Particle size powder flow

Oral solids Solubility, dissolution, polymorphism, chirality, particle size, powder flow, chemical stability, photostability, compressibility, hygroscopicity, and excipient interactions. 

A number of other studies can be performed on a candidate drug to determine other important solid-state properties, for example, particle size, powder flow and compression and polymorphism. Therefore, when a sample undergoes initial preformulation testing the following parameters should be noted particle size, true, bulk and tapped density, surface area, compression properties and, powder flow properties. Some of these factors will be discussed in this chapter others, however, are dealt with in more detail in Chapter 11 on Solid Oral Dosage Forms. 

Direct Compression. This process is relatively simple and time saving. AH the ingredients are blended and then compressed into the final tablet. This is an excellent method, but encumbered by a number of problems. Not all substances can be compressed directly, necessitating a granulation step. Likewise, the flow properties of many blends of fine, particle-sized powders are not such as to ensure even filling of the die cavities of tablet presses. In addition, air entrapment can occur. 

Chew, N. Chan, H. Influence of particle size, air, flow, and inhaler device on the dispersion of mannitol powders as aerosols. Pharm.Res. 1999,16 (7), 1098-1103. 151. 

Chew, N.Y.K. Chan, H.-K. Dispersion of mannitol powders as aerosols influence of particle size, air flow and inhaler device. Pharm. Res. 1999, 16, 1098-1103. 

Other characteristics of the mixed powder such as particle size, flavor, flow rate, and bulk density before and after tapping have to be verified. 

The particle size powders consisting of many small particles tend to show a poor flow. 

Table 1.2 Particle size and flow specification of common commercially available fine-grade polymer powder excipients.

Determination of the influence of surface coating and particle size on flow properties of organic pigment powders... 

Lubricants protect die and punch surfaces from wear and bum-out of the compact during sintering without objectionable effects or residues. They must have small particle size, and overcome the main share of friction generated between tool surfaces and powder particles during compaction and ejection. They must mix easily with the powder, and must not excessively impede powder flow (see Lubrication and lubricants). 

Because mass flow bins have stable flow patterns that mimic the shape of the bin, permeabihty values can be used to calculate critical, steady-state discharge rates from mass flow hoppers. Permeabihty values can also be used to calculate the time required for fine powders to settle in bins and silos. In general, permeabihty is affected by particle size and shape, ie, permeabihty decreases as particle size decreases and the better the fit between individual particles, the lower the permeabihty moisture content, ie, as moisture content increases, many materials tend to agglomerate which increases permeabihty and temperature, ie, because the permeabihty factor, K, is inversely proportional to the viscosity of the air or gas in the void spaces, heating causes the gas to become more viscous, making the sohd less permeable. 

Any refractory material that does not decompose or vaporize can be used for melt spraying. Particles do not coalesce within the spray. The temperature of the particles and the extent to which they melt depend on the flame temperature, which can be controlled by the fueLoxidizer ratio or electrical input, gas flow rate, residence time of the particle in the heat zone, the particle-size distribution of the powders, and the melting point and thermal conductivity of the particle. Quenching rates are very high, and the time required for the molten particle to soHdify after impingement is typically to... 

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