Foam Density Research Articles

Conversion of polystyrene foams into auxetic metamaterials

AbstractAuxetic foams have gained popularity within the research community because of their enhanced properties, such as low density combined with high relative stiffness, toughness, and damping properties. Low density polystyrene (PS) foams are commonly used in the packaging industry, but have a short service life and generate a high volume of waste (white pollution). This is why their recycling and valorizing is necessary and imperative. The objective of this work is to present a simple and environmentally friendly process combining low pressure (vacuum) and mechanical compression to convert recycled PS foams (15 kg/m3) into low density foams (50–63 kg/m3) having negative tensile and compressive Poisson's ratios (NPR). The effect of processing conditions (vacuum level, temperature, mechanical pressure, and time) were studied. Based on the optimized conditions, the tensile Poisson's ratio of the resulting auxetic foams reached −0.65 for the Y direction (width) and −0.74 for the Z direction (thickness) when stretching in the X direction (length). On the other hand, the minimum compressive Poisson's ratios were −0.32 for the Y direction and −0.28 for the Z direction. The foam structure was characterized via morphological analysis to determine the changes after treatment. Finally, tensile and compressive properties (Young's modulus, strain energy, energy dissipation, and damping capacity) are also discussed. It was observed that the mechanical properties of the resulting auxetic foams were improved compared to the original PS foam (PS‐O) in terms of resilience and strength. For example, the elongation at break of auxetic foams (31%–62%) were much higher compared to PS‐O (7%). These auxetic foams can be used in several applications, such as sports and military protective equipment.

Achieving Ultralow-Density, High-Purity Au Foam Hohlraum with Hierarchical Porous Structure

High Z (atomic number) metallic foams with a low density and high purity are urgent demands in high energy-density physical experiments. They suppress plasma expansion and convert the laser pulses to X-rays more uniformly and efficiently. Thus, we synthesized an ultralow-density and high-purity Au foam hohlraum with a hierarchical porous structure via a template-dealloying method in this paper. Silica (SiO2) beads were introduced as the sacrificial templates due to their high stability at an elevated temperature. The Au and Ag nanoparticles were successively deposited onto the SiO2 templates via an electroless deposition process to form an Ag@Au@SiO2 core-shell structure. Cylindrical Ag@Au@SiO2 hohlraum was achieved using a filter-casting technique with a patented mold. Afterward, an Au-Ag alloy was generated during 36 h of calcination at 400 °C. Self-supported Au foam hohlraum with the hierarchical porous structure was gained after the SiO2 templates were removed, followed by the dealloying of the Ag from the Au-Ag alloy. A self-supporting Au foam hohlraum with a density as low as 0.2 g/cm3 and a purity of 99.37% was achieved, and the density decreased by about 44.5% when compared with our previous Au foam (density: 0.36 g/cm3, purity: less than 96%) using microspherical polystyrene as the sacrificial template. Thus, the ultralow-density, high-purity Au foam hohlraum may exhibit profound application in high-energy physical experiments in the near future.

Development and research of syntactic foams for antenna devices parts manufacture

Foam plastics are always widely used in antenna-feeder systems due to the low values of the dielectric constant ε and the tangent of the dielectric loss angle tgδ. Structural elements of such antennas are usually made by gluing blanks cut from expanded polystyrene plates or from filling polyurethane foam. However, these methods turned out to be low-tech due to the high labor intensity of the process, the inhomogeneity of the dielectric properties of structures and the unsatisfactory quality of the painted surface due to the low chemical resistance of these materials to solvents of paint and varnish materials. Syntactic foams, which are a special type of gas-filled polymers, in which hollow spherical filler particles are distributed, in comparison with traditional foams, have increased mechanical strength, electrical strength, resistance to climatic factors, less density difference and better surface quality. It is the advantages of syntactic foams listed above that make them relevant materials in the manufacture of structural elements of antennas. The purpose of the work is to study the possibility of obtaining products from low-density syntactic foam by combining an expandable polymer matrix with a filler in the form of hollow glass microspheres. The limits of filling the polymer matrix by the filler have been established. The material dielectric characteristics (dielectric constant ε and the tangent of the dielectric loss angle tgδ) and strength (compression stress at 10% deformation) characteristics have been investigated. The resistance of the material to the influence of climatic factors has been investigated. The technology of manufacturing the product by the flooding method has been developed. Also the effect of paint and varnish coatings on surface quality and dielectric characteristics of foams of low density has been investigated. The obtained results can be used to create structural elements of antennas.

Study for the development of flyash and GGBS-based alkali activated foam concrete

This research project focuses on developing sustainable mix proportions for foam concrete with densities ranging from 1200 kg/m3 to 1400 kg/m3, suitable for use as a structural material. To achieve this, the study uses pre-formed foam of a specific density added to the mortar mix, with aluminium oxide powder as a foaming agent and a 12.5 molarity sodium hydroxide solution to densify the foam. To make the foam concrete sustainable, industrial waste products such as ultrafine GGBS and fly ash are added as partial replacements, and the study examines the qualities of the material in both fresh and hardened states by varying the amounts of GGBS, fly ash, and additives used. By examining the air-void-strength relationship of foam concrete with a compressive strength of 5.5 MPa, the study achieves a better understanding of the material's properties and how to achieve greater compressive strength by adjusting the amount of ultrafine GGBS and fly ash in the mix. In conclusion, this research project offers a sustainable solution for foam concrete as a structural material by utilising industrial waste products and exploring the material's qualities in both fresh and hardened states.

Crushing Responses of Expanded Polypropylene Foam.

This paper aimed to experimentally clarify the crushing mechanism and performance of expanded polypropylene foam (EPP) and analyze the influence of density and thickness on its mechanical behavior and energy absorption properties under static crushing loadings. Hence, a series of compression tests were carried out on EPP foams with different densities and thicknesses. For foam with a density of 60 kg/m3, the mean crushing strength, energy absorption (Ea), energy absorption efficiency (Ef), specific energy absorption (SEA), and energy absorption per unit volume (w) increased by 245.3%, 187.2%, 42.3%, 54.3%, and 242.8%, respectively, compared to foam with a density of 20 kg/m3. Meanwhile, compared to foam with a thickness of 30 mm, the mean crushing strength, energy absorption (Ea), energy absorption efficiency (Ef), SEA, and energy absorption per unit volume (w) for foam with a thickness of 75 mm increased by 53.3%, 25.2%, -10.8%, -4.7%, and -10.6%, respectively. The results show that foam density has a significantly greater influence on static compressive performance than foam thickness. The microstructures of the EPP foam before and after static compression were compared by observing with a scanning electron microscope (SEM), and the failure mechanism was analyzed. Results showed that the load and energy as well as the deformation and instability processes of its cells were transferred layer by layer. The influence of density on the degree of destruction of the internal cells was obvious. Due to its larger mass and larger internal damping, thicker foams were less damaged, and less deformation was produced. Additionally, the EPP foam exhibited a considerable ability to recover after compression.

Effects of polymethacrylimide foam reinforced aluminum honeycomb sandwich under quasi‐static compression

AbstractIn this study, aluminum honeycomb cells were filled with polymethacrylimide (PMI) foam of high strength and stiffness, and carbon fiber reinforced composite (CFRC) skins were added to create a composite sandwich structure. Nine types of specimens with varying cell node spacing and foam density were constructed, and stiffness equations were derived. To compare the performances of aluminum honeycomb and PMI foam sandwich structures, their compressive responses were examined using edgewise and flatwise compression tests. Moreover, the failure was analyzed using finite element methods (FEM). Analytical and numerical models were used to investigate the size effects of rib width, rib angle, and node spacing.

Influence of specimen size and density variation in the foam rise direction on the compressive behavior of PVC foams

Mechanical properties governing the localized deformation mechanisms, apparent elastic modulus and their correlation to specimen geometry in polymeric foams are important phenomena that are not well understood. Despite the well-studied density variation in Functionally Graded Foams (FGF), density variation in the foam rise direction of conventional foams has not received adequate attention in the current literature. The influence of specimen size and density variation on the deformation mechanisms and mechanical properties observed in the rise direction of H-series rigid PVC foams were experimentally investigated in this study by considering four distinct specimen sizes and five nominal densities. PVC foams with different nominal densities exhibited various density variation patterns, in a range of 2.6–26.3 % variation, in the foam rise direction which were found to govern the polymeric foams’ localized deformation mechanisms and the post-yield stress drop-off behavior. The plateau stress was observed as most sensitive to the foam density; specimens with higher densities exhibited up to 19 % higher plateau stress within the foam panel with a 200 kg/m3 nominal density. While specimen thickness significantly influenced the loading elastic modulus. Intermittent unloading-reloading cycle testing was conducted on thick and thin specimens to characterize the influence of specimen thickness on the apparent elastic modulus. The influence of thickness on the unloading elastic modulus was negligible, for example, reducing the specimen thickness from 25.40 mm to 6.35 mm decreased the loading and unloading elastic moduli by 39 % and 7 %, respectively, for PVC foams with a nominal density of 200 kg/m3. Therefore, the unloading elastic modulus should be utilized in future studies for more accurate cross-comparison between the mechanical properties of specimens with significantly different thicknesses.

Performance Evaluation Based on Exergy Analysis Through Partially Filled Metal Foams in Forced Convection

Abstract The intention of this paper is to present the numerical analysis of thermal performance and exergy transfer through high porosity metal foams filled partially in a horizontal pipe. The heater is embedded in the pipe's circumference and is assigned with known heat input. To enhance heat transfer, aluminum metal foam of pore density 10 with porosity 0.95 is inserted adjacent to the pipe's inner wall. To determine the optimal thickness of metal foam for enhancing its performance thermodynamically, metal foams with five different thicknesses (10, 20, 40, 60, and 80 mm) are examined in this research for a fluid velocity ranging from 0.7 to 7 m/s under forced convection heat transfer condition. The Darcy– Brinkman–Forchheimer and local thermal nonequilibrium (LTNE) models are used for forecasting the flow features and heat transfer through the metal foams, respectively. The numerical methodology implemented in this research is confirmed by comparing the present outcomes with the experimental outcomes accessible in the literature and found a fairly good agreement between them. The thermal performance is assessed in terms of heat transfer enhancement ratio and performance factor, and the thermodynamic performance is evaluated based on exergy analysis. In the exergy analysis, the parameters like mean exergy-based Nusselt number (Nue), merit function (MF), and nondimensional exergy destruction (I*) are considered for the evaluation. The result shows a better performance from partially filled metal foams than from completely filled metal foams.

Flexural Characterisation of Sandwich Panel with Corrugated Glass Reinforced Polymer

The corrugated foam core sandwich construction is used in variety of structural applications. These structures are subjected to flexural, impact, edgewise compression and shear loads. Traditional process for manufacturing of sandwich panel is not suitable for making corrugated core sandwich panel. In this work a novel methodology has been developed for construction of corrugated foam core sandwich panel. The present study focuses on the flexural behaviour of sandwich panel by varying the foam densities and corrugated cell. Two types of densities with one cell and two cells are used. The sandwich employs a Glass Reinforced Polymer (GRP) orthotropic material for both the two outer skins and the inner core web. In particular, the core is designed to have uneven topology to cooperate with GRP skins in membrane and flexural properties by adding a corrugated foam core. At first, a comparison has been performed between different density foams. Initially, 40 kg/m3 with 1 unit cell and 32 kg/m3 with 1 unit cell are compared, and then the same densities are compared with 2 cells. Among all, 40 kg/m3 with two cells shows highest flexural strength compared to the other specimens. Also, the sandwich panel with an empty core has been tested to understand the strength of the face sheet and corrugated core.

Pengaruh variasi ketebalan saluran dan temperatur tuang terhadap fluiditas dan porositas hasil pengecoran kuningan pada pengecoran evaporatif

The development of foundry technology continues to grow along with the increasingly complex needs for making products based on art and culture, one of which is sclupture. Evaporative casting based on non-permanent patterns made of polystyrene foam, with the advantage of precision casting results in complex shapes. The purpose of this study was to determine how variations in the pouring channel and pouring temperature affect the fluidity and porosity of brass castings in evaporative casting. Casting was carried out in castings with thicknesses of 1.5, 2, 3, 4, and 5 mm at pouring temperatures of 900°C, 950°C, and 1000°C using brass with a composition of Cu60% and Zn40%. The highest fluidity was found at a pattern density of 0.012 gr/cm3 at a pouring temperature of 1000°C with a flow length of 150 mm, while the lowest fluidity was obtained at a pattern density of 0.016 gr/cm3 at a pouring temperature of 900°C with a flow length of 13 mm. The results of scanning electron microscope (SEM) observations can be observed in spesimens with a density of polystyrene foam and a high casting temperature, an increase in the porosity formed.

A STUDY OF CORRELATION BETWEEN GAMMA GLUTAMYL TRANSFERASE AND METABOLIC SYNDROME

CONTEXT:The metabolic syndrome ( Syndrome X, or insulin resistance syndrome) is a combination of several risk factors that contribute to atherosclerotic cardiovascular disease (ASCVD). Elevated blood pressure, triglycerides, hyperglycemia, waist circumference and low HDL- cholesterol are all symptoms of accelerated dyslipidemic atherogenesis. Glutamyl transferase (GGT) has long been thought to be a biomarker for hepatic and biliary illness and alcoholic related disease. GGT is required for the extracellular catabolism of glutathione, which is the most important thiol antioxidant in humans.It co localizes with oxidised low density lipoprotein (LDL) and foam cells in the atheromatous core of coronary plaques. GGT can be a proinammatory sign. GGT was found to be a prognostic marker for Metabolic syndrome, CVD, and heart failure .AIM: Study of Gamma glutamyltransferase in metabolic syndrome patients. MATERIALS AD METHODS: A sample size of 100 patients admitted in medicine and other departments in nri general hospital are included in study Qualitative data was expressed in frequencies and percentages a STASTISTICAL ANALYSIS: nd Quantitative data in mean and standard deviation. Non parametric statistics i.e. Chisquare test was used to nd the signicant association between the two qualitative variables. Independent t test and ANOVA were used to nd the statistical signicance between quantitative variables. Pearson correlation coefcient was used to nd correlation between two variables. p value of <0.05was considered statistically signicant. CONCLUSION: It should be highlighted that elevated levels of GGT are not the only hepatic biomarker of hepatic steatosis, as evidenced by ndings from several research. lines of evidence point to a link between high GGT levels in the blood and the metabolic syndrome. As a result, higher GGT levels are associated with increased insulin resistance and a higher risk of type 2 diabetes .

Development of natural rubber foam by in-house Talalay method

The benefits of natural rubber foams (NRFs), include its buoyancy, sound absorption, supportability, and low weight. Generally, there are two main techniques to produce the NRFs: Dunlop method and Talalay method. The Dunlop technique is a cheap and conventional method, while the Talalay technique is a complicated method (cool down, vacuum and heating process). The objective of this research is to study the difference properties of NRFs between Dunlop and Talalay methods. Both techniques proposed the NRFs with similar foam density values. The mechanical properties of the NRF from in-house Talalay method were lower than those obtained by NRF from Dunlop method, may due to the in-house Talalay method generating the large bubble from the vacuum system. However, the FTIR spectrum of NRFs obtained from both methods showed the same functional groups.

A numerical study on mitigation of sloshing in a rectangular tank using floating foams

In this paper, the feasibility of using floating foams as a mitigation device to suppress water sloshing in a rectangular tank is numerically investigated. The sloshing in the tank is initiated using a harmonic excitation. To perform 3D numerical simulations, the Arbitrary Lagrangian-Eulerian technique (ALE) in the commercial software ABAQUS is utilized. The results of the model are validated by comparing the results of simulations with those of the experiments both quantitatively and qualitatively. Next, the efficacy of floating foams in suppressing water sloshing is evaluated for different cases with various layers of foam ranging from zero to three layers. In addition, the effects of various parameters on the wave height and kinetic energy variations are comprehensively analyzed. These parameters include water depth, density, friction factor, diameter of plastic foam spheres, frequency, amplitude and type of excitation. The numerical results show that the interactions between floating foams play a major role in mitigating water sloshing. Furthermore, the effects of plastic foam densities on decreasing the wave height are minor. A twofold increase in the foam density decreases the maximum kinetic energy by 9.68% and an almost threefold increase in the foam density reduces the maximum kinetic energy by 29.03%.

Effect of soy protein isolate concentration and whipping time on physicochemical and functional properties of strawberry powder

The objective of this work was to study the effect of soy protein isolate concentration (0.5–9%) and whipping time (1–8 min) on foam characteristics, physicochemical and functional properties of hot air foam-mat-dried strawberry powder. An optimization of foaming conditions was performed by response surface methodology to maintain the studied responses within acceptable limits. The foam was prepared using different concentrations of soy protein isolate solution (32%) and dried at 50 °C in a thin layer (4 mm as a thickness). The concentration of soy protein was the predominant parameter affecting foam density, expansion, and stability, and physicochemical and functional properties of strawberry powder. Total phenolic content, total flavonoid content, antioxidant activity, water holding capacity, and oil holding capacity increased by about 26, 47, 166, 21, and 48%, respectively, with an increase in the concentration of soy protein isolate, compared to the control sample. Contrary, the whipping time showed a contradicted effect on all studied responses except the foam expansion and oil holding capacity.

Tailoring lightweight, mechanical and thermal performance of PLA/recycled HDPE biocomposite foams reinforced with kenaf fibre

With an increase in environmental issues regarding industrial wastes, recent researches are shifted toward green environmentally material using natural biomass, polymer and composite. In this work, the foamed reinforced poly(lactic) acid/recycled high-density polyethylene (PLA/rHDPE)/kenaf fibre biocomposites were prepared by extrusion and compression molding technique for the synergism of lightweight and performance. To reduce density of kenaf fibre biocomposite foam, without over sacrificing the performance, the determination of PLA/rHDPE blend formulation as matrix and azodicarbonamide (ADC) loadings was assessed based on morphology, mechanical and thermal properties. A fixed kenaf fibre loading of 30 wt% was incorporated in the composite system. Results revealed that (90/10) and (70/30) (wt/wt) % compatibilized blends of PLA/rHDPE showed an improvement in flexural properties up to 54 – 1549% as compared to the neat PLA and rHDPE. The (70/30) (wt/wt) % based kenaf biocomposites exhibited a notable density reduction at 5 phr of ADC up to 7% as compared to (90/10) (wt/wt)% based biocomposites. The early formulation was appeared as a preferable blending composition for having homogenous porous structured PLA/rHDPE/kenaf fibre biocomposites foams with reduced density and improved mechanical strength. These foamed composites have a high potential to replace traditional foamed materials used in construction interior applications.

Factors Aff ecting Foam Stability of Clotrimazole Vaginal Foam

Clotrimazole (CLT) is a broad-spectrum antifungal, synthetic imidazole derivative, used for Candida albicans the major cause of vaginitis. Vulvovaginal candidiasis (VVC) symptoms can cause discomfort and lower a women’s quality of life. Foams are used to apply formulation without the use of fi ngertips, the more stable the foam the better for coverage of larger surface area. CLT 2% vaginal foam were prepared as an O/W emulsion using Tween 20 and Span 20, Lemon oil, PEG 400, SLS, cetyl alcohol, and the formulas were evaluated for foamability and foam stability, foam density, cycles of freezing and thawing, heating, and cooling, and the impact of the chosen formula on Candida culture are all taken into consideration. The results showed that the CLT prepared successfully as vaginal foam, and the selected formula (F24) considered as the best formula which has good miscibility, texture and acceptable homogeneity, pH (4.8), drug content (97.5%), acceptable foamability and foam stability; foam expansion FE (70%), foam liquid stability (FLS) (40%), foam volume stability FVS (23.5%), gas fraction (GF) (35 mL), acceptable foam density (0.90), good stability at temperature changes, freeze–thaw cycle (pass), heating–cooling cycle (pass) with no phase separation, fast complete drug release (100% in about 40 min), no interaction between the solid components of the formula and acceptable inhibition zone against Candida strains. Finally, we can conclude that formulation of CLT as vaginal foam is an optimum method to improve patients’ compliance and cure the disease with low recurrence possibility due to fast release and long contact time with the aff ected area.

Facile Synthesis of Hollow Glass Microsphere Filled PDMS Foam Composites with Exceptional Lightweight, Mechanical Flexibility, and Thermal Insulating Property.

The feature of low-density and thermal insulation properties of polydimethylsiloxane (PDMS) foam is one of the important challenges of the silicone industry seeking to make these products more competitive compared to traditional polymer foams. Herein, we report a green, simple, and low-cost strategy for synthesizing ultra-low-density porous silicone composite materials via Si-H cross-linking and foaming chemistry, and the sialylation-modified hollow glass microspheres (m-HM) were used to promote the HM/PDMS compatibility. Typically, the presence of 7.5 wt% m-HM decreases the density of pure foam from 135 mg/cm-3 to 104 mg/cm-3 without affecting the foaming reaction between Si-H and Si-OH and produces a stable porous structure. The optimized m-HM-modified PDMS foam composites showed excellent mechanical flexibility (unchanged maximum stress values at a strain of 70% after 100 compressive cycles) and good thermal insulation (from 150.0 °C to 52.1 °C for the sample with ~20 mm thickness). Our results suggest that the use of hollow microparticles is an effective strategy for fabricating lightweight, mechanically flexible, and thermal insulation PDMS foam composite materials for many potential applications.

Photothermal and thermoelectric performance of PCMs doped with nanoparticles and metal foam

Combination of solar thermal power generation and Phase Change Materials (PCMs) helps solve the disadvantages of solar instability. In order to improve the photothermal performance of PCMs, PCMs doped with high thermal conductivity metal foam and nanoparticles were applied. The influence of nanoparticle mass fractions (ω = 0%, 0.5%, 0.8%, 1.0%), pore densities of metal foam (PPI = 5, 10, 15), light intensities (I = 600–1000 mw/cm2) was discussed. Results showed that an increase in pore densities of metal foam is beneficial to improving the thermal conductivity and increasing the temperature difference, the metal foam PPI = 15 can bring a maximum temperature rise of 7.9%, and can increase the temperature difference growth rate by 24.82%. The addition of nanoparticles increases the maximum voltage and power by up to 8.53% and 8.0%, respectively. This research has certain reference and guiding value for the application of thermoelectric power generation.

Analysis of density-dependent bead and cell structure of expanded polypropylene bead foams from X-ray computed tomography of different resolution

Closed-cell bead foams with their hierarchical geometrical structure are a challenge for statistical reconstruction and finite element modelling. For the purpose of providing the fundamental micro- and meso-structural descriptors - wall thickness, cell as well as bead volume and sphericity - of expanded polypropylene bead foams of different density, 3D-images from X-ray computed tomography are analyzed. A detailed description of development and application of an image analysis methodology for the determination of feature distributions from CT-scans of different level of detail is provided. The methods are based on off-the-shelf algorithms provided by the open-source package distribution FIJI. It should be highlighted, that beside essential methods such as thresholding, euclidean distance and watershed transformation here the Trainable WEKA segmentation is applied for separating material phases in the images. Although the methods elaborated are generally very case sensitive, the reader benefits from the validation strategies applied, so that development of individual methods into the direction of reliability, repeatability and automation is supported.

Prediction of anisotropic foam stiffness properties by a Neural Network

In this work, an Artificial Neural Network is developed to predict the orthotropic stiffness tensor of anisotropic foam structures utilizing a tessellation-based foam RVE database. Based on a validated mesoscale simulation model, which is able to predict the mechanical properties of foams including the consideration of the cell structure, in a first step a simulative database is created. Variable parameters are: Foam density, Young’s modulus of foam base material, cell size, cell orientation, cell shape, etc. In total, more than 2000 simulations were performed leading to a novel RVE database. These simulations are subsequently used to train and compare different networks in a supervised manner. It can be seen that with suitable network settings a Mean Relative Error of max 2% compared to the RVE simulations occurs. As a result, the anisotropic mechanical stiffness values of complex foam structures can be determined via the Artificial Neural Network within seconds instead of performing time-consuming simulations (up to hours). In a final study, the effect of the database size on the prediction accuracy is examined. It can be observed that at least 500 training datapoints are required to obtain sufficient accuracy.