硬脂酸根插层水滑石的合成及应用

采用离子交换法制备了硬脂酸根插层水滑石,运用红外光谱对其进行了表征。通过Haake流变仪、颜色测定仪研究了硬脂酸根插层水滑石与钙/锌热稳定剂并用时的热稳定性,重点考察了水滑石的结构对PVC稳定性能的影响。结果表明,硬脂酸根插层水滑石与钙皂/锌皂复配显著改善了PVC热老化过程中的初期着色性。     

Effect of intercalated hydrotalcite on swelling and mechanical behavior for poly(acrylic acid‐co‐N‐isopropylacrylamide)/hydrotalcite nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from acrylic acid (AA), N‐isopropylacrylamide (NIPAAm), and intercalated hydrotalcite (IHT) by photopolymerization. The influence of the intercalating content of 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS) in HT on the swelling and mechanical properties for poly(AA‐co‐NIPAAm)/IHT nanocomposite hydrogels was investigated. The results showed that the higher the content of the AMPS‐HT was, the higher the swelling ratio of the gels and the higher the content of the intercalating agent was, the lower swelling ratio. It was also demonstrated that the swelling ratio of the gel was not affected by the counterion in HT. The gel strength and crosslinking density were not enhanced by adding AMPS‐HT into the gel composition, but the maximum effective crosslink density and shear modulus of the nanocomposite hydrogels were increased with an increase of the content of the intercalating agent in HT. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1572–1580, 2005     

浅色水滑石/红磷复合阻燃剂的制备及性能

采用白磷插层进入水滑石层间后再转化为红磷的方法制得红磷插层水滑石,从而得到了用于环氧树脂体系的浅色水滑石/红磷复合阻燃剂。考察了白磷和水滑石配比对转化率的影响及红磷含量对丙氨酸交换量的影响,并研究了白磷插层水滑石阻燃剂用于环氧树脂的阻燃性能。结果表明转化后红磷在水滑石中的含量与转化前白磷与水滑石的配比之间符合一定的线性关系,即y=-8.44373+0.72491x;丙氨酸的交换量随着红磷含量的增大而减小;以插层水滑石为阻燃剂,阻燃效果优于水滑石/红磷混合物,且颜色较浅,亨特白度为30.13,大于直接混合的23.93;当水滑石、红磷质量分数分别为5%、1.48%时,环氧树脂的阻燃性能就达到FV-0级。     

Superabsorbent polymeric materials. XIV. Preparation and water absorbency of nanocomposite superabsorbents containing intercalated hydrotalcite

A series of novel xerogels, based on sodium acrylate (NaA), intercalated hydrotalcite (IHT), and N,N′‐methylene‐bisacrylamide (NMBA), were prepared by inverse suspension polymerization. The influences of the HT intercalated with acrylic acid (AA–IHT) and with 2‐acryloylamido‐2‐methyl propane sulfonic acid (AMPS–IHT), the content of the IHT in the poly(NaA) gel on the water absorbency, and the initial absorption rate in deionized water and various salt solutions were investigated. Results showed that adding a small amount of IHT could effectively increase the water absorbency of the gels, but adding excess IHT could decrease the water absorbency of the gels. In addition, the water absorbency of the gels containing AA–IHT was lower than that containing AMPS–IHT. The initial absorption rate, for the present gels, increased with increasing content of IHT in the copolymeric gels. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2417–2424, 2004     

Corrosion inhibition of aluminum by coatings formulated with Al–Zn–vanadate hydrotalcite

The hydrotalcite structure is an ionic lamellar solid with positively charged layers incorporating two kinds of metallic cations and hydrated gallery anions. The ability of these compounds to retain aggressive ions and simultaneously release a corrosion inhibitor is the main reason for the development of hydrotalcite compounds to replace hexavalent chromium compounds (chromates) as inhibitive pigments.     

Structure and analgesic properties of layered double hydroxides intercalated with low amounts of ibuprofen

Ibuprofen‐intercalated layered double hydroxides (LDH‐IBU) have been successfully synthesized via a coprecipitation method with a nominal [Al³⁺]/[Mg²⁺] ratio of 0.5 and a variable molar IBU/([Al³⁺]+[Mg²⁺]) ratio of 0, 0.15, 0.18, 0.24, 0.36, and 0.72. After an accurate determination of the composition, the nature of the intercalated species and the effective intercalation yield from to IBU, it is shown that the synthesis route used allows a good control of the quantity of intercalated IBU within the LDH framework. This results in different samples with full or partial IBU intercalation in the interlayer space in exchange of nitrate anions. The analysis of the X‐ray diffraction basal reflections reveals that the intercalation of IBU in the framework only increases the basal distances with no alteration of the brucite‐type layers. Also, a computational study used to model the positions and shapes of the basal reflections showed that the structure of the nonfully intercalated compounds follows a random interstratification scheme. Finally, three samples ranging from slightly to fully IBU‐intercalated galleries were selected for preliminary in vivo assays. These tests showed a strong tendency that after 24 hours the low yield of IBU‐intercalated compounds are almost as efficient as the fully intercalated sample.     

Preparation of Mg‐Al hydrotalcite by urea method and its catalytic activity for transesterification

Layered double hydroxides based on the structure (Mg₆Al₂(OH)₁₆CO₃·4H₂O) were synthesized by urea hydrolysis method and characterized by XRD, FTIR, SEM, and EDS. The results revealed that pH played a crucial role in the Mg‐Al hydrotalcite precipitation by controlling [urea]/[NO] molar ratio in reaction solution at 378 K and the optimized [urea]/[NO] molar ratio was 4.0. The sample calcined at 773 K was used as a solid catalyst for biodiesel synthesis. The catalyst was found to have a high catalytic activity in transesterification of rape oil to methanol with about 94% oil conversion at 338 K for 3 h. The water content of the oil could be kept below 2.0 wt % and free fatty acid content of the oil could be kept below 3.0 mg KOH·g[oil]^?1 in order to get the best conversion. So, the solid catalyst was more tolerant to free fatty acid and water in rape oil than homogeneous basic‐catalysts. Moreover, the catalyst could be reused, but catalytic activity decreased on reuse of the catalyst although it remained highly active for the five uses. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Oxidation of mercaptans in light oil sweetening by cobalt(II) phthalocyanine–hydrotalcite catalysts

Three Mg–Al hydrotalcites containing cobalt(II) phthalocyanine were prepared by direct synthesis, anion exchange and structure reconstruction. Differences in physicochemical properties and mechanical resistance were observed. The results of the mercaptan oxidation reaction were compared to those obtained with an industrial non-basic impregnated active charcoal. An important activity difference in favor of the prepared catalysts was obtained, confirming that the adequate tuning of basic and oxidant properties lead to a promising catalyst.     

Iron intercalated in graphite as catalysts for ammonia synthesis

Catalysts for ammonia synthesis based on iron intercalated in graphite precursors were prepared. This study reveals that the catalysts' activity is associated with a broad electron paramagnetic resonance (EPR) line, and that the iron co-ordinated by both carbon and potassium influences both the intensity of the EPR signal and activity.     

Catalytic synthesis of chalcone and flavanone using Zn–Al hydrotalcite adhere ionic liquid

The Claisen–Schmidt condensation of 2′-hydroxy acetophenone and benzaldehyde to chalcone and flavanone show that calcined Zn–Al (6) hydrotalcite is active for this synthesis. Coating of ionic liquid ‘1-(tri-ethoxy-silyl-propyl)-3-methyl-imidazolium chloride’ on Zn–Al hydrotalcites was accomplished employing incipient wetness process and on NaY, NaX, MK-5 and silica gel employing co-condensation methodology. Impregnated IL on calcined Zn–Al (6) catalysts were characterized by XRD, SEM, BET, ¹³C and ²⁷Al NMR analysis and the activity of these catalysts were investigated for chalcone and flavanone synthesis. ²⁷Al CP MAS NMR technique was used to show that interaction of IL with hydrotalcite modifies the acid–base sites and is responsible for enhancement of catalyst activity. Several aromatic aldehydes were screened to assess the general applicability of the system.     

Intercalation of styrene–acrylonitrile copolymer in layered silicate by emulsion polymerization

A well‐defined styrene–acrylonitrile copolymer/montmorillonite (SAN‐MMT) nanocomposite has been prepared by emulsion copolymerization of styrene and acrylonitrile in the presence of sodium ion exchanged montmorillonite (Na⁺‐MMT). This direct and one‐step polymerization technique yielded nanocomposites intercalated with styrene‐acrylonitrile copolymer without occurrence of significant delamination of MMT. The purified products by hot tetrahydrofuran extraction for up to 5 days gave evidences of copolymer intercalation. Those infrared spectra obtained from the purified products revealed the characteristic absorbances due to styrene, acrylonitrile, and MMT. Room temperature powder X‐ray diffraction patterns of the purified product exhibited increased 001 d‐spacing about 1.60 nm. The transmission electron microscopy micrograph of unpurified products confirmed that the 1–2‐nm sized silicate layers are arranged in good order. The onset temperature of purified products are found to be moved to higher temperature, while the thermograms of differential scanning calorimetry show nothing observable transition. The modulus of elasticity of the product was increased with increasing content of MMT, whereas the stress at maximum load was decreased with the increments of MMT. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 179–188, 1999     

超声辐射下n(Mg)∶n(Al)水滑石催化合成

通过低饱和共轭沉淀法制备了不同n(Mg)∶n(Al)的水滑石，并用XRD和BET等技术对催化剂前驱体进行了表征。XRD表征表明，水的加入使得水滑石的结构能够得到部分重建。同时水的加入使水滑石表面的O^2- 生成了相应的B碱(OH^-)，大大提高了催化活性。BET表征结果表明，水滑石作为碱性催化剂的活性位点主要存在于暴露的板层边缘。以制备的水滑石为催化剂在超声辐射下合成了含有强吸电子取代基4,4′-二硝基查尔酮，并考察了超声、催化剂的组成、水合质量和溶剂对催化性能的影响。结果表明，当催化剂的n(Mg)∶n(Al)＝3.0、水合质量为其前驱体的35％和溶剂为甲醇时，在超声辐射下具有最高的催化活性，收率达91.3%，选择性为100%。     

Aliphatic–aromatic polyester–polyaniline composites: preparation,characterization, antibacterial activity and conducting properties

Poly(butylene adipate‐co‐terephthalate) (PBAT) composites containing polyaniline (PANI) were prepared using a melt blending process. Acrylic‐acid‐grafted PBAT (PBAT‐g‐AA) and PANI were used to improve the compatibility and dispersibility of PANI within the PBAT matrix. The composites were characterised morphologically using scanning electron microscopy, chemically using Fourier transform IR spectrometry and ¹³C solid‐state nuclear magnetic resonance, and optically using UV‐visible spectroscopy. The electrical conductivity of the composites was also evaluated with a resistance tester and a cyclic voltameter. Escherichia coli (BCRC 10239) was chosen as the standard bacterium for determining the antibacterial properties of the composite materials. The anti‐static properties of the composites were also evaluated. The PBAT‐g‐AA/PANI composite showed markedly enhanced antibacterial and anti‐static properties due to the formation of amide bonds by the condensation of the carboxylic acid groups of PBAT‐g‐AA with the amino groups of PANI. The optimal level of PANI was 9 wt%, as excess PANI led to separation of the two organic phases, lowering their compatibility. Copyright © 2012 Society of Chemical Industry     

Suzuki cross-coupling reaction over a palladium–pyridine complex immobilized on hydrotalcite

A catalyst consisting of a Pd(II) complex immobilized on the surface of a layered double hydroxide (LDH) was prepared. The Pd–LDH complex proved effective in the Suzuki cross-coupling reaction under very mild conditions (viz. a temperature of 55 °C and atmospheric pressure); in fact, it provided conversion and selectivity results surpassing those of existing heterogeneous phase catalysts and most homogeneous phase catalysts for the same purpose. The support and the active phase of the catalyst were characterized by using various instrumental techniques including X-ray diffraction and NMR spectroscopy. Of the inorganic bases used in combination with the catalyst, potassium carbonate was found to provide the best results in the reaction.     

Thermal,dynamic‐mechanical,and dielectric properties of surfactant intercalated graphite oxide filled maleated polypropylene nanocomposites

Graphite oxide (GO) and amine surfactant intercalated graphite oxide (GOS) filled maleated polypropylene (PPgMA) nanocomposites were prepared directly by solution blending. In this study, the effects of the surfactant intercalation on the crystalline structure, thermo‐mechanical, and dielectric properties of PPgMA/GO and GOS composites are reported. Wide‐angle X‐ray diffraction exhibited a lower intensity diffraction peak of the monoclinic (α) phase of PPgMA for PPgMA/GOS composites compared with the unfilled sample. Differential scanning calorimetry exhibited a single characteristic melting peak of monoclinic (α) crystalline phase. The incorporation of GOS hardly showed any change in T_m. However, the significant decrease in the melting enthalpy of PPgMA/GOS composite, which was lower than that of GO filled PPgMA, demonstrated the high degree of dispersion of the GOS flakes in the PPgMA matrix. Dynamical mechanical analysis indicated that incorporation of GO or GOS into PPgMA increased both the storage modulus and the glass transition temperature, due to the hydrogen bonding between GO and the maleic anhydride group of PPgMA. Dielectric analyzer showed significant increase in both dielectric permittivity and dielectric loss at high temperature regimes in the GOS nanocomposites. The finely dispersed GOS in the PPgMA matrix manifested the interfacial polarization, which gave rise to much greater ε′ and ε″ than that of PPgMA/GO hybrid. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrochemical behavior of lithium intercalated in a molybdenum disulfide-crown ether nanocomposite

A new nanocomposite, obtained from the intercalation of the cyclic ether 12-Crown-4 into MoS₂, Li_0.32MoS₂(12-Crown-4)_0.19, is described. The laminar product has an interlaminar distance of 14.4 Å. The electrical conductivity of the nanocomposite varies from 2.5 × 10⁻² to 4.3 × 10⁻² S cm⁻¹ in the range 25-77 °C, being about four times higher than the analogous poly(ethylene oxide) (PEO) derivative at room temperature. The electrochemical step-wise galvanostatic intercalation or de-intercalation of lithium, leading to Li_xMoS₂(12-Crown-4)_0.19 with x in the range 0.07-1.0, indicates a Li/Li⁺ pair average potential of 2.8 V. The electrochemical lithium diffusion coefficients in the crown ether intercalates, determined by galvanostatic pulse relaxation between 15 and 37 °C at different lithium intercalation degrees, are higher than those of the PEO derivatives under similar conditions, being however the diffusion mechanism rather more complex. The variation of both, the lithium diffusion activation enthalpy and the quasi-equilibrium potentials, with the lithium content shows there are two different limit behaviors, at low and high lithium intercalation degree, respectively. These features are discussed by considering the high stability of the Li-crown ether complex and the different chemical environments found by lithium along the intercalation process.     

Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers

Exfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry     

Frying as a science – An introduction

Frying is an ancient process, but it is only in the past fifty years that it has gained the attention it deserves from the scientific community. Early frying research tended to focus almost exclusively on the chemistry of the frying oil. Some of the pioneering work is summarized. Recent work has been looking at frying as a system, that is, the oil, the food, the fryer and the operation in general. This approach has yielded greater understanding of the process and has already led to improvements in frying operations. New ideas and aims are presented and these may lead to and create a framework for future work in deep‐fat frying.