Chemical compatibility of filter materials refers to the stability and tolerance of the filter when exposed to specific chemicals. When selecting suitable filter materials for application, it is of primary importance to understand their chemical compatibility with the process fluids they are in contact with, because incompatible chemicals may cause damage, dissolution or performance degradation of the filter membrane, thus affecting the filtration effect and filtrate quality.
Filter materials are generally divided into two types according to their interception capacity: absolute-rating filter membrane and deepth filter material. The pores of the absolute-rating filter membrane are smaller than the solid particles, and the particles or microorganisms of the corresponding particle size are completely retained; the pores of the deep filter material are not necessarily smaller than the solid particles, and it uses the tortuous channels in the filter layer to intercept the particles. Table 1 and Table 2 are the chemical compatibility tables of absolute-rating filter membrane and deepth filter material respectively.
Nylon | PES | MCE | PTFE | PVDF | |
Alcohols | R | R | NR | R | R |
Alkali | R | R | NR | R | LR |
ketone | LR | NR | NR | R | LR |
Oils | R | R | \ | R | R |
Aromatics | LR | NR | NR | R | LR |
Halocarbons | LR | NR | NR | R | LR |
Ethylene glycol | R | LR | NR | R | R |
Ethers | LR | R | NR | R | R |
acid | NR | R | LR | R | R |
Esters | LR | R | LR | R | R |
R：Resistance LR：Limited resistance NR：No resistance
Table 1 Chemical compatibility of absolute filtration membranes
PP | ACF | GF | PBT | Ti | Stainless steel (mesh/sintered felt/powder sintered) | |
Alcohols | R | R | R | R | R | R |
Alkali | R | R | NR | NR | LR | R |
ketone | R | R | NR | NR | R | R |
Oils | R | R | R | R | R | R |
Aromatics | NR | R | R | LR | R | R |
Halocarbons | LR | R | R | NR | LR | R |
Ethylene glycol | R | R | R | R | R | R |
Ethers | R | R | R | NR | R | R |
acid | R | R | LR | NR | NR | LR |
Esters | R | R | R | R | R | R |
R：Resistance LR：Limited resistance NR：No resistance
Table 2 Chemical compatibility of depth filter materials
The selection of appropriate filter cartridge material depends on the specific application requirements, including but not limited to the properties of the medium to be filtered, the desired flow rate, operating conditions(temperature and pressure), the adsorption capacity of specific substances, the cost acceptable to the user, and whether it is necessary to comply with specific industry standards or regulatory requirements. Tables 3 and 4 are the basic properties of absolute-rating filtration membranes and depth filtration materials, respectively.
Nylon | PES | MCE | PTFE | PVDF | |
Temperature resistance | -40℃~120℃ | ≤135℃ | ≤60℃ | -40℃~150℃ | -40℃~150℃ |
Hydrophilicity | Hydrophilic | Hydrophilic | Hydrophilic | Hydrophobic (can be modified to hydrophilic) | Hydrophobic (can be modified to hydrophilic) |
Mechanical strength* | Middle | High (suitable for high pressure operation) | Low (easy to break) | High (needs enhanced support) | High (tensile and compressive) |
Protein adsorption | Higher | Middle | Higher | Lower hydrophilicity, higher hydrophobicity | Very low hydrophilicity, high hydrophobicity |
Minimum filter pore size | 0.1μm | 0.03μm | 0.1μm | 0.05μm | 0.1μm |
Cost | Middle | Higher | Low | Middle | High |
Note*: To increase the strength and toughness of the filter membrane, all filter membrane materials can be made into reinforced filter membranes with support layers such as PET/PP.
Table 3 Basic characteristics of absolute filtration membrane (single material)
PP | ACF | GF | PBT | Ti | Stainless steel (mesh/sintered felt/powder sintered) | |
Temperature resistance | ≤80℃ | ≤80℃ | ≤200℃ | ≤160℃ | ≤200℃ | ≤300℃ |
Hydrophilicity | Hydrophobic (can be modified to hydrophilic) | Neutral | Hydrophobic | Hydrophilic | / | Neutral |
Mechanical strength | Medium (good toughness) | Low | Middle | Middle | High | High (high pressure, high flow rate) |
Protein adsorption | Middle | Middle | Low | Very low | / | Low |
Cost | Low | Low | Very low | Low | Very high | High |
Table 4 Basic characteristics of deep filter materials
Based on the chemical compatibility and other basic characteristics of various materials, The basic filtration material selection work was completed and the further subsequent filtration process research experiments Can be started. For example, a small filtration device can be set up in the laboratory to conduct preliminary tests on the selected materials. Through multiple experiments, test data of performance can be recorded and analyzed, such as filtration efficiency and retention rate. Once the results of the small test are satisfactory, the pilot stage would be moved forward, which include expanding the scale of the experiment, further verifying the stability and reliability of the materials and processes, By doing these, a solid foundation for the final large-scale production can be finished.
