Capillary torque

The capillary force and the capillary torque can be computed by virtual variations of U n, that is, taking into account only the dependence on d and tp explicit in Equation 2.14 ai if and Q were... 

Techniques for evaluating processing stabiHty and mechanochemical effects include using a Brabender torque rheometer (29,30), injection mol ding (26,28), capillary rheometry (26,28), and measuring melt index as a function of residence time (26). 

The melt-spinning process used to convert mesophase pitch into fiber form is similar to that employed for many thermoplastic polymers. Normally, an extruder melts the pitch and pumps it into the spin pack. Typically, the molten pitch is filtered before being extruded through a multi-holed spinnerette. The pitch is subjected to high extensional and shear stresses as it approaches and flows through the spinnerette capillaries. The associated torques tend to orient the liquid crystalline pitch in a regular transverse pattern. Upon emerging from the... 

The experimental methods for the determination of liquid viscosity are similar to those used for gases ( 8.VII F) (i) transpiration, through capillaries, (ii) torque on rotating cylinders, or the damping of oscillating solid discs or spheres, in the liquid, (iii) fall of solid spheres through the liquid, (iv) flow of liquid through an aperture in a plate, (v) capillary waves. Methods (i) and (ii) are mostly used for absolute, the others for comparative, measurements. 

Simulations of a number of dynamical processes in adsorbed films have been reported. These begin with the motions of individual molecules such as reorientation, either of the entire molecule or, for long chains, internal rotations. Of course, all these motions are affected by the torques exerted on a molecule due to its interactions either with neighboring adsorbate molecules or with the solid adsorbent. Other types of dynamics involve the translations that give rise to self-(or tracer) diffusion and to viscous flow in capillaries. Finally, simulations can be used to study the mechanism of lubrication by films between two closely spaced surfiices. Each of these topics will be discussed briefly here. 

As demonstrated previously (7), the ramping of rotor speeds can be used to obtain similar rheological information as is obtained via more traditional capillary rheometer methods. Specifically, it was shown that the following relation is applicable to torque and rotor speed data... 

PA-6 (90-10) or PA-11 / HOPE (10-90) or MDPE / E-MA (0-10) internal mixer at 200-300°C / torque rheometry / capillary rheometry / SEM / selective solvent extraction / FTIR Serpe etal., 1990... 

PA-66 (70-50) / PBT (30-50) / mutifunctional epoxide resin (0-5 phr) PA-6 (17) / PBT (83) / mutifunctional epoxide resin (0-12) TSE at 275X / SEM / TEM / extrudate swell / DSC / torque rheometry / capillary rheometry / effects of PA/PBT ratio and epoxy content on mechanical properties / blends optionally + core-shell elastomer TSE at 230-250°C / mechanical properties / SEM / DSC / DMA / WAXD Huang and Chang, 1997 a, b An etal., 1996... 

Melt viscosity can also be used for molar mass estimates. The measurements are, however, somewhat less precise because of the high viscosities due to entanglements of the molecules, and it is inconvenient to work at the higher temperatures needed to melt the polymer. A frequent measurement is that of the melt index. A basic extrusion-capillary is used to determine the (mass) rate of flow of the polymer through a specified capillary under controlled conditions of temperature and pressure. Similarly, the Mooney viscometer gives a measure of the torque to revolve a rotor at constant speed in a polymer at constant speed, which is linked ultimately to molar mass. The Mooney viscometer has found application in the rabber industry as an empirical measure of molar mass. Somewhat more information on melt viscosity is given in Sect. 5.6.6. 

In an attempt to follow the effect of concentration of stearic acid on the rheological properties, compounds from SBR rubber -filled with 50 phr carbon black N550, ZnO, and with varying the stearic acid concentration (0 0.5 1.0 1.5 and 2 phr) were prepared. Using Brabender plasticorder and capillary viscometer these compounds were studied. The observed effective (apparent) viscosity (30-5-120%) (Figure 1) and torque maxima (104-20%) (Figure... 

PET/HDPE/EBA-g-GMA Haake torque rheometer/capillary rheometry/SEM morphology/ effect of EBA-g-GMA level on blend properties Li and Lu 2008 Li et al. 2009d... 

PBT (70-30)/E-GMA (6 % GMA) (0-20)/PP (30-70) TSE at 255 °C/torque/capillary rheometry/ FriK/SEM/TEM/mechanical properties/ catalysis of acid + epoxide reaction using phosphonium salt Tsai and Chang 1996... 

EAA (9 % AA) (50-20)/PS (0-50)/ S-IPO (1.2 % IPO) (30-60) Internal mixer at 240 °C/FTIR/torque rheometry/capillary rheometry/also TSE with on-line rheometry and FTIR controls/optical microscopy Curry and Andersen, 1991/1992... 

Viscometers n. Instruments for measuring viscosity including mechanical probe and torque types as the Brookfield viscometer, capillary tube types as the Cannon-Fenske or Ostwald-Fenske, and flow through orifice types as the Ford cup. 

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