Morphological Analysis of Foamed HDPE/LLDPE Blends by X-ray Micro-Tomography: Effect of Blending, Mixing Intensity and Foaming Temperature

2017 ◽  
Vol 36 (5) ◽  
pp. 221-250 ◽  
Author(s):  
Peyman Shahi ◽  
Amir Hossein Behravesh ◽  
Sheikh Rasel ◽  
Ghaus Rizvi ◽  
Remon Pop-Iliev
Keyword(s):  
Cell Size ◽  
Void Fraction ◽  
Cellular Structure ◽  
3D Analysis ◽  
Average Cell Size ◽  
Cell Size Distribution ◽  
Average Cell ◽  
X Ray ◽  
Wide Range ◽  
Foaming Temperature

Non-invasive x-ray micro-computed tomography was employed for thorough quantitative and qualitative analysis of the cellular structure of foams made of linear low density polyethylene (LLDPE), high density polyethylene (HDPE) and their blends. Special emphasis was given to the differences between the results of 3D and 2D analyses, to evaluate the possible errors while studying the morphology using conventional 2D techniques (e.g. SEM). Blends with the weight compositions of 90%LLDPE/10%HDPE and 75%LLDPE/25%HDPE were produced at different rotor speeds of 10, 60 and 120 rpm and batch foaming was examined over a wide range of temperature. The void fraction values from 2D and 3D analysis were found to agree well with those obtained with the Archimedes method. Results showed more uniform cell size distribution for blends mixed at the lower spectrum of screw rotational speed. Among the blends with higher void fraction values and relatively uniform cellular structure, higher average cell size (3–30%) and cell population density (1.25–2.5 times) were noticed in 3D analysis compared with 2D data. The micro-CT images at different cross sections revealed anisotropic cell growth and more elongated cells along the thickness of the specimen. It was also observed that, with increase in foaming temperature, cell shrink prevailed over cell coalescence in the samples with lower viscosity (prepared at low rpm of 10), while for those with higher viscosity (prepared at an rpm of 60) cell coalescence was more dominant.

Growth and Cell-Size Distribution of Marine Planktonic Algae in Batch and Dialysis Cultures

1973 ◽  
Vol 30 (2) ◽  
pp. 143-155 ◽  
Author(s):  
A. Prakash ◽  
Liv Skoglund ◽  
Britt Rystad ◽  
Arne Jensen
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Growth Cycle ◽  
Exponential Growth Phase ◽  
Average Cell Size ◽  
Cell Size Distribution ◽  
Average Cell ◽  
Planktonic Algae ◽  
Maximum Cell ◽  
Dialysis Culture

An extended exponential growth phase and a higher maximum population characterized growth of planktonic algae in a dialysis system compared with that in a batch system. Algal cells grown in a dialysis culture had higher chlorophyll content and a larger average cell size than those grown in a batch culture. In both types of culture, changes in cell-size distribution were related to the phases of the growth cycle with maximum cell-size during the stationary phase. Various interactions of the component reactions of photosynthesis leading to changes in growth pattern and cell-size distribution are discussed.

Effect of Nanoclay on the Physical-Mechanical and Thermal Properties and Microstructure of Extruded Noncross-Linked LDPE Nanocomposite Foams

2011 ◽  
Vol 471-472 ◽  
pp. 751-756 ◽  
Author(s):  
F. Zandi ◽  
M. Rezaei ◽  
A. Kasiri
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Cell Size ◽  
Flame Retardancy ◽  
Image Analyzer ◽  
Mechanical And Thermal Properties ◽  
Average Cell Size ◽  
Cell Size Distribution ◽  
Average Cell ◽  
Nanocomposite Foams

Novel noncross-linked low density polyethylene (LDPE) foams were produced by extrusion process. In this study the effects of Organophilic Montmorillonite (OMMT) nanoclay (DK1) on thermal conductivity, flame retardancy, morphological and mechanical properties of LDPE foams have been investigated. Nanoclay dispersion in LDPE foam structure was examined by X-ray diffraction (XRD), microstructure was observed by an optical microscope and analyzed by Bel View image analyzer, thermal conductivity was studied by a simple transient method, mechanical properties was investigated using a tensile-compression Zwick-Roell machine as well as the flame retardancy of the samples was examined by flammability test. The optimum nanoclay content was determined by comparison of the properties in nanocomposite and neat LDPE foams. Due to the presence of nanoclay in the foam and decreasing the cell nucleation energy around the nanoclay, the average cell size was decreased as well as the cell density and microstructure uniformity was increased. In XRD patterns of LDPE nanocomposite foams, OMMT (DK1) characteristic peak was not observed as evidence of nanoclay intercalation-exfoliation in the polymer matrix, which led to the production of foams with homogenous microstructure. Furthermore, this nanocomposites showed lower thermal conductivity compared to neat LDPE foam, which can be attributed to the cell size reduction as well as narrow cell size distribution in nanocomposite foams. Compression test results demonstrated that LDPE nanocomposite foams with proper clay contents have improved mechanical properties (Young’s modulus, compressive strength). Furthermore due to the presence of DK1 nanoclay, LDPE foam showed a good char formation as an evidence of their flame retardancy.

Characterization of LDMMs

MRS Bulletin ◽  
1990 ◽  
Vol 15 (12) ◽  
pp. 41-43
Keyword(s):  
Spatial Scale ◽  
Cell Size ◽  
Three Dimensional ◽  
Morphological Properties ◽  
Sem Images ◽  
Average Cell Size ◽  
Cell Size Distribution ◽  
Average Cell ◽  
Process Step ◽  
Size Standard

The previous sections of this article described the synthesis, morphologies, and properties of a variety of low-density microcellular materials. This section discusses several of the analytical methods used and developed at the DOE laboratories to characterize these state-of-the-art materials.In some LDMM applications, quantitative measurements of the material's average cell size and cell size distribution are desired. Indeed, the term “microcellular” has little meaning without such information. As seen throughout this article, however, most LDMMs do not have a readily defined cellular character. The more general problem is to quantify the spatial scale(s) of the foam. For this purpose it is necessary to define one or more “measures” of the spatial scale. The possibilities are many and include not only single numbers (e.g., cell size and cell size standard deviation, where “cell size” is meaningful) but also functional descriptions (e.g., correlation functions).SEM provides direct images and, therefore, is the most popular technique for examining LDMM morphology. SEM, however, suffers from at least three limitations: (1) SEM examines only a very small volume of material, and thus is impractical for obtaining average morphological properties; (2) SEM requires that nonconductive LDMMs be coated, a process step that can alter the structure and introduce artifacts (particularly with delicate structures); and (3) SEM images are only two-dimensional projections of real three-dimensional structures.

Effect of Foaming Temperature Control on Cell Size and Cell Density of Microcellular Plastics

2005 ◽  
Vol 24 (2) ◽  
pp. 91-102 ◽  
Author(s):  
Hidetaka Kawashima ◽  
Minoru Shimbo
Keyword(s):  
Cell Size ◽  
Cell Density ◽  
Average Cell Size ◽  
Average Cell ◽  
Blowing Agent ◽  
Microcellular Plastics ◽  
Temperature Method ◽  
Foamed Plastics ◽  
Maximum Cell ◽  
Foaming Temperature

In this study, noticing foaming temperature as a factor, which induces thermodynamic instability for cell nucleation of Microcellular plastics, the effect of control method of foaming temperature on cell size and cell density - that is number per unit volume of foamed plastics - were investigated. Generally, foaming by using batch process is carried out as follows. First, blowing agent is soaked into plastics until saturation under high pressure and soaking temperature. After plastics were saturated with blowing agent, pressure is released rapidly and then temperature is raised to foaming temperature and cells are nucleated and grown. Finally, rapid cooling controls cell growth. In this case, two methods can be considered for the control of foaming temperature. One is the elevated temperature method in which temperature is raised to foaming temperature and cells are grown after decompression in the foaming process. The other is the constant temperature method in which the temperature is already kept at foaming temperature before decompression. That is, it is the method of performing soaking and foaming at the same temperature. Polymethylmethacrylate (PMMA) resins were foamed under foaming conditions which the same foaming magnification is produced by both methods and cell size and cell density of foamed PMMA were investigated. As results, in case of production of the foamed plastics having the same foam magnification, it turned out that cell density of foamed plastics becomes large and average cell size becomes small but the maximum cell size becomes large by the elevated temperature method. On the other hand, although the maximum cell size becomes small, average cell size becomes large by the constant temperature method.

scholarly journals Experimental Research on Detonation Cell Size of a Purified Biogas-Oxygen Mixture

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6605
Author(s):  
Stanislaw Siatkowski ◽  
Krzysztof Wacko ◽  
Jan Kindracki
Keyword(s):  
Cell Size ◽  
Cellular Structure ◽  
Renewable Energy Sources ◽  
Initial Pressure ◽  
Oxygen Mixture ◽  
Average Cell Size ◽  
Detonation Cell ◽  
Average Cell ◽  
Promising Alternative ◽  
Detonation Cell Size

Interest in alternative and renewable energy sources has risen significantly in recent years. Biogas is a prime example of a promising, alternative fuel that might be a possible replacement for fossil fuels. It is a mixture consisting mainly of CH4 and CO2 with various additions. Biogas is easily storable and as such is a more reliable and stable source of energy than solar and wind sources, which suffer from unreliability due to their dependence on weather conditions. In this paper, the authors report experimental results of detonation of a biogas-oxygen mixture. The composition of the biogas was 70% CH4 + 30% CO2 and the experiments were carried out for a range of equivalence ratios (Φ = 0.5 ÷ 1.5) and initial pressures (0.6 ÷ 1.6 bar). The aim of the research was to analyze the cellular structure of detonation. The soot foil technique was used to determine the width of the detonation cells (λ). The conducted experiments and subsequent analysis of the detonation cell size confirm that both the increase in the initial pressure of the mixture or move away from stoichiometric (Φ = 1) composition is accompanied by a decrease in the width of the detonation cell. The authors also argue that due to the unstable cellular structure of the detonation, it is insufficient to report only the average cell size. Instead, the researchers propose more detailed statistical description assured values.

The Influence of Melt Elongational Properties on the Morphology of PES Cellular Materials

2002 ◽  
Vol 21 (6) ◽  
pp. 445-454 ◽  
Author(s):  
Frank Wöllecke ◽  
Volker Altstädt ◽  
Jan Sandler ◽  
Dietmar Rakutt
Keyword(s):  
Molecular Weight ◽  
Cell Size ◽  
Foam Cell ◽  
Batch Process ◽  
Processing Conditions ◽  
Compressive Properties ◽  
Polymer Molecular Weight ◽  
Average Cell Size ◽  
Cell Size Distribution ◽  
Average Cell

Rheotens melt elongational experiments were performed to evaluate polyethersulfone with regard to its foamability. The effect of polymer molecular weight was correlated with the resulting foam cell morphology achieved under identical processing conditions in a batch process. It appears, that the melt strength of the polyethersulfone governs the average cell size, cell size distribution, as well as cell wall rupture during expansion and the corresponding compressive properties of the foam. These effects were further verified by a variation of the blowing agent content for polyethersulfone with a given molecular weight.

scholarly journals Foamability of Cellulose Palmitate Using Various Physical Blowing Agents in the Extrusion Process

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2416
Author(s):  
Teijo Rokkonen ◽  
Pia Willberg-Keyriläinen ◽  
Jarmo Ropponen ◽  
Tero Malm
Keyword(s):  
Cell Size ◽  
Extrusion Process ◽  
Foam Formation ◽  
Polymer Foams ◽  
Average Cell Size ◽  
Cell Size Distribution ◽  
Average Cell ◽  
Blowing Agents ◽  
Die Temperature ◽  
Carbon Dioxide Co2

Polymer foams are widely used in several fields such as thermal insulation, acoustics, automotive, and packaging. The most widely used polymer foams are made of polyurethane, polystyrene, and polyethylene but environmental awareness is boosting interest towards alternative bio-based materials. In this study, the suitability of bio-based thermoplastic cellulose palmitate for extrusion foaming was studied. Isobutane, carbon dioxide (CO2), and nitrogen (N2) were tested as blowing agents in different concentrations. Each of them enabled cellulose palmitate foam formation. Isobutane foams exhibited the lowest density with the largest average cell size and nitrogen foams indicated most uniform cell morphology. The effect of die temperature on foamability was further studied with isobutane (3 wt%) as a blowing agent. Die temperature had a relatively low impact on foam density and the differences were mainly encountered with regard to surface quality and cell size distribution. This study demonstrates that cellulose palmitate can be foamed but to produce foams with greater quality, the material homogeneity needs to be improved and researched further.

scholarly journals (230) Genetic Differences in Sweet Cherry Fruit Size Are Determined by Cell Number and Not Cell Size

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1008B-1008 ◽  
Author(s):  
James W. Olmstead ◽  
Amy F. Iezzoni ◽  
Matthew D. Whiting
Keyword(s):  
New York ◽  
Cell Size ◽  
Sweet Cherry ◽  
Fruit Size ◽  
Cell Number ◽  
Average Cell Size ◽  
Average Cell ◽  
Cell Numbers ◽  
Wide Range ◽  
Sweet Cherries

Although maximizing fruit size is critical for profitable sweet cherry (Prunusavium L.) production, little is known about the cellular differences among and between cultivars that contribute to fruit size differences. A wide range of fruit size exists among sweet cherries, and, due to cultural and environmental differences, significant variation exists among genetically identical fruit from the same cultivar. To determine the relative contributions of flesh cell number and cell size to final fruit size in sweet cherry, equatorial sections of three cultivars with a wide range in final average fruit size [`New York 54' (NY54; 1.4 g fresh weight, 11.8 mm diameter), `Emperor Francis' (EF; 6.1 g, 21.0 mm), and `Selah' (12.8 g, 25.5 mm)] were created from mature fruit. Cells intersecting a transverse line were counted and average cell length was calculated. The average cell numbers were significantly different (P ≤ 0.05) between `NY54', `EF', and `Selah' (26.7, 47.4, and 83.2, respectively), indicating that flesh cell number is the major contributor to differences in fruit size between cultivars. Flesh cell numbers of `NY54', `EF', and `Selah' were similar at bloom and increased rapidly for a short duration after fertilization, suggesting a key developmental period for fruit size differences. To determine the contribution of cell number differences to variation in fruit size within a cultivar, fruit from `Bing' and `Regina' trees exhibiting a range of size due to cultural and environmental differences were measured. In both cases, average cell number was not significantly different (P = 0.9, P = 0.3, respectively), while average cell size was (P ≤ 0.05), further indicating fruit flesh cell number is a genetically controlled trait.

Key Parameters Influencing Microcellular Polystyrene Cell Morphology Blowing with Supercritical CO2

2012 ◽  
Vol 501 ◽  
pp. 237-242 ◽  
Author(s):  
Chang Yun Gao ◽  
Nan Qiao Zhou ◽  
Ti Kun Shan ◽  
Zhen Xiang Xin
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Cell Density ◽  
Cell Morphology ◽  
Saturation Pressure ◽  
Processing Temperature ◽  
Polymer Foam ◽  
Cell Size Distribution ◽  
Average Cell ◽  
Foaming Temperature

Polystyrene microcellular foams blowing with supercritical CO2 were prepared with a novel polymer foam processing simulator. Key parameters influencing Polystyrene cell morphology were investigated. The effect of processing temperature and saturation pressure on cell morphology was observed by scanning electron microscope and the average cell diameter and cell size distribution was calculated. The results show that the cell density decrease and cell size increase with the increase of foaming temperature. The cell density increase and cell size decrease with the increase of saturation pressure. And the cell size distribution shows a narrow distribution at lower foaming temperature and higher saturation pressure.

scholarly journals Analysis of the Foaming Window for Thermoplastic Polyurethane with Different Hard Segment Contents

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3143
Author(s):  
Mercedes Santiago-Calvo ◽  
Haneen Naji ◽  
Victoria Bernardo ◽  
Judith Martín-de León ◽  
Alberto Saiani ◽  
...  
Keyword(s):  
Cell Size ◽  
Saturation Pressure ◽  
Final Conclusion ◽  
Nucleation Density ◽  
Scanning Calorimetry ◽  
Average Cell Size ◽  
Average Cell ◽  
Saturation Time ◽  
A Cell ◽  
Foaming Temperature

A series of thermoplastic polyurethanes (TPUs) with different amounts of hard segments (HS) (40, 50 and 60 wt.%) are synthesized by a pre-polymer method. These synthesized TPUs are characterized by Shore hardness, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and rheology. Then, these materials are foamed by a one-step gas dissolution foaming process and the processing window that allows producing homogeneous foams is analyzed. The effect of foaming temperature from 140 to 180 °C on the cellular structure and on density is evaluated, fixing a saturation pressure of 20 MPa and a saturation time of 1 h. Among the TPUs studied, only that with 50 wt.% HS allows obtaining a stable foam, whose better features are reached after foaming at 170 °C. Finally, the foaming of TPU with 50 wt.% HS is optimized by varying the saturation pressure from 10 to 25 MPa at 170 °C. The optimum saturation and foaming conditions are 25 MPa and 170 °C for 1 h, which gives foams with the lowest relative density of 0.74, the smallest average cell size of 4 μm, and the higher cell nucleation density of 8.0 × 109 nuclei/cm3. As a final conclusion of this investigation, the TPU with 50 wt.% HS is the only one that can be foamed under the saturation and foaming conditions used in this study. TPU foams containing 50 wt.% HS with a cell size below 15 microns and porosity of 1.4–18.6% can be obtained using foaming temperatures from 140 to 180 °C, saturation pressure of 20 MPa, and saturation time of 1 h. Varying the saturation pressure from 10 to 25 MPa and fixing the foaming temperature of 170 °C and saturation pressure of 1 h results in TPU foams with a cell size of below 37 microns and porosity of 1.7–21.2%.

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