Polymethylpentene Research Articles

Proton conductivity and performance in fuel cells of grafted membranes based on polymethylpentene with radiation-grafted crosslinked sulfonated polystyrene

In this work, a comparative study was carried out of the transport properties and performance in a hydrogen-air fuel cell of the membranes based on polymethylpentene (PMP) with grafted sulfonated polystyrene and the standard Nafion® 212 membrane. Grafted cation-exchange membranes (GCM) were obtained by radiation graft post-polymerization of styrene onto UV-exposed PMP film followed by sulfonation with chlorosulfonic acid. The proton-conductivity of the GCM membrane with an ion-exchange capacity of 2.9 ± 0.1 meq/g reaches 21 ± 1 mS cm−1 at room temperature and 95% relative humidity, which is twice higher the conductivity of the Nafion® under the same conditions. The GCM-1 H2-permeability of 2.06∙10−7 cm2 s−1 even slightly lower than that of the Nafion® 212 (2.14∙10−7 cm2 s−1). A comparison of these membranes in the membrane electrode assemblies (MEA) of hydrogen-air fuel cells (FC) shows that the use of the grafted membranes with the high ion-exchange capacity is highly promising. The maximum performance of FC with grafted and Nafion® 212 membrane are both close to 180 mW/cm2 at the current density of 400 mA/cm2. At the same time, the high degree of crosslinking of sulfonated polystyrene leads to a decrease in conductivity and does not give an advantage in gas permeability.

The effect of sorbitol and sweet sorghum to carrageenan ratio on the physicochemical properties of sweet sorghum/carrageenan bioplastics

The use of synthetic plastic films has raised several environmental issues. The use of bioplastics is therefore expected as an alternative. In this study, sorghum grain extract was explored as the source for bioplastic films considering the prediction of massive availability of sorghum grains as by-products of bioethanol production. Sorghum grain extracts are rich in carbohydrate and protein, the two principals of bioplastic making. Therefore, the ability to re-utilize sorghum grain extracts is further expected to reduce the production cost. In addition to sorghum grain extracts, additives were involved in the process, which were carrageenan and sorbitol. Carrageenan was used as a gelling agent during the bioplastic’s productions while sorbitol was involved as the plasticizer. The effect of sorbitol and the ratio of sorghum extract to carrageenan on the physical and mechanical properties of the bioplastic film were investigated. The concentration of sorbitol was varied at 0, 2, 4, and 6%; the ratio of sweet sorghum extract to carrageenan was varied as 5:5, 6:4, 7:3, and 8:2 at sorbitol concentration of 4%. The alkaline method was used to solubilize milled sorghum grain. The solution casting method was used to produce the bioplastic film. The film thickness was dependent on the concentration of the sorghum extract. The sorbitol incorporation reduced the tensile strength of the film while the concentration of the sorghum extract did not significantly alter the tensile strength. Improved flexibility was observed as the sorbitol concentration was increased. Water vapor transmission rate of the films is in the range of 100–147 g/m2 day, lower than polymethylpentene (PMP), a polyolefin petroleum-based plastic film, indicating the potential of the bioplastic films for future application. This further indicates the possible biorefinery of sorghum by-products as raw materials for bioplastic production.

Hypothermic preservation of endothelialized gas-exchange membranes.

Endothelialization of the blood contacting surfaces of blood-contacting medical devices, such as cardiovascular prostheses or biohybrid oxygenators, represents a plausible strategy for increasing their hemocompatibility. Nevertheless, isolation and expansion of autologous endothelial cells (ECs) usually requires multiple processing steps and time to obtain sufficient cell numbers. This excludes endothelialization from application in acute situations. Off-the-shelf availability of cell-seeded biohybrid devices could be potentially facilitated by hypothermic storage. In this study, the survival of cord-blood-derived endothelial colony forming cells (ECFCs) that were seeded onto polymethylpentene (PMP) gas-exchange membranes and stored for up to 2 weeks in different commercially available and commonly used preservation media was measured. While storage at 4°C in normal growth medium (EGM-2) for 3 days resulted in massive disruption of the ECFC monolayer and a significant decline in viability, ECFC monolayers preserved in Chillprotec could recover after up to 14 days with negligible effects on their integrity and viability. ECFC monolayers preserved in Celsior, HTS-FRS, or Rokepie medium showed a significant decrease in viability after 7 days or longer periods. These results demonstrated the feasibility of hypothermic preservation of ECFC monolayers on gas-exchange membranes for up to 2 weeks, with potential application on the preservation of pre-endothelialized oxygenators and further biohybrid cardiovascular devices.

Formation of Microfiltration Membranes from PMP/PIB Blends: Effect of PIB Molecular Weight on Membrane Properties.

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 (σstr = 9.1 MPa, E = 0.20 GPa), adhesion to steel (σadh = 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%).

Endothelialized TiO <sub>2</sub>- and Ti45Nb-Coated PMP, PDMS and PES/PVP Membranes for Biohybrid Lung Support

Lacking hemocompatibility of extracorporeal membrane oxygenation led to a biohybrid lung concept, in which gas exchange membranes are seeded with endothelial cells to form long-term stable surfaces. However, extensive surface modification of large oxygenator membranes is required for cell adhesion. In this study, polymethylpentene (PMP), polydimethylsiloxane (PDMS) and polyethersulfone/polyvinylpyrrolidone (PES/PVP) membranes were functionalized with thin films of titanium dioxide (TiO 2 ) or titanium-niobium (Ti45Nb), and characterized by field emission scanning electron microscopy, ellipsometry, X-ray photoelectron spectroscopy and gas permeability measurements. Endothelialized membranes were cultured under static conditions to evaluate cell coverage. Cell retention was investigated in a bioreactor system under flow conditions with a wall shear stress of 0.5 Pa, and cells were stained for endothelial markers CD31 and von Willebrand factor (vWf). Film thicknesses of 3.3±0.2 nm and 5.5±0.3 nm were determined for TiO2 and Ti45Nb coatings, respectively. With the exception of a slight decrease for PDMS+Ti45Nb, gas permeabilities of coated PMP and PDMS membranes did not deteriorate significantly compared to uncoated membranes. The microporous structure and the high hydrophilicity of PES/PVP prevented permeability measurements and subsequent dynamic culture due to membrane wetting. However, mean cell density increased substantially for all coated membranes compared to uncoated membranes. Although endothelialized PDMS+Ti45Nb showed minor cell layer defects, all coated PMP and PDMS membranes demonstrated integral cell layers after dynamic culture that stained positive for CD31 and vWf. This study has shown the suitability of thin TiO2 and Ti45Nb films for flow-stable endothelialization of gas exchange membranes for application in a biohybrid lung.

基于负曲率空芯光纤的光泵太赫兹光纤激光器的理论研究

Based on the compact and efficient optically pumped terahertz laser(OPTL) technology, an optically pumped terahertz fiber laser(OPTFL) based on a negative curvature hollow core fiber was designed. This OPTFL used a hollow-core fiber with polymethylpentene(PMP) material as operation gas chamber and was filled with methanol gas and pumped by 9P(36) continuous-wave(CW) CO2 laser. Based on rate equations and the transmission theory in hollow core fiber, factors affecting the output characteristics of OPTFL were analyzed. By investigating inner microstructure of hollow-core fiber, a negative curvature hollow-core fiber for efficiently transmitting terahertz waves was proposed. Considering the designed negative curvature hollow-core fiber, the feasibility of long cavity OPTFL was analyzed. Theoretical calculations showed that by appropriately increasing the cavity length of the proposed OPTFL, the terahertz output power was expected to reach the order of 100 milliwatts with optimal operating conditions. The results provide a new method for the OPTFL with high power and high performance.

Highly effective photon-to-cooling thermal device

Photon-to-cooling phenomenon relies on the atmospheric transparency window to dissipate heat from the earth into outer space, which is an energy-saving cooling technique. This work demonstrates a highly effective aluminized Polymethylpentene (PMP) thin-film thermal structure. The emissivity of aluminized PMP thin films matches well to the atmospheric transparency window so as to minimize parasitic heat losses. This photon-to-cooling structure yields a temperature drop of 8.5 K in comparison to the ambient temperature and a corresponding radiative cooling power of 193 W/m2 during a one-day cycle. The easy-to-manufacture feature of an aluminized PMP thin film makes it a practically scalable radiative cooling method.

72-Hour in vivo evaluation of nitric oxide generating artificial lung gas exchange fibers in sheep

The large, densely packed artificial surface area of artificial lungs results in rapid clotting and device failure. Surface generated nitric oxide (NO) can be used to reduce platelet activation and coagulation on gas exchange fibers, while not inducing patient bleeding due to its short half-life in blood. To generate NO, artificial lungs can be manufactured with PDMS hollow fibers embedded with copper nanoparticles (Cu NP) and supplied with an infusion of the NO donor S-nitroso-N-acetyl-penicillamine (SNAP). The SNAP reacts with Cu NP to generate NO. This study investigates clot formation and gas exchange performance of artificial lungs with either NO-generating Cu-PDMS or standard polymethylpentene (PMP) fibers. One miniature artificial lung (MAL) made with 10 wt% Cu-PDMS hollow fibers and one PMP control MAL were attached to sheep in parallel in a veno-venous extracorporeal membrane oxygenation circuit (n = 8). Blood flow through each device was set at 300 mL/min, and each device received a SNAP infusion of 0.12 μmol/min. The ACT was between 110 and 180 s in all cases. Blood flow resistance was calculated as a measure of clot formation on the fiber bundle. Gas exchange experiments comparing the two groups were conducted every 24 h at blood flow rates of 300 and 600 mL/min. Devices were removed once the resistance reached 3x baseline (failure) or following 72 h. All devices were imaged using scanning electron microscopy (SEM) at the inlet, outlet, and middle of the fiber bundle. The Cu-PDMS NO generating MALs had a significantly smaller increase in resistance compared to the control devices. Resistance rose from 26 ± 8 and 23 ± 5 in the control and Cu-PDMS devices, respectively, to 35 ± 8 mmHg/(mL/min) and 72 ± 23 mmHg/(mL/min) at the end of each experiment. The resistance and SEM imaging of fiber surfaces demonstrate lower clot formation on Cu-PDMS fibers. Although not statistically significant, oxygen transfer for the Cu-PDMS MALs was 13.3% less than the control at 600 mL/min blood flow rate. Future in vivo studies with larger Cu–PDMS devices are needed to define gas exchange capabilities and anticoagulant activity over a long-term study at clinically relevant ACTs. Statement of SignificanceIn artificial lungs, the large, densely-packed blood contacting surface area of the hollow fiber bundle is critical for gas exchange but also creates rapid, surface-generated clot requiring significant anticoagulation. Monitoring of anticoagulation, thrombosis, and resultant complications has kept permanent respiratory support from becoming a clinical reality. In this study, we use a hollow fiber material that generates nitric oxide (NO) to prevent platelet activation at the blood contacting surface. This material is tested in vivo in a miniature artificial lung and compared against the clinical standard. Results indicated significantly reduced clot formation. Surface-focused anticoagulation like this should reduce complication rates and allow for permanent respiratory support by extending the functional lifespan of artificial lungs and can further be applied to other medical devices.

Sedative and Analgesic Drug Sequestration After a Single Bolus Injection in an Ex Vivo Extracorporeal Membrane Oxygenation Infant Circuit.

Patient sedation and analgesia on extracorporeal membrane oxygenation (ECMO) is vital for safety and comfort. However, adsorption to the circuit may alter drug pharmacokinetics and remains poorly characterized. This study characterizes drug adsorption of morphine, fentanyl, midazolam, and dexmedetomidine in an ex vivo infant ECMO circuit utilizing polymethylpentene (PMP) membrane oxygenator (MO) with protein-bounded polyvinylchloride (PVC) tubing. Twelve closed-loop ex vivo ECMO circuits were prepared using P.h.i.s.i.o (phosphorylcholine)-coated PVC tubing (Sorin Group USA, Inc.) and a Quadrox-iD pediatric polymethylpentene MO (Maquet Cardiopulmonary AG). Once the circuits were primed and running, a single medication was injected as a bolus into the circuit with three circuits per drug. Drug samples were drawn following injection, at 2, 5, 15, 30, 60, 120 minutes and at 4, 12, 24, 36, and 48 hours and analyzed using ultra high-performance liquid chromatography with mass spectrometry. Compared with morphine, the other drugs are highly sequestered with fentanyl 68.5%, dexmedetomidine 50.8%, and midazolam 26.2% affecting the availability of free drug in the circuit. Sequestration of fentanyl, midazolam, and dexmedetomidine in an ECMO circuit with P.h.i.s.i.o-coated PVC tubing and PMP MO may limit drug delivery to infants. Future in vivo studies are needed to determine the clinical impact of sequestration.

Prospect of Oxyplus Hollow Fibre Membrane with Dense Polymethylpentene (PMP) Skin as Support-gutter Layer of Thin Film Composite (TFC) for Biogas upgrading

Prospect of Oxyplus Hollow Fibre Membrane with Dense Polymethylpentene (PMP) Skin as Support-gutter Layer of Thin Film Composite (TFC) for Biogas upgrading

Technical Advances in the Field of ECMO.

Although the fundamentals of extracorporeal membrane oxygenation (ECMO) have not changed in 3 decades, the technical elements continue to improve and have evolved from an assemblage of individual components to more integrated systems with added features, enhanced safety, and improved maneuverability. The introduction of polymethylpentene (PMP) fiber technology has expanded the development of artificial membranes that have low resistance, are more biocompatible, and can be used for extended durations. Extracorporeal carbon dioxide removal techniques continue to be enhanced as stand alone technology and modified renal dialysis systems are introduced. Research continues in the development of compact and wearable artificial lungs that are intended to support patients for prolonged periods (eg, patients awaiting lung transplantation). The use of high-fidelity simulation training has become a standard and important method for reinforcing technical skills, refining troubleshooting sequences, and enhancing team interactions. Modifications to mannequins and ECMO systems coupled with clinical and physiologic scenarios will help achieve greater realism and enhance learning. ECMO technology continues to improve, with adaptability and versatility being essential attributes.

Permselectivity and ion-conductivity of grafted cation-exchange membranes based on UV-oxidized polymethylpenten and sulfonated polystyrene

Abstract In the present study the properties of novel cation-exchange membranes based on UV-oxidized polymethylpentene (PMP) with grafted sulfonated polystyrene are described. A correlation between the composition of the grafted copolymer (grafting degree, cross-linking degree) and transport properties (Na+-conductivity, permselectivity, diffusion permeability) of resulted membranes are discussed. It is shown that with increasing of grafting degree (GD) and lowering of cross-linking degree (CD) the concentration of functional groups in the inner solution and permselectivity decrease, while ionic conductivity increases. The obtained membranes have the GD ranging from 29 to 120% and CD from 0 to 5%. The best membranes have ionic surface resistance of 0.3–0.6 Ω cm2 in 0.5 M NaCl, apparent cation transport numbers of 0.870–0.998 and NaCl diffusion permeability of 3.3 · 10−8–5.5 · 10−7 cm2 s−1, as well as satisfactory mechanical performance. A comparison of transport properties (conductivity and cation transport number) of the obtained membranes with a properties of number of available samples was made. It is noted that some of the obtained samples are at the level of the best perfluorinated homogeneous membranes in terms of the ratio of conductivity and cation transport numbers. High ionic conductivity and permselectivity make the prepared membranes promising candidates for possible applications in electrodialysis, dialysis, reverse electrodialysis, Red-Ox flow batteries and other membrane processes.

Plasma Free Hemoglobin Generation Using the EOS PMP™ Oxygenator and the CentriMag® Blood Pump

Hemolysis is a known consequence of extracorporeal membrane oxygenation (ECMO) resulting from shear force within the different components of the extracorporeal circuit. The primary aim of this study was to evaluate the EOS PMP™ oxygenator for generation of plasma free hemoglobin (PfHg) over 24 hours at nominal operating range flow rates. The EOS ECMO™ (LivaNova, Inc.; formerly Sorin, Arvada, CO) is equipped with a plasma tight polymethylpentene (PMP) hollow fiber oxygenator. We hypothesized that PfHg generation would be elevated in circuits with higher flow rates, because of the significant pressure drop across the oxygenator according to manufacturer provided flow charts. Generated PfHg concentrations were compared with PfHg concentrations from blood not exposed to an ECMO circuit. The secondary aim was to evaluate circuit flow-rate-induced changes in platelet count and platelet function over 24 hours. Circuits contained a CentriMag® (St. Jude Medical, St. Paul, MN) blood pump and an EOS ECMO PMP™ oxygenator. Circuits in triplicate were run continuously for 24 hours at three flow rates [1, 3, and 5 liters per minute {LPM}]. PfHg was analyzed at baseline, 6, 12, 18, and 24 hours. Platelet count and function were measured at baseline and 24 hours. Concentrations of PfHg at baseline for circuits operating at 1, 3, and 5 LPM were 24.4 ± 4.0, 38.4 ± 28.6, and 26.7 ± 6.9 mg/dL, respectively. PfHg concentrations after 24 hours were statistically compared for the three flow rates using analysis of variance; PfHg concentrations at 1 LPM (181.4 ± 29.1 mg/dL), 3 LPM (145.9 ± 8.7 mg/dL), and 5 LPM (100.1 ± 111.3 mg/dL) circuits. The F-test was not statistically significant (p = .632), indicating that PfHg generation at 24 hours was similar among the three flow rates. Excessive hemolysis using PfHg levels in the EOS PMP™ membrane oxygenator was not observed.

Development of zwitterionic sulfobetaine block copolymer conjugation strategies for reduced platelet deposition in respiratory assist devices.

Respiratory assist devices, that utilize ∼2 m2 of hollow fiber membranes (HFMs) to achieve desired gas transfer rates, have been limited in their adoption due to such blood biocompatibility limitations. This study reports two techniques for the functionalization and subsequent conjugation of zwitterionic sulfobetaine (SB) block copolymers to polymethylpentene (PMP) HFM surfaces with the intention of reducing thrombus formation in respiratory assist devices. Amine or hydroxyl functionalization of PMP HFMs (PMP-A or PMP-H) was accomplished using plasma-enhanced chemical vapor deposition. The generated functional groups were conjugated to low molecular weight SB block copolymers with N-hydroxysuccinimide ester or siloxane groups (SBNHS or SBNHSi) that were synthesized using reversible addition fragmentation chain transfer polymerization. The modified HFMs (PMP-A-SBNHS or PMP-H-SBNHSi) showed 80-95% reduction in platelet deposition from whole ovine blood, stability under the fluid shear of anticipated operating conditions, and uninhibited gas exchange performance relative to non-modified HFMs (PMP-C). Additionally, the functionalization and SBNHSi conjugation technique was shown to reduce platelet deposition on polycarbonate and poly(vinyl chloride), two other materials commonly found in extracorporeal circuits. The observed thromboresistance and stability of the SB modified surfaces, without degradation of HFM gas transfer performance, indicate that this approach is promising for longer term pre-clinical testing in respiratory assist devices and may ultimately allow for the reduction of anticoagulation levels in patients being supported for extended periods. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2681-2692, 2018.

Study on constancy of CT numbers of SIEMENS Sensation Open CT-simulator

Objective To evaluate the constancy of CT numbers of SIEMENS Sensation Open CT-simulator by analyzing the CT numbers of seven materials obtained from quality assurance (QA) tests. Methods QA tests for SIEMENS Sensation Open CT-simulator were performed with the Catphan504 phantom monthly. The CT images were obtained using three scan protocols (HeadSeq, RT_Head, and RT_Abdomen) for the CTP404 module in the phantom. The DoseLab software was used to analyze the 72 CT images acquired from January 2014 to December 2015, and the CT numbers (Y) of seven materials were obtained. Statistical analysis was performed on the Y data. The mean, standard deviation, maximum, minimum, and range values of Y for seven materials were calculated in three scan protocols. Results The standard deviation values of air, polymethylpentene, low-density polyethylene, polystyrene, acrylic acid, polyoxymethylene resin (Delrin), and polytetrafluoroethylene (Teflon) were as follows: (1) HeadSeq: 0.54, 0.60, 0.82, 0.58, 0.75, 0.66, and 1.83 HU; (2) RT_Head: 0.08, 0.69, 0.86, 0.66, 0.80, 0.89, and 2.49 HU; (3) RT_Abdomen: 0.11, 0.61, 0.76, 0.72, 0.78, 0.96, and 2.56 HU. According to the statistical data, the constancy of CT numbers of the SIEMENS Sensation Open CT-simulator was in good condition in two years. Conclusions The variation of CT numbers of Teflon is the biggest among the seven materials. The relative values of CT numbers between different scan protocols vary with the relative electron density of materials. Key words: Tomography, X-ray Computed; Quality control; Constancy; Catphan phantom

Thin-Film Coated Plastic Wrap for Food Packaging

In this study, the antimicrobial property and food package capability of polymethylpentene (PMP) substrate with silicon oxdie (SiOx) and organic silicon (SiCxHy) stacked layers deposited by an inductively coupled plasma chemical vapor deposition system were investigated. The experimental results show that the stacked pair number of SiOx/SiCxHy on PMP is limited to three pairs, beyond which the films will crack and cause package failure. The three-pair SiOx/SiCxHy on PMP shows a low water vapor transmission rate of 0.57 g/m2/day and a high water contact angle of 102°. Three-pair thin-film coated PMP demonstrates no microbe adhesion and exhibits antibacterial properties within 24 h. Food shelf life testing performed at 28 °C and 80% humidity reports that the three-pair thin-film coated PMP can enhance the food shelf-life to 120 h. The results indicate that the silicon-based thin film may be a promising material for antibacterial food packaging applications to extend the shelf-life of food products.

Hollow Fiber Oxygenator Composition Has a Significant Impact on Failure Rates in Neonates on Extracorporeal Membrane Oxygenation: A Retrospective Analysis.

In extracorporeal life support (ECLS), there are two main types of oxygenators in clinical use for neonates: polymethylpentene (PMP) hollow fiber and polypropylene (PP) hollow fiber. A retrospective study was performed on neonates ( n = 44) who had undergone ECLS for noncardiac indications from 2009 to 2015. Between the two groups (PMP n = 21, PP n = 23), the PP oxygenators failed 91% of the time, whereas the PMP oxygenators failed 43% of the time ( p < 0.05). Analysis suggests PMP oxygenators are less prone to failure than PP oxygenators, and they require fewer number of oxygenator changes during a neonatal ECLS.

Fine Filament Formation Behavior of Polymethylpentene and Polypropylene near Spinneret in Melt Blowing Process

Abstract Formation behavior of fine fibers of polymethylpentene (PMP) and polypropylene (PP) in the melt blowing process was investigated through the observation of the spin-line near the spinning nozzle using a high speed camera. Reduction of the polymer throughput rate and increase of the air flow rate were necessary to achieve fine diameter fibers, however these conditions generally cause the instability in the spinning process. Observation of the spin-line at the melt blowing die revealed the periodic accumulation of polymer flow near the spinning nozzle followed by the quick pulling down of the accumulated polymer by the air flow. This behavior caused the periodic fluctuation of fiber diameter as well as the intermittent breakage of the spin-line under extreme conditions. Because of high extrusion viscosity, PMP showed more stable spinning behavior than PP. Frequency of diameter fluctuation became higher with the increases of air flow rate and throughput rate, and the maximum frequency of about 60 Hz was observed for PP spinning with the throughput rate of 0.18 g/min. Diameter distribution of the fibers in the prepared web was also analyzed to compare with the spinning behavior. Fiber diameter distributions were narrow and symmetric under stable spinning conditions, whereas skewed diameter profiles with a maximum at low value and a long tail to the larger diameter region were observed under unstable conditions. Intermittent spin-line breakage caused flaws of “shot” and/or “fly”, and the skewed fiber diameter distribution with the presence of a small amount of fiber of extremely large diameter was confirmed.

Darcy Permeability of Hollow Fiber Membrane Bundles Made from Membrana Polymethylpentene Fibers Used in Respiratory Assist Devices.

Hollow fiber membranes (HFMs) are used in blood oxygenators for cardiopulmonary bypass or in next generation artificial lungs. Flow analyses of these devices is typically done using computational fluid dynamics (CFD) modeling HFM bundles as porous media, using a Darcy permeability coefficient estimated from the Blake-Kozeny (BK) equation to account for viscous drag from fibers. We recently published how well this approach can predict Darcy permeability for fiber bundles made from polypropylene HFMs, showing the prediction can be significantly improved using an experimentally derived correlation between the BK constant (A) and bundle porosity (ε). In this study, we assessed how well our correlation for A worked for predicting the Darcy permeability of fiber bundles made from Membrana polymethylpentene (PMP) HFMs, which are increasingly being used clinically. Swatches in the porosity range of 0.4 to 0.8 were assessed in which sheets of fiber were stacked in parallel, perpendicular, and angled configurations. Our previously published correlation predicted Darcy within ±8%. A new correlation based on current and past measured permeability was determined: A = 497ε - 103; using this correlation measured Darcy permeability was within ±6%. This correlation varied from 8% to -3.5% of our prior correlation over the tested porosity range.

Surface monofunctionalized polymethyl pentene hollow fiber membranes by plasma treatment and hemocompatibility modification for membrane oxygenators

The hemocompatibility of polymethyl pentene (PMP) hollow fiber membranes (HFMs) was improved through surface modification for membrane oxygenator applications. The modification was performed stepwise with the following: (1) oxygen plasma treatment, (2) functionalization of monosort hydroxyl groups through NaBH4 reduction, and (3) grafting 2-methacryloyloxyethyl phosphorylcholine (MPC) or heparin. SEM, ATR-FTIR, and XPS analyses were conducted to confirm successful grafting during the modification. The hemocompatibility of PMP HFMs was analyzed and compared through protein adsorption, platelet adhesion, and coagulation tests. Pure CO2 and O2 permeation rates, as well as in vitro gas exchange rates, were determined to evaluate the mass transfer properties of PMP HFMs. SEM results showed that different nanofibril topographies were introduced on the HFM surface. ATR-FTIR and XPS spectra indicated the presence of functionalization of monosort hydroxyl group and the grafting of MPC and heparin. Hemocompatibility evaluation results showed that the modified PMP HFMs presented optimal hemocompatibility compared with pristine HFMs. Gas permeation results revealed that gas permeation flux increased in the modified HFMs because of dense surface etching during the plasma treatment. The results of in vitro gas exchange rates showed that all modified PMP HFMs presented decreased gas exchange rates because of potential surface fluid wetting. The proposed strategy exhibits a potential for fabricating membrane oxygenators for biomedical applications to prevent coagulation formation and alter plasma-induced surface topology and composition.