Foaming of polypropylene with supercritical carbon dioxide

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

doi:10.1016/j.supflu.2006.09.007

Cited by 277 publications

(199 citation statements)

References 24 publications

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“…It may be possible that foaming occurred in the PP phase. This is similar to what Mei et al 36 reported for the foaming conditions of PP with carbon dioxide. To clarify this hypothesis, Figure 3 shows the cryogenically fractured surface of an unfoamed sample ( Figure 3a) and a foamed sample (Figure 3b) in BSE, which was stained with OSO 4 to highlight the EPDM phase before analysis.…”

Section: Resultssupporting

confidence: 92%

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Microcellular foaming of PP/EPDM/organoclay nanocomposites: the effect of the distribution of nanoclay on foam morphology

Keramati

Ghasemi

Karrabi

et al. 2012

Polym J

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In this study, microcellular foams based on polypropylene/ethylene propylene diene monomer/organoclay (PP/EPDM/organoclay) nanocomposites were produced via a batch process using supercritical nitrogen (N 2 ) as the physical blowing agent. The foaming temperature and morphological observation demonstrated that foaming occurred mostly in the PP phase. To evaluate the effect of organoclay distribution on the cell nucleation step and the final foam morphology, the location of the nanofillers in the nanocomposite blend was traced by means of surface energies and Young's equation. The calculated wetting coefficient predicted that the organoclays would have more affinity with PP and would primarily distribute into the PP phase. These results were confirmed by atomic force microscopy (AFM), dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM). The cell density and average cell sizes are the main foam characteristics that were determined using SEM micrographs, and it was found that these parameters were influenced by the presence of nanoclays. An improved foam morphology was obtained in the nanocomposite samples. INTRODUCTIONBecause polymeric materials are widely used in daily life, the need to reduce the amount of consumed materials has received significant attention. Currently, polymeric foams have become more popular because conventional foams exhibit two important limitations: weak mechanical properties and harmful residues. Hence, the idea of microcellular foaming was invented by Martini et al. 1 at the Massachusetts Institute of Technology to produce lightweight materials without compromising their functional performance. Microcellular foams are defined as foams with cell populations 410 9 cells cm -3 and cell sizes of approximately 10 mm. 2 The tiny size and uniform distribution of bubbles, which are smaller than the critical flaws that already exist in polymers, make microcellular plastics possible for use in daily life applications instead of conventional foams. 3 Microcellular foaming technology has been rapidly developed in the past 2 decades, and microcellular parts have been produced via batch, injection molding and extrusion processes. 4-9 Despite a variety of production methods, the main foaming mechanism is the same. In the first step, the polymer is saturated with an inert gas at high pressure. In the second step, by means of rapid depressurization, the solubility of the dissolved gas decreases, and a super-saturation state occurs. As a result, cell nucleation is thermodynamically favored, and then microcells form through stabilization. 8

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Section: Resultssupporting

confidence: 92%

“…However, there is an upper limit for the foaming temperature beyond which the viscosity drops and the cellular structure collapses before stabilizing. 36,37 Figure…”

Section: Resultsmentioning

confidence: 99%

Microcellular foaming of PP/EPDM/organoclay nanocomposites: the effect of the distribution of nanoclay on foam morphology

Keramati

Ghasemi

Karrabi

et al. 2012

Polym J

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“…Therefore, traditional blowing agents (such as pentane, butane, chlorofluoro hydrocarbons) have been withdrawn and replaced by gases like argon, nitrogen and carbon dioxide [1,4]. Recently, the usage of supercritical fluids (SFCs) has been considered as a valuable path to produce polymer foams [5][6][7][8][9][10][11][12][13]. SCFs possess physical properties intermediate between those of gases and fluids.…”

Section: Introductionmentioning

confidence: 99%

Mechanical behaviour of cyclic olefin copolymer/exfoliated graphite nanoplatelets nanocomposites foamed through supercritical carbon dioxide

Biani¹,

Dorigato²,

Bonani³

et al. 2016

Express Polym. Lett.

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Abstract.A cycloolefin copolymer matrix was melt mixed with exfoliated graphite nanoplatelets (xGnP) and the resulting nanocomposites were foamed by supercritical carbon dioxide. The density of the obtained foams decreased with the foaming pressure. Moreover, xGnP limited the cell growth during the expansion process thus reducing the cell diameter (from 1.08 to 0.22 mm with an XGnP amount of 10 wt% at 150 bar) and increasing the cell density (from 12 to 45 cells/mm 2 with a nanofiller content of 10 wt% at 150 bar). Electron microscopy observations of foams evidenced exfoliation and orientation of the nanoplatelets along the cell walls. Quasi-static compressive tests and tensile creep tests on foams clearly indicated that xGnP improved the modulus (up to a factor of 10 for a xGnP content of 10 wt%) and the creep stability.

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“…At 156 °C, the cell structure is relatively intact, but some cracks are observed on the cell walls. The results imply that the foaming temperature window of radiation cross-linked PP increases to 8 °C, compared to the 4 °C for non-cross-linked PP [4]. The increase of the foaming temperature window is due to the higher melt strength and decreased crystallinity of cross-linked PP.…”

Section: Foaming Temperature Window Of the Cross-linked Ppmentioning

confidence: 84%

“…Polypropylene (PP) foam has been considered as a substitute for other thermoplastic foams, as its mechanical properties are enhanced; these include increased toughness, impact strength, stiffness-to-weight ratio, fatigue life, and thermal stability, as well as its relatively high service temperature [1][2][3][4][5][6]. PP foam has been used in electronic packaging, food packaging, construction materials, traffic equipment, sports equipment, and thermal and sound insulators.…”

Section: Introductionmentioning

confidence: 99%

Supercritical CO2 Foaming of Radiation Cross-Linked Isotactic Polypropylene in the Presence of TAIC

et al. 2016

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Abstract:Since the maximum foaming temperature window is only about 4 • C for supercritical CO 2 (scCO 2 ) foaming of pristine polypropylene, it is important to raise the melt strength of polypropylene in order to more easily achieve scCO 2 foaming. In this work, radiation cross-linked isotactic polypropylene, assisted by the addition of a polyfunctional monomer (triallylisocyanurate, TAIC), was employed in the scCO 2 foaming process in order to understand the benefits of radiation cross-linking. Due to significantly enhanced melt strength and the decreased degree of crystallinity caused by cross-linking, the scCO 2 foaming behavior of polypropylene was dramatically changed. The cell size distribution, cell diameter, cell density, volume expansion ratio, and foaming rate of radiation-cross-linked polypropylene under different foaming conditions were analyzed and compared. It was found that radiation cross-linking favors the foamability and formation of well-defined cell structures. The optimal absorbed dose with the addition of 2 wt % TAIC was 30 kGy. Additionally, the foaming temperature window was expanded to about 8 • C, making the handling of scCO 2 foaming of isotactic polypropylene much easier.

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Foaming of polypropylene with supercritical carbon dioxide

Cited by 277 publications

References 24 publications

Microcellular foaming of PP/EPDM/organoclay nanocomposites: the effect of the distribution of nanoclay on foam morphology

Microcellular foaming of PP/EPDM/organoclay nanocomposites: the effect of the distribution of nanoclay on foam morphology

Mechanical behaviour of cyclic olefin copolymer/exfoliated graphite nanoplatelets nanocomposites foamed through supercritical carbon dioxide

Supercritical CO2 Foaming of Radiation Cross-Linked Isotactic Polypropylene in the Presence of TAIC

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