Foamed Research Articles

RF Welding of Dielectric Lossless Foam Particles by the Application of a Dielectric Heatable Coating with High Recycling Potential.

Due to its chemical structure and the resulting dielectric properties, the processing of the commonly used particle foam material, expanded polypropylene (ePP), is limited. Processing within the radio-frequency welding process is therefore only possible with the use of processing aids. In this paper, a new approach for the use of a solid and dielectric heatable coating for the production of three-dimensional welded components out of ePP is presented. For this purpose, three different types of water-soluble polymer polyvinyl alcohol (PVA) were analyzed as potential coating materials. The thermal and dielectric properties of the coating were further adjusted by a modification with glycerol. The maximum amount of glycerol tested was 25% by volume. It influences both the temperature development in the radio-frequency (RF) welding process as well as the adhesive bond between the ePP foam particles. It is shown that the 120 °C approach in the RF welding process resulted in a cohesive bond between the coating layers. In this way, bonded plates can be produced. In mechanical tests with compression of 20%, the manufactured plates show sufficient load capacity. Furthermore, it can be shown that a separation of PVA and ePP by type, and thereby a separation of the foam particles, is possible with the use of hot water. This might open a new way for recycling of particle foams.

Preparation and properties of polyetherimide fibers based on the synergistic effect of carbon nanotubes and ionic liquids

AbstractPolyetherimide (PEI) has been widely applied in the form of plastics, films, and foam materials. But PEI fiber is confronted with some challenges, such as high melt viscosity and high spinning temperature during the spinning process, poor mechanical properties because of its amorphous structure. In this study, ionic liquids (ILs) and carbon nanotubes (CNTs) were used to prepare PEI composite fibers (PEI/CNT‐IL) successfully, which were further characterized by scanning electron microscope (SEM), Raman spectra, differential scanning calorimetry, dynamic mechanical analysis, thermalgravimetric analysis, mechanical property, and conductivity measurements. IL showed a plasticizing effect to reduce the processing temperature of PEI and SEM images showed that CNTs were uniformly dispersed in the PEI matrix by the assistance of IL. The synergistic effect of CNT and IL thus improved the tensile strength and antistatic properties of PEI fibers. When the contents of CNT and IL were 0.5 and 1.0 wt%, respectively, the optimal properties were obtained. PEI/CNT‐IL fibers exhibited a maximum tensile strength of 2.0 cN/dtex with the elongation at break being 90%, and the enhanced electrical conductivity of 10−5 S·cm−1, which was increased by 13 orders of magnitude compared to that of pristine PEI fiber.Highlights PEI composite fibers were prepared via melt spinning with the assistance of IL and CNT. IL can effectively disperse CNT and plasticize PEI to reduce the processing temperature. The synergistic effect of CNT and IL has improved the tensile strength and antistatic properties of PEI fibers.

Exploiting the Use of the Decarboxylative S-Alkylation Reaction to Produce Self-Blowing, Recyclable Polycarbonate Foams.

Polymeric foams are widely used in many industrial applications due to their light weight and superior thermal, mechanical, and optical properties. Currently, increasing research efforts is being directed towards the development of greener foam formulations that circumvent the use of isocyanates/blowing agents that are commonly used in the production of foam materials. Here, a straightforward, one-pot method is presented to prepare self-blown polycarbonate (PC) foams by exploiting the (decarboxylative) S-alkylation reaction for in situ generation of the blowing agent (CO2 ). The concomitant formation of a reactive alcohol intermediate promotes a cascade ring-opening polymerization of the cyclic carbonates to yield a cross-linked polymer network. It is shown that these hydroxyl-functionalized polycarbonate-based foams can be easily recycled into films through thermal compression molding. Furthermore, it is demonstrated that complete hydrolytic degradation of the foams is possible, thus offering the potential for zero-waste materials. This straightforward and versatile process broadens the scope of isocyanate-free, self-foaming materials, opening a new pathway for next-generation environmentally friendly foams.

Porous Thermal Insulation Polyurethane Foam Materials.

Porous thermal insulation materials (PTIMs) are a class of materials characterized by low thermal conductivity, low bulk density and high porosity. The low thermal conductivity of the gas enclosed in their pores allows them to achieve efficient thermal insulation, and are they among the most widely used and effective materials in thermal insulation material systems. Among the PTIMs, polyurethane foam (PUF) stands out as particularly promising. Its appeal comes from its multiple beneficial features, such as low density, low thermal conductivity and superior mechanical properties. Such attributes have propelled its broad application across domains encompassing construction, heterogeneous chemical equipment, water conservation and hydropower, and the aviation and aerospace fields. First, this article outlines the structure and properties of porous thermal insulation PUF materials. Next, it explores the methods of preparing porous thermal insulation PUF materials, evaluating the associated advantages and disadvantages of each technique. Following this, the mechanical properties, thermal conductivity, thermal stability, and flame-retardant characteristics of porous thermal insulation PUF materials are characterized. Lastly, the article provides insight into the prospective development trends pertaining to porous thermal insulation PUF materials.

Exploiting the Use of the Decarboxylative S‐Alkylation Reaction to Produce Self‐Blowing, Recyclable Polycarbonate Foams

AbstractPolymeric foams are widely used in many industrial applications due to their light weight and superior thermal, mechanical, and optical properties. Currently, increasing research efforts is being directed towards the development of greener foam formulations that circumvent the use of isocyanates/blowing agents that are commonly used in the production of foam materials. Here, a straightforward, one‐pot method is presented to prepare self‐blown polycarbonate (PC) foams by exploiting the (decarboxylative) S‐alkylation reaction for in situ generation of the blowing agent (CO2). The concomitant formation of a reactive alcohol intermediate promotes a cascade ring‐opening polymerization of the cyclic carbonates to yield a cross‐linked polymer network. It is shown that these hydroxyl‐functionalized polycarbonate‐based foams can be easily recycled into films through thermal compression molding. Furthermore, it is demonstrated that complete hydrolytic degradation of the foams is possible, thus offering the potential for zero‐waste materials. This straightforward and versatile process broadens the scope of isocyanate‐free, self‐foaming materials, opening a new pathway for next‐generation environmentally friendly foams.

Modelling Porous Cementitious Media with/without Integrated Latent Heat Storage: Application Scenario

This paper presents a methodological approach for the evaluation of the thermal behavior of cementitious porous media with/without integrated latent-heat thermal energy storage (LHTES). To achieve this goal, the Lewis-Nielsen model has been calibrated to predict the insulation properties of mineralized foamed concretes. Two pore-related microstructural fitting parameters, A and Φm, are presented according to the available data in the literature. In this regard, new findings are implemented for the classification of pore structure and prediction of the homogenized thermal conductivity of two-phase cementitious foams with or without phase change materials. The calibration and predictive analyses have been extended to a wide range of experimental data, including variation of binder types, porosities, and latent components. The presented analytical approach appears to agree well with experimental results and can be employed in the design of two-phase mineral foam materials. Then, to assess the thermal behavior of the predicted insulating envelopes, a one-dimensional (1D) enthalpy-based model is used which combines Fourier’s law of heat conduction, the first law of thermodynamics, Lewis-Nielsen conductivities, and the mixture theory for LHTES additions. The results demonstrated the importance of volumetric heat capacity for the thermal inertia of building envelopes.

All-in-one self-floating porous foams as robust heat-blocking layers for efficient photothermal conversion and solar desalination

Solar-driven interfacial evaporation is a highly efficient and ecofriendly technology for producing freshwater. Herein, self-floating plasmon Ag/black TiO2/carbon porous layered foams (Ag-BTCFs) were demonstrated as efficient solar-thermal convectors using freeze-drying cast-molding and high-temperature surface hydrogenation strategies. This all-in-one three-dimensional (3D) cross-linked self-floating porous layered foam material with full-spectrum absorption can fully harvest sunlight (∼95.45%) and effectively block heat transfer to its sublayer. The synergy of sufficient utilization of absorbed ultraviolet radiation by black TiO2 (b-TiO2), visible light absorption by Ag nanoparticles (Ag NPs) via localized surface plasmon resonance, and near-infrared absorption by layered-amorphous carbon can achieve full-solar-spectrum absorption to concentrate thermal energy. In addition to their synergistic effect, they are conducive to the relaxation of hot electrons when utilizing photogenerated holes to degrade pollutants in domestic wastewater. The steam generation efficiency of Ag-BTCFs is up to 1.79 kg m−2h−1 due to their solar energy conversion efficiency of 81.74% under 1 sun irradiation, which is five times higher than the evaporation rate of pure water. Notably, the material’s efficient ion removal rate of 99.80% for solar desalination indicates its high potential for various applications. This strategy provides new insights for fabricating recyclable heat-blocking layer systems against thermal loss to enhance solar steam generation.

Fire-Retardant Composite Foam with Antioxidant Addition for Prevention and Control of Coal Spontaneous

ABSTRACT Given the shortcomings of existing fire-extinguishing materials, a new type of fire-retarding foam material with composite foaming agents and antioxidants as raw materials was developed. The formula of the composite foaming agent was determined by screening and compounding surfactants. Then, the inhibition characteristics of different antioxidants were tested using a cone calorimeter to determine the best antioxidant. Next, the inhibition characteristics and fire-extinguishing and cooling characteristics of fire-retarding foam were measured by a temperature programmed apparatus and a fire-extinguishing test bench. Results show that the prepared fire-retarding foam achieves the best performance when the mass ratio of the surfactants CAB-35 and MES is 2:3, the mass concentration is 0.4%, and the mass concentration of the tea polyphenols is 1%. In the aspect of low-temperature inhibition, the cross-point temperature of the fire-retarding foam increases from 119.4°C of raw coal to 142.7°C, which is 15.4°C and 6.5°C higher than that of ordinary foam and MgCl2 solution, respectively. At 180°C, the CO concentration is only 1613 ppm, which is about 67.3% of that of raw coal, 78.3% of that of coal treated with ordinary foam, and 85.8% of that of coal treated with MgCl2 solution. The fire-extinguishing times of common foam, MgCl2 solution, and fire-retarding foam are 1780 s, 1350 s, and 820 s, respectively, indicating that fire-retarding foam has the highest fire-extinguishing efficiency.

In vitro prevention and inactivation of biofilms using controlled-release iodine foam dressings for wound healing.

Microbial biofilms are a major hindrance in the wound healing process, prolonging the inflammatory response phase, thus making them a target in treatment. The aim of this study is to assess the antibacterial properties of commercially available wound dressings, of various material composition and antibacterial agents, towards multiple in vitro microbial and biofilm models. A variety of in vitro microbial and biofilm models were utilised to evaluate the ability of wound dressing materials to sequester microbes, prevent dissemination and manage bioburden. Sequestering and dissemination models were used to evaluate the ability of wound dressing materials to prevent the biofilm-forming bacterium, Pseudomonas aeruginosa, from migrating through dressing materials over a 24-72 h challenge period. Additionally, Centre for Disease Control (CDC) Bioreactor and Drip Flow models were used to evaluate antibacterial killing efficacy towards established P. aeruginosa and Staphylococcus aureus biofilms using more challenging, wound-like models. Controlled-release iodine foam and silver-impregnated carboxymethylcellulose (CMC) wound dressing materials demonstrated potent biofilm management properties in comparison to a methylene blue and gentian violet-containing foam dressing. Both the iodine-containing foam and silver-impregnated CMC materials effectively prevented viable P. aeruginosa dissemination for up to 72 h. In addition, the controlled-release iodine foam and silver-impregnated CMC materials reduced P. aeruginosa bioburden in the Drip Flow model. The controlled-release iodine foam demonstrated superiority in the CDC Bioreactor model, as both the silver- and iodine-containing materials reduced S. aureus to the limit of detection, but P. aeruginosa growth was only completely reduced by controlled-release iodine foam dressing materials. The data generated within the in vitro biofilm models supports the clinical data available in the public domain for the implementation of iodine foam dressings for effective biofilm management and control in wound care.

Design and evaluation of compressive properties of 3D-printed PLA stochastic open-cell foam

The deformation characteristics and mechanical behaviour of 3D-printed stochastic open-cell foam structures were experimentally studied under a quasi-static compression test. PLA foam specimens with irregular cell geometry, variable strut sections and prescribed relative density are constructed numerically using the Voronoi diagrams and prepared with fused deposition modelling. The design procedure allows controlling the strut topology easily, which makes the geometrical model suitable for studying the effect of local morphological characteristics on the mechanical performance of open-cell foam material. The effect of different morphological characteristics on the compressive mechanical behaviour of the fabricated PLA foam was examined in detail. Compression experiments prove that the mechanical properties are significantly dependent on the relative density and strut section shape. The main mechanical properties of the 3D-printed PLA foams for different cross-sectional shapes of struts were obtained via the energy-efficient method and expressed with the two common formulas existing in the literature.

Influence of Activated Carbon Concentration on Foam Material Properties: Design and Optimization

Influence of Activated Carbon Concentration on Foam Material Properties: Design and Optimization

A novel foam process with CO2 dissolved surfactant for improved sweep efficiency in EVGSAU field

A successful CO2-foam gas conformance enhancement technology pilot has operated at the East Vacuum Grayburg San Andres Unit (EVGSAU) since Jan 2018 by ConocoPhillips in cooperation with Dow. In early 2020, the scope of the pilot was expanded from one pattern to three patterns. The expansion phase was implemented to evaluate scalability of this technology to patterns with diverse conformance issues and productivity inefficiencies. Severe vertical and areal conformance issues were initially identified in these patterns, resulting in early gas breakthroughs and poor oil sweep efficiencies. Due to economic success of the first phase, the same surfactant with high foaming tendencies, high gas solubility, and low adsorption characteristics was implemented in the new patterns.The first phase of foam implementation on an inverted pattern showed a complete elimination of out-of-zone injection, redistribution of CO2 into previously un-swept flow intervals, and oil production uplift.In contrast to this first pattern, the gas injectivity was reduced by 20–50% after only two foam cycles in the new patterns. Based on injection profile logs (IPL), no out-of-zone injection was identified before the surfactant injection for the two new patterns, which can be the reason for such rapid injectivity responses. Similar to the first pattern, deep conformance corrections were confirmed as gas was redirected from highly connected producers to other producers within the new patterns. A lower surfactant dosage was applied to one of the new patterns to optimize chemical consumption, while sustaining the performance. The surfactant concentration was also reduced in the first pattern to study the effect of a lower dosage on a known performing pattern. During the foam implementation, the gas to water ratio (GWR) at the pattern injectors was increased to maintain the patterns at the baseline total fluid throughput. This adjustment resulted in more than a 50% reduction in water consumption and a 17% improvement in gas utilization. Overall, a sustainable increase in oil production rate (∼35% over the baseline for the last two years) was achieved in the three foam patterns. This robust solution of gas conformance enhancement required ∼2 lbs. of foaming material per barrel of incremental oil produced, which confirms economic success and commercial viability of the foam technology for a full field-scale implementation.The application of this foam technology has potential to extend the life of a mature asset like EVGSAU by arresting the historical decline in the oil production rate. Reduction in energy and water consumption per barrel of oil produced make the CO2-EOR process more sustainable and strengthen its potential in carbon capture, utilization and sequestration (CCUS) application.

A Mathematical Model Relating Foam Material Properties to Heightened Interface Pressure between a Human and Mattress Surface

Hospital patients often develop pressure injuries when lying in bed for an extended time due to relatively high contact pressures breaking down skin tissues. Pressure injuries adversely affect patients by potentially leading to infection and creating advanced health risks. Our prior research identified children experience highest risk of pressure ulcer in the head region. Thus, this study aimed to gather pressure data and create a corresponding model relating foam material properties to predicted interface pressure between the head and a foam mattress overlay surface. Research findings provide data guiding clinicians and designers to mattresses with material properties capable of reducing the incidence of pressure ulcers in children and adults.

NUMERICAL AND EXPERIMENTAL INVESTIGATION OF SEMICIRCULAR SOLAR UPDRAFT TOWER SYSTEM EMPLOYING POROUS COPPER METAL FOAM

The numerical and experimental study was carried out under Iraqi weather conditions to verify the improvement of the performance of the solar updraft tower system SUTS by introducing porous metal foam as a heat-absorbent plate. a semicircular basin of the solar collector was divided into two equal identical quarters. A porous foam material was fixed on one of the basins while the other basin was fixed on a traditional copper plate. The positions of the metal foam absorber plate are changed with two inclination angles (0֯ and 18֯) and the optimum position is achieved when it gives the highest thermal performance. A finite volume modeling technique is used to solve the governing equations and radiation heat transfer equations by using ANSYS Fluent. The experimental part was conducted in Baghdad / Iraq at latitude 33.3°. The presence of the metal foam absorber plate caused a significant decrease in the average temperatures of the heat-absorbent plate. The maximum airflow temperature was recorded with an inclined angle of 18◦. The metal foam as a heat-absorbent plate enhanced the efficiency and the output power of the SUTS to about 51.9% and 47.2% respectively compared to the traditional plate.

Toxic Effects and Mechanisms of Polybrominated Diphenyl Ethers.

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants used in plastics, textiles, polyurethane foam, and other materials. They contain two halogenated aromatic rings bonded by an ester bond and are classified according to the number and position of bromine atoms. Due to their widespread use, PBDEs have been detected in soil, air, water, dust, and animal tissues. Besides, PBDEs have been found in various tissues, including liver, kidney, adipose, brain, breast milk and plasma. The continued accumulation of PBDEs has raised concerns about their potential toxicity, including hepatotoxicity, kidney toxicity, gut toxicity, thyroid toxicity, embryotoxicity, reproductive toxicity, neurotoxicity, and immunotoxicity. Previous studies have suggested that there may be various mechanisms contributing to PBDEs toxicity. The present study aimed to outline PBDEs' toxic effects and mechanisms on different organ systems. Given PBDEs' bioaccumulation and adverse impacts on human health and other living organisms, we summarize PBDEs' effects and potential toxicity mechanisms and tend to broaden the horizons to facilitate the design of new prevention strategies for PBDEs-induced toxicity.

Various homogenisation schemes for vibration characteristics of axially FG core multilayered microbeams with metal foam face layers based on third order shear deformation theory

This study assesses the significance of homogenisation models in theoretically analysing the vibrations of three-layered microbeams with a core composed of axially functionally graded (AFG) material and with upper and lower face layers composed of metal foam material, especially when the third order shear deformation beam theory and the modified couple stress theory are used. The material of the core is assumed to vary following a power gradation profile. The range of homogenisation schemes, including the Voigt model, Reuss model, Voigt-Reuss-Hill model, Tamura model, Mori-Tanaka model, lower and upper bounds of Hashin-Shtrikman, and the local representative volume element (LRVE) model, are utilised to approximate the material properties of the AFG core. The upper and lower layers of metal foams are modelled using the closed-cell and open-cell solid porosity models. The coupled motion equations are solved for the natural frequencies of the system for the transverse, rotational and axial directions. A software-based finite element analysis (FEA) study of two simplified macrobeam systems was undertaken and the agreement between the FEA and numerical results, using the presented theoretical method, is found to be excellent. It has been confirmed that the homogenisation schemes have a notable effect on the mechanical properties of the AFG core, and hence on the coupled translational-rotational motion's natural frequencies. The largest difference in natural frequencies between different homogenisation schemes is found with a power gradation constant of approximately 0.53. A larger disparity of natural frequencies between different homogenisation methods was seen with an increase in the thickness of the AFG core and the microbeam's length-scale parameter of multilayered porous microbeam. The results of this study highlight the significance of homogenisation scheme employed when investigating the vibrations of a multilayered microbeam with an AFG core and metal foam porous face layers.

Effect of viscosity on foaming behavior and surface quality of foamed Polyamide 6

AbstractAlthough a large body of literature has reported that PA6 modification enhances melt strength and improves foam quality, the relationship between melt viscosity and foaming quality remains ambiguous. This paper aims to select four PA6 with different viscosities to explore the effect of the viscosity of the material on foaming quality. First, the foamed materials of four PA6 were prepared by core‐back injection foaming technology. In addition, the crystallization properties and rheological behavior of four PA6 were systematically studied by rotational rheometer and differential scanning calorimetry. The morphologies of composite foams with different viscosities were analyzed using scanning electron microscopy. It was found that the cell size and cell density of M2400 with low viscosity were 114 μm and 1.87 × 105 cells/cm3, respectively. With the increase of viscosity, the cell size and cell density of M2500I decreased to 98.3 μm and 2.66 × 105 cells/cm3, respectively. However, as the viscosity continues to increase, the cell size increases, and the cell density decreases. The findings indicate that the secret to good foaming is rheological behavior. The lower viscosity is challenging to prevent cell growth and easy to break, while high viscosity causes poor fluidity which deteriorates foaming quality and surface quality. It provides guidance for preparing foaming materials with excellent performance and surface through a modification that enhances melt strength.

Interaction of shock wave with closed cell foams: Effect of foam material, microstructure, and specimen configuration

This article discusses the experimental investigation of the dynamic mechanical behavior of polyethylene (PE) foam under shock wave loading. The experiments were conducted using a two-stage light shock tube, and the dynamic response of the foam was characterized by measuring the pressure wave transmitted through the foam and the load on the foam specimen using a pressure sensor and a load cell, respectively. High-speed imaging was also used to capture the deformation of the foam specimen during the shock loading. The results show that the deformation of the foam under shock wave loading is non-uniform along the length of the specimen and is influenced by the presence of metal plates inserted along the length of the foam specimen. The degree of compression of the foam specimen was quantified and found to depend on the number of segments and the presence of metal caps on the specimen. The results provide insight into the mechanical behavior of PE foam under dynamic loading conditions and can be useful for designing protective structures for impact and blast resistance applications.

Failure prediction of syntactic foam core L-shaped sandwich structures

L-shaped laminates with a syntactic foam core were manufactured to investigate the bending behavior of the sandwich structures including sharp corners. The bending behavior, initial, and progressive failure modes of the sandwich structure were analyzed by four-point bending tests and the finite element method. The cohesive zone model and Hashin’s failure criteria were used for inter-laminar and intra-laminar failure of the laminates, respectively. The concrete damage plasticity model was proposed to model the foam material with considering different material properties in tension and compression. Mode-I and Mode-II fracture toughness of the foam was obtained to characterize the foam/laminate interface. Load-displacement curves predicted under bending simulation were quite well compliant with experimental results. The difference between numerical and experimental failure loads was 10.6 %, 1.2 %, and 1.9 % for the foam with facesheet stacking sequence of [0/90]2s, [0/90]3s, and [0/45/-45/90]2s, respectively. Predicted radial and hoop direction strain fields in the foam section were also compared to the measured one using a digital image correlation technique. Strain fields and failed regions and their mechanisms were captured well using the model. The initial failure mechanism was delamination at the interface between the foam and facesheet followed by foam tensile fracture.

Thermodynamic study on the effect of foaming on the heat and moisture control ability of humidity control material

This study mainly investigates the effects and evaluation method of foaming on the thermodynamic treatment capacity of moist air of the humidity control materials. Firstly, the experimental results show that the foaming can increase the maximum adsorption to 1.2 times, the moisture buffering to 1.39 times, the water vapor permeability to 1.09 times, and the thermal insulation to 1.48 times, which indicates that foaming can help the humidity control materials have a better ability to treat the moist air and response the change of environment. Secondly, correlation analysis results indicate that foaming can change the pore structure, such as the specific surface area and average pore diameter, which are closely related to each properties. And the porosity also is a key parameter that can reflect the characteristics of the foaming materials. Thirdly, due to the decline of mechanical performance always come up with foaming, this study proposes a new evaluation method that can be used to compare the comprehensive performance of the foaming humidity control materials, so that this kind of foaming process can be used in buildings with different purposes. The new evaluation method, i.e., the dimensionless comprehensive performance evaluation method, its reliability and effectiveness can be verified by sensitivity analysis. In general, this work shows that the reasonable use of the foaming can be an effective way to improve the adaptability of hygroscopic materials, which can effectively control the indoor environment and help to achieve the goal of building energy conservation, and this study also can give the guides for the material design and optimization.