Littérature scientifique sur le sujet « P84 polyimide »

This research introduces zeolite carbon composite (ZCC) as a new filler on polymeric membranes based on the BTDA-TDI/MDI (P84) co-polyimide for the air separation process. The separation performance was further improved by a polydimethylsiloxane (PDMS) coating to cover up the surface defect. The incorporation of 1 wt% ZCC into P84 co-polyimide matrix enhanced the O2 permeability from 7.12 to 18.90 Barrer (2.65 times) and the O2/N2 selectivity from 4.11 to 4.92 Barrer (19.71% improvement). The PDMS coating on the membrane further improved the O2/N2 selectivity by up to 60%. The results showed that the incorporation of ZCC and PDMS coating onto the P84 co-polyimide membrane was able to increase the overall air separation performance.

Zeolite templated carbon (ZTC), a structurally unique carbon material was used as new fillers for the preparation of composite polymeric membrane derived from BTDA-TDI/MDI (P84) co-polyimide. The thermal stability of membrane, the structure evolution, morphology and topology, as well as gas separation performance of modified membranes were investigated. Zeolite-Y, a hard template for ZTC, was synthesized via hydrothermal method. The ZTC was synthesized via impregnation of sucrose as carbon precursor into zeolite pore and followed by carbonization at 800°C. The zeolite template was removed through acid treatment to obtain ZTC, which was used as fillers for membrane preparation. The membrane was prepared using P84 co-polyimide as membrane precursor via phase inversion process. Synthesized materials were characterized using SEM, XRD, N2 adsorption-desorption isotherm and TEM. The thermal stability of membrane was improved by the addition of ZTC. As the result of ZTC loading into P84 co-polyimide membrane, the gas permeability of CO2 increased thirty-four times, as well as the CO2/CH4 selectivity boosted from 0.76 to 5.23. The ordered pore structure in ZTC plays important role in increasing the permeability and selectivity performances of the P84 co-polyimide membrane.

Mixed Matrix Membranes (MMMs) which consist of 0.3 wt.% Zeolite-Carbon Composite (ZCC) dispersed in BTDA-TDI/MDI (P84 co-polyimide) have been prepared through phase inversion method by using N-methyl-2-pyrrolidone (NMP) as a solvent. Membranes were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Thermogravimetric Analysis (TGA), and Fourier Transform Infrared (FTIR). Membrane performance was measured by a single gas permeation of CO2 and CH4. The maximum permeability of CO2 and CH4, which up to 12.67 and 6.03 Barrer, respectively. P84/ZCC mixed matrix membrane also showed a great enhancement in ideal selectivity of CO2/CH4 2.10 compared to the pure P84 co-polyimide membrane.

In this study, multilayer graphene oxide (GO) was used to prepare the functional layer of polyimide/GO composite membrane with polyimide (P84) used as the supporting layer. Chitosan added in the functional layer was utilized to adjust the selectivity of the composite membrane. The effects of GO and chitosan contents on membrane morphology and separation performance were investigated in detail. The composite membrane showed high rejection to Congo red and Methyl orange with high flux but low rejection to Na2SO4 and MgCl2 at 0.2 MPa and ambient temperature. The membrane exhibited excellent solvent resistance in N,N-dimethylacetamide (DMAc) after being crosslinked with 0.5 wt.% triethylene tetramine. The result means that a highly selective and solvent-resistant P84/GO composite membrane was prepared with the facile filtration preparation method.

The elimination of the additional defect healing post-treatment step in asymmetric hollow fiber manufacturing would result in a significant reduction in membrane production cost. However, obtaining integrally skinned polymeric asymmetric hollow fiber membranes with an ultrathin and defect-free selective layer is quite challenging. In this study, P84® asymmetric hollow fiber membranes with a highly thin (~56 nm) defect-free skin were successfully fabricated by fine tuning the dope composition and spinning parameters using volatile additive (tetrahydrofuran, THF) as key parameters. An extensive experimental and theoretical study of the influence of volatile THF addition on the solubility parameter of the N-methylpyrrolidone/THF solvent mixture was performed. Although THF itself is not a solvent for P84®, in a mixture with a good solvent for the polymer, like N-Methyl-2-pyrrolidone (NMP), it can be dissolved at high THF concentrations (NMP/THF ratio > 0.52). The as-spun fibers had a reproducible ideal CO2/N2 selectivity of 40, and a CO2 permeance of 23 GPU at 35 °C. The fiber production can be scaled-up with retention of the selectivity.

La structuration de membranes composites est inévitable pour la prochaine étape de développement de membranes à matrices mixtes (MMM), car l’utilisation de membranes asymétriques couramment non composites signifierait que la majorité des additifs seraient gaspillées dans le support poreux. Dans cette thèse, la possibilité d'utiliser du poly(4-méthyl-1-pentène) (PMP) comme substrat et comme couche intermédiaire dans une membrane composite a été comparée au polydiméthylsiloxane (PDMS), qui est couramment utilisé comme couche intermédiaire. Il est supporté sur un support poreux en polyéthersulfone (PES), modifié avec du chlorure de lithium (LiCl) pour obtenir des architectures variables de surface de pores. La membrane composite à base de PDMS/PES a montré une perméance de 26,6 ± 2,6 GPU pour le N2 et de 354,4 ± 27,9 GPU pour le CO2 avec une épaisseur de revêtement minimale d'environ 1 µm. Cependant, cette valeur est inférieure à celle obtenue avec la membrane dense asymétrique à base de PMP ; 84,6 ± 6,2 GPU pour le N2 et 607,3 ± 31,3 GPU pour le CO2. Bien que le PDMS ait une perméabilité intrinsèque bien supérieure à celle du PMP, la membrane composite à base de PDMS/PES souffre d'un problème d'intrusion de solution et de restriction géométrique à son interface dense – poreux, ce qui réduit sa perméance à 4% de sa perméance supposée idéale, à faible épaisseur de revêtement. Il est en outre élucidé que l'uniformité de la surface du support poreux affecte également de manière significative la perméance de la membrane résultante. En comparaison, la membrane à base de PMP asymétrique avec une fine couche dense s'est avérée avantageuse en tant que support et couche intermédiaire, car elle permet d’atténuer le problème d'interface noté précédemment pour les membranes composites tout en étant très perméable, minimisant ainsi la résistance au transfert. Les gaz N2/CO2/CH4 ont été choisis comme gaz perméants modèles pour la fabrication ultérieure de membranes composites à base de polyimide P84 (P84 PI) comme couche sélective. Cependant, la faible énergie de surface du PMP limite sa compatibilité pour former une membrane composite. Il a été montré qu’il est possible de déposer par immersion le P84 PI sur une membrane PMP à couche dense, sans qu’il y ait besoin de prétraitement. Du P84 PI a été déposé par immersion à 5 mm/s sur une membrane de PMP à fibre creuse et à peau dense. Différentes concentrations de la solution de dépôt ont été étudiées. Les membranes composites ainsi fabriquées ont été testées pour vérifier leur performance de perméation des gaz. Les résultats ont montré une sélectivité idéale aussi élevée que 42,36 ± 19,08 pour le CO2/CH4 et 18,55 ± 6,06 pour le CO2/N2. Ces valeurs ont été atteintes pour des solutions de dépôt à 14 % en masse de P84 PI. Toutefois, malgré la résistance du PMP au solvant agressif N-méthyl-2-pyrrolidone (NMP), utilisé pour la solvatation du P84 PI, l'utilisation du P84 PI à faible concentration (2 - 10 % en masse) endommage la couche dense du PMP. Ceci compromet les performances de séparation de la membrane composite. Il est supposé que le rétrécissement du P84 PI lors du séchage a déchiré la couche de PMP sous-jacente. Ainsi, il existe une concentration minimale de polymère P84 PI pour laquelle une couche sélective sans défaut peut être réalisée (qui est d'environ 14 % en masse). À cette concentration, la vitesse de revêtement par immersion peut être contrôlée pour obtenir une couche sélective sans défaut et mince, adaptée à la fabrication de membranes composites. Ceci, bien que le démouillage de la solution de revêtement se produise encore et s'amplifie à mesure que l'épaisseur du revêtement est réduite
Composite membrane structures are inevitable for the next step of mixed matrix membrane development as the commonly used asymmetric membrane design would mean majority of the fillers to be wasted in the bulk porous substrate layer. In this research, the possibility of using poly(4-methyl-1-pentene) (PMP) as substrate – gutter layer in composite membrane was compared with commonly used polydimethylsiloxane (PDMS) as gutter layer, supported on lithium chloride (LiCl) modified polyethersulfone (PES) porous substrate of varying surface pore architectures. Composite PES/PDMS was able to obtain permeance as high as 26.6 ± 2.6 GPU for N2 and 354.4 ± 27.9 GPU for CO2 at about 1 µm minimum coating thickness. Nevertheless, this value is lower than asymmetric dense skin PMP membrane at 84.6 ± 6.2 GPU for N2 and 607.3 ± 31.3 GPU for CO2. Despite that PDMS has intrinsic permeability far higher than PMP, PES/PDMS composite suffers from solution intrusion & geometric restriction problem at its dense – substrate interface, which reduces its permeance efficiency as low as only 4% of its supposedly ideal permeance, at low coating thickness. It is further elucidated that substrate surface uniformity also significantly affects the resulting composite permeance. In comparison, asymmetric PMP with thin dense surface layer was noted to be advantageous as the substrate – gutter layer as it mitigates the interfacial problem noted earlier for composite membranes while still being highly permeable to minimize resistance. Hence, N2/CO2/CH4 gases were chosen as the model permeants for further composite fabrication with P84 polyimide (PI) as selective layer. Nevertheless, low surface energy of PMP limit its compatibility to form a composite layer. However, it was noted that PMP is compatible to form a bilayer through dip coating with P84 PI, without the need for pre-treatment. Hence, P84 PI of various concentration was dip coated at 5 mm/s onto PMP-based dense skin hollow fiber membrane and tested for gas permeation performance. Results showed that ideal selectivity as high as 42.36 ± 19.08 for CO2/CH4 and 18.55 ± 6.06 for CO2/N2 was achieved at 14 wt.% P84 PI coating. Nevertheless, despite of PMP’s resistibility to the harsh N-methyl-2-pyrrolidone (NMP) solvent used for P84 PI solvation, introduction of P84 PI at low concentration (2 – 10 wt.%) damages the thin, dense skin layer of the PMP’s membrane surface which jeopardize the composite’s separation performance. It is hypothesised that P84 PI’s shrinkage during drying teared the underlying PMP layer which caused this degradation. Hence, there exist a minimum P84 PI polymer concentration in which a defect free selective layer can be made (which is at about 14 wt.%). At this concentration, dip coating speed can be manipulated to obtain a thinner defect-free selective layer suitable for composite membrane fabrication, although dewetting of the coating solution still occurred and magnified as the coating thickness is reduced