Synthesis and characterization of pyridine‐containing poly(imide‐siloxane)s and their adhesion to copper foil

A series of pyridine‐containing poly(imide‐siloxane) (PIS) copolymers with different amounts of PDMS with various segmental lengths were synthesized from 2,6‐diaminopyridine (DAP), α,ω′‐aminopropylpoly(dimethylsiloxane) (PDMS), 1,3‐bis(4‐aminophenoxy)benzene (APB), and 4,4′‐oxydiphthalic dianhydride (ODPA). A modified synthetic approach was applied instead of approaches commonly reported in the literature, to ensure the incorporation of DAP and PDMS. The effects of the content and the segmental length of PDMS on the thermal glass transition temperature (T_g), dielectric constant, and surface electrical resistivity of the copolymer are investigated. The copolymers were attached to copper foil by hot‐pressing, and changes in wettability caused the peel strength of the laminates to increase with the PDMS content, but to decrease as the DAP content increased. Furthermore, X‐ray photoelectron spectroscopy was employed to determine the loci of failures (LOF) of the laminates and to monitor the movement of LOF, which varies with the PDMS content. For those laminates with good peel strengths, the LOF occur in the interior of PIS layer, indicating that the adhesion is cohesive rather than adhesive. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Determination of compounding formulation of cured rubber by reverse engineering

The present work deals with reverse engineering on four rubber formulations. Information about the material composition of the compounding formulations was obtained by using techniques such as acetone extract, thermogravimetric analysis, energy dispersive X‐ray fluorescence studies, and Fourier transform infrared (FTIR) spectroscopy in attenuated total reflection mode. The reverse engineered formulations were compared on a qualitative and quantitative basis with the initial formulations. The aim was to ascertain the validity of the methodology, which may be used as reverse engineering of rubber compounds to quantitatively analyze unknown ground tire rubber in future. The state of the art was based on a fractional mass transfer from acetone extract to the rubbers detected in TGA. Through this new approach, the formulations calculated were very consistent with the formulations employed, thus establishing the validity of the methodology used. POLYM. ENG. SCI., 55:1450–1458, 2015. © 2015 Society of Plastics Engineers     

Leaching kinetics of colemanite in ammonium hydrogen sulphate solutions

The aim of the study was to investigate the dissolution kinetics of colemanite in ammonium hydrogen sulphate solutions in a mechanical agitation system and to declare an alternative reactant to produce boric acid. Reaction temperature, concentration of ammonium hydrogen sulphate, stirring speed, solid/liquid ratio and particle size were selected as parameters on the dissolution rate of colemanite. The experimental results were successfully correlated by linear regression using Statistica Package Program. Dissolution curves were evaluated in order to test shrinking core models for solid–fluid systems. It was observed that increase in the reaction temperature and decrease in the solid/liquid ratio causes an increase the dissolution rate of colemanite. The dissolution extent is highly increased with increase the stirring speed rate between 100 and 500 rpm and the dissolution extent is slowly increased with increase the stirring speed between 500 and 700 rpm in experimental conditions. The activation energy was found to be 32.66 kJ/mol. The leaching of colemanite was controlled by diffusion through the ash or product layer. The rate expression associated with the dissolution rate of colemanite depending on the parameters chosen may be summarized as follows: 1 ? 3(1 ? X)^2/3 + 2(1 ? X) = 8.99 × C^1.08 × W^1.39 × D^?1.27 × (S/L)^?0.54 × e^(?32.66/RT)t.     

Effect of functional groups of carbon nanotubes on the cyclization mechanism of polyacrylonitrile (PAN)

The cyclization mechanism of polyacrylonitrile (PAN) in PAN/functionalized carbon nanotube (CNT) composites was examined. The surface functionalization of CNTs was carried out by using diazonium reagents with 4-substituted aniline. The results strongly suggest that the type of functional groups on the CNTs strongly influences the cyclization mechanism of PAN during the stabilization process. The nitrile of PAN in F–Ph–CNT/PAN composite was cyclized through the free radical reaction during thermal stabilization whereas nitrile of PAN in COOH–Ph–CNT/PAN composite underwent cyclization via the ionic reaction due to the acid groups on the surfaces of the CNTs. The fluoro functional groups on the CNTs can act as effective external initiators for nitrile cyclization in homo PAN, in contrast to acid functional groups. Consequently, a lower cyclization temperature (265 °C) and enthalpy value (688 J/g) of F–Ph–CNT were shown compared to those of homo PAN.     

纤维缠绕机网格型芯模零件库的建立

利用VC++6.0和Pro/Toolkit结合设计出纤维缠绕机网格型芯模的零件库,在零件库中可以根据实际需要生成相应的网格型芯模,在新生成的模型中建立网格型芯模的尺寸对象和关系式的对话框。使用时通过修改对话框中芯模的尺寸并更新来获得新的网格型芯模模型,同时在对话框中显示芯模的尺寸文本和关系式。通过对话框能够清楚地知道各个尺寸的具体含义,因此能够为纤维缠绕机数控程序的编写提供必要的尺寸参数。     

Further evidence of responsibility of impurities in MgO for variability in its basicity and catalytic performance in oxidative coupling of methane

Further evidence was delivered that certain impurities, which could be contained in MgO samples, might be responsible for observed variability in MgO basicity and catalytic performance in oxidative coupling of methane. The surface basicity/base strength distribution of a series of MgO samples containing or not containing Ca and Na impurities was determined by a temperature-programmed desorption of CO₂. It was revealed that samples containing Ca and Na impurities have much more medium, strong and very strong basic sites. The surface basicity of MgO samples containing added alkali or alkaline earth compounds or water was characterized by a test reaction of transformation of 2-butanol. It was confirmed that the introduction of these compounds to a pure MgO enhanced both its basicity and activity in oxidative coupling of methane.     

Thermal and mechanical properties of the polymers synthesized by the sequential polymerization of propylene and 1‐hexadecene

The block copolymer of poly(1‐hexadecene) (PHD) and polypropylene (PP) was effectively synthesized by the sequential polymerization of propylene and 1‐hexadecene by using highly isospecific TiCl₃/Cp₂Ti(CH₃)₂ (Cp = cyclopentadienyl). The block copolymers had two separate melting temperatures of constituent blocks. The modulus of PHD–PP block copolymer was enhanced as the content of sequentially polymerized PP block was increased. The elongation at break showed positive deviation at the intermediate compositions from the simple additive values of constituent homopolymers. Shape memory effect which utilizes the crystalline PHD block as a reversible phase and the crystalline PP block as a fixed structure was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1709–1715, 2002; DOI 10.1002/app.10551     

Coupling of N2O Decomposition and Ethylbenzene Dehydrogenation over γ-Al2O3-Supported Transition Metal Oxide Catalysts

Transition metal (Cr, Cu, Fe, Co and Ni) oxides supported on -alumina were characterized with respect to their textural parameters and reducibility and used as catalysts in decomposition of nitrous oxide and ethylbenzene (EB) dehydrogenation as well as coupling of both processes. High activity of -Al₂O₃ in N₂O decomposition coupled with EB dehydrogenation has been found. An increase in EB and N₂O conversion was observed when transition-metal-containing catalysts were used. The activity of catalysts depended on their reducibility. Maximum N₂O efficiency was observed for the Cr/-Al₂O₃ sample, whereas -Al₂O₃-supported Cu and Fe oxide systems showed about 50% efficiency of N₂O in the reaction. An influence of the molar ratio of N₂O/EB on activity and selectivity of the catalysts was found. An excess of N₂O resulted in an increase in CO₂ formation at nearly constant styrene yield.     

Study of the factors influencing colour yield of an ink-jet printed cotton fabric

In this study, the factors influencing the final colour yield of an ink-jet printed cotton fabric were investigated. The factors included the content of the pretreatment paste (the amounts of sodium alginate, sodium bicarbonate and urea) and the steaming time. Four different inks – cyan, magenta, yellow and black – were used in this study and the influences of these factors on the four different colours were studied through experimental design. The results showed that apart from the influence of individual factors, the final colour yield also depended on the interaction effect of the factors.