Effects of crystal structure on the foaming of isotactic polypropylene using supercritical carbon dioxide as a foaming agent

Jiang, Xiu-Lei; Liu, Tao; Xu, Zheng; Zhao, Ling; Hu, Guohua; Wang, Yuan

doi:10.1016/j.supflu.2008.10.006

Cited by 126 publications

(73 citation statements)

References 32 publications

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“…They claimed the shish-kebab structure became a template for creating nanocellular foams. The cell structure of their nanocellular foams was the same nanofibrillated structure as the one Xu et al reported [13,14].…”

Section: Introductionmentioning

confidence: 59%

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Miyamoto

Yasuhara

Shikuma

et al. 2013

Polymer Engineering & Sci

111

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Open‐cell, porous microcellular foams with nanofibrillated structures were prepared from high tacticity isotactic polypropylene (i‐PP) with a crystal nucleating and gelling agent. The 1,3:2,4 bis‐O‐(4‐methylbenzylidene)‐d‐sorbitol gelling agent (Gel‐all MD) was used as the crystal nucleating and gelling agent, which enhanced the crystallization and gelation of i‐PP with a three‐dimensional network of highly connected nanofibrils. The core‐back foam injection molding technique was employed to foam the i‐PP with nitrogen (N2) at a high expansion ratio, where the crystal nucleating agent induced bubble nucleation and bubble growth in the inter‐lamella region and opened the cell walls with a nanoscale‐fibrillated structure. The effects of the nucleating agent on the open cell content (OCC), density and crystallinity were thoroughly investigated. We prepared open‐cell micro/nanocellular foams with an average cell size of microscale voids of < 5 μm. Nanometer‐scale fibrillated structures were formed on the cell wall of the microscale void, the expansion ratio was five‐fold and the open cell content was over 90%. POLYM. ENG. SCI., 54:2075–2085, 2014. © 2013 Society of Plastics Engineers

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Section: Introductionmentioning

confidence: 59%

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Miyamoto

Yasuhara

Shikuma

et al. 2013

Polymer Engineering & Sci

111

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“…Xu [8], Jian [14], Zhai [15] and their respective coworkers have proved that despite its semicrystalline character, PP pellets or very thin sheets (50 lm thickness) can be foamed by gas dissolution using supercritical CO 2 as blowing agent. Nevertheless, all those works only deal with the structural characterization of the foamed samples.…”

Section: Introductionmentioning

confidence: 99%

“…The limitations imposed by the non-regular shape and small size of so-obtained PP foams have resulted in a lack of information about the influence of foaming parameters in the structure-properties relationship. Thus, although very good cellular structures (in terms of cell size and homogeneity) are obtained by using gas dissolution as foaming process [8,14] it is unknown its influence on the physical response of PP foams.…”

Section: Introductionmentioning

confidence: 99%

Moulded polypropylene foams produced using chemical or physical blowing agents: structure–properties relationship

et al. 2012

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Polypropylene (PP) foams have become\ud essential items due to their excellent properties. Nevertheless,\ud obtaining net-shaped PP foams with medium relative\ud densities is a complicated issue. In this article, two\ud processes able to produce moulded PP foams in this density\ud range are presented. One of them is based on a modification\ud of the pressure quench foaming method and therefore\ud uses a physical blowing agent (CO2). The second one is the\ud improved compression moulding technique which uses a\ud chemical blowing agent (azodicarbonamide). PP foams\ud with relative densities in the range between 0.25 and 0.6\ud and cylindrical shape were prepared using these foaming\ud techniques. A common PP grade (instead a highly branched\ud one) was used to obtain the samples, showing, that by\ud combining the appropriate foaming technique, the adequate\ud moulds, suitable blowing agent and proper foaming\ud parameters, net-shaped PP foams with excellent properties\ud can be produced starting from a conventional PP grade.\ud Samples were characterized by analyzing their cellular\ud structure and their mechanical properties. Results have\ud showed that depending on the chosen foaming route isotropic\ud or anisotropic structures with cell sizes ranging from 40 to 350 lm and open cell content in the range between 0\ud and 65% can be obtained. Moreover, mechanical properties\ud are highly influenced by the production route and chemical\ud composition of the foams. For instance, the stiffer materials\ud at relative densities higher than 0.4 are the ones produced\ud using the chemical blowing agent while at relative densities\ud lower than 0.4 are the ones produced using the physical\ud blowing agent.Peer ReviewedPostprint (published version

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“…[14] In contrast, the solid-state foaming of semi-crystalline polymers, like PCL, is more difficult owing to the different scCO 2 solubility and diffusivity within the amorphous and crystalline domains and due to the presence of non-plasticized crystal regions maintaining a high viscosity/stiffness and therefore hindering, when possible, uniform pore nucleation and growth. [14][15][16] This work reports for the first time the two step depressurization solid-state scCO 2 foaming of PCL and PCL-HA nanocomposite, with the aim of designing bimodal porous scaffolds for TE. The so-called ''solid-state'' means that the solubilization and foaming temperatures were chosen to be well below the melting temperature of PCL and, in particular, fixed at 37 8C, in order to open up the possibility of further incorporation of cells and bioactive moieties within the scaffolds during the fabrication process.…”

Section: Introductionmentioning

confidence: 99%

Design of Bimodal PCL and PCL‐HA Nanocomposite Scaffolds by Two Step Depressurization During Solid‐state Supercritical CO₂ Foaming

Salerno

Zeppetelli

Maio

et al. 2011

Macromol. Rapid Commun.

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This communication reports the design and fabrication of porous scaffolds of poly(ε-caprolactone) (PCL) and PCL loaded with hydroxyapatite (HA) nanoparticles with bimodal pore size distributions by a two step depressurization solid-state supercritical CO(2) (scCO(2) ) foaming process. Results show that the pore structure features of the scaffolds are strongly affected by the thermal history of the starting polymeric materials and by the depressurization profile. In particular, PCL and PCL-HA nanocomposite scaffolds with bimodal and uniform pore size distributions are fabricated by quenching molten samples in liquid N(2) , solubilizing the scCO(2) at 37 °C and 20 MPa, and further releasing the blowing agent in two steps: (1) from 20 to 10 MPa at a slow depressurization rate, and (2) from 10 MPa to the ambient pressure at a fast depressurization rate. The biocompatibility of the bimodal scaffolds is finally evaluated by the in vitro culture of human mesenchymal stem cells (MSCs), in order to assess their potential for tissue engineering applications.

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Effects of crystal structure on the foaming of isotactic polypropylene using supercritical carbon dioxide as a foaming agent

Cited by 126 publications

References 32 publications

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Moulded polypropylene foams produced using chemical or physical blowing agents: structure–properties relationship

Design of Bimodal PCL and PCL‐HA Nanocomposite Scaffolds by Two Step Depressurization During Solid‐state Supercritical CO₂ Foaming

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Effects of crystal structure on the foaming of isotactic polypropylene using supercritical carbon dioxide as a foaming agent

Cited by 126 publications

References 32 publications

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Preparation of micro/nanocellular polypropylene foam with crystal nucleating agents

Moulded polypropylene foams produced using chemical or physical blowing agents: structure–properties relationship

Design of Bimodal PCL and PCL‐HA Nanocomposite Scaffolds by Two Step Depressurization During Solid‐state Supercritical CO2 Foaming

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Design of Bimodal PCL and PCL‐HA Nanocomposite Scaffolds by Two Step Depressurization During Solid‐state Supercritical CO₂ Foaming