the insulating varnish resin is dissolved in the solvent and appears clear and transparent as a whole; the detection liquid contains water and a detection agent, and the detection agent is one or more solvents in the polyamide-imide insulating varnish. When the detection liquid contacts the polyamide-imide insulating varnish, the water in the detection liquid affects the solubility of the solvent, causing the insulating varnish to precipitate and agglomerate. If the water content is small, the water can be dispersed by stirring, so that the agglomerated insulating varnish resin is redissolved. If the added water exceeds the allowable value, the precipitated agglomerated insulating varnish resin cannot be dissolved again. At this time, the water absorption capacity of the polyamide-imide insulating varnish reaches the maximum value, and the water absorption capacity can reflect the moisture absorption and agglomeration performance of the polyamide-imide insulating varnish; in addition to water, the detection liquid of the present application also includes a detection agent. The detection agent is of the same type as the solvent in the polyamide-imide insulating varnish, so that the effect of the detection liquid on the solvent in the polyamide-imide insulating varnish is relatively mild, so that the precipitated insulating varnish resin is easy to dissolve under stirring conditions. The present application abandons the existing method of observing moisture absorption and agglomeration performance under natural conditions, and replaces the slow moisture absorption process in the natural environment by adding a quantitative water-containing detection liquid, thereby greatly shortening the detection cycle.

[0027] Example 1

[0028] A method for rapidly detecting the moisture absorption and agglomeration performance of polyamide-imide insulating varnish comprises the following steps:

[0029] S1: Prepare a detection liquid; the detection liquid includes water and a detection agent, and the detection agent is one or more solvents in the polyamide-imide insulating varnish.

[0030] Specifically, the polyamide-imide insulating varnish includes a solvent and an insulating varnish resin, wherein the solvent includes one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone, and the insulating varnish resin is dissolved in the solvent.

[0031] Specifically, the solid content of the insulating varnish resin in the polyamide-imide insulating varnish is 25%-35%.

[0032] Specifically, the detection agent is one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone. Since dimethylacetamide and dimethylformamide are easily volatile, N-methylpyrrolidone is preferably used as the detection agent.

[0033] The volume ratio of N-methylpyrrolidone to water in the detection solution is between 1:3 and 1:5.

[0034] S2: Add the test liquid dropwise to the polyamide-imide insulating varnish under stirring conditions. When the test liquid contacts the polyamide-imide insulating varnish, the water in the test liquid will affect the solubility of the solvent, causing the insulating varnish to precipitate and agglomerate. If there is less water, the water can be dispersed by stirring, so that the agglomerated insulating varnish resin can be redissolved.

[0035] The polyamide-imide insulating varnish is heated to maintain a temperature of 40-60° C. Excessively high heating temperatures will cause the solvent in the insulating varnish to evaporate more quickly. The temperature range set in this application refers to the temperature at which the polyamide-imide insulating varnish is actually used.

[0036] In this application, the polyamide-imide insulating varnish is placed in a sealed container with a dripping port. The relatively sealed environment can reduce the volatilization of the solvent in the polyamide-imide insulating varnish and ensure that the polyamide-imide insulating varnish does not absorb moisture in the environment as much as possible, which may cause errors in the test results.

[0037] The present application can use magnetic stirring to redissolve the precipitated insulating paint; specifically, a magnet can be placed in a sealed container, and a magnetic stirring device can be placed under the sealed container to achieve magnetic stirring.

[0038] S3: Repeat step S2 until, after adding the test liquid, the insulating varnish resin precipitates and becomes insoluble under stirring. Stop adding the test liquid. At this point, the polyamide-imide insulating varnish is no longer transparent and clear, but becomes turbid, indicating that the insulating varnish resin has precipitated. When the insulating varnish resin fails to dissolve, it indicates that the amount of water added has caused the solubility parameter of the entire solvent to exceed the allowable value, making the agglomerated portions insoluble by stirring. This also indicates that the solvent in the polyamide-imide insulating varnish has reached its maximum water absorption capacity; further water absorption will only cause the polyamide-imide insulating varnish to clump and become unusable.

[0039] S4: Calculate the volume ratio of water in the added test solution to the solvent in the polyamide-imide insulating varnish to determine the moisture absorption and agglomeration properties of the polyamide-imide insulating varnish.

[0040] The volume ratio in this step refers to the ratio of the volume of the added test liquid to the volume of the solvent in the polyamide-imide insulating varnish. For polyamide-imide insulating varnishes with the same formula, a larger volume ratio indicates that the polyamide-imide insulating varnish will only clump after absorbing more water; a smaller volume ratio indicates that the polyamide-imide insulating varnish will clump after absorbing less water. The prior art requires that the polyamide-imide insulating varnish be placed in a natural environment and absorb an equal amount of water before observing caking. In other words, the prior art measures the moisture absorption and caking properties of the polyamide-imide insulating varnish by the number of days it is placed in a natural environment. However, the present application uses a test liquid for direct testing, allowing the moisture absorption and caking properties of the polyamide-imide insulating varnish to be determined in a very short time.

[0041] Experimental example

[0042] Three samples of polyamide-imide insulating varnish were taken, which were respectively recorded as PA1 sample 1, PA1 sample 2 and PA1 sample 3. The moisture absorption and agglomeration performance of PA1 sample 1, PA1 sample 2 and PA1 sample 3 were tested respectively using the following method.

[0043] Specific detection methods include:

[0044] S1: Prepare 10 ml of detection solution by mixing N-methylpyrrolidone and water in a volume ratio of 1:5.

[0045] S2: Place 50ml of PA1 sample 1 into a 150ml stoppered Erlenmeyer flask. Place two magnetic beads inside the flask. Place the flask on a stirring and heating platform, set the heating temperature to 50°C, and start stirring. The polyamide-imide insulating varnish will become transparent and clear. After heating for five minutes, unstopper the flask and begin adding the test solution dropwise via a burette. When the test solution contacts the polyamide-imide insulating varnish, the insulating varnish resin precipitates. Stirring redissolves the insulating varnish resin, returning the polyamide-imide insulating varnish to its clear state.

[0046] S3: Repeat step S2 until the insulating varnish resin precipitates out after adding the test liquid and cannot be dissolved under stirring. At this point, the polyamide-imide insulating varnish is no longer transparent and clear, but becomes turbid, indicating that the insulating varnish resin has precipitated out.

[0047] S4: Calculate the volume ratio of water in the added test solution to the solvent in the polyamide-imide insulating varnish to be 14.4%. The above method takes about 30 minutes.

[0048] The above method was used to perform detection and calculation on PA1 sample 2, and it was calculated that the volume ratio of water in the added detection liquid to the solvent in the polyamide-imide insulating varnish was 6.3%.

[0049] The above method was used to perform detection and calculation on PA1 sample 3, and it was calculated that the volume ratio of water in the added detection liquid to the solvent in the polyamide-imide insulating varnish was 13.1%.

[0050] Comparative Example

[0051] Three samples of polyamide-imide insulating varnish were taken, which were respectively recorded as PA1 sample 1, PA1 sample 2 and PA1 sample 3. The moisture absorption and agglomeration performance of PA1 sample 1, PA1 sample 2 and PA1 sample 3 were tested respectively using the following method.

[0052] Specific detection methods include:

[0053] 50 ml of PA1 sample 1 was placed in a 150 ml open bottle, which was placed in a fume hood at 50° C. It was observed that the PA1 sample 1 was completely agglomerated after 6 days.

[0054] 50 ml of PA1 sample 2 was placed in a 150 ml open bottle, which was placed in a fume hood at 50° C. It was observed that the PA1 sample 1 was completely agglomerated after 2 days.

[0055] 50 ml of PA1 sample 3 was placed in a 150 ml open bottle, which was placed in a fume hood at 50° C. It was observed that the PA1 sample 1 was completely agglomerated after 6 days.

[0056] Comparison of the experimental examples and comparative examples shows that the present method detects caking in PA1 sample 1 after absorbing 14.4% water, PA1 sample 2 after absorbing 6.3% water, and PA1 sample 3 after absorbing 13.1% water within 30 minutes, while the comparative example requires six days to detect caking in PA1 samples 1, 2, and 3. Furthermore, the water absorption ratios in the experimental examples correspond to the caking times in the comparative examples. A higher water absorption ratio indicates that the sample absorbs more water before caking, reflecting its resistance to moisture absorption and caking. A lower water absorption ratio indicates that the sample absorbs less water before caking, reflecting its resistance to moisture absorption and caking.

[0057] It is understandable that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, all of which fall within the scope of protection of the present invention. Therefore, all equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of coverage of the claims of the present invention.

Claims

1. A method for rapidly detecting the moisture absorption and agglomeration properties of polyamide-imide insulating varnish, characterized in that: The steps include: S1: preparing a detection liquid; the detection liquid includes water and a detection agent, and the detection agent is one or more solvents in the polyamide-imide insulating varnish; S2: Add the test liquid dropwise to the polyamide-imide insulating varnish under stirring conditions. When the test liquid contacts the polyamide-imide insulating varnish, the insulating varnish resin precipitates. The insulating varnish resin is then redissolved by stirring. S3: Repeat step S2 until the insulating paint resin precipitates and cannot be dissolved under stirring after the test liquid is added, and then stop adding the test liquid; S4: Calculate the volume ratio of water in the added test solution to the solvent in the polyamide-imide insulating varnish to determine the moisture absorption and agglomeration properties of the polyamide-imide insulating varnish.

2. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 1, characterized in that: The polyamide-imide insulating varnish comprises a solvent and an insulating varnish resin, wherein the solvent comprises one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone, and the insulating varnish resin is dissolved in the solvent.

3. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 2, characterized in that: The solid content of the insulating varnish resin in the polyamide-imide insulating varnish is 25%-35%.

4. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 2, characterized in that: The detection agent is one or more of dimethylacetamide, dimethylformamide, and N-methylpyrrolidone.

5. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 2, characterized in that: The detection agent is N-methylpyrrolidone.

6. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 5, characterized in that: The volume ratio of N-methylpyrrolidone to water in the detection solution is between 1:3 and 1:

5.

7. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 1, characterized in that: In steps S2 and S3, magnetic stirring is used when the detection liquid is added dropwise.

8. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 1, characterized in that: In steps S2 and S3, while the detection liquid is added dropwise, the polyamide-imide insulating varnish is heated to maintain a temperature of 40-60°C.

9. The method for rapidly detecting moisture absorption and agglomeration properties of polyamide-imide insulating varnish according to claim 1, characterized in that: When the detection liquid is added drop by drop in steps S2 and S3, the polyamide-imide insulating varnish is in a sealed container, and the sealed container is provided with a dropping port.