scholarly journals The mechanics of solid-state nanofoaming

2019 ◽  
Vol 475 (2230) ◽  
pp. 20190339
Author(s):  
Frederik Van Loock ◽  
Victoria Bernardo ◽  
Miguel Angel Rodríguez Pérez ◽  
Norman A. Fleck
Keyword(s):  
Cell Wall ◽  
Solid State ◽  
Cell Walls ◽  
Uniaxial Stress ◽  
Nucleation Density ◽  
One Dimensional ◽  
Foaming Process ◽  
Cell Nucleation ◽  
Foaming Temperature ◽  
Versus Strain

Solid-state nanofoaming experiments are conducted on two polymethyl methacrylate (PMMA) grades of markedly different molecular weight using CO 2 as the blowing agent. The sensitivity of porosity to foaming time and foaming temperature is measured. Also, the microstructure of the PMMA nanofoams is characterized in terms of cell size and cell nucleation density. A one-dimensional numerical model is developed to predict the growth of spherical, gas-filled voids during the solid-state foaming process. Diffusion of CO 2 within the PMMA matrix is sufficiently rapid for the concentration of CO 2 to remain almost uniform spatially. The foaming model makes use of experimentally calibrated constitutive laws for the uniaxial stress versus strain response of the PMMA grades as a function of strain rate and temperature, and the effect of dissolved CO 2 is accounted for by a shift in the glass transition temperature of the PMMA. The maximum achievable porosity is interpreted in terms of cell wall tearing and comparisons are made between the predictions of the model and nanofoaming measurements; it is deduced that the failure strain of the cell walls is sensitive to cell wall thickness.

scholarly journals The mechanics of solid-state nanofoaming

2019 ◽  
Author(s):  
Frederik Van Loock
Keyword(s):  
Cell Wall ◽  
Solid State ◽  
Cell Walls ◽  
Uniaxial Stress ◽  
Nucleation Density ◽  
One Dimensional ◽  
Foaming Process ◽  
Cell Nucleation ◽  
Foaming Temperature ◽  
Versus Strain

Solid-state nanofoaming experiments are conducted on two polymethyl methacrylate (PMMA) grades of markedly different molecular weight using CO2 as the blowing agent. The sensitivity of porosity to foaming time and foaming temperature is measured. Also, the microstructure of the PMMA nanofoams is characterized in terms of cell size and cell nucleation density. A one-dimensional numerical model is developed to predict the growth of spherical, gas-filled voids during the solid-state foaming process. Diffusion of CO2 within the PMMA matrix is sufficiently rapid for the concentration of CO2 to remain almost uniform spatially. The foaming model makes use of experimentally calibrated constitutive laws for the uniaxial stress versus strain response of the PMMA grades as a function of strain rate and temperature, and the effect of dissolved CO2 is accounted for by a shift in the glass transition temperature of the PMMA. The maximum achievable porosity is interpreted in terms of cell wall tearing and comparisons are made between the predictions of the model and nanofoaming measurements; it is deduced that the failure strain of the cell walls is sensitive to cell wall thickness.

scholarly journals Percolation of Primary Crystals in Cell Walls of Aluminum Alloy Foam via Semi-Solid Route

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 847
Author(s):  
Satomi Takamatsu ◽  
Takashi Kuwahara ◽  
Ryunosuke Kochi ◽  
Shinsuke Suzuki
Keyword(s):  
Cell Wall ◽  
Aluminum Alloy ◽  
Solid State ◽  
Percolation Threshold ◽  
Percolation Theory ◽  
Cell Walls ◽  
Foaming Process ◽  
Semi Solid ◽  
The Stability ◽  
Primary Crystals

Herein, a uniform aluminum alloy foam was fabricated by the addition of TiH2 as a blowing agent to Al-6.4 mass % Si in the semi-solid state and subsequent solidification. This was aimed at propounding the stabilization mechanism of the proposed foaming process. The microscopic images, which were the cross section on the center of the foam etched with Weck’s reagent, showed the primary crystals in the semi-solid state and solidifying segregation surrounding the crystals. Thus, it became evident that the area ratio of primary crystals in the semi-solid state approximately equals to the set solid fraction. According to the percolation theory for the cell wall model, the drainage in the cell walls with primary crystals above the percolation threshold was found to be inhibited. By considering that each cell wall is a flow path of the foam, the percentage of the cell walls with inhibited drainage to all the other cell walls was observed to exceed the percolation threshold of the lattice model (0.33) as per the percolation theory. Therefore, it can be concluded that the primary crystals inhibit drainage in some cell walls, ensuring that the stability of the foam is maintained.

scholarly journals The Influence of Temperature on Stability of Aluminum Foam Cell Wall during Foaming Process

2018 ◽  
Vol 225 ◽  
pp. 01006 ◽  
Author(s):  
Dewi Puspitasari ◽  
Fatthie Khairullah Hishyam Rabie ◽  
Turnad Lenggo Ginta ◽  
Jundika Candra Kurnia ◽  
Mazli Mustapha
Keyword(s):  
Compressive Strength ◽  
Cell Wall ◽  
Aluminum Foam ◽  
Foam Cell ◽  
Testing Machine ◽  
Optical Microscope ◽  
Porosity Level ◽  
Foaming Process ◽  
E 92 ◽  
Foaming Temperature

This study concerns about the influence of foaming temperature which is applied to foaming process of aluminum foam to improve the stability of aluminum foam cell wall. Powder metallurgical method with four major foaming temperatures of 750°C, 800°C, 850°C and 900°C have been selected. Furthermore, the porosity of the foam was determined by ImageJ Analysis Software. Microhardness testing on the cell wall of aluminium foam was conducted according to ASTM E 92 using microhardness tester LM24AT with 200 grams and 15 s for loading time. The universal testing machine was applied to characterize the effect of foaming temperature on compression strength. The aluminum foam was observed in macroscopic and microscopic level using optical microscope (OM). The result revealed that the foaming temperature of 800°C gave the lowest value of porosity, with the highest hardness and compressive strength of 55.29 HV and 1.41 MPa, respectively. In addition, the highest porosity level was acquired by foaming temperature which was set at 900 °C. The lowest hardness value of 38.50 HV was obtained by foaming temperature of 700°C and the minimum compressive strength value of 0.75 MPa was exhibited when the foaming temperature was set at 900°C.

Comparison of Cell Wall Microstructure of Aluminum Foams Produced by Melt Foaming and Gas Injection Foaming Processes

2013 ◽  
Vol 457-458 ◽  
pp. 540-543
Author(s):  
Yu Tong Zhou ◽  
Yan Xiang Li ◽  
Xing Nan Liu ◽  
Wen Wen Yuan
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Base Alloy ◽  
Gas Injection ◽  
Secondary Phases ◽  
Practical Application ◽  
Aluminum Foams ◽  
Foaming Process ◽  
Metallurgical Structure ◽  
The Difference

Aluminum foams from A356 base alloy were produced by both the melt foaming process and gas injection foaming process. A comparison of microstructures between the two kinds of aluminum foams was carried out. The related causes were analyzed to form the difference in microstructure. Results indicate that aluminum foams produced by different processes are distinct in metallurgical structure. The average thickness of cell wall, the species and area fraction of secondary phases or particles and other metallurgical features have been all comparatively studied. The difference in microstructure features of the cell walls will also make the aluminum foams different in mechanical properties. Therefore, we need to select proper foaming process for aluminum foams according to the property requirements in practical application.

Solid-State Foaming of Polycaprolactone (PCL)

2007 ◽  
Author(s):  
Hai Wang ◽  
Wei Li ◽  
Vipin Kumar
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solid State ◽  
Room Temperature ◽  
Saturation Pressure ◽  
Crystalline Polymer ◽  
Foaming Process ◽  
Quenching Process ◽  
Foaming Temperature ◽  
Scanning Electron

Polycaprolacton (PCL) is a synthetic biodegradable polymer that is widely used in tissue engineering related studies. It is a semi-crystalline polymer, and has a glass transition temperature (Tg) of −60°C and a melting temperature of 60°C. In this paper, we report on the progress in creating porous PCL foams using the solid-state foaming process. The objective of this study is to examine the foam-ability of PCL using room temperature saturation. PCL specimens were made using compression molding. A “quenching” process was introduced to manipulate the crystallinity of PCL samples. CO2 was used for gas saturation. The effects of saturation pressure and foaming temperature were studied. The created microstructures were characterized using scanning electron microscopy (SEM). The preliminary results have shown that microstructures with pores on the scale of hundreds of nanometers were generated.

Foaming of Polystyrene with Supercritical Carbon Dioxide

2013 ◽  
Vol 669 ◽  
pp. 366-370
Author(s):  
Wei Hua Ma ◽  
Jie Ding ◽  
Qin Zhong
Keyword(s):  
Carbon Dioxide ◽  
Glass Transition ◽  
Supercritical Carbon Dioxide ◽  
General Purpose ◽  
High Impact ◽  
Foaming Process ◽  
Cell Nucleation ◽  
Cell Densities ◽  
Foaming Temperature ◽  
Supercritical Carbon

General Purpose Polystyrene (GPPS) and High Impact Polystyrene (HIPS) were foamed with supercritical carbon dioxide in the batch foaming process. Foaming behaviors of GPPS and HIPS were investigated. The cell diameters and cell densities of GPPS and HIPS vary strangely with foaming conditions and can be explained by the classical nucleation. The competition between cell growth and cell nucleation is used to explain these strange foaming behaviors. The glass transition temperature (Tg) almost remains constant with the foaming temperature rising.

scholarly journals Solid-State Foaming Process Optimization for the Production of Shape Memory Polymer Composite Foam

2021 ◽  
Vol 11 (8) ◽  
pp. 3433
Author(s):  
Tamem Salah ◽  
Aiman Ziout
Keyword(s):  
Solid State ◽  
Shape Memory Polymer ◽  
Sustainable Manufacturing ◽  
Holding Time ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Foaming Process ◽  
Optimum Parameters ◽  
Packing Pressure ◽  
Foaming Temperature

This research examined the optimization of the sustainable manufacturing process for polyester-based polymers/Fe3O4 nanocomposite foaming. The foamed structure was achieved by using a solid-state foaming process, where the prepared foams were tested in order to ascertain the optimum foaming parameters with the highest foaming ratios and the lowest foaming densities. The foaming parameters used in this research were the polymer type, nanoparticle percentage, packing pressure, holding time, foaming temperature, and foaming time. Two levels were selected for each factor, and a Taguchi plan was designed to determine the number of experiments required to reach a conclusion. Further characterization techniques, namely, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were used with the original samples to gain a better understanding of their structure and chemical composition. The data analysis showed that regardless of the parameters used, a high foaming ratio resulted in a low density. The introduction of nanoparticles (NPs) to the polymer structure resulted in higher foaming ratios. This increment in foaming ratio was noticeable on Corro-Coat PE Series 7® (CC) polymer more than Jotun Super Durable 2903® (JSD). The optimum parameters to prepare the highest foaming ratios were as follows: CC polymer with 2% NPs, compressed under a pressure of 10 K lbs. for a 3 min holding time and foamed at 290 °C for 15 min in the oven.

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