The Experts below are selected from a list of 7923 Experts worldwide ranked by ideXlab platform
Ling Zhao - One of the best experts on this subject based on the ideXlab platform.
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Dimensional Stability of LDPE Foams with CO2 + i-C4H10 Mixtures as Blowing Agent: Experimental and Numerical Simulation
Industrial & Engineering Chemistry Research, 2020Co-Authors: Hong Zhang, Zhiying Fang, Bin Li, Hui Li, Ling ZhaoAbstract:Polyethylene foams, which account for a large share of the total production of thermoplastic foams, are mainly produced through the extrusion foaming process with butane as the Blowing Agent. Drawb...
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foaming window for preparation of microcellular rigid polyurethanes using supercritical carbon dioxide as Blowing Agent
Journal of Supercritical Fluids, 2019Co-Authors: Ze Yang, Ling Zhao, Dongdong Hu, Zhimei XuAbstract:Abstract Rigid polyurethane (PU) microcellular foams with high expansion ratio and uniform cell morphology can be prepared directly using supercritical carbon dioxide (CO2) as Blowing Agent. The in-situ viscosity measurements during PU polymerization in high-pressure CO2 were adopted to investigate the melt strength change as well as the PU foaming windows. It was found that a certain viscosity window existed for available foaming, which changed little with the foaming temperature or CO2 pressure, but the required reaction time to reach this viscosity foaming windows changed a lot because the existence of CO2 significantly delayed the viscosity rising. Furthermore, the viscosity foaming windows varied with different PU formula systems, e.g., about (300–400) Pa∙s for C-1/PAPI-135C system which could be foamed with cell size smaller than 10 μm, and about (245–400) Pa∙s for R090/PM200 system which was foamed with bigger cell size of (20–40) μm.
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melt foamability of reactive extrusion modified poly ethylene terephthalate with pyromellitic dianhydride using supercritical carbon dioxide as Blowing Agent
Polymer Engineering and Science, 2015Co-Authors: Zhenhao Xi, Ling ZhaoAbstract:By reactive extrusion with pyromellitic dianhydride (PMDA), foamable poly(ethylene terephthalate) (PET) was obtained, which achieved a maximum intrinsic viscosity of 1.36 dL/g with PMDA content 0.8 wt%. Dynamic shear rheological properties were measured to characterize the structure evolution of modified PET. And the Avrami analysis was extended for the non-isothermal crystallization process of modified PET, which relates to cell stabilization in the melt foaming process. Based on the batch foaming process with supercritical carbon dioxide as Blowing Agent, broad foaming temperature windows were obtained for PETs modified with 0.8 and 0.5 wt% PMDA, in which PET foams with the expansion ratio between 10 and 50 times, the cell diameter between 15 and 37 μm, and the cell density between 6.2 × 108 and 1.6 × 109 cells/cm3 were controllably produced. POLYM. ENG. SCI., 55:1528–1535, 2015. © 2014 Society of Plastics Engineers
Chul B Park - One of the best experts on this subject based on the ideXlab platform.
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use of nitrogen as a Blowing Agent for the production of fine celled high density polyethylene foams
Macromolecular Materials and Engineering, 2006Co-Authors: Chul B ParkAbstract:Summary: While many experiments have been performed to examine the effects of administering CO2 as a Blowing Agent in the foaming process, very few studies have investigated the use of N2 for this purpose. In this study, foaming experiments were conducted in extrusion using HDPE as a polymeric material and N2 as a Blowing Agent. Talc was used as a nucleating Agent, and three different pressure-drop rates were applied to study the effects of pressure-drop rates on HDPE foams. The experimental results revealed that the void fraction of high-density foams blown with N2 was not affected by the die temperature, contrasting the situation in low-density foams. Surprisingly, it was the cell density which determined the void fraction of high-density foams. It was also found that the use of talc significantly increased the cell density and the void fraction of the foams and minimized the role played by the pressure-drop rate in cell nucleation. Effect of N2 content on the cell density of HDPE foams.
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increase of open cell content by plasticizing soft regions with secondary Blowing Agent
Polymer Engineering and Science, 2005Co-Authors: Hani E Naguib, Chul B Park, Jin WangAbstract:This article describes the effects of n-butane mixed with primary CO2 as a secondary Blowing Agent on the cell-population density, the volume expansion ratio, and the open-cell content of low-density polyethylene (LDPE) and LDPE/polystyrene (PS) blends in extrusion. With the plasticizing effect of n-butane, a high open-cell content (up to 100%) over a wide range of processing temperatures was successfully achieved. POLYM. ENG. SCI., 45:1445–1451, 2005. © 2005 Society of Plastics Engineers
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development of an extrusion system for producing fine celled hdpe wood fiber composite foams using co2 as a Blowing Agent
Advances in Polymer Technology, 2004Co-Authors: H Zhang, Ghaus Rizvi, Chul B ParkAbstract:This paper presents an innovative design of a tandem extrusion system for fine-celled foaming of plastic/wood-fiber composites using a physical Blowing Agent (PBA). The plastic/wood-fiber composites utilize wood-fibers (WF) as a reinforcing filler in the plastic matrix and are known to be advantageous over the neat plastics in terms of the materials cost and some improved mechanical properties such as stiffness and strength. However, these improvements are usually accompanied by sacrifices in the ductility and impact resistance. These shortcomings can be reduced by inducing fine-celled or microcellular foaming in these composites, thereby creating a new class of materials with unique properties. An innovative tandem extrusion system with continuous on-line moisture removal and PBA injection was successfully developed. The foamed composites, produced on the tandem extrusion system, were compared with those produced on a single extruder system, and demonstrated significant improvement in cell morphology, resulting from uniform mixing and effective moisture removal. The effects of WF and coupling Agent (CA) on the cell morphology were studied. An increase in the WF content had an adverse affect. The cell morphology and foam structures were improved when an appropriate CA was added. © 2004 Wiley Periodicals, Inc. Adv Polym Techn 23: 263–276, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20016
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foaming of ps wood fiber composites using moisture as a Blowing Agent
Polymer Engineering and Science, 2000Co-Authors: Ghaus Rizvi, Laurent M Matuana, Chul B ParkAbstract:This paper presents an experimental study on foam processing of polystyrene (PS) and high-impact polystyrene HIPS/wood-fiber composites in extrusion using moisture as a Blowing Agent. Wood-fiber inherently contains moisture that can potentially be used as a Blowing Agent. Undried wood-fiber was processed together with PS and HIPS materials in extrusion and wood-fiber composite foams were produced. The cellular morphology and volume expansion ratios of the foamed composites were characterized. Because of the high stiffness of styrenic materials, moisture condensation during cooling after expansion at high temperature did not cause much contraction of the foamed composite and a high volume expansion ratio up to 20 was successfully obtained. The experimental results showed that the expansion ratio could be controlled by varying the processing temperature and the moisture content in the wood fiber. The effects of a small amount of a chemical Blowing Agent and mineral oil on the cell morphologies of plastic/wood-fiber composite foams were also investigated.
Cailiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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layered silicate based polystyrene nanocomposite microcellular foam using supercritical carbon dioxide as Blowing Agent
Polymer, 2010Co-Authors: Jintao Yang, Cailiang ZhangAbstract:Abstract Exfoliated layered-silicate in the polystyrene (PS) block copolymer with different molecular weights was employed as a model material to investigate the PS nanocomposite microcellular foams expanded by supercritical carbon dioxide. Using a well-controlled foaming procedure, we investigated the influence of molecular weight of PS, dispersion and loading of layered-silicate and pressure drop rate of a Blowing Agent on the cell size and cell density. Our experimental results indicate that only exfoliated layered-silicate can inhibit the cell expansion and has high nucleation efficiency during foaming. The average cell diameter can be reduced from 6 μm to 1.4 μm and the cell density can be increased from 7.6 × 10 9 cells/cm 3 to 5.0 × 10 11 cells/cm 3 . On the contrary, aggregated layered-silicate in PS did not show any effect on the cell morphology of PS foam.
John Banhart - One of the best experts on this subject based on the ideXlab platform.
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foaming of Blowing Agent free aluminium powder compacts
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007Co-Authors: F Garciamoreno, John BanhartAbstract:Abstract We present a novel foaming method based on the powder metallurgical (PM) foaming route but working without a Blowing Agent. A precursor is produced by uniaxial hot compaction of metallic powders without any further additions. In a first step the samples are heated up to above their melting temperature under overpressure. Foaming is triggered just by pressure release to ambient pressure. Precursors made of pure Al were melted under different overpressures from 1 to 9 bar and foamed. In situ X-ray radioscopy was used to study the foaming step and to provide quantitative information on foam expansion. 2D pore size distributions of the solidified foams were also analysed. Different possible gas sources such as entrapped gas, dissolved gas, adsorbates, water vapour, hydroxides, etc. are discussed. As a result adsorbates seem to be the most likely gas source for the observed foaming effect.
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improvement of aluminium foam technology by tailoring of Blowing Agent
Scripta Materialia, 2006Co-Authors: Biljana Matijasevic, John BanhartAbstract:Abstract Aluminium foams produced by melting powder compacts containing a Blowing Agent are usually non-uniform which might lead to inferior mechanical properties. The reasons for this can be thermal gradients during foaming and a Blowing Agent which is not adapted to the melting range of the alloy to be foamed. We discuss various strategies to improve aluminium foams and then demonstrate that titanium hydride (TiH 2 ) can be tailored by selective oxidation and partial discharge to yield more uniform foams. We find that the expansion potential of the foams and the uniformity of cell size distribution is improved and that the individual cell walls are smoother and less corrugated when the foam is blown with pre-treated TiH 2 .
K Prabhakaran - One of the best experts on this subject based on the ideXlab platform.
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preparation of carbon foams with enhanced oxidation resistance by foaming molten sucrose using a boric acid Blowing Agent
Carbon, 2013Co-Authors: R Narasimman, K PrabhakaranAbstract:Abstract Boric acid was used as a Blowing Agent as well as a boron precursor for the preparation of boron-doped carbon foams from molten sucrose. The H + generated, due to the formation of a complex between sucrose and boric acid, catalyzes the –OH to –OH condensation reaction leading to the polymerization and the foaming of the molten sucrose. The char yield of the solid organic foams increased from 24 to 39 wt.% when the boric acid concentration increased from 0 to 8 wt.%, due to the formation of the B–O–C cross-links between sucrose polymer by B–OH to C–OH condensation. The inductively coupled plasma analysis showed the presence of 0.44–3.4 wt.% boron in the carbon foams. The density and compressive strength decreased and cell size increased with boric acid concentration. The room temperature thermal conductivity of the boron-doped carbon foams was in the range of 0.057–0.043 W m −1 K −1 . The weight loss studies by dynamic and isothermal heating showed the increased oxidation resistance with boron concentration.
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preparation of low density carbon foams by foaming molten sucrose using an aluminium nitrate Blowing Agent
Carbon, 2012Co-Authors: R Narasimman, K PrabhakaranAbstract:Abstract Low density carbon foams have been prepared by thermo-foaming of molten sucrose using aluminium nitrate as a Blowing Agent to produce solid organic foams followed by dehydration and carbonization. Gas bubbles are generated in the molten sucrose due to water vapour produced by the acid catalysed condensation between sucrose hydroxyl groups and NOx gases produced by the thermal decomposition of the aluminium nitrate. Higher melt viscosity achieved by cross-linking of the condensation products of sucrose through co-ordination of the aluminium ions with the hydroxyl groups stabilizes the bubbles against coalescence and rupture. The foam volume, foaming time and setting time depend on the aluminium nitrate concentrations. The carbon obtained by the pyrolysis of the solid organic foams has turbostratic graphite structure. The foams produced have an interconnected near-spherical cellular structure. The carbon foams prepared at aluminium nitrate concentrations in the range of 0.5–4 wt.% have a density and average cell size in the ranges of 0.085–0.053 g/cc and 1.55–0.83 mm, respectively. The alumina (∼0.17–1.34 wt.%) produced from the aluminium nitrate is concentrated more on the surface of cell walls, ligaments, and struts.
