Thermoplastic polyurethane ( TPU ) modifier to develop bimodal cell structure in polypropylene/ TPU microcellular foam in presence of supercritical CO 2

2020 ◽  
Author(s):  
Jie Wang ◽  
Jun Li ◽  
Hui Li ◽  
Hongfu Zhou
Keyword(s):  
Cell Structure ◽  
Thermoplastic Polyurethane ◽  
Microcellular Foam

scholarly journals Synthesis and Characterization of Polyurethane-Nanoclay Composites

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
Manasa Nayani ◽  
Subhashini Gunashekar ◽  
Nidal Abu-Zahra
Keyword(s):  
Thermal Properties ◽  
Cell Structure ◽  
Thermoplastic Polyurethane ◽  
Mechanical And Thermal Properties ◽  
Composite Foam ◽  
Weight Percentage ◽  
Nanocomposite Foams ◽  
Methylene Diphenyl Diisocyanate ◽  
Closed Mold

In this study polyurethane (PUR)-nanoclay composites were synthesized using methylene diphenyl diisocyanate, polyol, and hectorite clay. The weight percentage of hectorite clay was varied at three different levels to study its effect on the properties of the thermoplastic polyurethane nanocomposite. The nanocomposite polyurethane foam was synthesized in a 2-step reaction process. The first step involved the addition and dispersion of nanoclay into the isocyanate. The mixture was then mixed with the polyol, and the foam was cast in a preheated closed mold. The PUR-nanocomposite foams were analyzed for cell structure, physical, mechanical, and thermal properties. The composite foam showed significant increase in tensile and flexural strengths, abrasion resistance, and thermal properties.

Preparation of fluorescent thermoplastic polyurethane microcellular foam films blown by supercritical CO2

2019 ◽  
Vol 55 (5) ◽  
pp. 483-505 ◽  
Author(s):  
Shiping Wang ◽  
Shuaiwei Xue ◽  
Chengbiao Ge ◽  
Qian Ren ◽  
Dan Zhao ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Thermoplastic Polyurethane ◽  
Microcellular Foam ◽  
Foam Films

scholarly journals Compression Molding of Thermoplastic Polyurethane Foam Sheets with Beads Expanded by Supercritical CO2 Foaming

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 656
Author(s):  
Tao Zhang ◽  
Seung-Jun Lee ◽  
Yong Hwan Yoo ◽  
Kyu-Hwan Park ◽  
Ho-Jong Kang
Keyword(s):  
Cell Size ◽  
Supercritical Co2 ◽  
Cell Structure ◽  
Thermoplastic Polyurethane ◽  
Compression Molding ◽  
Expansion Ratio ◽  
Compression Pressure ◽  
Elongation At Break ◽  
Foaming Process ◽  
Foaming Temperature

Expanded thermoplastic polyurethane (ETPU) beads were prepared by a supercritical CO2 foaming process and compression molded to manufacture foam sheets. The effect of the cell structure of the foamed beads on the properties of the foam sheets was studied. Higher foaming pressure resulted in a greater number of cells and thus, smaller cell size, while increasing the foaming temperature at a fixed pressure lowered the viscosity to result in fewer cells and a larger cell size, increasing the expansion ratio of the ETPU. Although the processing window in which the cell structure of the ETPU beads can be maintained was very limited compared to that of steam chest molding, compression molding of ETPU beads to produce foam sheets was possible by controlling the compression pressure and temperature to obtain sintering of the bead surfaces. Properties of the foam sheets are influenced by the expansion ratio of the beads and the increase in the expansion ratio increased the foam resilience, decreased the hardness, and increased the tensile strength and elongation at break.

Foaming behavior of microcellular poly(lactic acid)/TPU composites in supercritical CO2

2017 ◽  
Vol 31 (1) ◽  
pp. 61-78 ◽  
Author(s):  
Daifang Xu ◽  
Kejing Yu ◽  
Kun Qian ◽  
Chul B Park
Keyword(s):  
Lactic Acid ◽  
Cell Structure ◽  
Thermoplastic Polyurethane ◽  
Optical Microscope ◽  
Expansion Ratio ◽  
Poly Lactic Acid ◽  
Free Energy Barrier ◽  
Scanning Calorimetry ◽  
Melt Strength ◽  
Cell Nucleation

This article presents the effects of thermoplastic polyurethane (TPU) on the crystallization and melt strength of poly(lactic acid) (PLA) and on the enhancement of cell nucleation and expansion ratio to manufacture microcellular thermoplastic PLA foams in supercritical carbon dioxide. Addition of TPU increased the crystallinity and decreased the crystallite size as observed by differential scanning calorimetry and polarized optical microscope. The formed crystal domains worked as cross-linking points to increase the melt strength of a polymer that potentially affected the cell growth. Scanning electron microscope confirmed the immiscibility between PLA and TPU, and TPU was dispersed as islands in the PLA matrix. This phase morphology further influenced the cell structure of the PLA/TPU foams. TPU acted as a nucleating agent to enhance heterogeneous cell nucleation that is caused by the decrease in free energy barrier. Tensile stress that generated around the TPU and in some local regions surrounding the crystals and crystallization was dominant to induce cell nucleation.

Influence of cell type and skin-core structure on the tensile elasticity of the microcellular thermoplastic polyurethane foam

2019 ◽  
Vol 56 (2) ◽  
pp. 207-226 ◽  
Author(s):  
Chengbiao Ge ◽  
Shiping Wang ◽  
Wentao Zhai
Keyword(s):  
Polyurethane Foam ◽  
Residual Strain ◽  
Cell Structure ◽  
Thermoplastic Polyurethane ◽  
Core Structure ◽  
Hysteresis Phenomenon ◽  
Cell Type ◽  
Open Cell ◽  
Foaming Process ◽  
Polyurethane Film

In this work, the foaming process was employed to achieve lightweight thermoplastic polyurethane materials, and then the hysteresis and residual strain of corresponding materials in the tensile process were quantitatively calculated. In order to study the deformed mechanism, the influences of cell type and skin-core structure on the tensile elasticity of thermoplastic polyurethane foam were investigated. The open-cell thermoplastic polyurethane foam exhibited much lower hysteresis and residual strain compared to thermoplastic polyurethane film without cell structure, which demonstrated that the open-cell structure benefited to the tensile elasticity. In the case of closed-cell thermoplastic polyurethane foam, it had lower hysteresis and residual strain than thermoplastic polyurethane film; however, higher value than the thermoplastic polyurethane film can be observed beyond 100% strain, resulting from the stress concentration in the skin-core structure. Consequently, the hysteresis phenomenon can be improved by adjusting the ratio of skin-core structure. Moreover, the influence of density on the elasticity of the open-cell thermoplastic polyurethane foam was also discussed in this study.

Microcellular morphology evolution of polystyrene/thermoplastic polyurethane blends in the presence of supercritical CO2

2019 ◽  
Vol 38 (3-4) ◽  
pp. 68-85 ◽  
Author(s):  
Zhongjie Qu ◽  
Jianguo Mi ◽  
Yang Jiao ◽  
Hongfu Zhou ◽  
Xiangdong Wang
Keyword(s):  
Cell Structure ◽  
Thermoplastic Polyurethane ◽  
Complex Viscosity ◽  
Morphology Evolution ◽  
Melt Blending ◽  
Insulation Property ◽  
Interesting Phenomenon ◽  
Cell Nucleation ◽  
Thermal Insulation Property ◽  
And Storage

In this article, a facile melt blending and solid batch foaming approach was proposed to prepare microcellular polystyrene/thermoplastic polyurethane (PS/TPU) blending foams with supercritical carbon dioxide (CO2). Compared with those of pure PS and pure TPU, an interesting phenomenon about the enhanced complex viscosity and storage modulus, as well as decreased loss factor of PS/TPU blends, was found. The solubility of CO2 in the PS/TPU blends was enhanced, owing to the CO2 solubilization effects of TPU. An interesting bimodal cell structure (BCS) was observed in the PS/TPU blending foams with the TPU content of 10, 15, and 20%. Consequently, a significant conclusion could be speculated that the generation of BCS in the PS/TPU blending system depended on not only the viscosity and morphology of the polymer blends but also the solubility and diffusivity of the CO2 as well as the type of cell nucleation. The thermal insulation property of PS foam was improved by the introduction of TPU.

scholarly journals Preparation of Microcellular Foams by Supercritical Carbon Dioxide: A Case Study of Thermoplastic Polyurethane 70A

Processes ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1650
Author(s):  
Yu-Ting Hsiao ◽  
Chieh-Ming Hsieh ◽  
Tsung-Mao Yang ◽  
Chie-Shaan Su
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Pore Size ◽  
Cell Density ◽  
Thermoplastic Polyurethane ◽  
Saturation Pressure ◽  
Saturation Temperature ◽  
Expansion Ratio ◽  
Microcellular Foam

In this study, a case study to produce microcellular foam of a commercial thermoplastic polyurethane (TPU) through the supercritical carbon dioxide (CO2) foaming process is presented. To explore the feasibility of TPU in medical device and biomedical application, a soft TPU with Shore hardness value of 70A was selected as the model compound. The effects of saturation temperature and saturation pressure ranging from 90 to 140 °C and 90 to 110 bar on the expansion ratio, cell size and cell density of the TPU foam were compared and discussed. Regarding the expansion ratio, the effect of saturation temperature was considerable and an intermediate saturation temperature of 100 °C was favorable to produce TPU microcellular foam with a high expansion ratio. On the other hand, the mean pore size and cell density of TPU foam can be efficiently manipulated by adjusting the saturation pressure. A high saturation pressure was beneficial to obtain TPU foam with small mean pore size and high cell density. This case study shows that the expansion ratio of TPU microcellular foam could be designed as high as 4.4. The cell size and cell density could be controlled within 12–40 μm and 5.0 × 107–1.3 × 109 cells/cm3, respectively.

High-pressure freezing of cells in suspension for low-voltage scanning electron microscopy (LVSEM)

1991 ◽  
Vol 49 ◽  
pp. 64-65
Author(s):  
Marek Malecki ◽  
James Pawley ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
High Pressure ◽  
Low Voltage ◽  
Culture Media ◽  
Cell Structure ◽  
Freeze Substitution ◽  
Ice Crystal ◽  
High Pressure Freezing ◽  
Cell Culture Media ◽  
Voltage Scanning

The ultrastructure of cells suspended in physiological fluids or cell culture media can only be studied if the living processes are stopped while the cells remain in suspension. Attachment of living cells to carrier surfaces to facilitate further processing for electron microscopy produces a rapid reorganization of cell structure eradicating most traces of the structures present when the cells were in suspension. The structure of cells in suspension can be immobilized by either chemical fixation or, much faster, by rapid freezing (cryo-immobilization). The fixation speed is particularly important in studies of cell surface reorganization over time. High pressure freezing provides conditions where specimens up to 500μm thick can be frozen in milliseconds without ice crystal damage. This volume is sufficient for cells to remain in suspension until frozen. However, special procedures are needed to assure that the unattached cells are not lost during subsequent processing for LVSEM or HVEM using freeze-substitution or freeze drying. We recently developed such a procedure.

Cell structure properties during in situ creep experiments in the H.V.E.M.

1978 ◽  
Vol 36 (1) ◽  
pp. 574-575
Author(s):  
D. Caillard ◽  
J.L. Martin
Keyword(s):  
Tensile Axis ◽  
Cell Structure ◽  
Image Intensifier ◽  
Foil Thickness ◽  
Average Cell Size ◽  
Average Cell ◽  
Voltage Electron ◽  
Steady Stage ◽  
Stationary Creep

The behaviour of the dislocation substructure during the steady stage regime of creep, as well as its contribution to the creep rate, are poorly known. In particular, the stability of the subboundaries has been questioned recently, on the basis of experimental observations |1||2| and theoretical estimates |1||3|. In situ deformation experiments in the high voltage electron microscope are well adapted to the direct observation of this behaviour. We report here recent results on dislocation and subboundary properties during stationary creep of an aluminium polycristal at 200°C.During a macroscopic creep test at 200°C, a cell substructure is developed with an average cell size of a few microns. Microsamples are cut out of these specimens |4| with the same tensile axis, and then further deformed in the microscope at the same temperature and stain rate. At 1 MeV, one or a few cells can be observed in the foil thickness |5|. Low electron fluxes and an image intensifier were used to reduce radiation damage effects.

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