High-pressure Polymer Research Articles

In Situ Changes in Mechanical Properties Based on Gas Saturation Inside Pressure Vessels.

In previous studies, difficulties were encountered in measuring changes within high-pressure vessels owing to limitations such as sensor connectors and sensor failures under high-pressure conditions. In addition, polymer-gas mixtures experience instantaneous gas desorption upon exiting high-pressure vessels owing to pressure differentials, leading to measurement errors. In this study, a device using magnetic sensors was developed to measure the real-time changes in gas-saturated polymers inside pressure vessels. Experiments on polymethyl methacrylate gas adsorption were conducted with parameters including pressure at 5 MPa and temperatures ranging from -20 to 40 °C for 60 and 180 min. It was observed that at -20 °C, the maximum magnetic field force density and deflection were 391.53 μT and 5.83 mm, respectively, whereas at 40 °C, deflection did not occur, with a value of 321.79 μT. Based on gas saturation experiments, a new model for deflection in high-pressure atmospheres is proposed. Additionally, an ANSYS analysis was conducted to predict the changes in Young's modulus based on gas saturation. In previous studies, mechanical properties were measured outside the pressure vessel, resulting in an error due to a pressure difference, while the proposed method is characterized by the ability to directly measure polymer behavior according to gas saturation in high-pressure vessels using a magnetic sensor in real time. Therefore, it is possible to predict polymer behavior, making it easy to control variables in high-pressure polymer processes.

Complex dielectric permeability and optical characteristics of polypropylene + Na-=SUP=-+-=/SUP=- montmorillonite composites

The paper presents the results of studying the frequency dependence of the real and imaginary parts of the dielectric constant of polypropylene modified with Na+ montmorillonite. Using the experimental values of the complex dielectric constant, the optical functions such as the real and imaginary parts of the refractive index, optical conductivity, reflection and absorption coefficients, the characteristic function of the electron energy losses of PP+x vol.% NaNa+ montmorillonite composites have been determined It is shown that on the basis of a high-pressure polymer with the use of Na + montmorillonite as a filler, it is possible to create composite materials with improved physical parameters. To obtain stable electrophysical properties, it is necessary to optimize the composition of the composite material and the volume of the filler. By the method of dielectric spectroscopy in the frequency course, information is obtained not only on the behavior of the complex dielectric constant, but also on the structure of the composite material, which is indispensable for the purposeful regulation of the volumetric content of the filler. Keywords: Na+-montmorillonite, polypropylene, dielectric constant, composite materials.

Комплексная диэлектрическая проницаемость и оптические характеристики композитов полипропилен + Na-=SUP=-+-=/SUP=--монтмориллонит

The paper presents the results of studying the frequency dependence of the real and imaginary parts of the dielectric constant of polypropylene modified with Na+ montmorillonite. Using the experimental values of the complex dielectric constant, the optical functions such as the real and imaginary parts of the refractive index, optical conductivity, reflection and absorption coefficients, the characteristic function of the electron energy losses of PP+x vol% Na+ montmorillonite composites have been determined It is shown that on the basis of a high-pressure polymer with the use of Na + montmorillonite as a filler, it is possible to create composite materials with improved physical parameters. To obtain stable electrophysical properties, it is necessary to optimize the composition of the composite material and the volume of the filler. By the method of dielectric spectroscopy in the frequency course, information is obtained not only on the behavior of the complex dielectric constant, but also on the structure of the composite material, which is indispensable for the purposeful regulation of the volumetric content of the filler.

High-Pressure Polymer Electrolyte Membrane Water Electrolyzers: Is It Worth It?

As a future fuel hydrogen should be stored at elevated pressure because of its low volumetric energy density. For transport in pipelines, a suitable pressure is about 200 bar. There are different paths conceivable to achieve this storage pressure. As an alternative to the conventional way of compressing the gas in external compressors subsequently, it is frequently discussed to operate electrolyzers at elevated pressure, which can save costly compressor stages. High Faraday efficiencies will be achieved by using improved materials with low permeation rates or thick membranes. However, thick membranes worsen the system performance since the decreased protonic conductivity of the cells ultimately reduces the amount of hydrogen produced. Therefore, it is recommendable to take a closer look at this context and to evaluate an optimized pressure operation depending on the application and cell parameters. In a comprehensive analytical model approach we discuss how voltage efficiency, Faraday efficiency and energy required for external gas compression are affected by a various number of system parameters. We demonstrate that the optimum gas pressure in electrolyzers is not only a function of the membrane thickness but strongly depends on the entire system configuration. To answer the question of whether high-pressure polymer electrolyte membrane electrolyzers are worthwhile both energetically and economically, our model was fed with a typical parameter set for systems based on Nafion 212 and Nafion 117. Our results demonstrate impressively why the use of thin membranes and their future development are a must for the meaningful use of PEM water electrolysis in a future energy grid.

Study on Optimization Application of Iron Ion Stabilizer in the Polymer Injection Process of Offshore Oilfield

A large amount of Fe2+/Fe3+ ions are produced by corrosion and fouling in the high-pressure polymer injection process of offshore platforms, which will affect the viscosity of the polymer solution, and is difficult to effectively control by the addition of stabilizers in the curing tank. In order to solve this problem, this paper has carried out related research and the results show that: 1) Fe2+ mainly generates free radicals (·OH) by oxidation catalysis, to destroy long chains of polymer molecules, causing irreversible fragment breakage, resulting in a significant decrease in polymer viscosity; 2) Fe3+ mainly binds to hydroxyl groups, resulting in flocculation and viscosity reduction of polymers; 3) Stabilizers with complexation can effectively control Fe3+ to form water-soluble complexes, while excess stabilizers increase salt content and reduce polymer viscosity by electrostatic shielding effect. In order to effectively control the influence of Fe2+/Fe3+ and the stabilizer on the polymer solution in the production process, an appropriate amount of complex stabilizer should be added to the diluent inlet of the mixture of the polymer mother liquor and the diluent.

Economic feasibility studies of high pressure PEM water electrolysis for distributed H2 refueling stations

In this paper, we report economic feasibility studies focusing on profitability analysis of high pressure polymer electrolyte membrane (PEM) water electrolysis for distributed H2 refueling stations in Korea. From capital and operating costs, a unit H2 production cost of 6.24 $ kgH2−1 was obtained for a H2 capacity of 700 m3 h−1, which is equivalent to handling about 300 fuel cell electric vehicles. Based on cost estimations, profitability analysis using cash flow diagrams was performed to assess the economic feasibility of high pressure PEM water electrolysis and various key economic indicators like net present value (NPV), discounted payback period (DPBP), and present value ratio were obtained for both different discount rates and capacity factors. In conclusion, employment of high pressure PEM water electrolysis was found to be economically profitable showing reasonably high NPVs (16–52 MM$) and short DPBPs (4–7 years).

The performance of armour steels with pre-layers against fragment simulating projectiles

Armour steels have proven to be promising solutions for protection against fragments from threat weapons. The area to cover for ship bulkheads is usually large, so cost of the raw material is an important driver. For new ships, additional mass can be compensated for in the design. Past research by TNO and other workers has shown that the ballistic limit V50 of armour steels against fragments is increased significantly by adding a front or pre-layer. This layer can be a variety of materials ranging from cardboard to glass. In TNO’s Laboratory for Ballistics Research a test program was conducted to study the effect of high pressure laminate, polymer and fire insulation pre-layers at the V50 and well above the ballistic limit. The high velocities are typically associated with fragments from relevant threats for warships. Fragment simulating projectiles were fired on armour steel plates of varying type and thickness with these pre-layers and measured the residual velocity and resulting hole sizes. The tests resulted in clear dependencies of the residual velocity as a function of impact velocity and pre-layer (type and thickness). Analysis of the data showed that there are several counteracting effects interacting when a pre-layer is applied to armour steel. The failure mechanism of the steel as well as the hardness and thickness of the pre-layer seem to influence the outcome of this interaction and hence the response of the steel to various pre-layers. The results of this research will be used in the design of fragment and blast resistant bulkheads for future naval ships.

High pressure polymer electrolyte water electrolysis: Test bench development and electrochemical analysis

A test bench for a polymer electrolyte water electrolysis (PEWE) cell for high pressure operation of up to 100 bar in differential and balanced pressure mode is described. Important aspects referring to the design, safety and operability of the test bench and the design of a small scale electrolysis cell are described. The electrolyzer cell comprises a special compression mechanism which allows accommodating porous transport layers of different thickness and setting of the compression pressure independent of the clamping pressure. In order to analyze the electrochemical results with respect to the overpotentials, a power source with integrated high frequency resistance (HFR) as well as electrochemical impedance spectroscopy (EIS) measurement capabilities is implemented. The versatility of the test environment is demonstrated by comparing the DC, HFR and EIS data as a function of operating pressure, temperature (up to 70 °C) and current density (up to 4 A/cm2). With respect to pressurized operation of PEWE cells, only the differential pressure mode (hydrogen pressurized) shows the expected isothermal compression behavior, for balanced pressure operation a different characteristic is observed.

Wettability Impact of Porous Current Supplier on Current Efficiency in Solid Polymer Water Electrolyzer

Introduction High pressure polymer electrolyte membrane water electrolyzer (PEMWE) is expected to efficiently produce high pressure hydrogen gas in direct manner. Couple of companies and research institutes continues to develop PEMWEs. PEMWEs can be utilized to fuel the hydrogen gas to FCV[1]. Also, PEMWEs with PEMFC can be a good candidate for load leveling of electricity between consumer demand and renewable energy.[2] However, high pressure PEMWEs, as disadvantage, have large concern on its current efficiency. Produced hydrogen gas crossovers PEM from cathode to anode, and the amount of crossover hydrogen gas directly corresponds to reduction of the current efficiency. An estimation based on the permeability suggests that current efficiency decreases up to 10 % under 40 MPa [3]. Experimental result shows 23 % reduction of current efficiency [4]. Authors have succeeded to decrease the crossover and increase the current efficiency with convection effect, where water is intentionally fed to cathode channel. This additional feeding of water promotes the drainage of hydrogen gas, leading to the 4% increase of current efficiency. However, this method suggests additional cost for a pump to feed water to cathode, although the power consumption of the pump is negligible. A further simple method is expected. This study proposes a current supplier, whose wettability is controlled so that it has hydrophobic or hydrophilic property. Carbon paper is built in a PEMWE as cathode current supplier, and experimentally evaluated if it can suppress the hydrogen gas crossover and increase the current efficiency. Also, this study conducts visualization, where the window placed in cathode separator can visualize the impact of the wettability on hydrogen gas bubble behavior. Experimental Method Experimental apparatus is shown in Fig. 1. In anode side, water is circulated, and the produce oxygen gas drains through gas/liquid separator. The water flow rate is adjusted so that electrolytic rate becomes 70 ppm. Anode side is operated at atmospheric pressure. Cathode piping has two cases, where water is circulated or not. The water flow rate in cathode is adjusted to be the same as anode case, and the operation pressure is controlled up to 2 MPa with back pressure valve. The flow meter located in the downstream of the valve measures the practically produced hydrogen gas amount, which is converted to current efficiency. The cell consists of cathode separator, cathode current supplier, CCM, anode current supplier, anode separator. Two type of the current supplier in cathode are prepared. One is carbon paper (SGL, 35AA), which has hydrophobicity with the contact angle of 135. The other one is the carbon paper, which shows the hydrophilic characteristic so that a water droplet is completely absorbed. This hydrophilic carbon paper is fabricated by the impregnation of titanium oxide into carbon paper. As anode current supplier, titanium sintered compact with Pt coating is used. CCM has Iridium oxide layer as for anode and Pt/C layer for cathode sprayed and hot-pressed on Nafion membrane. Results and discussion Figure 2 is the wettability impact of current supplier in the case of feeding water in cathode channel. Fig (a), (b) are hydrogen current efficiency and detachment frequency of the bubble, respectively. As expected, the case of hydrophilic current supplier has slightly higher current efficiency (approximately 1%). In the hydrophilic case, the current supplier actively absorbs water and may be fully saturated. This situation enhances to detach the hydrogen gas bubble from the supplier (Fig. 2 (c)), and increase the efficiency. Figure 3 is the wettability impact of current supplier without feeding water in cathode channel. Because of not feeding water, only the current efficiency is shown. Contrary to expectation, the hydrophobic supplier indicated higher efficiency (2%). In the case of not feeding water into cathode channel, the cathode current supplier is still impregnated with water, which is transported from anode by electro-osmosis flow. In this situation, gas path is thought to be formed in current supplier if it has hydrophobicity, and the path contributes to drain the produced hydrogen from catalyst layer to channel in cathode. Whereas, hydrophilic current supplier tend to saturate water, and the saturated water disturb the drainage of hydrogen gas from catalyst layer to channel. Thus, the hydrophobic current supplier indicated the higher efficiency.

A Monolithic Polyimide Micro Cryogenic Cooler: Design, Fabrication, and Test

In this paper, we present the design, fabrication, and testing of a monolithic polymer Joule-Thomson microcryogenic cooler (MCC) cold stage. The MCC cold stages were fabricated monolithically on a wafer out of polyimide. The fabrication was based on surface micromachining technologies using electroplated copper as the sacrificial layers and polyimide as the structural material. The process consisted of multilayers of metallization, coating of polyimide, and the patterning on each layer. One of the key techniques enabling this monolithic approach was the development of the wafer-level 3-D interconnect for making high pressure (e.g., 10 atm) polymer fluid microchannels. To evaluate the performance of the MCC, a five-component fluid mixture designed for cooling from 300 to 200 K was used as a refrigerant. The cold tip reached 190 K under a refrigerant pressure ratio of 6.2:1.1 bar. The heat-lift at 200 K was measured to be 5.2 mW.

Emerging Issues in the Mechanisms of High Pressure Free Radical Ethylene Polymerization: A Review

The need to improve the performance of the high pressure polymer production process, and timely introduction of new and functionalised products even at reduced production cost which is becoming critical to staying in business has given room for overall studies of the ethylene polymerization process. In this review, emerging issues in the high pressure ethylene polymerization process through free radical approach is unveiled and presented. Different views and approaches of several authors on the tasking issues were compiled, analysed and discussed. Future researchable areas were made clear in this study. Further investigations were also made to model kinetically the high pressure ethylene polymerization reaction in tubular reactors only using mass balances and moment analysis. Although not discussed in this paper, the modeling of heterogeneous polymerization reactions such as precipitation polymerization and emulsion polymerization remains a challenge.

Acoustic properties of Kel F-800 copolymer up to 85 GPa

Acoustic properties of the fluorinated copolymer Kel F-800 were determined with Brillouin spectroscopy up to pressures of 85 GPa at 300 K. This research addresses outstanding issues in high-pressure polymer behavior, as to date the acoustic properties and equation of state of any polymer have not been determined above 20 GPa. We observed both longitudinal and transverse modes in all pressure domains, allowing us to calculate the C(11) and C(12) moduli, bulk, shear, and Young's moduli, and the density of Kel F-800 as a function of pressure. We found the behavior of the polymer with respect to all parameters to change drastically with pressure. As a result, we find that the data are best understood when split into two pressure regimes. At low pressures (less than ∼5 GPa), analysis of the room temperature isotherm with a semi-empirical equation of state yielded a zero-pressure bulk modulus K(o) and its derivative K(0) (') of 12.8 ± 0.8 GPa and 9.6 ± 0.7, respectively. The same analysis for the higher pressure data yielded values for K(o) and K(0) (') of 34.9 ± 1.7 GPa and 5.1 ± 0.1, respectively. We discuss this significant difference in behavior with reference to the concept of effective free volume collapse.

Hydrogen safety aspects related to high-pressure polymer electrolyte membrane water electrolysis

Abstract Polymer electrolyte membrane (PEM) water electrolysis has demonstrated its potentialities in terms of cell efficiency (energy consumption ca. 4.0–4.2 kW/Nm 3 H 2 ) and gas purity (>99.99% H 2 ). Current research activities are aimed at increasing operating pressure up to several hundred bars for direct storage of hydrogen in pressurized vessels. Compared to atmospheric pressure electrolysis, high-pressure operation yields additional problems, especially with regard to safety considerations. In particular the rate of gases (H 2 and O 2 ) cross-permeation across the membrane and their water solubility both increase with pressure. As a result, gas purity is affected in both anodic and cathodic circuits, and this can lead to the formation of explosive gas mixtures. To prevent such risks, two different solutions, reported in this communication, have been investigated: first, the chemical modification of the solid polymer electrolyte, in order to reduce cross-permeation phenomena; second, the use of catalytic H 2 /O 2 recombiners to maintain H 2 levels in O 2 and O 2 levels in H 2 at values compatible with safety requirements.

Theoretical model and experimental analysis of a high pressure PEM water electrolyser for hydrogen production

This work aims at analysing the performances of a prototype of a high pressure Polymer Electrolyte Membrane water electrolyser. The whole work was funded in the framework of the Italian FISR (Research special supplementary funding) project. The high pressure electrolyser prototype was manufactured by Giner Inc. (Massachusetts, USA), whereas the test bench was expressly designed and built thanks to the collaboration with LAQ INTESE (High Quality Laboratory – Technological Innovation for Energetic Sustainability) and with Sapio SpA (Monza, Milan, Italy). An electrochemical model of the electrolyser stack is developed, which calculates the theoretical open-circuit voltage via a thermodynamic analysis of the process, and then obtains the expected real voltage during operation by calculating the different overvoltages as function of the current. The final result of the model is a theoretical polarisation curve. Experimental results are then presented and compared with the model theoretical results, and thanks to an experimental data fitting it is possible to obtain the estimated values of some important process parameters and their trend in different temperature and pressure conditions.

Retrofitting high-pressure polymer gear pumps for a cost-effective advantage

Today's polymer plants are always looking for ways to lower their ever-increasing operating costs. With many plants using regular maintenance and repair strategies to reduce operating costs, many plant managers should consider upgrading or retrofitting their current high-pressure polymer gear pumps to achieve lower operating costs and/or increase polymer throughputs. Stefan Kalt, global product manager for Maag Pump Systems Textron, argues the case.

Study of the reaction of Rh(acac)(CO) 2 with alkenes in polyethylene films under high-pressure hydrogen and the Rh-catalysed hydrogenation of alkenes

The thermal reaction of Rh(acac)(CO) 2 with alkenes has been studied both in the absence and in the presence of high-pressure hydrogen using in situ FTIR and polymer matrix techniques. A series of rhodium alkenes complexes, Rh(acac)(CO)(alkene) (alkene=ethene, propene, 1-butene, 1-octene and trans-3-octene), have been characterized using IR spectroscopy. In the presence of a high-pressure hydrogen, catalytic hydrogenation of alkenes was achieved using Rh(acac)(CO) 2 within the polyethylene matrix. These results suggest that this hydrogenation process follows the so-called “olefin route” operating via a sequence of ligand loss, binding of an alkene, oxidative addition of hydrogen to the rhodium metal centre, insertion of the coordinated alkene into the MH bond and finally reductive elimination of the alkane. Rh(acac)(CO) appears to be the active catalytic species in this process. High-pressure polymer matrix techniques have allowed us to unravel some of the interconversions of the catalytic species involved in this catalytic process.

A Novel High-Pressure NMR Cell Consisting of Double Tube Structure for the Convenient On-Line Measurements

Abstract We have newly developed a high-pressure polymer NMR cell, which has a versatile use for both batchwise and on-line operations. The high-pressure cell withstands temperatures and pressures, at least, up to 373 K and 35 MPa, respectively. It was demonstrated that the sample solutions of not only viscous carbon tetrachloride but also non-viscous subcritical carbon dioxide smoothly flow in and out at moderate flow rates by measuring the flow rate dependence of the longitudinal relaxation times.

High Pressure Polymerization of the Li-Intercalated Fulleride Li3CsC60

The structural features of the superconducting Li3CsC60 fulleride are studied by synchrotron X-ray powder diffraction as a function of pressure and temperature. In contrast with the behavior of Li2CsC60, Li3CsC60 shows a phase transition below room temperature from fcc (space group Fm3̄m) to an orientationally ordered primitive cubic phase (space group Pa3̄), isostructural with the metastable phases of Na2A‘C60. Despite the slow cooling protocols adopted, the system shows no other phase transitions even after prolonged standing at 200 K. The pressure dependence of the structure of Li3CsC60 at ambient temperature was followed up to 8.12 GPa. A phase transition occurs at 0.72 GPa to a low symmetry fullerene bridged polymeric phase with short center-to-center interfullerene separations of ∼9.38 Å. This phase was found to be monoclinic (space group P21/a), isostructural with the low-temperature polymer phase of Na2RbC60 and the high-pressure polymer phase of Na2CsC60. The pressure evolution of the monoclinic lattice constants reveals a highly incompressible, tightly packed, and strongly anisotropic polymeric structure.

High-pressure light scattering apparatus to study pressure-induced phase separation in polymer solutions

A new high-pressure time- and angle-resolved light scattering apparatus has been developed to study the kinetics of phase separation in polymer solutions and other fluid mixtures under pressure at near- and supercritical conditions. The system consists of a high-pressure polymer loading chamber, a solvent charge line, a variable-volume scattering cell (with a built-in movable piston connected to a pressure generator, and an expansion rod driven by an air-actuated diaphragm), and a recirculation pump which are all housed in a temperature-controlled oven. The system is operable at pressures up to 70 MPa, and temperatures up to 473 K. The scattering cell is a short path-length cell made of two flat sapphire windows that are separated by 250 μm. It is designed to permit measurements of transmitted and scattered light intensities over an angle range from 0° to 30°. A linear image sensor with 256 elements is used to monitor the time evolution of the scattered light intensities at different angles. With this sensor, the angle range from 2° to 13° is scanned at a sampling rate of 3.2 ms/scan. The pressure quenches are achieved by movement of the air-actuated movable expansion rod, or by the movement of the piston with the aid of the pressure generator to bring about either rapid (at rates approaching 2000 MPa/s) or slow pressure changes in the system. Quench depth is also adjustable, and very deep (70 MPa) or very shallow (as low as 0.1 MPa) pressure quenches are readily achievable. The temperature and the pressure of the solution in the scattering cell, and the transmitted and scattered light intensities at different angles are recorded in real time through a computerized data acquisition system before and during phase separation. The experimental system is especially suited to follow the kinetics of phase separation in polymer solutions and to assess the metastable and unstable regions where phase separation proceeds by the nucleation and growth, and the spinodal decomposition mechanisms, respectively. The capability of the instrument is demonstrated for polystyrene/methylcyclohexane solutions.

Textron Inc, USA

Today's polymer plants are always looking for ways to lower their ever-increasing operating costs. With many plants using regular maintenance and repair strategies to reduce operating costs, many plant managers should consider upgrading or retrofitting their current high-pressure polymer gear pumps to achieve lower operating costs and/or increase polymer throughputs. Stefan Kalt, global product manager for Maag Pump Systems Textron, argues the case.