Introduction
The chemical resistance of coatings is a key indicator for evaluating their resistance to solvents, detergents, or other chemicals in practical applications. The solvent resistance tester provides a reliable means to quantify this performance by simulating the synergistic effect of mechanical friction and chemical contact. Standardized operation is the basis for ensuring the accuracy and reproducibility of test results. This article will systematically explain the key operating points of this instrument in the evaluation of chemical resistance of coatings.
Instrument principle
The basic working principle of the solvent resistance wipe tester is to use a wipe tip impregnated with a specific chemical agent to wipe the coating surface in a reciprocating manner under a specified load. The resistance of the coating is evaluated by recording the number of wipes when it fails (e.g., exposed bottom, discoloration, loss of light, etc.), or evaluating the coating status after a fixed number of times. Its force F is usually provided by weight gravity, which can be expressed as: F = mg, where m is the weight mass and g is the acceleration of gravity.
Preparation before operation
Adequate preparation is the first step in a successful test. The following items need to be confirmed:
First, check the instrument status. Make sure the wiping arm moves smoothly, the counter is functioning properly, and the clamp is not loose. Second, prepare the sample. The specimen should be flat and clean, usually cut from the finished product or special test plate, and the size should meet the requirements of the fixture. It is recommended to condition the condition under standard temperature and humidity conditions for at least 24 hours before testing. Finally, prepare the chemical reagent and the wiping material. Select the solvents specified in the criteria (such as ethanol, acetone, ethyl acetate, etc.) and neutral cotton wool or specific fabrics according to the evaluation needs. Reagent purity, uniformity and consistency of the wipe material are critical.
Testing process essentials
Standardized testing processes minimize human error.
The first step is installation and fixing. The specimen is securely clamped on the test bench to ensure that the test area is flat and not suspended. The second step is to set the parameters. According to relevant standards or internal specifications, accurately set the load quality, wiping stroke, wiping speed (usually 30-60 round trips per minute), etc. The third step is to infiltrate and wipe the head. Wrap the wiping material around the wiping head and evenly saturate the specified volume of chemical reagents to avoid dripping. Step 4: Start the test. Place the wipe tip lightly on the surface of the specimen and start the instrument. During the wiping process, the wiping head should be kept perpendicular to the surface of the specimen and the contact should be stable. The fifth step is to observe and record. During testing or at specified intervals, pause and observe coating changes, accurately record the number of wipes at the time of specified failure, or describe the final condition.
Result evaluation and precautions
The evaluation of results needs to be objective and consistent. Common assessment methods include: the number of wipes recorded to the exposed bottom; or after fixing the number of wipes, evaluate the severity of the coating's gloss change, color change, blistering, softening, peeling and other phenomena according to the standard grade chart.
Special attention should be paid to the operation: a new wiping area should be used or the wiping material should be replaced for each test to avoid cross-contamination; The erosion rate of the same chemical reagent on different coatings is different, so it is recommended to set a reasonable observation frequency. The temperature and humidity of the laboratory environment may affect the volatilization rate of solvents, so it is recommended to do so in a controlled environment. To ensure the reliability of the results, it is recommended to test at least three parallel specimens under the same conditions.
Maintenance and calibration
Regular maintenance and calibration are key to ensuring long-term stable operation and data comparability. Reagent residues should be cleaned in time after daily use. It is recommended to regularly check or calibrate the operating speed of the instrument, the accuracy of the counter, and the nominal value of the applied load. Wear and tear on critical components should also be included in the regular inspection schedule.
Epilogue
Solvent resistance test is an effective method to evaluate the chemical resistance of coatings. Strictly follow the standard operation points, pay attention to detail control, and manage the whole process from sample preparation, parameter setting, process observation to equipment maintenance, so as to obtain scientific, accurate and repeatable test data, so as to provide a solid technical basis for the formula research and development, quality control and practical application of coatings.
References
1. Introduction and principle: refer to a number of domestic and foreign basic standards for coating performance testing on the purpose of chemical resistance testing.
2. Key points of pre-operation preparation and testing process: The core requirements of the general industrial coating testing standard for specimen handling, reagent selection and wiping procedures are integrated.
3. Result evaluation and precautions: The guidelines for evaluating common coating defects and the suggestions for error control in inter-laboratory comparison studies are summarized.
4. Maintenance and calibration: According to the general specification document for measuring instrument management and calibration.