Characteristics and Flow Properties

The external shape of the crystal can be described in terms of its habit, which is affected by the rate of crystallisation and by the presence of impurities, particularly surfactants. The habit of a crystal is of pharmaceutical importance, since it affects the compression characteristics and flow properties of the dmg during tableting and also the ease with which the suspensions of insoluble dmgs will pass through syringe needles. 

Minimum viscosity (Li) Joint effect of accelerators and processing characteristics and flow properties in moulding, sheeting and extruding... 

Materials should have good flow characteristics and cohesive properties. Feed preparation, binder, lubricants used to meet requirements. Can produce compacts of simple shape with controlled properties at high rates. 

The rheological and flow properties of ordered block copolymers are extraordinarily complex these materials are well-deserving of the apellation complex fluids. Like the liquid-crystalline polymers described in Chapter 11, block copolymers combine the complexities of small-molecule liquid crystals with those of polymeric liquids. Hence, at low frequencies or shear rates, the rheology and flow-alignment characteristics of block copolymers are in some respects similar to those of small-molecule liquid crystals, while at high shear rates or frequencies, polymeric modes of behavior are more important. 

Powder properties may be important for the processing characteristics of solid dosage forms and if sufficient material is available, the bulk powder density and flow properties of salt candidates should be determined. However, it should be noted that powder properties could change quite significantly by the time the recrystaUization process for the bulk drug is optimized. 

Establishing the flow regime involves determining the Baker parameters B, and By from the two-phase system s characteristics and physical properties. The Baker parameters can be expressed as ... 

In the case of heat or material transfer in flowing media the dependency of the Nu -and the Sh -number on flow characteristics and material properties is often given in the following form ... 

Cadmium has the effect of lowering the melting temperature and represents the best combination of melting range, flow characteristics and mechanical properties but can produce toxic fumes during brazing (covered by COSHH Regulations). 

The Cube-Square law can also guide the evaluation of power density for microturbines. The fluid-to-mechanical power conversion for a turbine is expressed as the product of mass flow and change of specific total enthalpy across the turbomachine, A/tf Thermodynamic properties of a fluid, such as pressure, temperature, and enthalpy, do not fundamentally change with scale. For equivalent thermodynamic cycles, the power of a turbine therefore scales simply as the mass flow, which can be expressed in terms of an average flow velocity, V, through a characteristic flow area. A, proportional to r. For constant thermodynamic and flow properties, the power density of a turbine therefore scales as... 

In view of this situation, the capture coefficient must be determined as a function of some parameter accounting for the flow characteristics and the properties of the particle and the surface. This need can be met by the parameter Cl, as the capture coefficient depends unambiguously on this parameter (see Fig. IX.6) [256] ... 

Plastics analysis can be broadly grouped into two main categories. Physical analysis refers to the evaluation of the physical behavior of the material. Properties such as strength, thermal behavior, and flow properties fall into this category, as do failure and morphological characteristics. Chemical analysis seeks to evaluate the compositional characteristics of the polymer. The combination of these two broad approaches has been used successfully to correlate the behavior of plastics to their composition. 

Not all materials or products have the same flow characteristics. Some have plastic characteristics and flow easily. Others do not self-adhere and tend to separate when pumped or mechanically conveyed. As a result, the volumetric efficiency is directly affected by the properties of each product. This also impacts screw performance. 

All these studies have shown that high-raolecular-weight, partially hydrolyzed polyacrylamides are retained during flow through porous media by combined mechanisms of adsorption and mechanical entrapment. The contribution of each mechanism to the resistance factor, residual resistance factor, and inaccessible pore volume of the polymer solution has not been clearly demonstrated since all experimental investigations were carried out in porous media with finite adsorption characteristics. The purpose of this study was to characterize the entrapment and flow properties of partially hydrolyzed polyacrylamide in a porous medium on which adsorption was considered to be negligible. 

An examination is made of the performance of dicyclohexyl benzothiazole sulphenamide (DCBS) as an accelerator in tyre compounds. Cure characteristics, adhesion and flow properties are discussed, and it is shown that DCBS does not form carcinogenic N-nitrosamines. 8 refs. 

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