A laboratory study of rheological properties of mudflows in Hangzhou Bay, China

A laboratory study of the rheology of mudflows in Hangzhou Bay, China, is reported in this paper. Both the steady and oscillatory (dynamic) rheological properties are studied using RMS-605 rheometer. A Dual-Bingham model is proposed for analyzing flow curves and compared with Worrall-Tuliani model. It is found that Dual-Bingham plastic rheological model is easier to implement than Worrall-Tuliani model and can provide satisfactory representations of the steady mudflows in Hangzhou Bay and other published data. The dependence of the yield stress and viscosity on sediment concentration is discussed based on the data from Hangzhou Bay mud and other published data. For the dynamic rheological properties of Hangzhou Bay mud, empirical expressions for elastic modulus and dynamic viscosity are provided in the form of exponential functions of sediment volume concentration, and comparisons with other published data also discussed.

The rheological behavior and dynamic mechanical properties of syndiotactic 1,2-polybutadiene

The rheological behavior and the dynamic mechanical properties of syndiotactic 1,2-polybutadiene (sPB) were investigated by a rotational rheometer (MCR-300) and a dynamic mechanical analyzer (DMA-242C). Rheological behavior of sPB-830, a sPB with crystalline degree of 20.1% and syndiotactic content of 65.1%, showed that storage modulus (G ') and loss modulus (G '') decreased, and the zero shear viscosity (eta(0)) decreased slightly with increasing temperature when measuring temperatures were lower than 160 degrees C. However, G ' and G '' increased at the end region of relaxation curves with increasing temperature and)10 increased with increasing temperature as the measuring temperatures were higher than 160 degrees C. Furthermore, critical crosslinked reaction temperature was detected at about 160 degrees C for sPB-830. The crosslinked reaction was not detected when test temperature was lower than 150 degrees C for measuring the dynamic mechanical properties of sample. The relationship between processing temperature and crosslinked reaction was proposed for the sPB-830 sample.

The effect of multiwall carbon nanotube on the crystallization, morphology, and rheological properties of nylon1010 nanocomposites

Nanocomposites based on poly(iminosebacoyl imino-decamethylene) (PA1010) and multiwall carbon nanotubes (MWNTs) were successfully prepared by melt blending technique. environmental scanning electron microscope micrographs of the fracture surfaces showed that not only is there an evenly dispersion of MWNTs throughout the PA1010 matrix but also a strongly interfacial adhesion with the matrix. The combined effect of more defects on MWNTs and low temperature buckling fracture is mainly responsible for the broken tubes. Differential scanning calorimeter results showed that the MWNTs acted as a nucleation agent and increased the crystallization rate and decreased crystallite size. In the linear region, rheological measurements showed a distinct change in the frequency dependence of storage modulus, loss modulus, and complex viscosity particularly at low frequencies. We conclude that the rheological percolation threshold might occur when the content of MWNTs is over 2 wt% in the composites.

Melt rheological properties of polypropylene-polyarnide6 blends compatibilized with maleic anhydride-grafted polypropylene

The melt rheological properties of binary uncompatibilized polypropylene -polyamide6 (PP-PA6) blends and ternary blends compatibilized with maleic anhydride-grafted PP (PP-PP-g-MAH-PA6) were studied using a capillary rheometer. The experimental shear viscosities of blends were compared with those calculated from Utracki's relation. The deviation value delta between these two series of data was obtained. In binary PP-PA6 blends, when the compatibility between PP and PA6 was poor, the deformation recovery of dispersed PA6 particles played the dominant role during the capillary flow, the experimental values were smaller than those calculated, and delta was negative. The higher the dispersed phase content, the more deformed the droplets were and the lower the apparent shear viscosity. Also, the absolute value of delta increased with the dispersed phase composition. In ternary PP-PP-g-MAH-PA6 systems, when the compatibility between PP and PA6 was enhanced by PP-g-MAH, the elongation and break-up of the dispersed particles played the dominant role, and the experimental values were higher than calculated. It was observed that the higher the dispersion of the PA6 phase, the higher the delta values of the ternary blends and the larger the positive deviation.

Rheological properties in blends of poly(aryl ether ether ketone) and liquid crystalline poly(aryl ether ketone)

Rheological properties of the blends of poly(aryl ether ether ketone) (PEEK) with liquid crystalline poly(aryl ether ketone) containing substituted 3-trifluoro-methylbenzene side group (F-PAEK), prepared by solution precipitation, have been investigated by rheometer. Dynamic rheological behaviors of the blends under the oscillatory shear mode are strongly dependent on blend composition. For PEEK-rich blends, the systems show flow curves similar to those of the pure PEEK, i.e., dynamic storage modulus G' is larger than dynamic loss modulus G", showing the feature of elastic fluid. For F-PAEK-rich systems, the rheological behavior of the blends has a resemblance to pure F-PAEK, i.e., G" is greater than G', showing the characteristic of viscous fluid. When the PEEK content is in the range of 50-70%, the blends exhibit an unusual rheological behavior, which is the result of phase inversion between the two components. Moreover, as a whole, the complex viscosity values of the blends are between those of two pure polymers and decrease with increasing F-PAEK content. However, at 50% weight fraction of PEEK, the viscosity-composition curves exhibit a local maximum, which may be mainly attributed to the phase separation of two components at such a composition.

Morphology, structure, and rheological property of linear low-density polyethylene grafted with acrylic acid

The chain structure, spherulite morphology, and theological property of LL-DPE-g-AA were studied by using electronspray mass spectroscopy, C-13-NMR, and rheometer. Experimental evidence proved that AA monomers grafted onto the LLDPE backbone formed multiunit AA branch chains. It was found that AA branch chains could hinder movement of the LLDPE main chain during crystallization. Spherulites of LLDPE became more anomalous because of the presence of AA branch chains. Rheological behavior showed that AA branch chains could act as an inner plasticizer at the temperature range of 170-200 degreesC, which made LLDPE-g-AA easy to further process. (C) 2001 John Wiley & Sons, Inc.

Rheological, thermal, and morphological properties of ABS-PA1010 blends

Noncompatibilized and compatibilized ABS-nylon1010 blends were prepared by melt mixing. Polystyrene and glycidyl methacrylate (SG) copolymer was used as a compatibilizer to enhance the interfacial adhesion and to control the morphology. This SG copolymer contains reactive glycidyl groups that are able to react with PA1010 end groups (-NH2 or -COOH) under melt conditions to form SG-g-Nylon copolymer. Effects of the compatibilizer SG on the rheological, thermal, and morphological properties were investigated by capillary rheometer, DSC, and SEM techniques. The compatibilized ABS-PA1010 blend has higher viscosity, lower crystallinity, and smaller phase domain compared to the corresponding noncompatibilized blend. (C) 1999 John Wiley & Sons, Inc.

The rheological and extrusion behaviour of blends based on phenolphthalein poly(ether-ether-sulfone) and thermotropic liquid crystalline polymer

A novel engineering thermoplastic, phenolphthalein poly (ether-ether-sulfone) (PES-C) was blended with a commercial thermotropic liquid crystalline polymer(TLCP), Vectra A950, up to 30 weight percent of TLCP. A rheometrics dynamic spectrometer (RDS-I) and a CEAST capillary rheometer, a rheoscope 1000 were employed to investigate the melt rheology and extrusion behaviour at both the low and high shearing rates. The morphologies of the blends under different shearing were observed with a scanning electron microscope(SEM) and correlated to the observed rheology. The principal normal stress differences measured with cone-and-plate geometry give a temperature-independent correlation for both blend and PES-C when they are plotted against shear stress. But the extrudate swell of the blends showed a strong temperature dependence at each shear stress. The concentration dependence of extrudate swell shows a contrary behaviour to that of the inorganic filled system. A reasonable hypothesis based on the relaxation and disorientation of TLCP during flowing in the capillary and exiting was given to explain it. The melt fracture was checked after extrusion from capillary and was discussed.

Tremolite-reinforced nylon 66 composites: Mechanical and rheological properties

The reinforcement effect of an acicular inorganic filler, tremolite, on nylon 66 was studied. The mechanical properties of tremolite-filled nylon 66 composites and the effect of the filler particle size on them were obtained. The dynamic mechanical properties and rheological properties of the composites were measured. Two treatments, silane and unsaturated polyester, were used to improve the interface between tremolite and the nylon matrix. The morphologies of the composites were investigated using SEM. (C) 1998 John Wiley & Sons, Inc.

Rheological studies on the phase dissolution in a block copolymer

The microphase transition in a styrene-butadiene-styrene triblock copolymer was studied by rheometric mechanical spectroscopy. A high-temperature-melt rheological transition from the highly elastic, nonlinear viscous behavior typical of a multiphase structure to linear viscous behavior with insignificant elasticity typical of a single-phase structure was observed. The transition temperature is determined according to the discontinuity of the rheological properties across the transition region, which agrees well with the results obtained from the small angle X-ray scattering data and the expectation of the random phase approximation theory. Maybe for the first time, microphase dissolution was investigated theologically. The storage modulus (G') and the loss modulus (G '') increase with time during the process. An entanglement fluctuation model based on the segmental density fluctuations is presented to explain the rheological behavior in this dissolution process. (C) 1997 John Wiley & Sons.

Rheological properties of phenophthalein poly(ether ether ketone)

The rheological properties of the novel engineering thermoplastic phenophthalein poly(ether ether ketone) (PEK-C) have been investigated using both a rotational and a capillary rheometer. The dependence of the viscosity on the shear rate and temperature was obtained. The activation energy was evaluated both from the Arrhenius and the Williams-Landel-Ferry (WLF) equation. An estimate for the proper E(eta) (dependent only on the chemical structure of the polymer) has been found from the WLF equation at temperatures about T-g + 200 degrees C. Measurements of the die swell have been performed. The first normal stress differences were evaluated from the die swell results and compared with the values obtained from the rotational rheometer at low shear rates.