Synergetic effect of crystal nucleating agent and melt self-enhancement of isotactic polypropylene on its rheological and microcellular foaming properties

Crystal nucleating agent Bis (3, 4- dimethylbenzylidene) sorbitol (DMDBS) was used to tune the melt strength and microcellular foaming properties of isotactic polypropylene (iPP) in this study. Rheological testing results reveal that the introduction of DMDBS could enhance the storage modulus and complex viscosity of iPP, obviously increase its crystallization onset temperature, compared to its counterparts without DMDBS. The addition of DMDBS could also significantly increase the cell nucleating ability of iPP, due to its large surface, cooperating with a thermal history control treatment. Quite fine microcellular iPP/DMDBS foams were fabricated with relatively small average cell sizes of nano to several micrometers, and cell densities up to 1011∼1012 cells/cm3, using the synergy effect of DMDBS and iPP’s melt self-enhancement. Under a comparatively low re-saturation pressure of 8 to 12 MPa, ideal microcellular foams could be generated, at a temperature zone of 158 to 162°C, which is slightly below to iPP’s original pellets nominal melting point.

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Effect of Processing Parameters on Cellular Structures and Mechanical Properties of PMMA Microcellular Foams

Cellular Polymers ◽

10.1177/026248930502400401 ◽

2005 ◽

Vol 24 (4) ◽

pp. 177-195 ◽

Cited By ~ 25

Author(s):

Jin Fu ◽

Choonghee Jo ◽

Hani E. Naguib

Keyword(s):

Mechanical Properties ◽

Saturation Pressure ◽

Viscoelastic Model ◽

Batch Process ◽

Processing Parameters ◽

Analytical Models ◽

Elastic Behavior ◽

Average Cell Size ◽

Average Cell ◽

Microcellular Foams

In this study, the effect of processing parameters on the cellular morphologies and mechanical properties of PMMA microcellular foams is investigated. Microcellular closed cell Poly(methyl-methacrylate) (PMMA) foams were prepared using a two stage batch process method. The foam structure was controlled by altering the processing parameters such as foaming temperature, foaming time and saturation pressure. The foam morphologies were characterized in terms of the average cell size, cell density and foam density. Elastic modulus, tensile strength and elongation at break were studied as functions of the different foaming parameters. The mechanical properties were found to be greatly affected by the foaming parameters and vary with changing the cell morphologies. The experimental results were compared with existing analytical models to validate them and to predict the mechanical properties of microcellular polymeric PMMA foams prepared with different processing parameters. A constitutive equation for the nonlinear elastic behavior of polymeric microcellular foams was developed based on the Maxwell viscoelastic model. The results of this work can help designers optimize the foam processing parameters and achieve desired foam morphology and mechanical properties.

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Effect of Processing Parameters on the Cellular Morphology and Mechanical Properties of Thermoplastic Polyolefin (TPO) Microcellular Foams

Materials, Nondestructive Evaluation, and Pressure Vessels and Piping ◽

10.1115/imece2006-15212 ◽

2006 ◽

Author(s):

Steven Wong ◽

Hani E. Naguib ◽

Chul B. Park

Keyword(s):

Mechanical Properties ◽

Saturation Pressure ◽

Batch Process ◽

Processing Parameters ◽

Average Cell Size ◽

Average Cell ◽

Microcellular Foams ◽

Closed Cell ◽

Foaming Temperature ◽

Thermoplastic Polyolefin

In this study, the effects of processing parameters on the cellular morphologies and mechanical properties of TPO70 (Thermoplastic Polyolefin) microcellular foams are investigated. Microcellular closed cell TPO70 foams were prepared using a two-stage batch process method. The microstructure of these foamed samples was controlled by carefully altering the processing parameters such as saturation pressure, foaming temperature and foaming time. The foam morphologies were characterized in terms of the cell density, foam density and average cell size. Elastic modulus, tensile strength, and elongation at break of the foamed TPO70 samples were measured for different cell morphologies. The findings show that the mechanical properties were significantly affected by the foaming parameters which varied with the cell morphologies. The experimental results can be used to predict the microstructure and mechanical properties of microcellular polymeric TPO70 foams prepared with different processing parameters.

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Influence of Polylactide (PLA) Stereocomplexation on the Microstructure of PLA/PBS Blends and the Cell Morphology of Their Microcellular Foams

Polymers ◽

10.3390/polym12102362 ◽

2020 ◽

Vol 12 (10) ◽

pp. 2362

Author(s):

Zhiyuan Sun ◽

Long Wang ◽

Jinyang Zhou ◽

Xun Fan ◽

Hanghai Xie ◽

...

Keyword(s):

Gas Adsorption ◽

Average Cell Size ◽

Butylene Succinate ◽

Average Cell ◽

Melt Strength ◽

Biological Scaffolds ◽

Microcellular Foams ◽

Microcellular Foaming ◽

Cell Nucleation ◽

Cell Stability

Polylactide foaming materials with promising biocompatibility balance the lightweight and mechanical properties well, and thus they can be desirable candidates for biological scaffolds used in tissue engineering. However, the cells are likely to coalesce and collapse during the foaming process of polylactide (PLA) due to its intrinsic low melt strength. This work introduces a unique PLA stereocomplexation into the microcellular foaming of poly (l-lactide)/poly (butylene succinate) (PLLA/PBS) based on supercritical carbon dioxide. The rheological properties of PLA/PBS with 5 wt% or 10 wt% poly (d-lactide) (PDLA) present enhanced melt strength owing to the formation of PLA stereocomplex crystals (sc-PLA), which act as physical pseudo-cross-link points in the molten blends by virtue of the strong intermolecular interaction between PLLA and the added PDLA. Notably, the introduction of either PBS or PDLA into the PLLA matrix could enhance its crystallization, while introducing both in the blend triggers a decreasing trend in the PLA crystallinity, which it is believed occurs due to the constrained molecular chain mobility by formed sc-PLA. Nevertheless, the enhanced melt strength and decreased crystallinity of PLA/PBS/PDLA blends are favorable for the microcellular foaming behavior, which enhanced the cell stability and provided amorphous regions for gas adsorption and homogeneous nucleation of PLLA cells, respectively. Furthermore, although the microstructure of PLA/PBS presents immiscible sea-island morphology, the miscibility was improved while the PBS domains were also refined by the introduction of PDLA. Overall, with the addition of PDLA into PLA/10PBS blends, the microcellular average cell size decreased from 3.21 to 0.66 μm with highest cell density of 2.23 × 1010 cells cm−3 achieved, confirming a stable growth of cells was achieved and more cell nucleation sites were initiated on the heterogeneous interface.

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Unusual Tuning of Mechanical Properties of Isotactic Polypropylene Using Counteraction of Shear Flow and β-Nucleating Agent on β-Form Nucleation

Macromolecules ◽

10.1021/ma900411f ◽

2009 ◽

Vol 42 (12) ◽

pp. 4343-4348 ◽

Cited By ~ 169

Author(s):

Yan-Hui Chen ◽

Gan-Ji Zhong ◽

Yan Wang ◽

Zhong-Ming Li ◽

Liangbin Li

Keyword(s):

Mechanical Properties ◽

Shear Flow ◽

Isotactic Polypropylene ◽

Nucleating Agent

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A novel highly efficient β-nucleating agent for isotactic polypropylene

Journal of Applied Polymer Science ◽

10.1002/app.34441 ◽

2011 ◽

Vol 123 (1) ◽

pp. 108-117 ◽

Cited By ~ 15

Author(s):

Shicheng Zhao ◽

Na Xu ◽

Zhong Xin ◽

Changquan Jiang

Keyword(s):

Isotactic Polypropylene ◽

Nucleating Agent ◽

Highly Efficient

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Isothermal Crystallization and Rheology Properties of Isotactic Polypropylene/Bacterial Cellulose Composite

Polymers ◽

10.3390/polym10111284 ◽

2018 ◽

Vol 10 (11) ◽

pp. 1284 ◽

Cited By ~ 3

Author(s):

Bo Wang ◽

Fu-hua Lin ◽

Xiang-yang Li ◽

Zhong-wei Zhang ◽

Xiao-rong Xue ◽

...

Keyword(s):

Bacterial Cellulose ◽

Storage Modulus ◽

Isotactic Polypropylene ◽

Crystallization Temperature ◽

Isothermal Crystallization ◽

Complex Viscosity ◽

Isothermal Crystallization Kinetics ◽

Interfacial Compatibility ◽

And Storage ◽

Better Than

Bacterial cellulose (BC) is a new kind of cellulose with great potential in enhancing preparation of isotactic Polypropylene (iPP) composites, which have been found with excellent performance. However, the interface compatibility between BC and iPP is poor. In this study, iPP/BC composites were prepared by solution mixing. Esterification modified BC (CO) and Maleic anhydride grafted polypropylene (MAPP) added as a compatibilizer was both used to improve the interfacial compatibility of the iPP/BC composites. The rheology and isothermal crystallization behavior of the composites was tested and discussed. The result shows that the complex viscosity and storage modulus of the composite significantly increase in the rule iPP, iPP/BC2, iPP/CO2, and M-iPP/BC3, which indicates that the compatibility of the composite increases as this rule. According to the isothermal crystallization kinetics result, the crystal growth mode of iPP was not affected by the addition of BC and the interfacial compatibility. The spherulite growth rate of the iPP/BC composite increases with increasing crystallization temperature. Especially, the value decreases as the same rule with the complex viscosity and storage modulus of the composite at the same isothermal crystallization temperature. These results suggest that the interface compatibility of iPP/BC composites is greatly improved and the interface compatibility of the M-iPP/BC3 is better than the iPP/CO2.

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Crystalline modification of a rare earth nucleating agent for isotactic polypropylene based on its self-assembly

Royal Society Open Science ◽

10.1098/rsos.180247 ◽

2018 ◽

Vol 5 (5) ◽

pp. 180247 ◽

Cited By ~ 4

Author(s):

Yuanming Zhang ◽

Tingting Sun ◽

Wei Jiang ◽

Guangting Han

Keyword(s):

Hydrogen Bond ◽

Rare Earth ◽

Isotactic Polypropylene ◽

Self Assembly ◽

Dendritic Structure ◽

Nucleating Agent ◽

The Self ◽

Structure Evolution ◽

Crystalline Modification ◽

Assembly Structure

In this paper, the crystalline modification of a rare earth nucleating agent (WBG) for isotactic polypropylene (PP) based on its supramolecular self-assembly was investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy. In addition, the relationship between the self-assembly structure of the nucleating agent and the crystalline structure, as well as the possible reason for the self-assembly behaviour, was further studied. The structure evolution of WBG showed that the self-assembly structure changed from a needle-like structure to a dendritic structure with increase in the content of WBG. When the content of WBG exceeded a critical value (0.4 wt%), it self-assembled into a strip structure. This revealed that the structure evolution of WBG contributed to the K β and the crystallization morphology of PP with different content of WBG. In addition, further studies implied that the behaviour of self-assembly was a liquid–solid transformation of WBG, followed by a liquid–liquid phase separation of molten isotactic PP and WBG. The formation of the self-assembly structure was based on the free molecules by hydrogen bond dissociation while being heated, followed by aggregation into another structure by hydrogen bond association while being cooled. Furthermore, self-assembly behaviour depends largely on the interaction between WBG themselves.

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