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1.
Nanocellular foaming of polystyrene (PS) and a polystyrene copolymer (PS‐b‐PFDA) with fluorinated block (1,1,2,2‐tetrahydroperfluorodecyl acrylate block, PFDA) was studied in supercritical CO2 (scCO2) via a one‐step foaming batch process. Atom Transfer Radical Polymerization (ATRP) was used to synthesize all the polymers. Neat PS and PS‐b‐PFDA copolymer samples were produced by extrusion and solid thick plaques were shaped in a hot‐press, and then subsequently foamed in a single‐step foaming process using scCO2 to analyze the effect of the addition of the fluorinated block copolymer in the foaming behaviour of neat PS. Samples were saturated under high pressures of CO2 (30 MPa) at low temperatures (e.g., 0°C) followed by a depressurization at a rate of 5 MPa/min. Foamed materials of neat PS and PS‐b‐PFDA copolymer were produced in the same conditions showing that the presence of high CO2‐philic perfluoro blocks, in the form of submicrometric separated domains in the PS matrix, acts as nucleating agents during the foaming process. The preponderance of the fluorinated blocks in the foaming behavior is evidenced, leading to PS‐b‐PFDA nanocellular foams with cell sizes in the order of 100 nm, and bulk densities about 0.7 g/cm3. The use of fluorinated blocks improve drastically the foam morphology, leading to ultramicro cellular and possibly nanocellular foams with a great homogeneity of the porous structure directly related to the dispersion of highly CO2‐philic fluorinated blocks in the PS matrix. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
2.
Stabilization of CO2‐in‐water emulsions with high internal phase volume using PVAc‐b‐PVP and PVP‐b‐PVAc‐b‐PVP as emulsifying agents
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Li Wen Liwen Wang Shuyi Fang Lei Bao Dongdong Hu Yuan Zong Ling Zhao Tao Liu 《应用聚合物科学杂志》2018,135(23)
Two newly‐designed hydrocarbon surfactants, that is, poly(vinyl acetate)‐block‐poly(1‐vinyl‐2‐pyrrolidone) (PVAc‐b‐PVP) and PVP‐b‐PVAc‐b‐PVP, were synthesized using reversible addition–fragmentation chain transfer polymerization and used to form CO2/water (C/W) emulsions with high internal phase volume and good stability against flocculation and coalescence up to 60 h. Their structures were precisely determined by nuclear magnetic resonance, gel permeation chromatography, thermal gravimetric analysis, and differential scanning calorimetry. Besides low temperature and high CO2 pressure, the surfactant structures were the key factors affecting the formation and stability of high internal phase C/W emulsions, including the polymerization degrees of CO2‐philic block (PVAc) and hydrophilic block (PVP), as well as the number of hydrophilic tail. The surface tension of the surfactant aqueous solution and the apparent viscosity of the C/W emulsions were also measured to characterize the surfactants efficiency and effectiveness. The surfactants with double hydrophilic tails showed stronger emulsifying ability than those with single hydrophilic tail. The great enhancement of the emulsions stability was due to decrease of the interface tension as well as increase of the steric hindrance in the water lamellae, preventing a frequent collision of CO2 droplets and their fast coalescence. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46351. 相似文献
3.
A strategy for the preparation of closed‐cell and crosslinked polypropylene foam by supercritical CO2 foaming
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We report the preparation of a closed‐cell polypropylene (PP) foam material by supercritical carbon dioxide foaming with the assistance of γ‐ray radiation crosslinking. Styrene–ethylene–butadiene–styrene (SEBS) copolymer was added to PP to enhance radiation crosslinking and nucleation. Radiation effects on the foaming of the PP/SEBS blend with different ratios were investigated. A significant improvement in the foaming of the crosslinked PP/SEBS blend was achieved as compared to pristine PP. The cell density of the crosslinked PP/SEBS foam greatly increased at a dose of 10 kGy and a high closed‐cell ratio was obtained. The tensile strength of the crosslinked PP/SEBS foams (10 kGy) was improved from 14 to 20.7 MPa compared to pristine PP foam (0 kGy). In addition, the crosslinked PP/SEBS blend exhibited a wider foaming temperature window (10 °C) as compared to the non‐crosslinked ones (4 °C). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45809. 相似文献
4.
To reveal the possibility of supercritical (SC)‐CO2‐assisted devolatilization of polystyrene, the equilibrium composition data for the CO2 phase in a styrene/CO2/polystyrene ternary system is determined by a semistatic experimental technique. The parameters in the lattice–fluid equation of state of Sanchez and Lacombe are determined for the investigated system. The distribution coefficients of styrene between the polymer and the supercritical fluid phases are investigated experimentally at 318 and 328 K over the pressure range of 12–20 MPa. The binary interaction parameter between styrene and CO2 is obtained by regression of the vapor–liquid equilibrium data. The interaction parameter between CO2 and polystyrene is calculated by using the sorption data from the literature, and the interaction parameter between styrene and polystyrene is optimized by using the measured data of this study. The investigation of the distribution coefficients indicates that styrene can be removed from polystyrene by SC‐CO2 at near room temperature and moderately high pressures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1938–1944, 2002 相似文献
5.
Experimental study and thermodynamic model for respective solubilities of CO2 and ethanol for CO2‐ethanol‐polystyrene ternary system at elevated pressure and temperature
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Ying‐Hui Qian Jun‐Ming Cao Xue‐Kun Li Gui‐Ping Cao Chang‐Chun Wang Yun‐Hai Shi 《应用聚合物科学杂志》2018,135(21)
Foamed non‐Fickian diffusion (FNFD) model for a ternary system was proposed for the first time to regress the desorption data obtained by the gravimetric method. Results showed that FNFD model could accurately describe the diffusion behavior of CO2 and ethanol out of foamed polystyrene (PS) and well predict total solubilities of CO2 and ethanol in foamed PS. Meanwhile, Sanchez–Lacombe equation of state (S–L EoS) was adopted to calculate the respective solubilities (solubility of CO2 in PS or solubility of ethanol in PS) and total solubilities of CO2 and ethanol in PS for CO2‐ethanol‐PS ternary system. Results showed that the total solubility of CO2 and ethanol obtained from S–L EoS agreed well with values obtained by FNFD model. Furthermore, the respective and total solubilities of CO2 and ethanol at 313.15, 338.15, and 343.15 K were calculated by S–L EoS. Results indicated that in the dissolving process, ethanol would be accelerated by CO2 to dissolve into PS, and ethanol would compete with CO2 to dissolve into PS, simultaneously. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46281. 相似文献