Structure and Mechanical Stability of Epoxy Modified Polyurethane Foam Under Heat and Stress

A series of phenolic epoxy resin (PEP) modified polyurethane foams (PUF) were prepared via an in-situ polymerization, one step process. It was found that the epoxy modified PUF foam exhibited a perforated network structure with larger cell size, higher open cell porosity and enhanced ovality compared with pure PUF. With increasing content of PEP, the tensile strength, elongation at break and low temperature modulus of PUF decreased. A single T_g was observed for PEP modified PUF, indicating that the two component phases of the polyurethane-epoxy were miscible. With increasing PEP content, the T_g of PUF shifted slightly to higher temperature, tan δ_max dropped to lower values, and the retention value of the storage modulus at ?20 and ?10?°C increased. For pure PUF, the cell walls degraded and the structure became disordered after aging under heat and stress, while for PUF/20wt%PEP, the degradation degree was obviously reduced, and an orientation of the cells along the stress direction and a density increase was observed. During aging at 200?°C, the retention of the mechanical properties of PUF/20wt% PEP was much higher than that of pure PUF, and it showed superior stability under heat and stress, attributed to incorporation of the thermally resistant oxazolidone rings and benzene rings in the PU backbones, the highly cross-linked networks of the polyurethane-epoxy systems and the obvious orientation of the cells under stress.     

Cu/CuO-Graphene Foam with Laccase-like Activity for Identification of Phenolic Compounds and Detection of Epinephrine

Although great progress has been made in the advancement of nanozymes, most of the studies focus on mimicking peroxidase, oxidase, and catalase, while relatively few studies are used to mimic laccase. However, the use of nanomaterials to mimic laccase activity will have great potential in environmental and industrial catalysis. Herein, Cu/CuO-graphene foam with laccase-like activity was designed for the identification of phenolic compounds and the detection of epinephrine. In a typical experiment, the formation mechanism of Cu/CuO-graphene foam was investigated during the pyrolysis process by thermogravimetric-mass spectrometry. As a laccase mimic, Cu/CuO-graphene foam exhibited excellent catalytic activity with a Michaelis-Menten constant and a maximum initial velocity of 0.17 mmol/L and 0.012 mmol∙L^-1∙s^-1, respectively. Based on this principle, Cu/CuO-graphene foam nanozyme could differentially catalyze phenolic compounds and 4-aminoantipyrine for simultaneous identification of phenolic compounds. Furthermore, a colorimetric sensing platform was fabricated for the quantitative determination of epinephrine, showing linear responses to epinephrine in the range of 3 mg/mL to 20 mg/mL with the detection limit of 0.2 mg/mL. The proposed Cu/CuO-graphene foam nanozyme could be applied for the identification of phenolic compounds and the detection of epinephrine, showing great potential applications for environmental monitoring, biomedical sensing, and food detection fields.     

Self‐assembled polyurea macromer nanodispersion and resulting hybrid polyurea‐acrylic emulsions and films

A polyurea macromer (PUM) was synthesized and dispersed in basic conditions to form self‐assembled nanoparticles (<20 nm dispersions, up to 30 wt % aq. soln.). These nanoparticles enabled surfactant‐free emulsion polymerization to form hybrid polyurea‐acrylic particles despite the absence of a measureable water‐soluble fraction. The T_g of the starting PUM material was a strong function of the PUM's extent of neutralization and hydration (varying between 100 °C and >175 °C) due to changes in hydrogen and ionic bonding. Two separate hybrid polyurea‐acrylic emulsion systems were prepared: one by direct polymerization of (meth)acrylic monomers in the presence of the nanodispersion and a second by a physical blend of PUM nanodispersion with an acrylic latex control. The direct polymerization method resulted in a hybrid emulsion particle size that developed by a mechanism resembling conventional emulsion polymerization and was unlike that described for seeded polyurethane dispersion systems. Film hardness was shown to increase with increasing coating thickness for the hybrid film prepared by direct polymerization. The resulting mechanical properties could be explained by applying mechanical models for a composite foam structure. These results were unprecedented for normal elastomer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1373–1388     

One-step synthesis of Fe-Ni hydroxide nanosheets derived from bimetallic foam for efficient electrocatalytic oxygen evolution and overall water splitting

For the first time, the Fe-Ni LDH nanosheets were prepared through simple one-step hydrothermal treatment of Fe-Ni bimetallic foam both as the substrate and Fe/Ni sources. The ratio of Ni/Fe elements played the important role in realizing the optimal catalytic activities for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). An alkaline water electrolyzer was constructed with the Fe-Ni hydroxide nanosheets/Fe-Ni alloy foam-60% Fe as anode and Ni(OH)₂/Fe-Ni alloy foam-25% Fe as cathode, which displays superior electrolytic performance (affording 10 mA/cm² at 1.62 V) and lasting durability.     

纳米-微米复合孔泡沫陶瓷固定化脂肪酶

考察了泡沫陶瓷的孔径分布和表面性质对脂肪酶固定化的影响.研究表明,泡沫陶瓷的纳米孔孔径分布非常适合脂肪酶的固定化,对固定化酶的催化效率有决定性的影响.经1h的定化,泡沫陶瓷固定化酶的活性达商业化硅藻土固定化酶的1.33倍,体积活力为其2.63倍,蛋白载量为45.36mg/g陶瓷,比活为1215.39U/g,活力回收为41.2%.泡沫陶瓷固定化脂肪酶在有机相乙酸乙酯合成中表现优良,连续使用5次,每次反应3h,乙酸转化率均在93%左右.     

Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface

Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br⁻ counterions compared to smaller Na⁺ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H⁺ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H⁺ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.     

Synthesis of ZnTiO3/tourmaline/Ni foam catalyst and enhanced photocatalytic performance

ZnTiO₃/tourmaline loaded on the nickel foam (ZnTiO₃/tourmaline/Ni-foam) is prepared by a facile coating method. Morphology and structure of the photocatalyst were characterized by X-ray diffraction (XRD), scanning electrons microscopy (SEM), raman spectroscopy, UV–vis diffuse reflectance spectrum (UV–vis DRS) and photoluminescence spectroscopy (PL). The photocatalytic properties of the materials were tested by using the Rhodamine B (RhB) solution as the target pollutant. The results indicates that the ZnTiO₃/tourmaline/Ni foam exhibited higher photocatalytic activity than that of ZnTiO₃ and ZnTiO₃/Ni foam under ultraviolet (UV) light irradiation, and its degradation rate was up to 99.2%. Moreover, the degradation rate remained at 91.3% after eight consecutive photocatalytic reaction cycles. The outstanding photocatalytic performances of ZnTiO₃/tourmaline/Ni foam was mainly attributed to the existence of tourmaline, which can help to inhibit the recombination of electron-hole paris, and the proper pore structure of the carrier. Meanwhile, the trapping experiments indicated that ·O₂^– was the main active species in the photocatalytic degradation of RhB.     

Treatment of Oily Wastewater by Using Porous PVA Hydrogels as Oil Adsorbent

The adsorption of crude oil from wastewater on the crosslinked poly(vinyl alcohol) hydrogel (HPVA) and its foam (HPVAF) was reported. The macroporous HPVAF was prepared by adding CaCO₃ and epichlorohydrin as pore-forming agent and crosslinker, respectively. The prepared hydrogels were characterized, and their ability to adsorb and immobilize the crude oil was assessed by gravimetric method at the optimum condition. The HPVAF carrier demonstrated the improvement in the hydrocarbon trapping than the HPVA one. Scanning electron microscopy showed the presence of extracellular structures that could play an important role in the immobilization stability of crude oil on polymers. As well, the percentage removal ability of the crude oil by HPVAF was approximately, 82%. The results suggest the potential of using HPVA and HPVAF films as trapping for crude oil to enhance the treatment of oily wastewater with a low cost in an open marine environment.     

Absorption characteristics of masjid carpets

This work investigated the absorption characteristics of eight types of carpets that are especially designed and manufactured for masjids and two types of carpets pads. Measurements were carried out in the reverberation room according to ISO 354. Each type was tested three times: first when it was installed directly on the floor, second when it was installed above 5.7 mm of polyurethane foam, and last when it was installed above 10 mm of polyethylene foam. The results showed that the absorption coefficient is directly proportional to frequency and knot density. The results also demonstrated that adding pads of polyurethane or polyethylene foam increased the absorption, principally in the mid-frequency range. The effect of polyurethane foam on absorption was higher than that of polyethylene foam. Finally, the absorption coefficients of the examined carpets were found to be close to those of Muslim worshippers when they are in the position known as “standing in rows”.     

Hierarchically Structured Porous Silica Spheres by Microemulsion/Vesicle Templating for Hydrodesulfurization of Fluid Catalytic Cracking Diesel

A series of hierarchically structured porous silica sphere (HSPSS) materials are successfully fabricated by a facile, one‐step microemulsion/vesicle bimodal method in a multicomponent microemulsion system of P123/n‐butanol/1,3,5‐trimethylbenzene/KCl/H₂O (surfactant/cosurfactant/oil/salt/water). The pore structures of the obtained HSPSS products consist of mesocellular foam and mesostructured vesicles. In contrast to the traditional porous silica materials the new structures combine two separate, distinct mesophases with different‐sized mesovoids in a single porous sphere. Moreover, the proportion of every mesophase in obtained HSPSS can be easily adjusted by tuning the initially added amount of n‐butanol or KCl in this multicomponent microemulsion system. When the molar ratio of KCl/tetraethoxysilane is 2.15, the obtained HSPSS material is turned into uniform mesostructured vesicle silica spheres, which consist of many small diameter vesicle particles. The hydrodesulfurization (HDS) activity of fluid catalytic cracking diesel over the HSPSS was tested. HSPSS‐0.75‐1.43 catalyst support with multiple mesoporous structures shows the highest HDS efficiency (98.5%) among all the studied catalysts.