Plastic, viscosity

Plastisol Viscosity and Viscosity Stability. After the primary contribution of the resin type in terms of its particle size and particle size distribution, for a given PVC resin, plastisol viscosity has a secondary dependence on plasticizer viscosity. The lower molecular weight and more linear esters have the lowest viscosity and hence show the lowest plastisol viscosity, ie, plastisol viscosity for a common set of other formulation ingredients... 

Of the models Hsted in Table 1, the Newtonian is the simplest. It fits water, solvents, and many polymer solutions over a wide strain rate range. The plastic or Bingham body model predicts constant plastic viscosity above a yield stress. This model works for a number of dispersions, including some pigment pastes. Yield stress, Tq, and plastic (Bingham) viscosity, = (t — Tq )/7, may be determined from the intercept and the slope beyond the intercept, respectively, of a shear stress vs shear rate plot. 

Direct Indicating Viscometer. This is a rotational type instrument powered by an electric motor or by a hand crank. Mud is contained in the annular space between two cylinders. The outer cylinder or rotor sleeve is driven at a constant rotational velocity its rotation in the mud produces a torque on the inner cylinder or bob. A torsion spring restrains the movement. A dial attached to the bob indicates its displacement. Instrument constants have been so adjusted that plastic viscosity, apparent viscosity, and yield point are obtained by using readings from rotor sleeve speeds of 300 and 600 rpm. 

Plastic viscosity (PV) is centipoises equals the 600 rpm reading minus the 300 rpm reading. Yield point (YP) in pounds per 100 ft equals the 300-rpm reading minus plastic viscosity. Apparent viscosity in centipoises equals the 600-rpm reading, divided by two. The interpretations of PV and YP measurements are presented in Figure 4-107. 

Plastic Viscosity and Yield Point. Plastic viscosity and yield point measurements are obtained from a direct indicating viscometer. Due to the temperature effect on the flow properties of oil-base mud, the testing procedure is modified. The mud sample in the container is placed into a cup heater [23]. The heated viscometer cup provides flow property data under atmospheric pressure and bottomhole temperature. 

Figure 4-111. Suggested range of plastic viscosity and yield point for bentonite muds [29],...

KCl-polymer (potassium chloride-polymer) muds can be classified as low solids-polymer muds or as inhibitive muds, due to their application to drilling in water-sensitive, sloughing shales. The use of polymers and the concentration of potassium chloride provide inhibition of shales and clays for maximum hole stability. The inverted flow properties (high yield point, low plastic viscosity) achieved with polymers and prehydrated bentonite provide good hole cleaning with minimum hole erosion. 

Mud Weight ppg Plastic Viscosity cP Yield Point Ibs/IOOft Oil-Water Ratio Electrical Stability... 

Drilled solids include active drilled solids and inactive drilled solids. Clays and shales are considered to be active drilled solids they disperse into colloidal size readily and become detrimental to drilling by increasing the apparent viscosity and gel strength of the mud. Inactive drilled solids are sand, dolomite, limestone, etc. if they occur in colloidal size, these solids may increase plastic viscosity of the drilling mud. 

The rheological properties of a particular suspension may be approximated reasonably well by either a power-law or a Bingham-plastic model over the shear rate range of 10 to 50 s. If the consistency coefficient k is 10 N s, /m-2 and the flow behaviour index n is 0.2 in the power law model, what will be the approximate values of the yield stress and of the plastic viscosity in the Bingham-plastic model ... 

A fluid with a finite yield. stress is sheared between two concentric cylinders, 50 mm long. The inner cylinder is 30 mm diameter and the gap is 20 mm. The outer cylinder is held stationary while a torque is applied to the inner. The moment required just to produce motion was 0.01 N m. Calculate the force needed to ensure all the fluid is flowing under shear if the plastic viscosity is 0.1 Ns/ni2. 

In nondispersed systems no special agents are added to deflocculate the solids in the fluid. The main advantages of these systems are the higher viscosities and the higher yield point-to-plastics viscosity ratio. These alterated flow properties provide a better cleaning of the bore hole, allow a lower annular circulating rate, and minimize wash out of the bore hole. 

Drilling mud has to be pumped down into an oil well that is 8000 ft deep. The mud is to be pumped at a rate of 50 gpm to the bottom of the well and back to the surface, through a pipe having an effective ID of 4 in. The pressure at the bottom of the well is 4500 psi. What pump head is required to do this The drilling mud has properties of a Bingham plastic, with a yield stress of 100 dyn/cm2, a limiting (plastic) viscosity of 35 cP, and a density of 1.2 g/cm3. 

Melvin M. Mooney is best known for the development of an instrument for determining the plasticity (viscosity) of unvulcanised elastomers. 

An early cure instrument which combined in one operation the functions of a Mooney viscometer and of a curometer or vulcameter, i.e., it measures in one quick test the plasticity (viscosity) of the (uncured) mix, its scorch time and cure rate. Now superseded by instruments such as the moving die rheometer. 

A Casson fluid is Theologically identified by two parameters yield value and plastic viscosity. The plastic viscosity relates to the asymmetry of the flow particles and the yield value is connected with the forces of attraction between particles. The... 

Here the fitting parameters are the slope of the line (the plastic viscosity, rip) and the Bingham or dynamic yield stress (the intercept, constitutive equations will be introduced later in this volume as appropriate. 

Here the yield stress is the Bingham yield value and the value of rj(co) is the linear value reached at high shear, often referred to as the plastic viscosity. The calculation of the material behaviour follows the same route as with the Newtonian case so ... 

The term /pj is the plastic viscosity and aB> 0c and [Pg.215]

The extrapolated yield stress gives 0.06 Pa and a plastic viscosity of 3.88 mPas. We can use this to estimate the force between the particles, which gives 425kBT/a, in fair agreement with the value determined using pair potential curves. Here the Casson model has been used to partially linearise a pseudoplastic system rather than a system with a true yield stress. 

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