A new experimental system for combinatorial exploration of foaming of polymers in carbon dioxide: The gradient foaming of PMMA

Ngo, Mai; Dickmann, James S.; Hassler, J. C.; Kiran, Erdoǧan

doi:10.1016/j.supflu.2015.09.030

Cited by 31 publications

(20 citation statements)

References 53 publications

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“…A gradient in the foaming parameters might also induce the formation of a non-homogeneous structure. For instance, Ngo et al [14] designed an experimental setup to generate nonconstant temperature profiles to induce the formation of graded structures. Another approach is related to the use of non-constant distributions of the blowing agent.…”

Section: Doi: 101002/mame201900428mentioning

confidence: 99%

Nanocellular Polymers with a Gradient Cellular Structure Based on Poly(methyl methacrylate)/Thermoplastic Polyurethane Blends Produced by Gas Dissolution Foaming

Bernardo

León

Sánchez-Calderón

et al. 2019

Macro Materials & Eng

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Graded structures and nanocellular polymers are two examples of advanced cellular morphologies. In this work, a methodology to obtain low‐density graded nanocellular polymers based on poly(methyl methacrylate) (PMMA)/thermoplastic polyurethane (TPU) blends produced by gas dissolution foaming is reported. A systematic study of the effect of the processing condition is presented. Results show that the melt‐blending results in a solid nanostructured material formed by nanometric TPU domains. The PMMA/TPU foamed samples show a gradient cellular structure, with a homogeneous nanocellular core. In the core, the TPU domains act as nucleating sites, enhancing nucleation compared to pure PMMA and allowing the change from a microcellular to a nanocellular structure. Nonetheless, the outer region shows a gradient of cell sizes from nano‐ to micron‐sized cells. This gradient structure is attributed to a non‐constant pressure profile in the samples due to gas desorption before foaming. The nucleation in the PMMA/TPU increases as the saturation pressure increases. Regarding the effect of the foaming conditions, it is proved that it is necessary to have a fine control to avoid degeneration of the cellular materials. Graded nanocellular polymers with relative densities of 0.16–0.30 and cell sizes ranging 310–480 nm (in the nanocellular core) are obtained.

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Section: Doi: 101002/mame201900428mentioning

confidence: 99%

Nanocellular Polymers with a Gradient Cellular Structure Based on Poly(methyl methacrylate)/Thermoplastic Polyurethane Blends Produced by Gas Dissolution Foaming

Bernardo

León

Sánchez-Calderón

et al. 2019

Macro Materials & Eng

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“…6 Control of anisotropy can potentially open avenues for optimization of mechanical properties, energy absorption and thermal insulation that would be difficult to achieve in isotropic analogues. [7][8][9] Recent studies to generate anisotropic foams have been relying on non-trivial, multistep fabrication processes [10][11][12][13][14][15][16][17][18][19] ; thus, developing a facile method for synthesizing anisotropic cellular materials would be of tremendous interest.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic cellular structures from semi‐crystalline polymer templates

Kanbargi

Erp

Lesser

2020

Journal of Polymer Science

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We report an investigation to determine the effect of an anisotropic semicrystalline template on the resulting cell morphology of microcellular polymeric foams generated in these materials. Poly(ethylene terephthalate) (PET)-polystyrene (PS) composite foams are prepared by using supercritical carbon dioxide (scCO 2) not only as a foaming agent but also as a transport medium of styrene and initiator into a biaxially-oriented PET templating film. The composite foam so obtained demonstrates a highly interpenetrating network verified by a single Tg of 98 C. Substrate orientation is observed not to dictate the cell formation; however highly anisotropic swelling and a shapetemplating phenomenon is observed, with the most significant dimension change in the thickness of the film. Introducing confinement in the direction of maximum dimension change is found to introduce a highly anisotropic lamellar cell architecture.

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“…The cell densities N (as number of pores per cm 3 ) were evaluated using the relationship

N = {true(n / A true)}^{3 / 2} true(R_{v} true)

where n is the number of pores, A is the area, and R v is the volume expansion ratio which is equal to ratio of the density of the polymer before and after foaming, that is R v = [ρ unfoamed polymer /ρ foamed polymer ] . For these evaluations, the number of pores per unit area and the pore size ranges were determined manually using enlarged portions of the SEM micrographs following procedures described earlier . Densities were evaluated by determining the weight of the polymers and the foams in air and in water using a modified analytical balance.…”

Section: Resultsmentioning

confidence: 99%

“…Details of the foaming system have been presented in an earlier publication . Briefly, it is a high pressure cell which is 25.2 cm long with an inside diameter of 1.9 cm.…”

Section: Methodsmentioning

confidence: 99%

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Foaming of poly(ethylene‐co‐vinyl acetate) and poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) and their blends with carbon dioxide

Sarver

Sumey

Williams

et al. 2017

J of Applied Polymer Sci

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Poly(ethylene‐co‐vinyl acetate) (EVA‐25) and poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) (EVACO‐2410) and their blends with EVACO:EVA ratios of 80:20, 60:40, 40:60, and 20:80 were foamed using CO2. These foams are of interest for applications ranging from footwear to medical devices. Foaming experiments were carried out using 1 mm thick melt‐extruded films in CO2 at a range of pressures (100, 200, and 300 bar) and temperatures (30, 40, 50, and 60 °C). Foamability of the polymers was explored both under isothermal and gradient temperature conditions. Foams of EVACO‐2410 displayed high initial expansions followed by postfoaming relaxation and shrinkage while foams generated from EVA‐25 showed more dimensional stability. Blending EVACO‐2410 with EVA‐25 was explored as an approach to reduce postfoaming relaxation and shrinkage. The surfaces of the foamed samples displayed blistering that was linked to CO2 bubble entrapment and coalescence at the surface. Scanning electron micrographs of the foams generated from blends displayed distinct morphologies reflecting whether the sections were representing the machine‐ or cross‐machine direction of extruded films. In going from EVACO‐2410 to EVA‐25, the cell densities ranged from about 106 to 1010 cells/cm3. Foams with low bulk densities of about 0.11 g/cm3 could be generated. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45841.

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A new experimental system for combinatorial exploration of foaming of polymers in carbon dioxide: The gradient foaming of PMMA

Cited by 31 publications

References 53 publications

Nanocellular Polymers with a Gradient Cellular Structure Based on Poly(methyl methacrylate)/Thermoplastic Polyurethane Blends Produced by Gas Dissolution Foaming

Nanocellular Polymers with a Gradient Cellular Structure Based on Poly(methyl methacrylate)/Thermoplastic Polyurethane Blends Produced by Gas Dissolution Foaming

Anisotropic cellular structures from semi‐crystalline polymer templates

Foaming of poly(ethylene‐co‐vinyl acetate) and poly(ethylene‐co‐vinyl acetate‐co‐carbon monoxide) and their blends with carbon dioxide

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