Synthesis of novel polyimides containing side‐chain azo‐2‐naphthol moieties

An amine‐ester derivative of isoeugenol was prepared in three steps. This amine‐ester was converted to diazonium salt and subsequently was reacted with 2‐naphthol and a novel isoeugenol ester‐azo derivative as a new monomer was obtained in quantitative yield. This monomer was characterized by high‐field ¹H‐NMR, IR, and elemental analysis and then was used for the preparation of model compound and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione was allowed to react with this new monomer. The reaction was very fast and gave only one double adduct by Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer with bistriazolinediones [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] were carried out in N,N‐dimethylacetamide at room temperature. The reactions were exothermic, fast, and gave novel heterocyclic polyimides by repetitive Diels–Alder‐ene polyaddition reactions. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1942–1951, 2003     

Conformation of polyacrylamide in aqueous solution with interactive additives and cosolvents

The viscosity of polyacrylamide (PAM) dilute aqueous solutions with NaCl, glucose, and SDS as additives was measured by Ubbelohde viscometry. There was linear relationship between reduced viscosity vs. PAM concentration in aqueous solutions. The Huggins constant k and intrinsic viscosity [η] were used to study the conformation of the polymer chains and the degree of polymer–solvent interaction. In addition, the viscosity of diluted PAM solutions in water with acetone, ethanol, DMF, and ethylene glycol as cosolvent was measured. It was found that the polymer chain conformation contracted as the acetone, ethanol, and DMF cosolvent composition ratio increased, but there was no distinguishing difference between water–ethylene glycol compositions. The solution properties of PAM were used to estimate the swelling properties of PAM gel in the same external conditions, as gel is formed by crosslinking of linear polymer. In good solvent the polymer chain should be expanded, and gel is expected to have large swelling ratio. In water cosolvent systems, when the linear polymer chain underwent coil–globule transition, PAM gel should have volume phase transition under corresponding external conditions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3122–3129, 2003     

光固化氧化铝陶瓷浆料流变性能研究进展

立体光固化成型技术是一种生产高精度、高性能陶瓷部件的新兴增材制造工艺。制备具有良好流动性和高固相含量的陶瓷浆料是立体光固化增材制造工艺的优势。本文讨论了固相含量、单体、分散剂、粉体级配等因素对浆料流变性能的影响规律,总结了目前配制高固相含量和低黏度光固化Al₂O₃陶瓷浆料的材料选择原则,归纳了制备高固相含量、低黏度Al₂O₃陶瓷浆料的指导方法,指出了高性能光固化Al₂O₃陶瓷浆料开发的主要趋势和面临的挑战。     

不同种类硫化剂对氢化丁腈橡胶性能的影响

研究了硫化剂过氧化二异丙苯（DCP）、双叔丁基过氧化异丙基苯（BIPB）和2,5-二甲基-2,5-双(叔丁基过氧化)己烷（DHBP）对氢化丁腈橡胶性能的影响。结果表明,在分解出相同自由基数量的情况下,使用DCP胶料的门尼黏度增值最小,焦烧时间最短、硫化速率最快,硫化胶的拉伸强度最小,耐老化性能最好;使用DHBP胶料的焦烧时间最长、硫化速率最慢,硫化胶的硬度和定伸应力都更低,拉伸强度和扯断伸长率均为最高,压缩永久变形和耐油性能都是最差;使用BIPB橡胶的焦烧时间、硫化速率和拉伸强度均居于前二者中间,压缩永久变形最小,耐老化性能最差,门尼黏度增值与使用DHBP相当,其他物理机械性能和耐油性能与使用DCP相当。     

Slag resistance mechanism of MgO–Mg2SiO4–SiC–C refractories containing porous multiphase aggregates

The slag resistance of MgO–SiC–C (MSC) refractories should be improved because of the mismatch in the thermal expansion coefficient between the aggregates and matrix, as well as the defects caused by the affinity between periclase and slag. In this study, MgO–Mg₂SiO₄–SiC–C (MMSC) refractories were prepared using porous multiphase MgO–Mg₂SiO₄ (M-M₂S) aggregates to replace dense fused magnesia aggregates. Compared to MSC, the slag penetration index of MMSC decreased by 43.5%. The structure of the porous aggregates increased the surface roughness, and the multiphase composition of the aggregates decreased the mismatch of the thermal expansion coefficient with the matrix, thus reducing debonding between the aggregates and matrix. The aggregates and matrix in the MMSC formed an interlocking structure, which bound them more tightly to improve the slag resistance. The slag viscosity at different depths from the initial slag/refractory interface was calculated using the Ribond model. The M-M₂S aggregates increased Si_xO_y^z− in the slag, which increased the slag polymerization and slag viscosity. The aggregates and matrix in the MMSC reacted with the slag to form high melting point phases, which reduced the channel of the slag. In addition, the penetration depth and velocity derived from the Washburn Equation were modified for the CaO–SiO₂–Al₂O₃–MgO–FeO slag and magnesia based refractory to accurately evaluate slag penetration.     

Time-dependent viscosity of structured clay suspensions

Time-dependent viscosity of structured clay suspensions under a fixed shear was revealed in the prepared slurry samples of clay lenses from the Athabasca oil sands deposit, differing from thixotropic or rheopectic suspensions. At a lower salt (Na or Ca) concentration, the viscosity oscillated with time, which was slowly damped with increasing salt concentrations. The viscosity increased without reaching a maximum plateau, even after a run of a few hours. At 1000 ppm Na concentration, a maximum viscosity was reached, followed by viscosity fluctuation within a narrow range to approach an equilibrium value with time. Both sample ageing and shear history affected the slurry viscosity. It was speculated that the Brownian motion of colloidal clay particles and the applied shear induced rearrangement and continued formation of clay microstructures with time, due to the rotation of anisotropic colloidal clay particles under simple shear flow. Its implications to oil sands research and operation were briefly discussed.     

Isolating the effects of thixotropy in geopolymer pastes

The rheological properties of potassium-based geopolymers were investigated through a series of experiments intended to isolate the influence of shear rate, recovery time, and shear ramping on thixotropy for a greater understanding of geopolymer thixotropic properties within the context of the geopolymer setting reaction. It is shown that for thixotropic disruption to occur a critical shear rate of 100 s⁻¹ must be reached or surpassed, full thixotropic restructuring occurs at around 90–100 min of total undisturbed rest time, and that reaching a state of full thixotropic disturbance heavily depends on subjected processing parameters. In addition, a consistent crossover between the storage and loss modulus within 1–3 min of oscillation during cyclical oscillatory measurements greatly indicates the repeatability and reversibility of thixotropy in geopolymers and the potential for tailorable viscosity. Overall, it is found that geopolymer pastes exhibit strong evidence of thixotropy, which is favorable for additive manufacturing, and that allotted rest time before shear and shear rate greatly influence the overall rheological properties.     

A rigid double-tailed surfactant preparation method and its application in clean fracturing fluid

Using 1,8-dihydroxynaphthalene, thionyl chloride and long-chain tertiary amine as the main raw materials, a facile preparation method and formulation of a rigid double-tailed surfactant for clean fracturing fluid were developed. The temperature resistance test and the determination of hydrogen spectrum reveal that the clean fracturing fluid with the prepared surfactant as thickener has excellent salt and temperature resistance. The shear viscosity of the best product at 120°C and 170 s⁻¹ is not less than 65 mPa s, which meets the requirements of 25 mPa s for the field construction of clean fracturing fluid.     

Improvement of the surface quality of foam injection molded products from a material property perspective

Microcellular injection molding is an attractive method. However, their surface imperfections have been a major problem hindering wide industrial applications. Several methods have been proposed to improve the surface appearance of foams. In this study, we proposed a method to improve the surface appearance of polypropylene (PP) foams from the material property perspective, especially with regard to crystallization and viscosity. The basic idea of the surface improvement is to reduce the size of bubbles generated at the flow front, delay the solidification behavior of the polymer at the mold interface, squeeze the bubbles existing at the mold–polymer interface, and redissolve the bubbles into the polymer by holding pressure. Blending a low-modulus PP delays the crystallization of the polymers at the skin layer and solidification, taking enough time to squeeze the bubbles smaller. A sorbitol-based gelling agent, bis-O-([4 methylphenyl]methylene)-D-Glucitol, was used to increase the viscosity at a low strain rate to reduce the size of the bubbles generated at the flow front during the filling stage. The foam injection molding experiments demonstrated that the proposed method effectively improved the surface appearance of the foams. In particular, the surface appearance of the foams became almost equivalent to that of solid samples using low-modulus PP.     

Natural gas viscosity estimation using density based models

Accurate value determination of natural gas viscosity plays a key role in its management as it is one of the most important parameters in natural gas engineering calculations. In this study, a comprehensive model is suggested for prediction of natural gas viscosity in a wide range of pressures, temperatures, densities and compositions. The new model can be applicable for gases containing heptane plus and non‐hydrocarbon components. It is validated by the 2011 viscosity data from 18 different gas mixtures. Compared to existing similar models and correlations, its results are quite satisfactory. © 2012 Canadian Society for Chemical Engineering