Polystyrene/magnetite hybrid foams prepared via 60Co γ-ray radiation of high internal phase emulsions

In this study, polystyrene (PS) solid foam with cell size of about 1 um and low polydispersity is prepared via γ-ray radiation induced high internal phase emulsions (HIPEs) at room temperature. The density of the foams can be as low as 0.05 g/cm³. The kinetics and molecule weight of styrene (S) polymerizing in continuous phase of HIPEs is studied. It is found that the molecule weight is greatly lower than the PS obtained from the polymerization in dispersed phase of emulsion. In addition, the authors study the mechanical properties of solid foam. The compression resistance of solid foam obtained from radiation method is better than these obtained from conventional method. At the same time, magnetite is added into the dispersed phase when prepared the HIPEs to fabricate magnetite hybrid PS foam. The saturation magnetization (Ms), remanent magnetization (Mr), and coercivity (Hc) of the hybrid foam are 25 emu/g, 15 emu/g, and 350 Oe, respectively. The results revealed that the hybrid foams have some superparamagnetic.     

Hydrophilic porous polymers based on high internal phase emulsions solely stabilized by poly(urethane urea) nanoparticles

Stable oil-in-water (o/w) Pickering high internal phase emulsions (HIPEs) having an internal phase of up to 95 vol% were prepared with a low-energy emulsification method. A poly(urethane urea) (PUU) aqueous nanodispersion was used as aqueous phase. The PUU nanoparticles of the aqueous nanodispersion acted as a mechanical barrier, and prevented droplet coalescence in the Pickering HIPEs. In addition, open porous hydrophilic polymer foams were obtained by polymerization of the Pickering HIPEs, and the morphology of the foams were tailored by changing the oil:water ratio, PUU nanoparticle and NaCl concentrations. The method used herein provides a simple way to prepare morphology controlled hydrophilic polymer foams using o/w Pickering HIPEs as template.     

Recent progress in micro-/nano-fibrillar reinforced polymeric composite foams

Manufacture of thermoplastic foams with a fine cellular structure (a higher expansion ratio, a higher cell density, and smaller cell sizes) is challenging work due to the weak viscoelastic behavior and the unsuitable crystallization behavior of common thermoplastic materials. In this work, a novel method of making microcellular foams with micro-/nano-fibrillar reinforced polymeric composites (M/NFC) is introduced, which shows various advantages compared to conventional foams. The M/NFC foams have improved cellular structures, excellent mechanical properties, and enhanced thermal insulation properties, which make them popular candidates for structural applications and insulative products. Various methods to manufacture of M/NFC foam are summarized. To understand the fundamental mechanisms of the foaming enhancement by incorporating micro-/nano-size fibrils, the rheological and crystallization behavior of the M/NFC are analyzed. It is shown that the micro-/nano-fibrils can strengthen the melt strength, induce faster crystallization, and increase the number of crystals. Due to the improvement of the cell morphology and the stiffness of the cell walls, the reinforced foams have superior mechanical properties. A hierarchically porous structure in high expansion ratio reinforced foams has also been developed. It is believed that the nano-size holes in the cell walls can further reduce the thermal conductivity of the foams.     

Preparation of highly open porous styrene/acrylonitrile and styrene/acrylonitrile/organoclay polymerized high internal phase emulsion (PolyHIPE) foams via emulsion templating

Highly open porous crosslinked styrene/ acrylonitrile (SAN) polymerized high internal phase emulsion (PolyHIPE) foams containing various amounts of acrylonitrile (AN) were prepared by the polymerization of the continuous organic phase of high internal phase emulsions with an 85 vol % aqueous internal phase. The mean diameter of voids varied in the range 12.4–19.8 μm. The void diameter increased up to 10% AN, but beyond this limit, the diameter decreased. To improve the mechanical properties of the copolymer foams, the organic phase of the emulsion containing 20% AN was reinforced with organomontmorillonites with different surface modifiers. The effects of the organoclay on the equilibrium torque value of the emulsifying systems, as an approximate characteristic of the emulsion viscosity, and on the morphology and mechanical properties of the resulting foam were investigated. Scanning electron micrographs exhibited an open‐cell polyHIPE structure for all of the SAN/organoclay polyHIPE foams. The incorporation of organoclays within the emulsion copolymer foam significantly decreased the mean size of voids and intercellular pores compared with those of the copolymer foam without reinforcement. In fact, the presence of organoclay may have acted as a cosurfactant to improve the performance of the nonionic surfactant in the concentrated emulsions. The X‐ray diffraction patterns and transmission electron micrographs showed an intercalated nanocomposite structure for the organoclay‐reinforced copolymer foams. On the other hand, the addition of a more hydrophilic organoclay, that is, 3 wt % Cloisite30B, to the concentrated emulsion decreased the Young's modulus and significantly improved the crush strength of the emulsion copolymer foam. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Drying of Foamed Biological Materials: Opportunities and Challenges

An overview is provided on hot air drying of foamed materials in a thin layer (foam-mat drying), foam-spray drying, microwave-assisted drying of liquid foams, as well as microwave drying of frozen foams with and without dielectric solid inserts, used as complementary heat sources. In particular, the mechanisms of heat and moisture transport during the drying of foams are identified. The effects of foam characteristics (e.g., foam density and stability) and drying conditions (temperature, air velocity) on drying kinetics and product quality are examined, and the differences between the drying of non-foamed and foamed materials are discussed.     

Drying of Foamed Biological Materials: Opportunities and Challenges

An overview is provided on hot air drying of foamed materials in a thin layer (foam-mat drying), foam-spray drying, microwave-assisted drying of liquid foams, as well as microwave drying of frozen foams with and without dielectric solid inserts, used as complementary heat sources. In particular, the mechanisms of heat and moisture transport during the drying of foams are identified. The effects of foam characteristics (e.g., foam density and stability) and drying conditions (temperature, air velocity) on drying kinetics and product quality are examined, and the differences between the drying of non-foamed and foamed materials are discussed.     

Aerogel-like ceramic foams with super-high porosity and nanoscale cell wall from sol nanoparticles stabilized foams

Ultralight ceramic foam materials with high porosity play an important role in increasingly hi-tech areas due to the combinative merit of ceramic material and highly porous structure. So far, it remains challenging to fabricate alumina ceramic foams with extremely high porosity and high specific surface area that are comparable to aerogel materials by employing a low cost, eco-friendly and convenient approach. For the first time, we propose the preparation of aerogel-like ceramic foams with nanoscale cell wall and unprecedentedly high porosity using boehmite sol as both ceramic source and bubble interface stabilizer, based on sol nanoparticles stabilized foams using sodium lauryl sulfate (SDS) as modifier. The obtained ultra-stable sol foams allow for the achievement of bulk foams with ultrathin cell wall with thickness in the range of 30-90 nm, super-high porosity up to 99%, and large specific surface area of 280 m²/g, which is attributed to the well-organized assembly of nanoparticles at the liquid/air interfaces. This novel foam material demonstrates excellent adsorption ability for polar volatile organic gases (VOCs) due to its extremely high porosity and large specific surface area.     

八甲基环四硅氧烷开环聚合反应机理及动力学研究进展

有机硅匀泡剂是制备聚氨酯泡沫塑料的重要助剂,主要以八甲基环四硅氧烷(以下简称D4)、高含氢硅油及聚醚多元醇等为原料经开环和共聚及硅氢加成等反应制得,其中,D4的开环聚合反应是制备有机硅匀泡剂的关键之一。评述了国内外D4开环聚合机理及动力学研究进展,以期为聚氨酯泡沫塑料用有机硅匀泡剂的研发和生产提供参考。     

Rapid preparation of hierarchically porous ceramic microspheres based on UV-curing-assisted molding

Ceramic microspheres have attracted significant attention, while the preparation of hierarchically porous ceramic microspheres with high porosity, good sphericity, and controllable size or shape in a short time remains a challenge. Herein, we developed a highly adaptable methodology for the preparation hierarchically porous ceramic microspheres with high porosity and favorable shape in a short time. The UV-curing assisted molding method combined with the Pickering emulsion method was utilized to prepare hierarchically porous ceramic microspheres. Under the irradiation of a UV-curing lamp (395 nm, 50 W), the Pickering emulsion can be cured within as short as 10 s. The microstructures of the three microspheres with different shapes were characterized by scanning electron microscopes (SEM). The as-prepared microspheres had a high sphericity, the interconnectivity of pores was as high as 54 %, and its porosity was as high as 73.4 % ± 3.0 %, while the density was quite low at ∼ 1.02 g/cm³.     

Molecularly imprinted polymer prepared by Pickering emulsion polymerization for removal of acephate residues from contaminated waters

A molecularly imprinted polymer (MIP) prepared with Pickering emulsion polymerization was designed by a computational approach for removal of acephate from aqueous solution. Methacrylic acid, ethylene glycol dimethacrylate, and chloroform were screened as the optimal functional monomer, crosslinker, and porogen by the Gaussian 03 package using the density functional theory method. The polymerization was carried out in an oil‐in‐water emulsion using nano‐SiO₂ particles as stabilizer instead of a toxic surfactant. The characterization results indicated that the prepared MIP had a porous and hollow core, and the particle size was approximately 20 μm. The binding and recognition abilities of MIP for acephate were studied through equilibrium adsorption analysis and selectivity analysis. The results showed that the MIP had high binding capacity and excellent selectivity for acephate. The saturated binding amount could reach 6.59 × 10³ μg/g. The Langmuir isotherm model gave a good fit to the experimental data. Moreover, the results of a reusability analysis and practical application suggested that the prepared MIP provides the potential for removal of acephate residues from aqueous solution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43126.     

Structure and electrically conductive properties of porous PAN-based nanocomposites prepared by Pickering emulsion template method

A carbon nanohybrid Pickering stabilizer was synthesized by the hydrothermal reaction of 2-ethyl-4-methylimidazole (EMI), graphene oxide (GO), and carbon nanotubes (CNTs). A water-in-oil (w/o) type Pickering emulsion was achieved using the mixed carbon nanohybrids/Span 80 to form a porous and conductive polyacrylonitrile (PAN) nanocomposites after polymerization. Contact angle and X-ray photoelectron spectroscopy (XPS) results show that the carbon nanohybrid stabilizer is amphiphilic. The effects of the composition and concentration of stabilizers were investigated. When the concentration of the carbon nanohybrid stabilizer is 4 mg ml⁻¹, the conductivity of the resulting material is 2.31 × 10⁻⁹ S m⁻¹, which is six orders of magnitude higher than that of porous PAN composites without carbon nanohybrid stabilizer. At the mass ratio of 6GO:1CNTs, the conductivity of porous PAN-based composites reaches 2.47 × 10⁻⁸ S m⁻¹. The significantly increased conductivity is the evidence for the three dimensional conductive network constructed by carbon nanohybrid stabilizer at the oil/water interface.     

Porous polymers prepared via high internal phase emulsion polymerization for reversible CO2 capture

A series of porous polymers with different pore volumes, pore sizes, and crosslinking densities were synthesized by high internal phase emulsion (HIPE) polymerization. The crosslinked polymerized HIPEs (polyHIPEs) were formed by the copolymerization of 4-vinylbenzyl chloride and divinylbenzene using water droplets in conventional or Pickering HIPEs as the templates. These porous materials were further modified by quaternization and ion exchange to introduce quaternary ammonium hydroxide groups. The resulting polyHIPEs were utilized as sorbents for reversible CO₂ capture from air using the humidity swing. The effect of pore structure on the CO₂ adsorption and desorption processes was studied. The polyHIPEs containing large pores and interconnected porous structures showed improved swing sizes and faster adsorption/desorption kinetics of CO₂ compared to a commercial Excellion membrane with similar functional groups.     

Fabrication of PEI-grafted porous polymer foam for CO2 capture

A polymer foam material with both the open-cell porous structure and the polyethylenemine (PEI)-grafted inner face was constructed for CO₂ capture. The porous poly(tert-butyl acrylate) foam was first prepared via a concentrated emulsion polymerization, and then the carboxyl groups were introduced on the interface of porous polymer after the hydrolysis reaction. Subsequently, the surface of the foam was grafted with PEI, and finally the PEI-grafted porous polymer foam designed as a CO₂ capture material was obtained. The structures of the foams were characterized by infrared spectroscopy, EDS, and SEM. The CO₂ adsorption properties were measured by adsorption/desorption cycles. As a result, the polymer foam contained a large number of amine groups (13.9 wt % N), and therefore possessed a high CO₂ adsorption capacity (5.91 mmol g⁻¹ at 40°C and 100 kPa). In addition, they also exhibited high CO₂ adsorption rate, good selectivity for CO₂-N₂ separation, and good stability according to CO₂ cyclic adsorption/desorption test. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47844.     

A Novel PEEK Foam with Ultra-High Temperature-Resistant by Temperature Induced Phase Separation

Polyaryletherketone is a kind of special engineering plastics with excellent comprehensive properties, high strength, good stability, and almost insoluble in any common solvent except concentrated sulfuric acid at room temperature. However, its high processing temperature also hinders its application and development in the foam. Here, a series of polyetheretherketone (PEEK) and diphenyl polyetheretherketone (PEDEK) composite foams are prepared by temperature induced phase separation, using diphenyl sulfone as solvent. The microstructure, thermal and mechanical properties of PEEK and PEDEK foam are compared. Highly porous PEEK and PEDEK foams with densities ranging from 0.13 to 0.25 g cm⁻³, with compressive strength ranging from 0.68 to 2.6 MPa, respectively, are produced. Meanwhile, the introduction of diphenyl structure can effectively improve the performance of PEEK foams at high temperature. It is found that PEDEK foam has a higher operating temperature than PEEK, and the compressive strength of 0.24 g cm⁻³ foam is still ≈1 MPa at 200 °C.     

Hierarchical porous ceramics with multiple open pores from boehmite gel emulsions

Ceramic foam materials with highly porous microstructure are playing vital role in increasing areas, especially for those with requirements for open channels and superior specific surface area. In this work, a simple and versatile approach to prepare ceramic foams with open pores has been proposed, that is gelation of boehmite nanoparticle-assembled emulsions. Notably, hierarchical porous microstructure with open channels and uniform pore structure has been built. High specific surface area up to389.4 m²/g is attainable, making it excellent adsorption material when combining the merit of hierarchical pore structure. Furthermore, lattice-shaped ceramics are prepared via direct ink writing gelled emulsion, displaying the potential of forming lightweight material with complex shape and designable macrostructure. The three-dimensional (3D) printed foams exhibit multiple open pores, which cover length scale from mm scale, to μm scale and nm scale, making them promising materials in several fields like adsorption and gas filtrations, etc.     

Processing of Particle-Stabilized Wet Foams Into Porous Ceramics

Direct foaming of colloidal suspensions is a simple and versatile approach for the fabrication of macroporous ceramic materials. Wet foams produced by this method can be stabilized by long-chain surfactants or by colloidal particles. In this work, we investigate the processing of particle-stabilized wet foams into crack-free macroporous ceramics. The processing steps are discussed with particular emphasis on the consolidation and drying process of wet foams. Macroporous alumina ceramics prepared using different consolidation and drying methods are compared in terms of their final microstructure, porosity, and compressive strength. Consolidation of the wet foam by particle coagulation before drying resulted in porous alumina with a closed-cell structure, a porosity of 86.5%, an average cell size of 35 μm, and a remarkable compressive strength of 16.3 MPa. On the other hand, wet foams consolidated via gelation of the liquid within the foam lamella led to porous structures with interconnected cells in the size range from 100 to 150 μm. The tailored microstructure and high mechanical strength of the macroporous ceramics can be of interest for the manufacture of bio-scaffolds, thermal insulators, impact absorbers, separation membranes, and light weight ceramics.     

Janus graphene oxide nanosheets prepared via Pickering emulsion template

Janus graphene oxide (GO) nanosheets functionalized by amino-containing chemicals were prepared via Pickering emulsion template. A wax-in-water Pickering emulsion was used to mask one side of GO nanosheets in order to achieve asymmetric chemical functionalization. Janus particles were obtained by removing the oil phase. The successful reaction of epoxy groups on the surface of GO with amino-containing chemicals was confirmed by Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). The asymmetric surface structure of Janus GO nanosheets was detected by atomic force microscope (AFM) and X-ray diffraction (XRD). The efficient stabilization of an oil-in-water Pickering emulsion by Janus GO was proved. Polymer microspheres fabricated by using Janus GO as Pickering stabilizer had a more hydrophilic surface compared with those stabilized by symmetrically modified GO.     

碳泡沫的乳液法制备条件研究

采用轧液聚合的方法,以间苯二酚、甲醛的水溶液为水相,以液体石蜡为油相,经搅拌、固化、碳化等过程后得到破泡沫样品.其密度为(0.25～0.4)g/cm2,比表面积为(500～700)m2/g,该方法制备的碳泡沫,具有开孔结构,孔径分布比较均匀,且孔径大小可调节,制备条件对乳液体系的稳定性以及所得的碳泡沫样品结构形耽有较大的影响.     

Preparation and in vitro evaluation of hydrophobic‐modified montmorillonite stabilized pickering emulsion for overdose acetaminophen removal

Pickering emulsion stabilized with hydrophobic‐modified montmorillonite (HMMT) was proposed for treating acute overdose acetaminophen intoxication, with a rapid removal rate, better stability, and good biocompatibility. The tiny HMMT was able to adsorb at the oil‐water interface of the Pickering emulsion to reduce the interfacial energy along with the formation of solid particle layer, in order to enhance the stability of the emulsion and improve the removal performance. With a fast removal rate, the detoxifying Pickering emulsion removed 0.5 g/L acetaminophen in the simulated gastric fluid to 0.13 g/L in 6 min, which is less than the intoxication content of 0.15 g/L, with a leakage ratio of lower than 4 % in simulated intestinal fluid over 4 h. Such a detoxifying emulsion was prepared at 55 °C with 2 % organoclay (HMMT) as the emulsifier, 6 % tributyl phosphate (TBP) as the extractant, and 0.1 mol/L NaOH as the inner phase in the volume ratio of 5:7. All the results denoted that the Pickering emulsion could be a promising candidate for the acute oral intoxication treatment.     

Preparation and characterization of polyurethane foam/activated carbon composite adsorbents

A polyurethane foam (PU)/activated carbon (AC) composite was prepared by adding granular AC during the synthesis of PU foam, and subsequent carbonization. Nitrogen adsorption?Cdesorption isotherms and scanning electron microscopy were used to ascertain the pore structure and surface morphology of the samples. The prepared composite foams possess well-developed open cell structures. Under the conditions investigated, a higher carbonization temperature promoted development of porous structures. Thermogravimetric and derivative thermogravimetric analyses revealed the thermostability of the PU foam precursor/AC composites. The adsorption performance of the composites was evaluated using phenol, iodine and methylene blue (MB) as model compounds. A PU foam/AC composite with a maximum specific surface area of 655.0?m²/g, maximum iodine number of 525.2?mg/g, and maximum adsorption capacity of MB and phenol of 100 and 66.5?mg/g, respectively, was achieved.