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.

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%.

Influence of Cell Morphology on the Compressive Deformation Behavior of Aluminum Foams

2018 ◽  
Vol 933 ◽  
pp. 215-219
Author(s):  
Min Li ◽  
Zhuo Kun Cao ◽  
Yang Yu ◽  
Hong Jie Luo ◽  
Jian Chao Shi ◽  
...  
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Deformation Behavior ◽  
Cellular Structure ◽  
Aluminum Foams ◽  
Reduced Pressure ◽  
Cell Size Distribution ◽  
Closed Cell ◽  
Similar Density ◽  
Compressive Tests

Closed-cell aluminum foams with different morphology were fabricated under both increased and reduced pressure. It is shown that the cell size distribution and cell wall thickness is significantly influenced by foaming pressure. Quasi-static compressive tests were performed on foam specimens with similar density but different cellular structure. Results indicates that compressive stress of aluminum foams with homogenous structure is much higher than that of specimen with wide cell size distribution.

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 Thermoplastic polyurethane foams: From autoclave batch foaming to bead foam extrusion

2020 ◽  
pp. 0021955X2091220
Author(s):  
Amin Shabani ◽  
Amir Fathi ◽  
Sebastian Erlwein ◽  
Volker Altstädt
Keyword(s):  
Cell Size ◽  
Thermoplastic Polyurethane ◽  
Polyurethane Foams ◽  
Morphological Properties ◽  
Cell Size Distribution ◽  
Foam Expansion ◽  
Foam Extrusion ◽  
Foaming Process ◽  
First Time ◽  
Batch Foaming

Two ester-based and one ether-based thermoplastic polyurethane grades have been used to produce thermoplastic polyurethane foams. The foaming process comprised pressure-induced batch foaming, foam extrusion, and bead foam extrusion by using an underwater granulator. Foam density and morphological properties, such as cell size, cell size distribution, and cell density, were measured through different analytical methods. Through autoclave batch foaming a minimum cell size of 10 µm and density of 202 kg/m3 is obtained, which is lower than the densities previously reported in the literature for thermoplastic polyurethane. Extrusion foaming however could not achieve the same range of foam expansion given that the lowest density achieved is 635 kg/m3 and a minimum cell size equal to 46 µm. The production of thermoplastic polyurethane bead foams is also reported for the first time. The minimum density of the obtained foamed beads is 306 kg/m3 and the lowest cell size is 55 µm.

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.

Effect of Kaolin Clay Content on the Cell Morphology and Physical Properties of Injection Molded PS Foams

2011 ◽  
Vol 233-235 ◽  
pp. 2451-2455
Author(s):  
Ming Jiang ◽  
Heng Chi
Keyword(s):  
Physical Properties ◽  
Cell Size ◽  
Cell Density ◽  
Cell Structure ◽  
Clay Content ◽  
Nucleating Agent ◽  
Cell Nucleation ◽  
Cell Structures ◽  
The Matrix ◽  
The Impact

The effect of kaolin content on the cell structure of PS foam and the correlation between the cell structure and the physical properties were evaluated in this work. The kaolin as a nucleating agent did facilitate the cell nucleation. The cell structures were apparently enhanced with increasing kaolin content. In addition to facilitating nucleation, the kaolin confined the motion of chain segments of the matrix polymer, which contributed to the change in cell structure by confining cell growth and cell coalescence to some extent. The foam with smaller cell size and larger cell density absorbed more energy, hence the impact strength increased remarkably with decreasing cell size and increasing cell density.

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.

Effect of Processing Conditions on the Cellular Morphology of Polypropylene Foamed Films for Piezoelectric Applications

2017 ◽  
Vol 36 (1) ◽  
pp. 13-34 ◽  
Author(s):  
Abolfazl Mohebbi ◽  
Frej Mighri ◽  
Abdellah Ajji ◽  
Denis Rodrigue
Keyword(s):  
Calcium Carbonate ◽  
Cellular Structure ◽  
Nucleating Agent ◽  
Processing Conditions ◽  
Cell Size Distribution ◽  
Foam Films ◽  
Screw Design ◽  
Blowing Agent ◽  
Foam Morphology ◽  
Continuous Extrusion

In this work, continuous extrusion-calendering was used to produce polypropylene (PP) foam films for piezoelectric applications. The setup is based on physical foaming using supercritical nitrogen (SC-N2) and calcium carbonate (CaCO3) as nucleating agent. In particular, the extrusion parameters (screw design, temperature profile, blowing agent and nucleating agent content) and post-extrusion conditions (calendaring temperature and speed) were optimized to achieve a specific stretched eye-like cellular structure with uniform cell size distribution. The morphology in both machine and transverse directions, as well as tensile properties were characterized. The results show that a cellular structure with a higher cell aspect ratio has a lower Young's modulus, which is appropriate for piezoelectric cellular films. Generally, the developed foam morphology presents high potential for the production of ferroelectret PP films used in different piezoelectric applications.

scholarly journals Nanoparticles Addition in PU Foams: The Dramatic Effect of Trapped-Air on Nucleation

Polymers ◽  
2021 ◽  
Vol 13 (17) ◽  
pp. 2952
Author(s):  
Beatriz Merillas ◽  
Fernando Villafañe ◽  
Miguel Ángel Rodríguez-Pérez
Keyword(s):  
Polyurethane Foams ◽  
Nucleation Density ◽  
Atmospheric Conditions ◽  
Manufacturing Method ◽  
Trapped Air ◽  
Cell Nucleation ◽  
Magnetic Stirring ◽  
Pu Foams ◽  
Different Levels ◽  
Nucleating Effect

To determine the effect of nanoclays and trapped air on the formation of rigid polyurethane foams, three different production procedures were used. To study the influence of mixing at atmospheric pressure, two approaches were carried out employing either an electric or a magnetic stirrer. The third approach was executed by mixing under vacuum conditions with magnetic stirring. The samples thus obtained were characterized, and the effect of trapped air into the reactive mixtures was evaluated by analyzing the cellular structures. Different levels of trapped air were achieved when employing each manufacturing method. A correlation between the trapped air and the increase in the nucleation density when nanoclays were added was found: the cell nucleation density increased by 1.54 and 1.25 times under atmospheric conditions with electric and magnetic stirring, respectively. Nevertheless, samples fabricated without the presence of air did not show any nucleating effect despite the nanoclay addition (ratio of 1.09). This result suggests that the inclusion of air into the components is key for improving nucleation and that this effect is more pronounced when the polyol viscosity increases due to nanoclay addition. This is the most important feature determining the nucleating effect and, therefore, the corresponding cell size decreases.

Sign in / Sign up

Export Citation Format

Share Document