scholarly journals Improving the Supercritical CO2 Foaming of Polypropylene by the Addition of Fluoroelastomer as a Nucleation Agent

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 226 ◽  
Author(s):  
Chenguang Yang ◽  
Quan Zhao ◽  
Zhe Xing ◽  
Wenli Zhang ◽  
Maojiang Zhang ◽  
...  
Keyword(s):  
Cell Size ◽  
Supercritical Co2 ◽  
Deep Understanding ◽  
Local Strain ◽  
Nucleating Agent ◽  
Phase System ◽  
Nucleation Agent ◽  
Cell Size Distribution ◽  
Multiple Phase ◽  
Foaming Behavior

In this study, a small amount of fluoroelastomer (FKM) was used as a nucleating agent to prepare well-defined microporous PP foam by supercritical CO2. It was observed that solid FKM was present as the nanoscale independent phase in PP matrix and the FKM could induce a mass of CO2 aggregation, which significantly enhanced the diffusion rate of CO2 in PP. The resultant PP/FKM foams exhibited much smaller cell size (~24 μm), and more than 16 times cell density (3.2 × 108 cells/cm3) as well as a much more uniform cell size distribution. PP/FKM foams possessed major concurrent enhancement in their tensile stress and compressive stress compared to neat PP foam. We believe that the added FKM played a key role in enhancing the heterogeneous nucleation, combined with the change of local strain in the multiple-phase system, which was responsible for the considerably improved cell morphology of PP foaming. This work provides a deep understanding of the scCO2 foaming behavior of PP in the presence of FKM.

scholarly journals Improving the Supercritical CO2 Foaming of Polypropylene by the Addition of Fluoroelastomer as a Nucleation Agent

2018 ◽  
Author(s):  
Chenguang Yang ◽  
Quan Zhao ◽  
Zhe Xing ◽  
Wenli Zhang ◽  
Maojiang Zhang ◽  
...  
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Cell Density ◽  
Deep Understanding ◽  
Local Strain ◽  
Nucleating Agent ◽  
Phase System ◽  
Field Variation ◽  
Nucleation Agent ◽  
Cell Size Distribution

Polypropylene (PP) foam has a great deal of application since it normally exhibits non-uniform cell size distribution, low cell density, and cracked cells. In this study, a small amount of fluoroelastomer (FKM) was used as a nucleating agent to prepare well-defined microporous PP foam by supercritical CO2. It was observed that solid FKM was present as the nanoscale independent phase in PP matrix and the FKM could induce a mass of CO2 aggregation, which significantly enhanced the diffusion rate of CO2 in PP. The resultant PP/FKM foams exhibited much smaller cell size (～24 μm), and more than 16 times cell density (3.2×108 cells/cm3) as well as a much more uniform cell size distribution than that of the neat PP foam. PP/FKM foams possessed major concurrent enhancement in their tensile stress and compressive stress compared to neat PP foam. We believed that the added FKM played a key role in enhancing the heterogeneous nucleation, combined with the local strain field variation in the multiple-phase system, which was responsible for the considerably improved cell morphology of PP foaming. This paper provides a deep understanding of the scCO2 foaming behavior of PP in the presence of FKM.

Morphological, thermo-mechanical, and thermal conductivity properties of halloysite nanotube-filled polypropylene nanocomposite foam

2016 ◽  
Vol 54 (2) ◽  
pp. 217-233 ◽  
Author(s):  
Renan Demori ◽  
Eveline Bischoff ◽  
Ana P de Azeredo ◽  
Susana A Liberman ◽  
Joao Maia ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cell Size ◽  
Cell Density ◽  
Void Fraction ◽  
Cell Structure ◽  
Cell Size Distribution ◽  
Halloysite Nanotube ◽  
Dynamic Mechanical ◽  
Foaming Behavior ◽  
Homogeneous Cell

Studies about polypropylene nanocomposite foams are receiving attention because nanoparticles can change physical and mechanical properties, as well as improve foaming behavior in terms of homogeneous cell structure, cell density, and void fraction. In this research, the foaming behavior of polypropylene, polypropylene/long-chain branched polypropylene (LCBPP) 100/20 blend, and polypropylene/LCBPP/halloysite nanocomposites with 0.5 and 3 parts per hundred of resin (phr) is studied. The LCBPP was used to improve the rheological properties of polypropylene/LCBPP blend, namely the degree of strain-hardening. Transmission electron microscopy observation indicated that halloysite nanotube particles are well distributed in the matrix by aggregates. Subsequent foaming experiments were conducted using chemical blowing agent in injection-molding processing. Polypropylene foam exhibited high cell density and cell size as well as a collapsing effect, whereas the polypropylene/LCBPP blend showed a reduction of the void fraction and cell density compared to expanded polypropylene. Also, the blend showed reduction of the collapsing effect and increase of homogeneous cell size distribution. The introduction of a small amount of halloysite nanotube in the polypropylene/LCBPP blend improved the foaming behavior of the polypropylene, with a uniform cell structure distribution in the resultant foams. In addition, the cell density of the composite sample was higher than the polypropylene/LCBPP sample, having increased 82% and 136% for 0.5 and 3 phr of loaded halloysite nanotube, respectively. Furthermore, the presence of halloysite nanotube increased crystallization temperature (Tc) and slightly increased dynamic-mechanical properties measured by dynamic-mechanical thermal analysis. By increasing halloysite nanotube content to 3 phr, the insulating effect increased by 13% compared to polypropylene/LCBPP blend. For comparative purposes, the effect on foaming behavior of polypropylene/LCBPP was also investigated using talc microparticles.

scholarly journals Effect of the Molecular Structure of TPU on the Cellular Structure of Nanocellular Polymers Based on PMMA/TPU Blends

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3055
Author(s):  
Ismael Sánchez-Calderón ◽  
Victoria Bernardo ◽  
Mercedes Santiago-Calvo ◽  
Haneen Naji ◽  
Alberto Saiani ◽  
...  
Keyword(s):  
Cell Size ◽  
Cellular Structure ◽  
Thermoplastic Polyurethane ◽  
Nucleating Agent ◽  
Nucleation Density ◽  
Cell Size Distribution ◽  
Cell Nucleation ◽  
Hard Segments ◽  
Different Characteristics ◽  
Nucleating Effect

In this work, the effects of thermoplastic polyurethane (TPU) chemistry and concentration on the cellular structure of nanocellular polymers based on poly(methyl-methacrylate) (PMMA) are presented. Three grades of TPU with different fractions of hard segments (HS) (60%, 70%, and 80%) have been synthesized by the prepolymer method. Nanocellular polymers based on PMMA have been produced by gas dissolution foaming using TPU as a nucleating agent in different contents (0.5 wt%, 2 wt%, and 5 wt%). TPU characterization shows that as the content of HS increases, the density, hardness, and molecular weight of the TPU are higher. PMMA/TPU cellular materials show a gradient cell size distribution from the edge of the sample towards the nanocellular core. In the core region, the addition of TPU has a strong nucleating effect in PMMA. Core structure depends on the HS content and the TPU content. As the HS or TPU content increases, the cell nucleation density increases, and the cell size is reduced. Then, the use of TPUs with different characteristics allows controlling the cellular structure. Nanocellular polymers have been obtained with a core relative density between 0.15 and 0.20 and cell sizes between 220 and 640 nm.

1465 - Cell size distribution of planktonic bacteria in shallow lakes

2018 ◽  
Author(s):  
Zsuzsanna Márton ◽  
Bianka Csitári ◽  
Tamas Felfoldi ◽  
Anna J Szekely ◽  
Attila Szabo
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Shallow Lakes ◽  
Cell Size Distribution ◽  
Planktonic Bacteria

scholarly journals Experimental-numerical studies of the effect of cell structure on the mechanical properties of polypropylene foams

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 713-723
Author(s):  
Wei Gong ◽  
Tuan-Hui Jiang ◽  
Xiang-Bu Zeng ◽  
Li He ◽  
Chun Zhang
Keyword(s):  
Mechanical Properties ◽  
Size Distribution ◽  
Cell Size ◽  
Cell Structure ◽  
Structure Parameters ◽  
Cell Size Distribution ◽  
Numerical Studies ◽  
Polypropylene Foam ◽  
The Impact ◽  
The Relationship

AbstractThe effects of the cell size and distribution on the mechanical properties of polypropylene foam were simulated and analyzed by finite element modeling with ANSYS and supporting experiments. The results show that the reduced cell size and narrow size distribution have beneficial influences on both the tensile and impact strengths. Decreasing the cell size or narrowing the cell size distribution was more effective for increasing the impact strength than the tensile strength in the same case. The relationship between the mechanical properties and cell structure parameters has a good correlation with the theoretical model.

scholarly journals SEBS as an Effective Nucleating Agent for Polystyrene Foams

Polymers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 3836
Author(s):  
Alberto Ballesteros ◽  
Ester Laguna-Gutiérrez ◽  
Miguel Ángel Rodríguez-Pérez
Keyword(s):  
Glass Transition ◽  
Cellular Structure ◽  
Nucleating Agent ◽  
Cellular Materials ◽  
Cell Content ◽  
Open Cell ◽  
Nucleation Effect ◽  
Foaming Behavior ◽  
Hardening Coefficient ◽  
Nucleating Effect

Different percentages of an elastomeric phase of styrene-ethylene-butylene-styrene (SEBS) were added to a polystyrene (PS) matrix to evaluate its nucleating effect in PS foams. It has been demonstrated that a minimum quantity of SEBS produces a high nucleation effect on the cellular materials that are produced. In particular, the results show that by adding 2% of SEBS, it is possible to reduce the cell size by 10 times while maintaining the density and open cell content of the foamed materials. The influence of this polymeric phase on the glass transition temperature (Tg) and the shear and extensional rheological properties has been studied to understand the foaming behavior. The results indicate a slight increase in the Tg and a decrease of the shear viscosity, extensional viscosity, and strain hardening coefficient as the percentage of SEBS increases. Consequently, an increase in the density and a deterioration of the cellular structure is detected for SEBS amounts higher than 3%.

scholarly journals The cell size distribution of tomato fruit can be changed by overexpression ofCDKA1

2014 ◽  
Vol 13 (2) ◽  
pp. 259-268 ◽  
Author(s):  
Anna Czerednik ◽  
Marco Busscher ◽  
Gerco C. Angenent ◽  
Ruud A. de Maagd
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Tomato Fruit ◽  
Cell Size Distribution

Core–shell structures with metallic silver as nucleation agent of low expansion phases in BaO/SrO/ZnO/SiO2 glasses

CrystEngComm ◽  
2019 ◽  
Vol 21 (29) ◽  
pp. 4373-4386 ◽  
Author(s):  
Christian Thieme ◽  
Michael Kracker ◽  
Katrin Thieme ◽  
Christian Patzig ◽  
Thomas Höche ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Nucleating Agent ◽  
Shell Structures ◽  
Metallic Silver ◽  
X Ray Diffraction ◽  
Nucleation Agent ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission

The role of silver as a nucleating agent in BaO/SrO/ZnO/SiO2 glasses is studied with a range of microstructure-characterization techniques, such as scanning transmission electron microscopy, ultraviolet-visible spectroscopy, and X-ray diffraction.

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