Behavior Of Foams Research Articles

Exploring Foam Drainage in Fiber-Foam: A Review

The foam drainage is extremely important in many situations where fiber foams are used. Enhancing wet foam stability requires a complete understanding of the mechanisms and factors affecting wet foam drainage. Investigation of the drainage behavior of fiber foams has been studied in this review. The mechanics behind fiber foam drainage are discussed in detail, along with the influence of surfactant concentration, fiber consistency, and other variables. It also investigated adding additives, such as chemi-thermo-mechanical pulp (CTMP), affects foam drainage. Highlighting the most recent developments in experimental and theoretical methods for describing and forecasting foam drainage behavior are presented. This review acts as a reference to offer useful understanding of the essential factors of foam drainage in fiber foams solution.

Static and dynamic behaviour of aluminium infiltrated ceramic foam at high volume fraction

Ceramics are used in ballistic protection applications for their high hardness and compressive strength; however, they are brittle and shock-sensitive. Co-continuous ceramic composite (C4) infused with a ductile phase can compensate for the brittleness of the ceramic and increase energy absorption with a potential weight reduction in comparison with present multilayer armours. Nevertheless, the research on C4 for armour applications is in its infant stage. This article aims to investigate the energy absorption characteristics of C4 composites with ballistic grade Al5083 infiltrated into different volume fractions of SiC foam (10PPI, 20PPI and 30PPI). The infiltrated C4 samples have 13, 15 and 18 volume percent of SiC in 10PPI-C4, 20PPI-C4 and 30PPI-C4 respectively. The uniaxial compression test of C4 samples revealed that 30PPI-C4 samples have 135 times high compression strength than ceramic preforms and hardness of C4 also enhanced by 13% for 30PPI-C4 samples. The gas gun impact and Split Hopkinson Pressure Bar (SHPB) tests on the 30PPI-C4 specimens reveals that their specific energy absorption (SEA) are 78% and 30% higher than those of 10PPI-C4 and 20PPI-C4 respectively.

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.

Compressive deformation behavior of closed-cell aluminium syntactic foam

The present study investigates the compressive deformation behaviour of aluminium matrix syntactic foam. Thecenosphere hollow filler was incorporated into the aluminium matrix to fabricate the syntactic foam using stir casting technique. A compressive test was conducted on the syntactic foam to evaluate their mechanical properties, and the results were compared with the finite element ABAQUS explicit simulation software. The plateau strength and energy absorption capacities of the experimental and numerical results show a deviation of 1.76 and 7.13% respectively. The numerical results are good, in agreement with the obtained experimental results, and beneficial in understanding the compressive behaviour of closed-cell syntactic foam.

Water chemistry role in the stability of CO2 foam for carbon sequestration in water aquifers

Injection of CO2 foam into saline aquifers is a practical method to store CO2; however, generating stable CO2 foam at high temperatures and salinities remains a challenging task. Therefore, this research fully explains the effect of formation water components (NaCl, CaCl2, MgCl2, Na2SO4, and NaHCO3) on the stability of generated foam under harsh conditions. In this regard, a high-temperature and high-pressure (HPHT) foam analyzer was used to investigate the foamability and stability of CO2 foam at 100 °C and 1000 psi. The liquid phase contained 0.5 wt% of Armovis surfactant dissolved into 0.1, 0.5, and 1M concentrations of formation water ions. Moreover, the dynamic surface tension of the selected surfactant solutions was investigated using an optical tensiometer. For the first time, this paper investigates the behavior of foam during the foaming process. During the injection of CO2, the average bubble count for the low salt concentration increased sharply and then dropped until it plateaued. However, the average bubble count for the higher salt concentration gradually increased until the foaming process stopped. These phenomena occurred because of the kinetic adsorption rate of the surfactant micelles at the interface. Additionally, we studied the effect of salt concentrations on bubble count half-life, bubble coarsening, and foam volume decay during the static condition. We observed that the increase in salt concentration resulted in more stable foam due to the reduction of CO2 solubility in water. The foam half-life for 0.1 M of NaCl was 190 min, while it was more than 250 min for 1M of NaCl. A similar trend was observed for CaCl2 and MgCl2. The results of the HPHT foam analyzer concluded that the higher concentration of salt ions presented a more stable foam. Also, the use of Armovis surfactant is promising for the stabilization of CO2 foam at high temperatures and salinities.

Investigation of the Impact of Biochar Application on Foaming Slags with Varied Compositions in Electric Arc Furnace-Based Steel Production

This paper investigates the influence of biochar, either as an individual component or in combination with high-temperature coke, on the slag foaming behavior. High-temperature coke serves as a reference. Three scenarios were considered to study the slag foaming behavior, each characterized by different slag chemical compositions. The results indicate that biochar can promote steady foaming for specific slags when the basicity (CaO/SiO2) falls within a range of 1.2 to 3.4. Experimental findings also reveal that stable foaming can be achieved when a mixture containing biochar and coke with a ratio of 1:1 is employed, with a minimum slag basicity of 1.0 and FeO content of 25 wt.%. The foaming range obtained using different FeO contents (15 wt.% to 40 wt.%) in the mixture surpasses the range observed with the individual application of coke or biochar. The X-ray diffraction (XRD) analysis showed that unrelated to the carbon source applied, the general pattern was that the phases larnite (Ca2SiO4) or dicalcium silicate were detected for slag foams with high basicity. Monticellite (CaMgSiO4) and magnesium iron oxide (Fe2MgO4) were predominant in slag foam samples, with the highest MgO content. The presence of monticellite and merwinite (Ca3MgSi2O8) occurred in samples with the lowest basicity. Eventually, the application of the mixture of coke and biochar showed the potential to obtain stable foaming across a wide range of slag compositions.

Effect of particle size and distribution of hollow spheres on the compressive behavior of aluminum matrix syntactic foams

Effect of particle size and distribution of hollow spheres on the compressive behavior of aluminum matrix syntactic foams

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.

On the Creation and Optical Microstructure Characterisation of Additively Manufactured Foam Structures (AMF).

Plastic-based additive manufacturing processes are becoming increasingly popular in the production of structural parts. Based on the idea of lightweight design and the aim of extending the functionality of additive structures, the production of additively manufactured foam structures has emerged as a new field of application. The optical characterisation of these structures is of particular importance for process adjustments and the identification of (unwanted) changes in the foam structure. The degree of foaming and the fineness of a foam structure are of interest at this point. In this context, only the part of a structure dominated by foam pores is considered a foam structure. So far, there are no sophisticated methods for such an optical characterisation. Therefore, in this work, microscope images of manufactured as well as artificially created additively manufactured foam structures were evaluated. On these images, the features porosity, pore size, pore amount and a measure for the textural change were determined in order to obtain information about changes within an additively manufactured foam structure. It is shown that additive structures show changing pore shapes depending on the orientation of the cutting plane, although there are no changes in the foaming behaviour. Therefore, caution is required when identifying changes within the foam structure. It was also found that, owing to the additive process, the total porosity is already set in the slicing process and remains constant even if the degree of foaming of individual tracks is changed. Therefore, the degree of foaming cannot be determined on the basis of the total porosity, but it can be assessed on the basis of the formation of large networks of process-related pores.

Fabrication of poly(lactic acid) foam with high expansion ratio and oriented cellular structure by restricting cold crystallization

The foaming behavior of semi-crystalline polymers is significantly affected by their crystallization. To achieve high expansion ratio of poly(lactic acid) (PLA) foams, we thought its cold crystallization should be restricted. Therefore, we used a short soaking time of CO2 to fabricate high-expansion PLA foams. Dynamic mechanical analysis of unfoamed PLA showed that only one rubbery plateau was observed owing to complete cold crystallization under a soaking time of 40 min at 10 MPa. The crystal morphology demonstrated that a short soaking time of 3 min could restrict the cold crystallization of PLA. Owing to plasticization of CO2, PLA crystallization of was accelerated at low temperatures (40–80 °C) but hindered at high temperatures (80–130 °C) at 10 MPa. Foaming results showed that under a soaking time of 3 min, a high expansion ratio exceeding 10 was achievable over a wide foaming temperature range of 90 to 115 °C because more amorphous regions were preserved at 10 MPa. In addition, the prepared foams presented an oriented cellular structure. Compared with the isotropic foam, the anisotropic foam exhibited higher compressive strength and heat resistance. The prepared PLA foams have good application prospects in the fields such as cushioning, packaging, and construction.

Influence of the loading regime on the uniaxial compressive behaviour of density graded Citrus Maxima peel

To conceive more efficient protective structures, it is possible to draw inspiration from natural structures. However, the origin of the mechanical absorption properties of natural structures is not always clear. Among the multitude of existing natural structures, the density graded peel of the Citrus Maxima was studied in this work to characterize its mechanical behaviour under uniaxial compression, from the quasi-static regime to the dynamic regime. The resulting behaviour is very different from a classical foam behaviour as no linear part is observed for small strains. Furthermore, the mechanical behaviour is deeply influenced by the loading regime: a stair-case response appears under dynamic loading.

Foaming behaviors and mechanical properties investigation of high‐strength polyethylene terephthalate/polycarbonate bead foam

AbstractDue to the low melt strength, PET foam cells easily grow, and due to the low CO2 concentration in PET, generating more nucleation sites during the foaming process is difficult. As a result, PET foam produced using the supercritical CO2 foaming method possesses a large cell size and a low expansion ratio, which leads to poor mechanical performance. In addition, there has not been much research on how to improve CO2 concentration in PET. In this work, the PC with higher melt strength and CO2 absorption capacity was incorporated into the PET matrix to improve the foaming behaviors of the blend. The results showed that the melt strength and CO2 concentration of PET/PC blends are much higher than that of pure PET. For instance, the melt strength and CO2 concentration of the PET/PC10 blend would be more than twice that of pure PET when the PC content is only 10%wt. By studying the foaming behavior, it was found that high melt strength inhibited the cell overgrowth and collapse of PET/PC foam, resulting in the foam with good cell structure was obtained. In addition, the high CO2 concentration in PET/PC blend is conducive to cell nucleation, thereby increasing the foam expansion ratio during the CO2 foaming process. Finally, the PET/PC blend foam with excellent mechanical properties was obtained. To be specific, the expansion ratio of the PET/PC blend foam was about 9.61, and the average cell size was only 40.38 μm. And the PET/PC blend foam possessed an excellent compressive strength of 7.41 MPa due to the strong interfacial bead cohesion, which showed the application prospect in the field of construction engineering.

Influence of Microstructure on the Dynamic Behaviour of Polyurethane Foam with Various Densities

Polyurethane foam is reinforced with varying proportions of metal loads and other components to increase shock absorption and mechanical impact. The main objective is to develop high-performance polymeric materials based on polyurethane foam developed with different compositions and specific densities. We monitor the growth distances and temperatures of the polyurethane foam in time to reach the optimum formulations. We conduct static compression tests and investigate the effect of drop weight on the deformation of polyurethane foam structures by dropping a weight from a specified height. Dynamic collisions cause deformations of the polyurethane foam structure. After investigating the low weight, we found that polyurethane foams have a good absorption coefficient at certain frequencies. Dynamic stress-strain response curves are used to characterize different stress rates. High-stress levels and similar strains indicate a high resistance to shock. We follow the evolution of microstructure structures by scanning electron microscopy (SEM) to observe deformation and fracture behavior with reversibility and recovery.

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.

Preparing β-SiAlON ceramic foam filters with high oxidation resistance

Herein, to develop ceramic foam filters (CFFs) with high porosity and strength, porous β-SiAlON ceramic foam was prepared using Si, α-Al2O3, and AlN via foam impregnation. Experiments were performed to investigate the effects of the slurry solid content, impregnation times, and sintering temperature on the sample properties. The best green bodies were obtained at a slurry solid content of ∼70 wt%, and the sample subjected to two impregnation times effectively filled the defects. The sintering temperature was found to affect the phase composition, microstructure, sintering behavior, mechanical properties, and oxidation resistance of β-SiAlON ceramic foams. Granular β-SiAlON started to develop at 1550 °C and was almost completely developed at 1600 °C. After sintering at 1650 °C, the porosity remained as high as 85.93% and the compressive strength reached 1.57 MPa. In a nonisothermal oxidation experiment, the maximum oxidation weight gain rate was 14.1% and the sample strength still reached 1.54 MPa at 1600 °C. A high sintering temperature promoted the development of material phases and liquefaction of grains, while the oxidized surface generated an amorphous layer with a high melting point, effectively preventing oxygen diffusion. Therefore, β-SiAlON can be employed to develop CFFs with high strength and excellent oxidation resistance.

High performance plant-derived thermoplastic polyester elastomer foams achieved by manipulating charging order of mixed blowing agents

Plant-derived thermoplastic polyester elastomer (TPEE) is an environment friendly polymer known for its exceptional tear strength and mechanical properties, whose monomers are generated from crops. To prepare high-performance TPEE foams is still challenging due to the intrinsic shrinkage behavior. Herein, two microcellular foaming routes with different charging orders of mixed blowing agents, namely “CO2 firstly charging process (CO2-F-process)” and “N2 firstly charging process (N2-F-process)”, were developed to elucidate the effects of mixed blowing agents on foaming behavior. Compared with the case in N2-F-process, more carbon dioxide and less nitrogen were adsorbed in CO2-F-process. Thus, TPEE foams prepared by N2-F-process show less shrinkage and higher creep recovery ratio than those prepared by CO2-F-process. Thanks to better structural stability and smaller shrinkage, TPEE foams prepared by N2-F-process exhibited enhanced strength and resilience. For the foams with similar density, compression strength can be increased by 52 %, and energy loss coefficient can be reduced to 50 %, by using N2-F-process. Thus, not only biomass TPEE foams with enhanced mechanical performance shows promising prospects in those areas that needs lightweight, insulation and high resilience, but also novel microcellular foaming technique with mixed blowing agents opens a new way for developing high-performance polymeric foams.

Crush behaviour and vibration damping properties of syntactic foam incorporating waste tyre-derived crumb rubber

Syntactic foams, containing up to 23 wt% of untreated waste tyre-derived rubber particles mixed with hollow glass microspheres (HGMs) and epoxy, were produced via compressed air-assisted injection moulding. This study investigated the effect of rubber particles on the through-the-thickness compression properties and the vibration-damping response of the ternary syntactic foams. The interaction between foam constituents was investigated using SEM, with the objective to establish a microstructure-compression property relationship for rubber-incorporated foam. The effect of rubber particles on the energy absorbed by the foam under compression deformation was also studied. The substitution of epoxy for rubber particles did not alter the compression properties (crush behaviour) of the foam. A laser Doppler vibrometer was used to measure the vibration-damping response and natural resonance frequency. The vibration-damping ratio of the rubber-incorporated foam increased by up to 75% upon the addition of 23 vol % rubber particles.

Burning capability of the flame refluxer under the influence of waves

Environmental oil spills pose a significant hazard to marine ecosystems. In-situ burning is an effectively employed means of cleanup and containment due to its low cost and speed for removing large volumes of oil. Previous studies have demonstrated that new Flame Refluxer™ (FR) technology can improve the burning rate of crude oil spilled on water. This study examines the FR-enhanced burning behavior of crude oil spilled on water under the influence of waves. The wave tank platform at the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory was used for these experiments. A grid-type FR was examined with no waves and under the impingement of two different waves. Thermocouple data was used to evaluate thermal penetration rates and in-depth temperature gradients, as well as a distinct foaming behavior. It is observed that waves lowered fuel temperatures, reduced thermal penetration rates, and increased heat loss to the water sublayer. It was concluded that wave steepness is proportional to the increase in heat loss to the water and inversely proportional to the thermal penetration rate.

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

AbstractAlthough the vitrification of nuclear waste has a decades‐long history, numerous opportunities still exist to improve its efficiency and to increase the waste loading in glass. This is especially true for the vitrification of low‐activity waste (LAW), which has been historically treated by other immobilization technologies and is less mature than high‐level waste (HLW) vitrification. In this work, we address one of the least understood phenomena during the conversion of nuclear waste feeds to glass—the formation of molten salt and transient glass‐forming melt. Using high‐temperature environmental scanning electron microscopy (HT‐ESEM) in combination with X‐ray diffraction, thermogravimetry, and evolved gas analysis, we have analyzed the complex chemical reactions and phase transitions as they occur during melting of representative HLW and LAW melter feeds. We evaluated the compositions of amorphous phases and the fractions of salt components, and estimated the fractions of molten salt phases present in the feeds as a function of temperature. We show that the maximum fraction of molten salts is ∼4 % and ∼28 % during HLW and LAW feed melting, respectively, and discuss the possibility of molten salt migration in LAW feeds. We also argue that the presence of significant fractions of molten salt phase can hinder the retention of rhenium (and, hence, radioactive technetium), and discuss how the properties of molten salt phase and transient glass‐forming melt are related to primary foam formation and behavior. Finally, we summarize key unanswered questions requiring further research to increase the understanding of the conversion process and enhance the nuclear waste vitrification efficiency.

Compressive behavior and energy absorption analysis of casting skin-wrapped aluminum foams

The mechanical properties are an indispensable factor affecting the energy absorption capability of aluminum foam. In the past few decades, various aluminum foam sandwich structures, including casting skin-wrapped aluminum foams (CWFs), have been developed and proven to be effective in enhancing the integral mechanical properties. This study investigates how adding casting skin affects the compressive behavior and energy absorption of closed-cell aluminum foam. The aluminum foams were produced using the melt route and then used as the core material for manufacturing CWFs through counter-gravity casting solution after pre-heating. Axial and radial compressions were applied to columnar CWFs with pores falling within two size ranges and three ratios (D/T) of outer diameter to casting skin thickness. The failure mode of CWFs was dominated by brittle fracture of casting skin and progressive crush of foam core. Adding casting skin significantly enhanced the mechanical properties in axial compression, while it had no significant effect in radial compression, with both types of compression varying depending on D/T values. Samples with smaller pore sizes exhibited better overall performance. The influence of the addition of mass on the specific energy absorption should be considered in the design of lightweight crashworthy components.