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Formation of Microfiltration Membranes from PMP/PIB Blends: Effect of PIB Molecular Weight on Membrane Properties
Sergey Ilyin1, Viktoria Ignatenko1, Tatyana Anokhina1
1A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, 29 Eninsky Prospect, 119991 Moscow, Russia.
Abstract:
A series of microfiltration membranes were fabricated by the extraction of polyisobutylene (PIB) from its immiscible blends with polymethylpentene (PMP). Three PIB with different molecular weight of 7.5 × 104 (Oppanol B15), 34 × 104 (Oppanol B50) and 110 × 104 (Oppanol B100) g/mol, respectively, were used to evaluate the effect of molecular weight on the porous structure and transport properties of resulting PMP-based membranes. To mimic the conditions of 3D printing, the flat-sheet membranes were fabricated by means of melting of mixtures of various PMP and PIB concentrations through the hot rolls at 240 ∘ C followed by a quick cooling. The rheology study of individual components and blends at 240 ∘ C revealed that PIB B50 possessed the most close flow curve to the pure PMP, and their blends demonstrated the lowest viscosity comparing to the compositions made of PIB with other molecular weights (B15 or B100). SEM images of the cross-section PMP membranes after PIB extraction (PMP/PIB = 55/45) showed that the use of PIB B50 allowed obtaining the sponge-like porous structure, whereas the slit-shaped pores were found in the case of PIB B15 and PIB B100. Additionally, PMP/B50 blends demonstrated the optimum combinations of mechanical properties (str = 9.1 MPa, E = 0.20 GPa), adhesion to steel (adh = 0.8 kPa) and retention performance (R240 nm = 99%, R38 nm = 39%). The resulting membranes were non- or low-permeable for water if the concentration of PIB B50 in the initial blends was 40 wt.% or lower. The optimal filtration performance was observed in the case of PMP/B50 blends with a ratio of 55/45 (Pwater = 1.9 kg/m2hbar, R240 nm = 99%, R38 nm = 39%) and 50/50 (Pwater = 1100 kg/m2hbar, R240 nm = 91%, R38 nm = 36%).
Insights
This study developed novel microfiltration membranes from polymethylpentene (PMP) and polyisobutylene (PIB) blends. The PMP/PIB B50 blend yielded optimal sponge-like porous structures and filtration properties, ideal for advanced separation applications.
Area of Science:
- Materials Science
- Polymer Science
- Membrane Technology
Background:
- Fabrication of microfiltration membranes is crucial for various separation processes.
- Tuning polymer blend properties allows for tailored membrane structures and functionalities.
- Polymethylpentene (PMP) and polyisobutylene (PIB) are suitable polymers for membrane development.
Purpose of the Study:
- To investigate the effect of polyisobutylene (PIB) molecular weight on the porous structure and transport properties of polymethylpentene (PMP)-based microfiltration membranes.
- To optimize membrane fabrication mimicking 3D printing conditions for enhanced performance.
- To evaluate the mechanical, adhesive, and retention properties of the developed PMP/PIB membranes.
Main Methods:
- Fabrication of flat-sheet membranes by melting immiscible PMP/PIB blends at 240°C followed by rapid cooling.
- Extraction of PIB from PMP/PIB blends to create porous structures.
- Rheological studies, Scanning Electron Microscopy (SEM) for morphology analysis, and filtration performance testing (water permeability, retention efficiency).
Main Results:
- PIB B50 exhibited the closest rheological behavior to PMP, resulting in lower blend viscosity.
- PMP membranes fabricated with PIB B50 (55/45 ratio) showed a sponge-like porous structure, unlike slit-shaped pores from PIB B15 and B100.
- PMP/PIB B50 blends demonstrated superior mechanical properties, adhesion to steel, and high retention rates for 240 nm particles (99%). Optimal filtration performance was achieved with 55/45 and 50/50 PMP/PIB B50 blends.
Conclusions:
- The molecular weight of PIB significantly influences the porous morphology and transport characteristics of PMP-based membranes.
- The PMP/PIB B50 blend is ideal for creating membranes with desirable sponge-like structures and excellent filtration capabilities.
- These PMP/PIB membranes offer a promising platform for advanced microfiltration applications, particularly when fabricated using 3D printing-compatible methods.
