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Melt rheometer

Melt viscosities were measured using an Instron capillary melt rheometer (Model 3210) using a 0.050-in. diameter capillary (L D = 40 1). Corrected viscosities were calculated in the conventional manner. In all cases, samples were preheated for 7 min prior to data acquisition. [Pg.83]

At the time of writing this article, there are only two instruments in the market in the U.S.A. - the Rheometrics Extensional Rheometer, the RFX, and the Rheometrics Elongation Melt Rheometer, based on Meissner s rotary clamp method. The RFX is based on the opposing jet method. [Pg.294]

The melt viscosities of the materials were measured employing a melt rheometer as previously described (11) where the melt viscosities were obtained at constant shear stress as a function of time. Those results are summarized in Table III. The polymer isolated by freeze drying from the more dilute solution exhibits an initial melt viscosity which is less than the material derived from the concentrated solution (or the original stock S-PS) by a factor of 10. Direction-ally it appears that the viscosity of the product isolated from the dilute solution increases significantly with time. [Pg.208]

We need to be able to convert data from a melt rheometer into a flow curve, and to use such a curve to estimate pressure drops in simple melt processing equipment. Figure B.l shows four types of flow in channels. These are assumed to be steady laminar flows. The first task is to quantify the shear strain rates. Polymer melts adhere to metal surfaces so the melt velocity is zero at the stationary channel walls. [Pg.478]

Melt rheometers either impose a fixed flow rate and measure the pressure drop across a die, or, as in the melt flow indexer, impose a fixed pressure and measure the flow rate. Equation (B.5) gives the shear stress, but Eq. (B.IO) requires knowledge of n to calculate the shear strain rate. It is conventional to plot shear stress data against the apparent shear rate y, calculated using n = 1 (assuming Newtonian behaviour). If the data is used subsequently to compute the pressure drop in a cylindrical die, there will be no error. However, if a flow curve determined with a cylindrical die is used to predict... [Pg.481]

Experimentally it is extremely difficult to conduct a reactive blending process within a melt rheometer in order to determine the rheological evolution in a model flow field. Rheometric flows such as simple shear in a cone and plate or parallel plate apparatus are... [Pg.133]

The direct measurement of rjg is often practically impossible, especially for polydisperse samples. This is because standard melt rheometers are often unable to provide reliable data at sufficiently low shear rates to reach the region of Newtonian behavior. While this issue is discussed in Section 10.8, it is important to note here that the use of empirical equations for the viscosity function rj y) to extrapolate data is an unreliable procedure. Sometimes it is found that within a given family of polymers (same structure and shape of the MWD) a... [Pg.131]

So-called sandwich rheometers have sometimes been used in the study of rubber elasticity and melt viscoelasticity [141]. In a sandwich rheometer, twin sample plaques are placed in gaps formed by a central steel plate and two outer plates that are part of the same frame. These instruments are difficult to load and clean, and there is no direct control of the gap. Sliding plate melt rheometers were developed to make measurements of nonlinear viscoelastic behavior under conditions under which cone-plate flow is unstable, ie. in large, rapid deformations [ 142 ]. The sample is placed between two rectangular plates, one of which translates relative to the other, generating, in principle, an ideal rectilinear simple shear deformation. Creep tests can be carried out either by use of a feedback loop that generates a plate displacement that gives rise to a constant stress, or by use of a pneumatic drive, as in Laun s sandwich rheometer [143]. [Pg.377]

Figure 10.22 Sketch showing the principle of operation of the Sentmanat extensional rheometer (SER), which is designed to be used as a fixture in a standard rotational melt rheometer. One of two cylinders is driven directly by the rheometer motor, while a gear train drives the slave drum.The thin, rectangular sample is clamped at its ends to the cylinders.The torque on the drive shaft is proportional to the tensile stress in the sample. Sketch courtesy of Jen Tiang. Figure 10.22 Sketch showing the principle of operation of the Sentmanat extensional rheometer (SER), which is designed to be used as a fixture in a standard rotational melt rheometer. One of two cylinders is driven directly by the rheometer motor, while a gear train drives the slave drum.The thin, rectangular sample is clamped at its ends to the cylinders.The torque on the drive shaft is proportional to the tensile stress in the sample. Sketch courtesy of Jen Tiang.

See other pages where Melt rheometer is mentioned: [Pg.187]    [Pg.11]    [Pg.187]    [Pg.610]    [Pg.351]    [Pg.352]    [Pg.475]    [Pg.535]    [Pg.536]    [Pg.560]    [Pg.505]    [Pg.137]    [Pg.368]    [Pg.267]    [Pg.267]   


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