Ammonia‐gas and liquid ammonia treatments of silk fabric

Silk fabric, Habutae, was treated with 100% ammonia‐gas under atmospheric pressure and at pressures of 2, 4, and 6 kgf/cm², and with liquid ammonia at ?33°C. The effects of the treatment were investigated on the basis of the X‐ray diffraction, DSC thermogram, moisture regain, water absorption, dyeing property, and mechanical property of the fabric. Crystallinity and equilibrium dye uptake were increased apparently by the liquid ammonia treatment, whereas effect of the ammonia‐gas treatment was less than the liquid ammonia treatment. KES (Kawabata Evaluation System) shearing, bending, and tensile parameters were obtained. The modulus G, B, and hysteresis widths 2HG, 2HG5, and 2HB were decreased with the ammonia‐gas treatment. On the contrary, the liquid ammonia treatment increased the parameters considerably. Therefore, it seemed that the ammonia‐gas treatment is effective in enhancing the soft hand of the silk fabric. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3487–3492, 2006     

High‐temperature and high‐pressure ethylene polymerization using a cationic activated metallocene catalytic system

BACKGROUND: Normally, olefin polymerization via metallocene‐based catalysis occurs under mild conditions. However, most technology developed for polyolefin production is designed for more severe temperature and pressure processes. Attaining more thermally stable metallocene systems for industrial applications is an important challenge for researchers. RESULTS: A systematic study of ethylene homopolymerization at higher temperatures and pressures, employing the ternary system Ph₂C(Cp)(Flu)ZrCl₂/PhNHMe₂B(C₆F₅)₄/(i‐Bu)₃Al, is presented The optimal activity for this system is achieved with a Zr/B/Al molar ratio of 1/6/250 and a temperatures of around 130 °C. However, the amount of activator strongly affects the molecular weight and the polydispersity of the polymers produced. Polyethylene produced with Zr/B/Al molar ratios between 1/2/250 and 1/6/250 show no significant difference in their temperature of fusion (T_m) and their crystallinity (X_c). In contrast, in the presence of activator amounts higher than 1/6/250, both the temperature of fusion and polymer crystallinity undergo a steep decrease. All polymers presented lamellar morphology when the activator was present, and an amorphous aspect when the activator was not employed. CONCLUSION: The presence of the activator is essential for thermal stabilization of the catalytic system. Variation of the Zr/B/Al ratio leads to modifications of the catalytic activity as well as to the properties of the polymers synthesized. Copyright © 2008 Society of Chemical Industry     

Effect of atmospheric pressure helium plasma on felting and low temperature dyeing of wool

Wool fabrics were treated with atmospheric pressure helium glow discharge plasma in an attempt to improve felting and dyeing behavior with cold brand reactive dyes using cold pad‐batch method at neutral pH. On glow plasma treatment, the hydrophilicity of wool surface and its resistance toward felting was greatly improved without any significant damage to the cuticle layer. The color strength of the plasma treated dyed wool on the surface (in terms of K/S) was found to be nearly double of the color strength of dyed untreated wool fabric. However, the corresponding total dye uptake of the treated wool increased by a much lower value of 40%–50%. The reason behind this altered dyeing behavior was investigated by studying the dye kinetics using infinite bath and surface characteristics using SEM and SIMS. It was found that the glow plasma treatment greatly transformed the chemical surface of the wool fibers. It resulted in uniform removal of hydrophobic cuticular layer, which resulted in better diffusion of the dye molecules into the fiber, and formation of hydrophilic ? NH₂ groups near the surface, which helped in anchoring the dye molecules close to the surface giving higher color strength than expected. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Characterization of ethylene‐propylene copolymers with high‐temperature gradient adsorption liquid chromatography and CRYSTAF

Blends of linear polyethylene (PE) and isotactic polypropylene (iPP) with different average molar masses and a series of ethylene‐propylene (EP) copolymers with different chemical composition as well as blends of PE, Ipp, and EP copolymers were separated using a carbon‐column packing (Hypercarb®) and gradients of 1‐decanol or 2‐ethyl‐1‐hexanol → 1,2,4‐trichlorobenzene (TCB). The separation is based on full adsorption of linear PE on the carbon sorbent at temperature 160°C. However, iPP is not adsorbed and elutes in size exclusion mode. The random EP copolymers have been adsorbed in the column packing and separated according to their average chemical composition after application of the gradient starting with alcohol and ending with pure TCB. The elution volumes of the copolymers depended linearly on the average concentration of ethylene in the copolymers. The HPLC elution profiles were correlated with the CRYSTAF elution profiles. In contrast to CRYSTAF, fully amorphous polyolefin samples were separated with the high‐temperature adsorption liquid chromatography. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Prediction of temperature,pressure, density,velocity distribution in H‐T‐H‐P gas wells

In this paper, we build a model of coupled differential equations concerning pressure, temperature density and velocity in H‐T‐H‐P (High Temperature‐High Pressure) gas wells according to the conservation of mass, momentum and energy. We present an algorithm‐solving model by the fourth‐order Runge–Kutta method. Basic data from the Dayi Well, 7100 m deep in China, are used for case history calculations and a sensitivity analysis is done for the model. Gas pressure, temperature, velocity and density along the depth of the well are plotted with different productions, different geothermal gradients and different thermal conductivities, intuitively reflecting gas flow law and the characteristics of heat transfer in formation. The results can provide a dynamic analysis of production for H‐T‐H‐P gas wells. © 2011 Canadian Society for Chemical Engineering     

Preparation and high‐temperature behavior of HfC–SiC nanocomposites derived from a non‐oxygen single‐source‐precursor

A single‐source precursor for the preparation of HfC‐SiC ceramics was synthesized via a Grignard reaction using bis(cyclopentadienyl)hafnium(IV) dichloride, trans‐1,4‐dibromo‐2‐butene, and (chloromethyl)trimethylsilane as raw materials. The composition, structure, pyrolysis process and high‐temperature behavior of the precursor were investigated. The results show that the precursor with a backbone comprising Hf–C, Si–C and CH=CH groups exhibits good solubility in common solvents, such as tetrahydrofuran, dimethylbenzene, and chloroform. Pyrolysis of the precursor at 1000°C yielded a microcrystalline HfC phase with a ceramic yield of 63.86 wt%. The pyrolytic products at 1600°C were HfC–SiC nanocomposite ceramics, which exhibited good thermal stability up to 2400°C. The formation of a (Hf,Si)C solid‐solution would be beneficial for densification during the sintering process. The non‐oxygen structure, high ceramic yield, homogeneous composition and excellent high‐temperature behavior of the pyrolytic products make the as‐prepared precursor a promising material for the preparation of high‐performance ultra‐high‐temperature ceramics.     

Recent advances in polybenzimidazole/phosphoric acid membranes for high‐temperature fuel cells

Proton exchange membrane fuel cells are one of the most promising technologies for sustainable power generation in the future. In particular, high‐temperature proton exchange membrane fuel cells (HT‐PEMFCs) offer several advantages such as increased kinetics, reduced catalyst poisoning and better heat management. One of the essential components of a HT‐PEMFC is the proton exchange membrane, which has to possess good proton conductivity as well as stability and durability at the required operating temperatures. Amongst the various membrane candidates, phosphoric acid‐impregnated polybenzimidazole‐type polymer membranes (PBI/PA) are considered the most mature and some of the most promising, providing the necessary characteristics for good performance in HT‐PEMFCs. This review aims to examine the recent advances made in the understanding and fabrication of PBI/PA membranes, and offers a perspective on the future and prospects of deployment of this technology in the fuel cell market. © 2014 Society of Chemical Industry     

高压常温制液氯工艺研究

讨论了高压常温法制备液氯的工艺，介绍了液化温度、原料氯气纯度等对工艺的影响及对液化温度、氯压机输出压力的控制方法。通过对比，认为一级压缩与二级压缩在能耗上无大的差别，高压常温法氯气液化工艺安全性较高。     

Preparation and characterization of low molecular weight silk fibroin by high‐temperature and high‐pressure method

A low molecular weight silk fibroin powder (LMSF) was prepared through high temperature (200°C) and high pressure (20 kgf/cm²), without any addition of chemicals. The carbonized adducts produced during this process were then removed by treatment with activated charcoal. The yield of LMSF by this preparation method was over 60% after the removal of carbonized adducts by using activated charcoal. Amino acid analysis showed an observable decrease in contents of serine and tyrosine in LMSF prepared by this method, as compared to those prepared by neutral salt. The molecular weight of this LMSF was also observably decreased with an increase in the reaction time. From the measurements of differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), thermal properties of LMSF through high temperature and high pressure were also decreased as compared to those produced by neutral salts. In addition, wide‐angle X‐ray diffraction (WAXD) patterns showed that the crystallinity of LMSF differed from that of the original silk fibroin. It can be said that the preparation method of LMSF in this study is a simple, economical, and environmentally compatible process with many advantages. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2890–2895, 2002     

Phase transition of Eu2Ti2O7 under high pressure and a new ferroelectric phase with perovskite‐like layered structure

Ferroelectrics with perovskite‐like layered (PL) structure are well‐known for their high T_c and the application prospect of high‐temperature‐piezoelectric sensing. In this study, the PL‐structure Eu₂Ti₂O₇ was prepared by 1‐step high‐pressure sintering, which show the pyrochlore structure of Eu₂Ti₂O₇ would change into PL structure at 11 GPa, 1300°C. The PL‐structure Eu₂Ti₂O₇ is metastable, which will change back to pyrochlore structure at about 900°C in the air. The PL‐structure Eu₂Ti₂O₇ was confirmed as a high‐temperature ferroelectric material for the first time. The ferroelectric domain switching was directly observed using piezoelectric force microscope. The piezoelectric constant of the PL Eu₂Ti₂O₇ ceramic was measured as 0.7‐0.9 pC/N and its thermal depoling temperature (T_d) was determined as 800°C, which is associated with the PL‐pyrochlore transition.     

Pneumatic impact ignition of selected polymers in high‐pressure oxygen environments

One likely cause of polymer ignition in high‐pressure oxygen systems is adiabatic‐compression heating of polymers, caused by pneumatic impact. This study investigates ignition by pneumatic impact of selected polymers in high‐pressure oxygen environments. Six polymers commonly used in high‐pressure oxygen systems were tested in a pneumatic‐impact test system at 8.3–37.9 MPa oxygen pressures. The six polymers tested were Teflon^®(polytetrafluoroethylene), Neoflon^®(polychlorotrifluoroethylene), PEEK (polyetheretherketone), Zytel^® 42 (Nylon 6/6), Buna N (nitrile rubber), and Viton^® A (copolymer of vinylidene fluoride and hexafluoropropylene). This study shows that the ignition of polymers due to pneumatic impact could be initiated by a local heterogeneous reaction between the hot oxygen and the oxidation sites of the polymer, and proposes an ignition mechanism. Ignition susceptibility of a material to the pneumatic impact can be expressed by its ignition probability. The ignition probabilities of the six polymers at the various oxygen pressures are presented. There is no good correlation between the ignition probability and the autoignition temperature. Copyright © 2006 John Wiley & Sons, Ltd.     

Variations of the glass‐transition temperature in the imidization of poly(styrene‐co‐maleic anhydride)

The imidization of poly(styrene‐co‐maleic anhydride) (SMA) was conducted, and the glass‐transition temperatures (T_g's) of the resulting products were measured with differential scanning calorimetry. The contributions from functional groups of maleic anhydride, N‐phenylmaleamic acid, and N‐phenylmaleimide to T_g were examined. T_g increased in the order of SMA < styrene–N‐phenyl maleimide copolymer < styrene–N‐phenyl maleamic acid copolymer and followed the Fox equation. T_g of the imidized products of SMA could be controlled by the conversions of both ring‐opening and ring‐closing reactions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2418–2422, 2007     

Study on the high‐temperature behavior and rehydration characteristics of hardened cement paste

The high‐temperature behavior and rehydration characteristics of the hardened cement paste and their mechanisms have been studied in this paper. X‐ray diffraction and thermogravimetry are used to establish the effect of elevated temperatures on the mineralogical changes that occurred in the hardened cement paste. The change of microstructure was characterized by scanning electron microscopy. The results showed that with the temperature increased, the compressive strength of hardened cement paste first increased and then decreased. According to micromeasurements, at 400°C, the porosity and average pore diameter of hardened cement paste increased slightly, while at 800°C, the porosity and average pore diameter of hardened cement paste increased sharply. When hardened cement paste was cured after exposing to 400°C, its pore structure and phase composition had no change, while when hardened cement paste was cured after exposing to 800°C, there are new hydration products, and its pore structure may be finer, but it cannot fully recover to the original state. Copyright © 2014 John Wiley & Sons, Ltd.     

Thermal degradation of high‐temperature fluorinated polyimide and its carbon fiber composite

High‐temperature polymers are being used for a broad range of applications, such as composite matrices for structural applications (e.g., high speed aircraft). Polyimides are a special class of polymers that meet the thermal and oxidative stability requirements for high temperature composite aerospace applications. A weight loss study was performed on a fluorinated polyimide resin and its carbon fiber composite in an effort to determine its thermal stability and degradation mechanisms. Experiments were conducted using a preheated oven and thermogravimetric analysis to obtain the weight loss. Regardless of the method used, the resin and composite exhibited excellent thermal stability (less than 1% weight loss) below 430°C, regardless of 2–20 min of exposure. After 20 min of exposure at 510°C, the composite remained relatively stable with only 5.3% weight loss using the oven technique, whereas the neat polyimide sustained 12.6%. When degradation occurred, it was found to be the result of thermolysis and oxidation (to a lesser extent). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of comonomer type and concentration on the equilibrium swelling and volume phase transition temperature of N‐isopropylacrylamide‐based hydrogels

The effect of incorporating a hydrophilic monomer into poly(N‐isopropylacrylamide) (polyNIPA) hydrogels on the equilibrium swelling and the volume phase transition temperature is reported here. A nonionizable monomer (acrylamide) and three ionizable monomers (itaconic acid, 2‐ethoxyethyl monoitaconate, and 2,2‐(2‐ethoxyethyl) monoitaconate) were studied. Hydrogels with larger swelling capacity than that of the polyNIPA hydrogel were obtained. With the exception of the hydrogel containing 2,2‐(2‐ethoxyethyl) monoitaconate, which did not exhibit the de‐swelling phenomena, the rest showed a volume phase transition. The hydrogels containing 85 wt % acrylamide and 15 wt % comonomer presented the higher shrinking ratio. For some compositions, the T_c of the polyNIPA hydrogel was within the desired temperature range (38–41°C) for controlled‐drug delivery in the human body. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of liquid viscosity and bed porosity on two‐phase pressure drop in concurrent gas‐liquid upflow through packed beds

It was observed in the experimental investigations that the concurrent upflow of air‐Monoethanol amine system through the packed bed gave higher pressure drop in bubble flow regime than the air‐water system. But when the flow regime changed to spray flow, air‐water system showed higher pressure drop than the other. This phenomenon was observed for the two column packing used in this study. An attempt is made to explain this phenomenon.     

Facile high‐performance film thermocouple made of strontium lanthanum chromate for temperature sensing in air

Film thermocouples as the most effective tool are used to monitor the real‐time and accurate in situ temperature in harsh environment, which will demand their electrodes with high thermal‐resistant properties, high sensitivity, and stability. In this work, a series of solid solutions based on strontium lanthanum chromate were systematically investigated as new electrodes. LaCrO₃ and La_0.8Sr_0.2CrO₃ with some glass additives were chosen to fabricate high‐performance thick‐film thermocouple due to a bigger Fermi level difference between them. The thermocouple shows a high sensitivity (107.8 μV/°C) during static calibration, and an excellent reproducibility and stability during multicycle calibrations carried out up to 1550°C, resulting in a record ultra‐high temperature sensing in film thermocouples. This facile thermocouple may open up a new way to measure high temperature in air or oxidation atmosphere accurately.     

Study on the extraction of dyes into a room‐temperature ionic liquid and their mechanisms

The investigation of liquid–liquid extraction of dyes is carried out by using ionic liquid—1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF₆])—as extraction phase. The effects of its process parameters are studied in detail, such as extraction phase ratio, pH of the aqueous phase, and concentration of dicyclohexyl‐18‐crown‐6 (DCH‐18C6) in the organic phase. Important results are obtained as follows: acid dyes can be extracted with [BMIM][PF₆] quantitatively; the removal of reactive dyes is low; however, it can be greatly increased by the addition of DCH‐18C6. The pH value has a great impact on the removal of the acid dye and the reactive dye. However, it does not influence the extraction of the weak acid dye. It is found that the extraction process of acid dyes adopts the form of anion exchange and the soluble part of the ionic liquid plays an important role as counter‐ions. Copyright © 2007 Society of Chemical Industry     

Synthesis of hyperbranched organo‐montmorillonite and its application into high‐temperature vulcanizated silicone rubber systems

N,N‐Di(2‐hydroxyethyl)‐N‐dodecyl‐N‐methyl ammonium chloride was used as intercalation agent to treat Na⁺‐montmorillonite and form a type of organic montmorillonite (OMMT). Hyperbranched OMMT (HOMMT) was prepared by condensation reaction between OMMT and the monomer we synthesized. It was then used in the preparation of high‐temperature vulcanizated silicone rubber (HTV‐SR)/HOMMT nanocomposite. Different types of HTV‐SR/HOMMT nanocomposites were prepared with different amounts of HOMMT and compared with the composites directly incorporated with OMMT. Tensile properties such as tensile strength, elongation at break, permanent distortion, and shore A hardness were researched and compared. A combination of Fourier transform infrared spectroscopy, wide angle X‐ray diffraction, and transmission electron microscopy studies showed that HTV‐SR/HOMMT composites were on the nanometer scale, and the structure of HTV‐SR was not interfered by the presence of HOMMT. Results showed that the tensile properties of HTV‐SR/HOMMT systems were better than that of the HTV‐SR/HOMMT and HTV‐SR. This was probably due to the surface effect of the exfoliated silicate layers and anchor effect of HOMMT in the SR matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009