Rolling ball

There is disagreement in the analysis even for Newtonian fluids (Bennett, 1982). 

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Almost all raw materials requite grinding after primary cmshing. For coarse grinding, a dry pan or occasionally a wet pan is used. The dry pan is similar to a grist mill but has a perforated bottom through which the cmshed material is continuously removed. The wet pan is similar, but has a soUd bottom. For very fine grinding, a ring-roll, ball, or impact mill is employed. 

More recent developments in the rolling ball area include an automated micro viscometer, the Paar AMV 200, from Paar Physica. The specimen to be measured is introduced into a glass capillary down which a gold-covered steel ball roUs. The rolling time is measured automatically. The shear stress may be varied by changing the inclination angle of the capillary tube. The shear rate range is 10 1000, which makes the instmment useflil for... 

Fig. 9. Size reduction in a ball mill (a) rolling balls and (b) tumbling balls.

In another tack test, a steel ball of specified diameter is rolled down a grooved incline onto a conditioned surface area of pressure sensitive adhesive (ASTM D 3121, PSTC-6). The length of travel before it stops is the rolling ball tack (Fig. 2d) reported in millimeters. It is relatively inexpensive and simple to set up. Similar test variables to the probe tack test apply. 

Fig. 2. Tack tests and results, (a) Probe tack, (b) Probe tack vs. temperature for a natural rubber PSA. (c) Loop tack, (d) Rolling ball.

Rolling ball. A small steel ball with specific weight and diameter is rolled down an inclined plane onto a thin film of adhesive placed at the bottom. The distance the ball rolls on the adhesive film before stopping is a measure of the tack (the longer the distance, the lower the tack). 

Rolling ball viscometers, 21 738 Roll mills, 16 722 Rolls, high pressure, 16 612-613 Romanechite, 15 540 Romascone, 24 571 Romet-30/Romet-B. See Ormetoprim ROMP catalysts, 17 707, 708 ROM polymers. See also Ring-opening metathesis (ROM) polymers, 26 947-948 Roof coatings... 

The methods to evaluate PSAs include the rolling ball test (ASTM D3121, PSTC-6, BS EN 1721), loop tack test (ASTM D6195, FINAT Test Method 9, BS EN 1719), and quick stick test (PSTC-S). ... 

Fig. 256. Larger balls may be flattened to reduce their dimensions and burning time. E.g. U.S. 0.45 ammunition requires balls of 0.006-0.010 in. dia. They may be produced by rolling balls to a web (minimum) thickness of 0.004 in. Rolled powder grains are shown in Fig. 257.

Figure 8.1 Graph of (a) G( ), (b) A(i ) for an exoergic reaction (AG° < 0), showing the equilibrium point of minimum Gibbs free energy (triangle) at eq (dotted line). In (a), the direction of spontaneous reaction ( rolling ball ) is shown both for initial 0.15 (where 4 < 0) and 0.85 (where A > 0), both tending toward equilibrium at eq — 0.60 (where A = 0).

The rolling-ball viscometer shown in Fig. 4.3-32 is designed for pressures up to 200 MPa and temperatures of 250°C. It consists of a standard viscometer made of glass (1), which is arranged inside a high pressure autoclave (2). The autoclave is heated by silicone oil in a jacket (3). When the steel ball (4) passes the measuring coils (6) a timer is started. From the rolling time between the coils the viscosity can be evaluated [46]. 

Oil viscosity is measured in a rolling-ball viscosimeter or a capillary viscosimeter, either designed to simulate differential liberation. Measurements are made at several values of pressure in a stepwise process. The liquid used in each measurement is the liquid remaining after gas has been removed at that pressure. See page 6 of Table 10-1. 

The structure of hard gels is best elucidated using SAXS or SANS because the periods of the ordered structures are on the scale 10-100nm. In addition to tube inversion and rolling ball viscometry, which are sensitive to yield stress, the formation of a hard gel can be identified by other techniques. These include DSC (gelation is an endothermic process), NMR (via transverse relaxation time, T2, measurements), polarized light microscopy and rheometry. 

D 3121 Test Method for Tack of Pressure Sensitive Adhesives by Rolling Ball... 

PSA Formulation and Properties. The formulations used in this study for the Hycar 2103-Prepolymer C and Hycar 2106-Prepolymer C PSA contain OH/NCO ratios of 1.7 and 1.3, respectively. Dibutyltin dilaurate catalyst is used at a 0.2 wt.% level based on the total adhesive solids. PSA samples are made from an 80% solids solution (by wt.) with a dry solvent system (27/73 by wt. of ethyl acetate-toluene) and cured at 150°C for 45 seconds. The samples are then evaluated by running 180° peel, static shear, rolling ball tack, and vinyl film shrinkage tests. 

These adhesive systems give an excellent combination of static shear (at both room temperature and 70°C) and rolling ball tack along with excellent vinyl film shrinkage resistance. The results of these tests are summarized in Table III. 

Performance Flexibility. Figure IV illustrates the effect of the 0H/NC0 ratio of 180° peel strength and rolling ball tack for both the Hycar 2103-Prepolymer C and Hycar 2106-Prepolymer C adhesive systems. Peel strength values of 493 N/m (45 oz./in.) or lower are possible for the Hycar 2103 system simply by altering the 0H/NC0 ratio. Likewise for the Hycar 2106 system, peel strengths of 657 N/m (60 oz./in.) or lower are possible. 

In both cases, rolling ball tack remains relatively constant unless the 0H/NC0 ratio becomes too low. In addition, no creep in static shear is observed at room temperature or 70°C at the ratio shown. 

Figure V demonstrates the effect of adhesive dry coating weight on 180° peel strength and rolling ball tack with OH/NCO ratios of 1.7 and 1.3 for Hycar 2103 and Hycar 2106, respectively. Static shear tests run both at room temperature and 70°C show no creep for both systems throughout the thickness range tested.

Only at low adhesive coating weight does the rolling ball tack begin to increase slightly. 

A rolling ball viscosimeter consists essentially of a cylindrical tube which is inclined at a definite angle. The tube is filled with the fluid whose viscosity is to be measured and a metal ball is allowed to roll down through the tube. The bottom of the tube is closed so that as the ball travels downward the fluid passes upward through the space between the rolling ball and the walls of the tube. The time for the descent of the ball is accurately measured. It may be shown that the velocity of the ball is given by... 

When the rolling ball viscosimeter is employed to measure gas viscosities it is necessary to use a ball which just flts the tube. Under these conditions the rate of fall is slow enough so that it can be accurately measured. Notice that for gases at low pressures equation 12 reduces to... 

Now we consider roller ball indentations. Let us consider first a rigid ball that does not roll but indents a viscoelastic half-space this analysis will be extended to a rolling ball. This is a typical situation in which the elastic-viscoelastic analogy is, in general, no longer applicable. 

Rolling Ball Test 180° Peel Test 20° Hold Test... 

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