Interfacial torque

In computer-controlled machines, sensors continuously monitor the three parameters— rotational speed, axial pressure, and weld time—in addition to the weld penetration, weld or penetration veloeity, and interfacial torque. For reprodueible results and eonsistent weld strength, proeess monitoring is reeommended. Figure 14.24 is a sensor output traee obtained during welding ofpolyvinylidene fluoride (PVDF). Axialpressure and rotational speed were set at 4.3 MPa and 3500 rpm, respectively. 

Figure 14.24 Sensor output data from computer-controlled monitoring of the spin welding of PVDF. When rotational speed reaches its set value, axial pressure is engaged, and weld penetration begins. Interfacial torque, penetration velocity, and weld penetration are monitored throughout the spin welding cycle.

CT = Standard deviation (statistics), or interfacial tension T = Torque on shaft, consistent units, FL or MLVt ... 

O = Standard deviation (statistics), or interfacial tension x = Torque on shaft, consistent units, FL or ML2/t2 = Np = P0 = Power number, dimensionless 3> = Power number, POJ or ratio of power number to Fioude number, Njrr, to exponential power, n... 

Equations 12 through 14 may be derived from thermodynamic and mechanical expressions for the transverse force and torque acting on a surface which intersects the interfacial region ( ). Moments of an isotropic pressure force and a surface tension acting at R are... 

In Equations 21.9 and 21.10, the interfacial force 21.6 is used by employing a contact angle equal to rc/2. Generally in Equation 21.9 the droplet height is substituted by the droplet radius, Dd/2. These equations permit calculation of which diameter torques in clockwise and anticlockwise directions are balanced, beyond this value the droplet detaches. However, for a short period the droplet still maintains its... 

In this example of model reactive polymer processing of two immiscible blend components, as with Example 11.1, we have three characteristic process times tD,, and the time to increase the interfacial area, all affecting the RME results. This example of stacked miscible layers is appealing because of the simple and direct connection between the interfacial layer and the stress required to stretch the multilayer sample. In Example 11.1 the initially segregated samples do create with time at 270°C an interfacial layer around each PET particulate, but the torsional dynamic steady deformation torques can not be simply related to the thickness of the interfacial layer, <5/. However, the initially segregated morphology of the powder samples of Example 11.1 are more representative of real particulate blend reaction systems. 

A biconical disk interfacial rheometer is available from Anton Paar, known as the Physica Interfacial Rheology System (IRS). A schematic of the rheometer tool is shown in Figure 4.22. Current specifications of the instrument include a torque range of 0.02 xNm to 150 mNm with temperature control from 5 to 70°C. All rheological test modes are available for the interfacial rheometer including oscillatory testing [59],... 

FIGURE 10.33 Principles of interfacial rheological measurements, (a) In shear. A thin disc (D) is at an O-W interface and is made to rotate (or oscillate) the torque on the disc can be measured, e.g., via a torsion wire (T). (b) In expansion/compression. Barriers (B) at an O-W interface are moved, thereby increasing or decreasing the interfacial area between them the interfacial tension is measured by means of a Wilhelmy plate (P). Both kinds of measurement can also be made at A-W and A-O surfaces. 

As the La-Hu transition proceeds, the mean interfacial molecular area drops and the mean area at the chain end of the molecule increases (2, 23). Effectively, the molecular volume has been subjected to a torque due to an expansive chain pressure relative to a net cohesive interaction near the head groups (4). This torque is conveniently described as a spontaneous curvature, C0 (4, 17), to a specific radius of curvature, R0 = 1/C0, at which point the net torque is almost zero. All Hu phases swell only to a limited degree. In a transition in coexistence with excess water, there is generally a change in the... 

Favis [1994] and Willis andFavis [1988] prepared compatibilized PA blends with PP and carboxylic acid-functionalized EMAA ionomer. Blends containing 90-10 parts PA-6, 0-30 parts EMAA ionomer, and 10-90 parts PP were combined in an internal mixer at 250°C and characterized by torque rheometry and SEM. Dispersed phase particle size vs. interfacial modifier concentration was determined. Emulsification curves were constructed. Effects of mixing protocol on blend properties were studied. Blends were also prepared containing HOPE in place of PP. 

PA-12 or PA-1212 or PA-612 or PA-610 or PA-69 or PA-46 /SEES (0-20) / SEBS-g-MA (1.8% MA) (0-20) properties / TEM / ductile-brittle transition temperatures / interfacial tension estimates / effects of PA amine end-group concentration on copolymer formation (titration before and after extrusion) / torque rheometry ... 

We have investigated the alteration in mechanical properties of the protein layer caused by the PFBC using a modified surface viscometer. The protein film was placed under a shearing stress by the application of a small torque to a teflon paddle wheel inserted into the interfacial boundary, and the angular deformation of the film was measured. From this data it was possible to obtain stress-strain curves and to determine the surface shear modulus and surface fracture point for the protein layer. In most studies protein was adsorbed to the interface of perfluorotributylamine from either a buffered... 

Com-Stir tools (TWI) combine rotary motion (tool shoulder) with orbital motion (tool pin) to maximize the volume of material swept by pin-to-pin volume ratio (Ref 108) (Fig. 2.24). Moving the pin in an orbital motion produces a wider weld and increases oxide fragmentation on the interfacial (also known as faying) surfaces. In addition, the motion of the Com-Stir tool produces lower torque than the typical rotary motion FSW tool, reducing the amount of fixturing necessary to secure the workpiece. 

In materials with high anisotropy in the grain boundary energy and, thus, with faceted grain boundaries, the angles between boundaries may not be uniquely defined by an interfacial tension condition because of torque on facets. ... 

The AG,p due to SO4 and emerged charged groups apply a torque to the double-stranded a-helical coiled coil section of the y-rotor that would give a counterclockwise rotation when functioning as an ATPase. (Adapted from Urry Function of the Fi-motor (Fi-ATPase) of ATP synthase by Apolar-polar Repulsion through Internal Interfacial Water. Cell Biol. Int., 30(1), 44-55, 2006. Prepared using (Adapted from Urry. )... 

PA-6 (90-10)/HDPE (10-90)/ EMAA ionomer (0-30) Internal mixer at 250 °C/torque rheometry/ SEM/dispCTsed phase particle size vs. interfacial modifier concentration/ miulsificatimi cnrves/effects of mixing protocol/also blcmds ctmtaining PP in place of HOPE Favis 1994 Willis and Favis 1988... 

PP-g-MA (0.1 mol% MA). Characterization methods included SEM, ESCA, and interfacial tension measurement. Tselios et al. (1998) have prepared compatibilized blends of LDPE and PP through inclusion of PP-g-MA (0.8 mol% MA) and EVAl (7.5 mol% vinyl alcohol). Blends were characterized using SEM, torque rheometry, mechanical properties, FTIR, and micro-Raman spectroscopy. 

EPDM/PP/DCP RI Internal mixer/torque measurement/ estimate of interfacial tension/also added trimethylolpropane triacrylate coupling agent Shariatpanahi et al. 2002... 

FIGURE 5.21 The torque pendulum. The description of the stressed state in the interfacial film. 

Many surface viscometers utilize torsional stress measurements upon a rotating ring, disk or knife edge (shown schematically in Fig. 5.16) within or near to the liquid/liquid interface [17]. This type of viscometer is moderately sensitive for a disk viscometer the interfacial shear viscosity can be measured in the range q > 10 Surface Pas. The disk is rotated within the plane of the interface with angular velocity w. A torque is exerted upon the disk of radius R by both the surfactant film with surface viscosity qg and the viscous liquid (with bulk viscosity q) that is given by the expression... 

Biswas and Haydon [20] found some correlation between the viscoelastic properties of protein (albumin or arabinic acid) films at the 0/W interface and the stability of emulsion drops against coalescence. Viscoelastic measurements were carried out using creep and stress relaxation measurements (using a specially designed interfacial rheometer). A constant torque or stress a (mN m ) was applied and the deformation y was measured as a function of time for 30 minutes. After this period the torque was removed and y (which changes sign) was measured as a function of time to obtain the recovery curve. The results are illustrated in Fig. 5.18. From the creep curves one... 

Below, we first introduce the most general mechanical description of the surface moments (torques) exerted on the boundary between two fluid phases. Then, we consider the thermodynamics of a curved interface (membrane) in terms of the work of flexural deformation. Next, we specify the bending rheology by means of the model of Helfiich [202]. Finally, we review the available expressions for the contributions of the electrostatic, steric, and van der Waals interactions to the interfacial bending moment and curvature elastic moduli. These expressions relate the interfacial flexural properties to the properties of the adsorbed surfactant molecules. 

Two approaches, mechanical and thermodynamical, exist for the theoretical description of general curved interfaces and membranes. The first approach originates from the classical theory of shells and plates, reviewed in Refs. 202 and 204. The surface is regarded as a two-dimensional continuum whose deformation is described in terms of the rate-of-strain tensor and the tensor of curvature. In addition, the forces and the force moments acting in the interface are expressed by the tensors of the interfacial stresses, , and moments (torques), M. Figure 11 illustrates the physical meaning of the components of the latter two tensors. Usually, they are expressed in the form... 

Generally, the range of cocontinuity is dependent on the viscosity (torque) ratio. In blends with a viscosity ratio near unity, a fully cocontinuous structure appears around 50 50 composition otherwise, the component vhth a lower viscosity tends to form a continuous phase and the range of cocontinuity is shifted to the lower amounts of less-viscous component (Figure 3.11). A second important parameter determining the formation of cocontinuous structure is the interfacial tension. With increasing interfacial tension, the minor phase forms more spherical... 

The interfacial chemical reaction changes the dynamics of the phase inversion process. Sundaiaraj et al. [25] systematically studied the phase inversion process in a reactive polyarylate/ethylene-ethyl acrylate-glycidyl methacrylate rubber blend where the extent of interfacial chemical reaction was controlled by the addition of stearic acid. The primary effects of the interfacial reaction were to delay phase inversion and increase the mixing torque rise associated with it. Figure 5.6 illustrates both of these points. They attributed these effects to the fact that in reactive blends steric stabilization of the... 

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