Strength Of Foams Research Articles

Preparation of lightweight polycarbonate composite foams with robust hollow glass microspheres via CO2 foaming

AbstractPolycarbonate (PC) composites are often used in the production of high value‐added products, but it is necessary to improve its environment stress cracking condition in the presence of pre‐strain and soluble solvents. In this work, the effect of weight reduction and strengthening is realized by introducing microstructures and hollow glass microspheres (HGMs) into the PC composites. It is found that the addition of HGMs can reduce the melt viscosity and Tg value of the composite materials, which will change the foaming behavior of PC/HGMs composites. Besides, the effect of different content of HGMS and foaming temperature on the foaming behavior of PC/HGMs composite foams are studied. The PC/HGMs composite foams exhibit a typical structure of both large and small cellular pores, because of the existence of hollow beads and cellular structures. Moreover, compared to the neat PC foam, the tensile strength as well as the flexural strength of the composite foams are significantly increased by 110.9% and 364.7%, respectively. Furthermore, the as‐prepared PC/HGMs composite foams have low thermal conductivity (lower than 0.07 W/mK), which can effectively insulate heat propagation.Highlights Hollow glass microsphere can reduce melt viscosity and Tg of composites. The mechanical properties of composite foams have been greatly improved. Composite foams exhibit excellent thermal stability due to their microstructure.

Enhancing the Strength, Electrical Properties and Versatility of Epoxy Polymer Composite Foam with Carbon Nanostructures

Enhancing the Strength, Electrical Properties and Versatility of Epoxy Polymer Composite Foam with Carbon Nanostructures

Ultrahigh compressive strength and heat resistance of polystyrene/polyphenylene oxide foams of supercritical carbon dioxide foaming

AbstractPolystyrene (PS) foam materials are lightweight, but suffer from poor compressive strength and heat resistance, among other problems, which limit their application. Herein, a method for preparing PS foam with high compressive strength and high heat resistance using supercritical CO2 is proposed. PS/polyphenylene oxide (PPO) blends were prepared using a corotating intermeshing twin‐screw extruder. The results showed that PPO exhibited excellent molecular‐level compatibility with PS, which substantially improved mechanical properties and heat resistance of PS. Foam samples of PS/PPO blends with the same expansion ratio were prepared via batch foaming experiments, and the compressive strength of different foams was determined at different temperatures. At room temperature, the compressive strength of the PS/PPO‐30% foam increased by 173% compared with pure PS foam. As the testing temperature increased from 30 to 120°C, the compressive strength of pure PS foams decreased rapidly. Nevertheless, PS/PPO foams maintained high compressive strength at high temperatures.

Compressive Strength and Morphology of Rigid Polyurethane Foam for Road Applications

Compressive Strength and Morphology of Rigid Polyurethane Foam for Road Applications

The effects of wettability and permeability on hydrocarbon foam performance in unconsolidated porous media: An experimental investigation at elevated pressure and temperature conditions

Propped fractures in hydraulically fractured reservoirs function as unconsolidated porous media with permeability orders of magnitude greater than the matrix. This disparity in permeabilities leads to poor conformance control and sweep efficiency. The foam generated inside the fractures can be effective in addressing such challenges. It can reduce the gas mobility and enhancing the fracture-matrix interactions. However, the foam performance is influenced by the wetting conditions and pore space properties of the porous medium. In this work, for the first time, the effect of a complex interplay between permeability and wettability on hydrocarbon foam performance was investigated in unconsolidated porous media. To this end, methane foam experiments were conducted on sandpacks of varying wettability and permeability at high-pressure and high-temperature conditions. Additionally, interdependence between permeability and key foam parameters, including surfactant concentration and foam quality, were probed. Foam performance was evaluated based on the steady-state pressure drops across the medium and the foam’s apparent viscosity. The results showed a non-monotonic dependency of foam strength on the permeability of porous media, irrespective of their wetting conditions. We observed that foamability and foam stability were significantly enhanced at ascending permeability due to enlarged pores and pore-to-throat ratios, leading to reduced gas mobility. However, excessively large pore bodies adversely affected the bubble generation and downgraded the foam performance. Furthermore, foam quality significantly influenced the foam performance at all permeabilities. Distinct foam behavior was observed vis-à-vis variations in foam quality and separated by the low- and high-quality regimes. The results showed a modulated correlation between steady-state foam strength and permeability throughout the low-quality regime; however, no common trends were observed in the high-quality counterpart. Additionally, the transition foam quality was higher in oil-wet media than in water-wet systems. This shift broadened with ascending permeability and can be attributed to the wettability of porous media. Interestingly, variations in surfactant concentration produced similar trends in all wettability cases and displayed insensitivity to permeability. The results indicate that an increase in concentration improved the viscoelastic properties of the aqueous films, improving the foam strength in water- and oil-wet media of all permeabilities.

Cellulose rubber foam composite use as oil absorbent

The focus of this study was to explore the fabrication of cellulose rubber foam (CRF) using kapok fibers (KF) as an oil absorbent material. Chemical methods such as sodium hydroxide surface treatment, hydrogen peroxide treatment, and acid hydrolysis were employed to prepare cellulose nanocrystals (CNC). The results of the nuclear magnetic resonance (NMR) spectroscopy test indicated that the chemical modification of kapok fiber resulted in the removal of lignin and hemicellulose by a disappearing peak at 17, 52, and 148 ppm, respectively. Hydrolysis process of the kapok fiber resulted in nanometer-sized cellulose, with a yield of 72% as revealed by transmission electron microscopy (TEM). The amount of cellulose nanocrystals from kapok fiber (KF-CNC) used in the study varied from 0 to 5 phr during the formation of the cellulose rubber foam, and it was found that the foam density increased as the number of cellulose nanocrystals from kapok fiber increased. Additionally, the percentage of collapse from the compressive strength of cellulose rubber foam decreased as the amount of cellulose nanocrystals from kapok fiber increased. Fourier transform infrared spectroscopy (FTIR) confirmed the incorporation of cellulose nanocrystals from kapok fiber into the rubber foam (RF) as the amount of cellulose nanocrystals from kapok fiber increased. The oil absorbent of cellulose rubber foam composite with 1 phr cellulose nanocrystals from kapok fiber show highest absorption capacity was 17.8 g/g. The cellulose rubber foam composite absorbs oil before absorbing water when water and oil are combined. Moreover, the cellulose rubber foam could be reused more than 50 times.

Tensile strength and damage of open-cell ceramic foams under cylindrical splitting test

Tensile strength and damage of open-cell ceramic foams under cylindrical splitting test

Effect of curing agents and hollow glass microspheres on the compression properties of syntactic foams

To investigate the compression properties and failure mechanisms of syntactic foams, two different resin matrices and three types of hollow glass microspheres (HGMs) were used to prepare syntactic foams with different properties. Results showed that the compression strength of syntactic foams increases with the increase in the compression strength of HGMs or resin matrix. Low-strength HGMs will be the first to break down as a source of cracks under stress. When the stress value exceeds the compression strength of the matrix, the matrix will deform and break, leading to the overall destruction of syntactic foam. High-strength HGMs not only act as a lightweight filler but also act as a reinforcing phase to improve the strength of the syntactic foam. The matrix located at the interface will experience initial cracking when subjected to stress, becoming the origin of subsequent cracks. Consequently, the weaker part between the HGMs and the matrix will be the initial point of failure, resulting in the formation of a crack source. The failure of the matrix will ultimately result in the complete destruction of the syntactic foam.

Structure–Property Correlation in Natural Rubber Nanocomposite Foams: A Comparison between Nanoclay and Cellulose Nanofiber Used as Nanofillers

Nanocomposite foams of natural rubber (NR) with 5 phr of two kinds of nanofillers, nanoclay (NC) and cellulose nanofiber (CNF), were produced using the latex mixing method and foaming with azodicarbonamide. The effect of the nanofiller on the structure and mechanical properties of NR foams was investigated through SEM, TEM, tensile tests, WAXD, and compression set measurements. Smaller cells with a narrower distribution were attained in the NC/NR foam when compared to the NR and CNF/NR foams, and the expansion ratio was larger due to the suppression of the shrinkage in the NC/NR foam. The foaming of the NR nanocomposites reduced the size of the filler aggregates and improved the dispersion and alignment of nanofillers in the cell walls. The addition of NC and CNF enhanced the tensile strength of the NR foam by 139% and 62%, respectively, without sacrificing the excellent strain of the NR, due to the acceleration of the strain-induced crystallization and small size of the filler aggregates. The compression set of the NR foam could also be reduced in the NC/NR foam compared with the NR and CNF/NR foams.

High‐pressure high‐temperature fluid displacement by foam injection within a multiblock matrix‐fracture system

AbstractFoam injection has been suggested and demonstrated as a potential gas‐based solution for enhancing oil recovery from underground reservoirs. While the pore‐scale behavior of foam has been investigated for many years, most of those studies were done at room temperature and pressure. A high‐pressure high‐temperature (HPHT) cell was constructed to relax this contributing simplification and evaluate foam behavior under reservoir conditions. The performance of foam injection into a fractured reservoir was investigated experimentally at vertical and horizontal pathways utilizing a 2D microfluidic device. The results showed foam had a higher lamellae density in the fracture network and could direct fluids to the matrix. This was mainly attributed to the created pressure drop in the fractured media dictated by foam self‐tuning ability, which is a higher viscosity in areas with higher conductivity. Generating a viscous crossflow in horizontal tests leads to enhanced recovery relative to gas injection. But the presence of gravity in the vertical tests causes the drainage of the foam film and the segregation of the gas and surfactant solution due to gravity, which ultimately reduces the stability of the foam. Comparing the performance of gas and foam in the vertical injection scenario reveals that foam injection results in a considerably more enhanced oil recovery. The oleic phase had a detrimental impact on foam strength and reduced fluids diversion from fracture to matrix. The sizes of gas bubbles were also larger in the presence of the oleic phase.

The Effect of Multiple Cycles of Surfactant-Alternating-Gas Process on Foam Transient Flow and Propagation in a Homogeneous Sandstone

Summary Years of laboratory studies and field tests show that there is still uncertainty about the ability of foam to propagate deep into a reservoir. Many factors have been identified as potential causes of nonpropagation, the most concerning being the lack of sufficient pressure gradient required to propagate foam at locations far from the point of injection. Most researchers that investigated foam propagation did so by coinjecting surfactant and gas. Coinjection offers limited information about transient foam processes due to limitations in the experimental methods needed to measure foam dynamics during transient flow. Foam injection by surfactant-alternating-gas (SAG) has proven to be more effective and common in field application. Repeated drainage and imbibition cycle offer a more favorable condition for the quick generation of foam. Foam can also be propagated at a lower pressure gradient in SAG mode. The objective of this study is to experimentally investigate how transient foam dynamics (trapping, mobilization, and bubble texture) change with multiple cycles of SAG and also with distance from the point of injection. A pair of X-ray source and receiver, differential pressure transducers, and electrical resistance sensors were placed along a 27-cm long, homogeneous, and high-permeability (KL = 70 md) Berea sandstone core. Foam was then generated in situ by SAG injection and allowed to propagate through the core sample under a capillary displacement by brine (brine injection rate = 0.5 cm3/min, Nca = 3×10-7). By use of a novel analytical method on coreflood data obtained from axial pressure and saturation sensors, we obtained trapped foam saturation, in-situ foam flow rates, apparent viscosities, and inferred qualitative foam texture at different core sections. We then observed the following: (i) Maximum trapped foam is uniform across the core sections, with saturation ranging from 47% to 52%. At the vicinity of foam injection, foam apparent viscosity is dominantly caused by gas trapping. At locations farther away, foam apparent viscosity is dominated by both gas trapping and refinement of foam texture. (ii) Cyclic injection of foam further enhances the refinement of foam texture. (iii) Textural refinement increases foam apparent viscosity as it propagates away from the point of injection. (iv) As the foam strength increases, the average gas flow rate in the core sample decreases from 0.5 cm3/min to 0.06 cm3/min. (v) There is no stagnation of foam as remobilization of trapped gas occurs during each cycle at an average flow rate of 0.002 cm3/min.

Tensile properties of transversely isotropic closed-cell PVC foam under quasi-static and dynamic loadings

The uniaxial tensile mechanical properties of PVC foam considering the effects of strain rate ([Formula: see text]) and anisotropy ([Formula: see text]) have been investigated by quasi-static and dynamic (Split Hopkinson Tensile Bar, SHTB) tests. Combined high-speed camera system and Digital Image Correlation (DIC) technique, the real-time surface strain field of the specimen during the whole tensile process was obtained. On this basis, the macroscopic response and failure mode of PVC foam were investigated. The failure mechanism of PVC foam under tensile loading was revealed through Scanning Electron Microscope (SEM) images on fracture cross-section of loaded specimen. Finally, based on experimental data, a prediction equation on tensile strength of PVC foam considering the effects of strain rate and loading angle (anisotropy) is proposed. Furthermore, a nonlinear constitutive model is developed to describe the uniaxial tensile mechanical properties of PVC foam.

Approximative approach to optimize concrete foaming concentration in two stage foaming

The article presents the results of a study on foam concentration for the production of foam concrete using a two-stage foam introduction method. The research was conducted by evaluating the strength and density of foam concrete samples manufactured using both the proposed and conventional methods. The optimal composition was determined through several iterations, considering adjustments to the overall quantity of foaming agent and the water-cement ratio. The study revealed that the two-stage foam introduction method enhances the strength properties of foam concrete by promoting the formation of a more uniform porous structure within the material. The initial introduction of a low-concentration foam solution in water creates favorable conditions for the subsequent introduction of a high-concentration foam solution, serving as a structural-forming component. The optimal approach for achieving a stable porous structure involves an initial foam introduction of 15% and a subsequent introduction of 85%. Furthermore, the research highlights the nuances of the relationship between foam concentration, strength, and density of foam concrete, offering deeper insights into the structural properties of the material. The effectiveness of the proposed methodology is substantiated by the achieved technological solution, which provides a pragmatic approach to enhancing the efficiency of foam concrete production through precise foam concentration at both the initial and subsequent stages of the manufacturing process.

Analysis of the effects of region and direction on the mechanical strength of polyurethane foams in white goods refrigerators

This research focuses on investigating the mechanical properties of polyurethane foam, specifically in the context of the refrigeration industry. Tensile, compression, and flexural tests were conducted to gather comprehensive data on the foam's mechanical behavior under various loading conditions. Samples were collected from different regions within a specific cabinet model to analyze the effects of region and direction of the foam growth on the foam's mechanical properties. The results revealed that samples collected from the top of the cabinet exhibited superior performance compared to those obtained from the bottom. The foam demonstrated isotropic behavior under compression, while exhibiting anisotropic behavior under tensile and flexure. When aligned parallel to the foam growth, the foam displayed slightly higher maximum stress in the tensile and flexural tests. However, the compression test showed comparable strength in both directions. These findings contribute to a better understanding and utilization of PU foam in various industrial sectors, particularly in refrigeration. The data obtained from this research can support the optimization of project designs and facilitate the development of more efficient and economically viable solutions.

Synergistic effect of thermoplastic polyester elastomer and polytetrafluoroethylene in situ fibrillation on the resilience and compression strength of long‐chain branched polypropylene foam

AbstractExcellent resilience and compression resistance are the key characteristics of cushioning and water–oil separation materials. Although polypropylene (PP) offers excellent performance and affordability of PP, it exhibits poor resilience. To address this shortcoming, polymer blends with long‐chain branched PP (LCBPP), thermoplastic polyester elastomer (TPEE), and polytetrafluoroethylene (PTFE) were prepared via melt blending, and their mechanical properties were tested. The LCBPP/TPEE/PTFE composites were subjected to physical foaming using supercritical CO2 (scCO2) as the blowing agent. The synergistic toughening mechanism of the elastomer/nanofiber and the effect of the structure and crystallization of the dispersed phase on the foam resilience and foam compression strength were investigated. The results revealed that fibrous PTFE and spherical TPEE formed a composite dispersed phase in LCBPP. The impact and tensile strengths of the unfoamed LCBPP were found to have been simultaneously optimized owing to the synergistic effect of the elastomeric toughening of TPEE and the reinforcement of the PTFE fiber–induced fibrous crystal structure. Compared with pure LCBPP, the impact strength of the LCBPP/TPEE/PTFE composite increased by 216%, whereas its tensile strength decreased by only 6%. In particular, the synergistic effect of TPEE/PTFE improved the resilience and compression strength of the LCBPP foam. Compared with the pure LCBPP foam, the permanent strain of the LCBPP/TPEE/PTFE foam was reduced by 13.8% after five cycles of compression and its compression strength increased by 27.3%. The experimental results of our study could be used to prepare LCBPP foams with exceptional resilience, high compression strength, and good application prospects.

Pore-level Ostwald ripening of CO2 foams at reservoir pressure

The success of foam to reduce CO2 mobility in CO2 enhanced oil recovery and CO2 storage operations depends on foam stability in the reservoir. Foams are thermodynamically unstable, and factors such as surfactant adsorption, the presence of oil, and harsh reservoir conditions can cause the foam to destabilize. Pore-level foam coarsening and anti-coarsening mechanisms are not, however, fully understood and characterized at reservoir pressure. Using lab-on-a-chip technology, we probe dense (liquid) phase CO2 foam stability and the impact of Ostwald ripening at 100 bars using dynamic pore-scale observations. Three types of pore-level coarsening were observed: (1) large bubbles growing at the expense of small bubbles, at high aqueous phase saturations, unrestricted by the grains; (2) large bubbles growing at the expense of small bubbles, at low aqueous phase saturation, restricted by the grains; and (3) equilibration of plateau borders. Type 3 coarsening led to stable CO2 foam states eight times faster than type 2 and ten times faster than type 1. Anti-coarsening where CO2 diffused from a large bubble to a small bubble was also observed. The experimental results also compared stabilities of CO2 foam generated with hybrid nanoparticle–surfactant solution to CO2 foam stabilized by only surfactant or nanoparticles. Doubling the surfactant concentration from 2500 to 5000 ppm and adding 1500 ppm of nanoparticles to the 2500 ppm surfactant-based solution resulted in stronger foam, which resisted Ostwald ripening. Dynamic pore-scale observations of dense phase CO2 foam revealed gas diffusion from small, high-curvature bubbles to large, low-curvature bubbles and that the overall curvature of the bubbles decreased with time. Overall, this study provides in situ quantification of CO2 foam strength and stability dynamics at high-pressure conditions.Article HighlightsA comprehensive laboratory investigation of CO2 foam stability and the impact of Ostwald ripening.Pore-level foam coarsening and anti-coarsening mechanisms insights.

Eco-Friendly Coal Gangue and/or Metakaolin-Based Lightweight Geopolymer with the Addition of Waste Glass.

Massive amounts of deposited coal gangue derived from the mining industry constitute a crucial problem that must be solved. On the other hand, common knowledge about the recycling of glass products and the reuse of waste glass is still insufficient, which in turn causes economic and environmental problems. Therefore, this work investigated lightweight geopolymer foams manufactured based on coal gangue, metakaolin, and a mix of them to evaluate the influence of such waste on the geopolymer matrix. In addition, the effect of 20% (wt.) of waste glass on the foams was determined. Mineralogical and chemical composition, thermal behaviour, thermal conductivity, compressive strength, morphology, and density of foams were investigated. Furthermore, the structure of the geopolymers was examined in detail, including pore and structure thickness, homogeneity, degree of anisotropy, porosity with division for closed and open pores, as well as distribution of additives and pores using micro-computed tomography (microCT). The results show that the incorporation of waste glass increased compressive strength by approximately 54% and 9% in the case of coal-gangue-based and metakaolin-based samples, respectively. The porosity of samples ranged from 67.3% to 58.7%, in which closed pores constituted 0.3-1.8%. Samples had homogeneous distributions of pores and additions. Furthermore, the thermal conductivity ranged from 0.080 W/(m·K) to 0.117 W/(m·K), whereas the degree of anisotropy was 0.126-0.187, indicating that the structure of foams was approximate to isotropic.

The Cellular Structure and Mechanical Properties of Polypropylene/Nano-CaCO3/Ethylene-propylene-diene-monomer Composites Prepared by an In-Mold-Decoration/Microcellular-Injection-Molding Process.

Polypropylene (PP)-composite foams were prepared by a combination process of microcellular injection molding (MIM) and in-mold decoration (IMD). The effect of ethylene propylene diene monomer (EPDM) on the crystallization properties, rheological properties, microstructure, and mechanical properties of PP-composite foams was studied. The effect of the additives on the strength and toughness of PP-composite foam as determined by the multiscale simulation method is discussed. The results showed that an appropriate amount of EPDM was beneficial to the cell growth and toughening of the PP blends. When the content of EPDM was 15 wt%, the PP-composite foams obtained the minimum cellular size, the maximum cellular density, and the best impact toughness. At the same time, the mesoscopic simulation shows that the stress concentration is the smallest, which indicates that 15 wt% EPDM has the best toughening effect in these composite materials.

PENGARUH PENAMBAHAN CACO3 DARI LIMBAH KULIT TELUR DAN WAKTU PENGADUKAN PADA PEMBUATAN ALUMINIUM FOAM MENGGUNAKAN METODE MELT ROUTE

Aluminum is a lightweight material that has good corrosion resistance and electrical conductivity. It can be used for making aluminum foam. One of the methods for making aluminum foam is the melt route method. Making aluminum foam using the melt route process, is called melting aluminum metal, adding foaming agent, and stirring. This study aims to determine the effect of adding CaCO3 from eggshells and stirring time on the foaming ability of aluminum foam. The characteristics that will be observed include the type of aluminum foam, height, pore size, density, porosity, and compressive strength. This research used the melt route method with adding variations in the mass composition of CaCO3 is 4, 5, and 6 wt% on smelted aluminum with stirring times of 30, 45, and 60 seconds. The process is carried out by heating aluminum to 760 °C and adding Al2O3 as a viscosity modifier then adding variations in the mass composition of CaCO3 and stirring with a variation of stirring time. The results show that the highest aluminum foam gets a value of 75 mm. The pore sizes of aluminum foam are obtained ranged from 0.287 to 1.109 mm. The optimal value obtained from the addition of CaCO3 with a mass composition of 4 wt% with a stirring time of 45 seconds, has a density value of 0.388 g/cm3, a porosity percentage of 85.848%, and a compressive strength of 1.777 MPa.

Study of the microstructure, foaming property and cyclic compression performance of poly(ether-block-amide) foams fabricated by supercritical CO2 foaming

This paper systematically explored the effects of molecular structure on the foaming behavior of poly(ether-block-amide) (PEBA) and its influence on foam cyclic compression properties. It was demonstrated that increasing the hard segment (HS) content of PEBA not only improved crystallization and melting strength, but also narrowed the melting peak and shifted it to higher temperatures. In contrast to other thermoplastic elastomers such as TPU, PEBA with a higher HS content showed a lager foam expansion ratio but a narrower foaming window. Increasing HS content improved compression strength but deteriorated resilience of PEBA foams. As the expansion ratio increased to 5-fold, there was no significant reinforcing effect of HS on strength and modulus of PEBA foams, while the resilience of the foams increased constantly with decreasing HS content and increasing expansion ratio.