Technical cleanliness analysis - How to choose the filter membrane

The purpose of automotive cleanliness analysis is to reduce the damage caused by particle wear and improve the service life and reliability of the product. Cleanliness detection methods include weighing method and microscopic particle size counting method. Among these two detection methods, the selection of detection filter membrane is particularly critical. At present, there are many materials for cleanliness detection filter membranes, such as mixed cellulose lipid membrane (MCE membrane), nylon membrane (N66 membrane), polytetrafluoroethylene membrane (PTFE membrane) and nylon grid membrane. So, what factors should we consider when choosing a filter membrane for cleanliness testing?

1. First of all, chemical compatibility with commonly used cleaning agents should be considered.

2. Whether there will be curling phenomenon in the drying process after the filter membrane is filtered. This phenomenon is related to the shrinkage rate of the membrane material and the membrane making process.

3. The membrane is easy to maintain a constant weight, and the weight difference between before and after filtration (according to the standard process to filter the clean cleaning solution that has been filtered by 0.45um) is less than 0.5mg.

4. In the case of excessive oil contamination of parts, it is not suitable to choose mixed cellulose lipid film.

5. The grid film may reflect light in the microparticle counting method. It is recommended to choose a cleanliness meter with a filter, in order to avoid misjudgment of the grid reflection as metal particles and reduce the qualified rate of the sample.