Properties of poly(ethylene terephthalate)–poly(ethylene naphthalene 2,6‐dicarboxylate) blends with montmorillonite clay

The production and properties of blends of poly(ethylene terephthalate) (PET) and poly(ethylene naphthalene 2,6‐dicarboxylate) (PEN) with three modified clays are reported. Octadecylammonium chloride and maleic anhydride (MAH) are used to modify the surface of the montmorillonite–Na⁺ clay particles (clay–Na⁺) to produce clay–C18 and clay–MAH, respectively, before they are mixed with the PET/PEN system. The transesterification degree, hydrophobicity and the effect of the clays on the mechanical, rheological and thermal properties are analysed. The PET–PEN/clay–C18 system does not show any improvements in the mechanical properties, which is attributed to poor exfoliation. On the other hand, in the PET–PEN/clay–MAH blends, the modified clay restricts crystallization of the matrix, as evidenced in the low value of the crystallization enthalpy. The process‐induced PET–PEN transesterification reaction is affected by the clay particles. Clay–C18 induces the largest proportion of naphthalate–ethylene–terephthalate (NET) blocks, as opposed to clay–Na⁺ which renders the lowest proportion. The clay readily incorporates in the bulk polymer, but receding contact‐angle measurements reveal a small influence of the particles on the surface properties of the sample. The clay–Na⁺ blend shows a predominant solid‐like behaviour, as evidenced by the magnitude of the storage modulus in the low‐frequency range, which reflects a high entanglement density and a substantial degree of polymer–particle interactions. Copyright © 2005 Society of Chemical Industry     

Rheological and drug‐release behaviour of a scleroglucan gel matrix at different drug loadings

The aim of this study was to investigate the drug‐loading effects on release and mechanical properties of a scleroglucan gel, with the intention of considering them in delivery systems formulations. The rheological and kinetic properties of a 2 % w/w scleroglucan gel matrix loaded with 0, 0.02, 0.04, 0.06, 0.2 and 0.4 % w/w of theophylline (Th, used as a model drug) were investigated. Rheological measurements were performed in a controlled‐stress rotational‐shear rheometer under isothermal conditions. For theophylline release from the gel a flat Franz cell was used and the kinetic parameters were derived applying a semi‐empirical power law. The influence of scleroglucan molar weight on kinetic and rheological behaviour was also studied. Results suggest two possible effects of drug loading on the gel network: in the 0.04–0.06 % w/w Th range a plasticizing effect and in the 0.2–0.4 % w/w Th range a rigidization effect. In the first range mentioned, the changes in the gel structural properties tested by means of rheological measurements are coincident with changes in drug‐release kinetics. Copyright © 2005 Society of Chemical Industry     

Rheological properties of polypropylene modified by high‐intensity ultrasonic waves

A new method using high‐intensity ultrasonic waves, instead of peroxide‐aided reactive extrusion, was applied to modify a linear polypropylene into a branched structure. The ultrasonic waves induced chain scission and created reactive macromolecules of polypropylene successfully in the melt state without any peroxide. To enhance and control the recombination reaction during sonication, a multifunctional agent and an antioxidant were used. The rheological property measurements clearly confirmed that the modified polypropylene had a nonlinear branched structure. It showed shear‐thinning behaviors in its viscosities at low frequencies, high elastic behaviors in Cole–Cole plots, and a high rheological polydispersity index in comparison with a linear polypropylene. The degradation or recombination of polypropylene was adequately controlled by an antioxidant, which stabilized the structure during sonication. Also, the use of an antioxidant was quite effective in improving the extrusion processability by delaying the instability of the extrudate to a higher shear rate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Structural Disruption of Toothpastes Under Deformation — An Easy Release of Active Ingredients

The author suggests a technological approach relevant to the optimization of toothpaste compositions with regard to the easy release of the therapeutic ingredients under shear deformation. It is based on the comparative assessment of the steady‐state viscous behaviour of placebo samples (mixtures containing all the components except the therapeutic ingredients) and the final products. It is presumed that the maximum beneficial effect of the toothpastes, as therapeutic agents, is achieved if the final products and the placebo blends display similar shear‐thinning characteristics.     

Measuring and modeling the rheological data of diglycidylether of bisphenol‐A during polymerization for finite element analyses

Finite element analyses (FEA) of thermosets are often performed on the basis of rheological data for fully cured resin. For the FEA of thermosets during curing, a material model is established and a technique is demonstrated, which allows the rheological data of the linear viscoelastic material to be derived. As the moduli are sensitive to conversion, all measured properties are related to temperature and conversion. Therefore the basis for the rheological data has to be a suitable reaction kinetic. Based on the kinetics shear and compression properties are measured independently and modeled mathematically with the focus to gain a formulation, which is suitable for FEA. The considered time constants are in the range between one second and one month as these times are relevant for the investigated relaxation times. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1868–1872, 2003     

Rheology in Processing of in Situ Composites of Polypropylene and Low Melting Poing Metals

The low melting point metallic tin powder or alloy of tin and lead was blended with polypropy-lene. A kind of in situ composite has been prepared. The variations of torque were studied when the composites were mixed in Haake torque rheogeniometer. By way of capillary extrusion, effects upon rheology of the in situ com-posites of the low melting point metals (LMPM) and coupling agent for their different variety and content, were investigated. From flow curves, the results indicate that in situ composites mixed with the LMPM are a kind of pseudoplastic fluid. If the LMPM were melted, the higher the content of the LMPM , the lower apparent viscosity of composites. Meanwhile, when the coupling agent is added into composites, the viscosity of composite will go up first and drop then. This shows that the LMPM have a promoter flow action on the polypropylene.     

高聚物共混物及嵌段共聚物熔体的流变性（Ⅰ）共混物熔体的流动特性

综述了高聚物二元共混物及嵌段共聚物熔体的静态流变性，分析了不同共混体系的流动曲线，总结了共混物的流动特性及规律     

DG抗高温隔离液在古深1井的应用

古深1井是大庆油田在古龙地区的一口风险探井,设计井深5 500 m,实际完钻井深为4 739 m。钻进过程中,多次出现塌、漏、卡等事故,造成井径不规则。为平衡压力,压稳地层,更好地隔离钻井液和水泥浆,提高顶替效率,设计采用DG抗高温隔离液。DG抗高温隔离液抗高温可达150℃,密度调节范围宽,抗高温悬浮稳定性好,失水量少,与水泥浆和钻井液相容性好。古深1井采用双级注水泥工艺,固井施工过程十分顺利,隔离液密度均匀,泵送容易,无发泡现象。从声幅测井情况来看,水泥面上部与隔离液交界处界面清楚,水泥环胶结良好,水泥返高达到了设计要求,混浆过渡段短,固井质量合格。