Why does the porosity of each batch in the production of composite membranes vary greatly?

In the production of composite membranes, the porosity or other indicators of each batch often vary greatly. The reason for this should be a more complicated problem, because the situations that occur are different according to the various composite processes. Here are some common problems in some common processes in the production process. The following points can be analyzed to find out the reasons for the differences in porosity of some batches based on the actual situation of the process used:

1. Differences in raw materials from different batches. The composition and properties of the raw materials used in the manufacturing process of composite membranes may vary. Even slight changes in the quality or properties of raw materials (such as polymer matrix or additives, melt-blown cloth, non-woven fabric, etc.) will affect the final porosity of the membrane. The impact of the upper and lower deviations in the normal range and the differences in the measurement methods will also cause differences. However, most of the changes in raw materials are initially within the qualified range but cause large deviations during use. This may be caused by differences in suppliers, batches or storage conditions.

2. The different mixing and dispersion process methods of composite components also play a vital role in membrane formation. In the manufacture of composite membranes, there will be a mixture of different materials, such as polymer matrix and filler particles or fibers. If the mixing process is uneven or inconsistent, of course, the uniformity mentioned here is also relative, it may lead to uneven distribution of components, resulting in changes in the porosity of different parts of the membrane.

3. The influence of manufacturing process parameter deviation. In actual production, the control process of the same finished product (including temperature, pressure and curing time) will affect the porosity of the composite membrane, because slight changes in these parameters will affect the polymerization or cross-linking reaction, resulting in differences in the formation of membrane structure, such as higher temperature or longer curing time, which may lead to higher porosity, while lower temperature or shorter curing time may lead to lower porosity.

4. The thickness of the material used and the interaction between the substrate. The presence of the substrate or support layer in the composite membrane will also affect the porosity. The interaction between the polymer matrix and the substrate and the thickness of the membrane will affect the formation and distribution of pores. Under external conditions, changes in the properties of the substrate (such as surface roughness or adhesion) will also affect the final porosity.

5. The impact of quality control and process changes in membrane production. Quality control measures are usually taken during the manufacturing process to ensure the consistency of product performance. However, even with a quality control protocol, there may be slight process changes between batches. Slight deviations in process parameters, equipment calibration, or operator techniques in the process may lead to changes in the final porosity.

6. As we said before, the specific reason for the large batch differences in composite membrane porosity may depend on the manufacturing method used for the composite membrane. Different processes and different technologies, such as phase inversion, electrospinning, or layer-by-layer deposition, have their own unique factors that affect the porosity differences between batches. Of course, this article should discuss the impact of porosity differences in different batches under the same process.

In short, the raw materials and processes of this type of composite membrane determine that it is impossible to have a precisely controllable porosity. In order to reduce the excessive porosity variation, it is possible to combine the characteristics of each process, comprehensively establish some material deviation ranges and process control conditions, and eliminate the factors affecting the porosity variation to the maximum extent by implementing process optimization and strictly controlling quality.