https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 14 May 2026 20:28:52 GMT 2026-05-14T20:28:52Z http://hdl.handle.net/10985/8262 Microcellular Foaming of Polymethylmethacrylate in a Batch Supercritical CO2 Process: Effect of Microstructure on Compression Behavior REGLERO RUIZ, Jose Antonio; DUMON, Michel; VIOT, Philippe Microcellular foaming of reinforced core/ shell Polymethylmethacrylate (PMMA) was carried out bymeans of supercritical CO2 in a single-step process. Samples were produced using a technique based on the saturation of the polymer under high pressure of CO2(300 bars,40 C), and cellular structure was controlled by varying the depressurization rate from 0.5 bar/s to 1.6 x10-2 bar/sleading to cell sizes from 1lm to 200l m, and densities from 0.8 to 1.0 g/cm3. It was found that the key parameter to control cell size was depressurization rate, and larger depressurization rates generated bigger cell sizes. On the other hand, variation of the density of the samples was not so considerable. Low rate compression tests were carried out, analyzing the dependence of mechanical parameters such as elastic modulus, yield stress and densification strain with cell size. Moreover, the calculation of the energy absorbed for each sample is presented, showing an optimum of energy absorption up to 50% of deformation in the micrometer cellular range (here at a cell size of about 5 µm). To conclude, a brief comparison between neat PMMA and the core/shell reinforced PMMA has been carried out, analyzing the effect of the core/shell particles in the foaming behavior and mechanical properties. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/10985/8262 2010-01-01T00:00:00Z REGLERO RUIZ, Jose Antonio DUMON, Michel VIOT, Philippe Microcellular foaming of reinforced core/ shell Polymethylmethacrylate (PMMA) was carried out bymeans of supercritical CO2 in a single-step process. Samples were produced using a technique based on the saturation of the polymer under high pressure of CO2(300 bars,40 C), and cellular structure was controlled by varying the depressurization rate from 0.5 bar/s to 1.6 x10-2 bar/sleading to cell sizes from 1lm to 200l m, and densities from 0.8 to 1.0 g/cm3. It was found that the key parameter to control cell size was depressurization rate, and larger depressurization rates generated bigger cell sizes. On the other hand, variation of the density of the samples was not so considerable. Low rate compression tests were carried out, analyzing the dependence of mechanical parameters such as elastic modulus, yield stress and densification strain with cell size. Moreover, the calculation of the energy absorbed for each sample is presented, showing an optimum of energy absorption up to 50% of deformation in the micrometer cellular range (here at a cell size of about 5 µm). To conclude, a brief comparison between neat PMMA and the core/shell reinforced PMMA has been carried out, analyzing the effect of the core/shell particles in the foaming behavior and mechanical properties. http://hdl.handle.net/10985/23143 Supercritical CO2‐assisted extrusion foaming: A suitable process to produce very lightweight acrylic polymer micro foams HAURAT, Margaux; SAUCEAU, Martial; BAILLON, Fabien; LE BARBENCHON, Louise; PEDROS, Matthieu; DUMON, Michel A strategy of CO2-assisted extrusion foaming of PMMA-based materials was established to minimize both foam density and porosities dimension. First a highly CO2-philic block copolymer (MAM: PMMA-PBA-PMMA) was added in PMMA in order to improve CO2 saturation before foaming. Then the extruding conditions were optimized to maximize CO2 uptake and prevent coalescence. The extruding temperature reduction led to an increase of pressure in the barrel, favorable to cell size reduction. With the combination of material formulation and extruding strategy, very lightweight homogeneous foams with small porosities have been produced. Lightest PMMA micro foams (ρ = 0.06 g cm−3) are demonstrated with 7 wt% CO2 at 130°C and lightest blend micro foams (ρ = 0.04 g cm−3) are obtained at lower temperature (110°C, 7.7 wt% CO2). If MAM allows a reduction of Tfoaming, it also allows a much better cell homogeneity, an increase in cell density (e.g., from 3.6 107 cells cm−3 to 2 to 6 108 cells cm−3) and an overall decrease in cell size (from 100 to 40 μm). These acrylic foams produced through scCO2-assisted extrusion has a much lower density than those ever produced in batch (ρ ≥ 0.2 g cm−3). Tue, 15 Nov 2022 00:00:00 GMT http://hdl.handle.net/10985/23143 2022-11-15T00:00:00Z HAURAT, Margaux SAUCEAU, Martial BAILLON, Fabien LE BARBENCHON, Louise PEDROS, Matthieu DUMON, Michel A strategy of CO2-assisted extrusion foaming of PMMA-based materials was established to minimize both foam density and porosities dimension. First a highly CO2-philic block copolymer (MAM: PMMA-PBA-PMMA) was added in PMMA in order to improve CO2 saturation before foaming. Then the extruding conditions were optimized to maximize CO2 uptake and prevent coalescence. The extruding temperature reduction led to an increase of pressure in the barrel, favorable to cell size reduction. With the combination of material formulation and extruding strategy, very lightweight homogeneous foams with small porosities have been produced. Lightest PMMA micro foams (ρ = 0.06 g cm−3) are demonstrated with 7 wt% CO2 at 130°C and lightest blend micro foams (ρ = 0.04 g cm−3) are obtained at lower temperature (110°C, 7.7 wt% CO2). If MAM allows a reduction of Tfoaming, it also allows a much better cell homogeneity, an increase in cell density (e.g., from 3.6 107 cells cm−3 to 2 to 6 108 cells cm−3) and an overall decrease in cell size (from 100 to 40 μm). These acrylic foams produced through scCO2-assisted extrusion has a much lower density than those ever produced in batch (ρ ≥ 0.2 g cm−3). http://hdl.handle.net/10985/24861 High-pressure drop rates in solid-state batch one-step scCO2 foaming of acrylic polymers: A way to stabilize the structure of micro-nano foams HAURAT, Margaux; ANGUY, Yannick; GABORIEAU, Cécile; AUBERT, Guillaume; AYMONIER, Cyril; DUMON, Michel One-step solid-state batch scCO2 foaming is used with the target of achieving acrylic polymer micro-nano foams. Foaming is triggered by an average pressure drop (APDR), covering two decades, from 0.3 to 30 MPa.s−1. This study principally addresses the combined beneficial effects of block copolymer addition (BCP, here denoted as MAM) and high APDR. Numerous subtle kinetic parameters actually interplay and compete in the production of the final foams. In particular, the material effective temperature, the effective glass transition temperature of the plasticized system and the instantaneous PDR are physical quantities each having their own kinetics during foaming. The resulting foam morphologies are quantified by SEM microscopy and image analysis. A high APDR and the presence of BCP are shown to play a key role in the final structure of the foams. Over the scrutinized range of saturation temperature (40 °C to 60 °C i.e. rather ‘low’ temperatures in the CO2 supercritical state), the APDR is the main factor for significantly reducing cell size and increasing nuclei density in foams from neat PMMA. In the block copolymer approach, increasing the APDR is of secondary importance as the targeted reduction of the porosity dimensions and augmentation of nuclei density are mostly the consequence of MAM presence. In this latter case, increasing the APDR still promotes the ‘efficiency’ of the BCP nucleants. A real efficient nucleation activity of MAM additive is observed at a very high APDR (30 MPa.s−1), leading to monomodal homogeneous distribution of tiny pores in nearly nanosized foams. At lower APDR, an interesting reproducible double porosity (foams containing intra-wall and inter-wall pores) is detected in PMMA/MAM systems. In such double porosity foams, benefits from the Knudsen effect achieved within well expanded local domains (showing micron-sized pores) may remain meaningful thanks to a locally poorly expanded nanoporous thick solid skeleton encapsulating these local domains. Thereby, the radiative thermal conduction can be minimized and does not override the conductive component at the sample scale. This work provides further insight on acrylic polymer BCP foams influenced by different kinetics. Wed, 01 Nov 2023 00:00:00 GMT http://hdl.handle.net/10985/24861 2023-11-01T00:00:00Z HAURAT, Margaux ANGUY, Yannick GABORIEAU, Cécile AUBERT, Guillaume AYMONIER, Cyril DUMON, Michel One-step solid-state batch scCO2 foaming is used with the target of achieving acrylic polymer micro-nano foams. Foaming is triggered by an average pressure drop (APDR), covering two decades, from 0.3 to 30 MPa.s−1. This study principally addresses the combined beneficial effects of block copolymer addition (BCP, here denoted as MAM) and high APDR. Numerous subtle kinetic parameters actually interplay and compete in the production of the final foams. In particular, the material effective temperature, the effective glass transition temperature of the plasticized system and the instantaneous PDR are physical quantities each having their own kinetics during foaming. The resulting foam morphologies are quantified by SEM microscopy and image analysis. A high APDR and the presence of BCP are shown to play a key role in the final structure of the foams. Over the scrutinized range of saturation temperature (40 °C to 60 °C i.e. rather ‘low’ temperatures in the CO2 supercritical state), the APDR is the main factor for significantly reducing cell size and increasing nuclei density in foams from neat PMMA. In the block copolymer approach, increasing the APDR is of secondary importance as the targeted reduction of the porosity dimensions and augmentation of nuclei density are mostly the consequence of MAM presence. In this latter case, increasing the APDR still promotes the ‘efficiency’ of the BCP nucleants. A real efficient nucleation activity of MAM additive is observed at a very high APDR (30 MPa.s−1), leading to monomodal homogeneous distribution of tiny pores in nearly nanosized foams. At lower APDR, an interesting reproducible double porosity (foams containing intra-wall and inter-wall pores) is detected in PMMA/MAM systems. In such double porosity foams, benefits from the Knudsen effect achieved within well expanded local domains (showing micron-sized pores) may remain meaningful thanks to a locally poorly expanded nanoporous thick solid skeleton encapsulating these local domains. Thereby, the radiative thermal conduction can be minimized and does not override the conductive component at the sample scale. This work provides further insight on acrylic polymer BCP foams influenced by different kinetics.