Powder blending cohesive blends

The angle of repose of a powder blend, effective angle of internal friction (EAIF) from shear cell measurements, and the mean time to avalanche (MTA) in powder cohesivity tests are useful for assessing the flow of a tableting mixture at various scales (15 18). 

For low-dose, immediate-release drug products, the formulation should be designed with cohesive diluents, such as lactose, to enhance ordered mixing prior to the dry granulation process. Based on the two case studies reported here, it was also demonstrated that this formulation approach reduced the propensity for the powder blend to segregate. 

The Jenike shear cell tester is classified as a direct shear tester that is capable of providing information on a solids cohesive strength as well as its wall friction properties. The tester allows us to measure the strength of a powder blend as a function of pressure applied to it. These are two main considerations when design a bin or hopper to ensure reliable material flow. The tester consists of a base, a moveable shear ring resting on top of the base, and a top cover lid (Fig. 7.3).61 The base is fixed while the lid rotates at a constant low rate. Powder blend is placed in the ring and base and a... 

The wet granulation process is the traditional method of manufacture and is frequently used in the pharmaceutical industry. Expertise in wet granulation is widely available, as is the required equipment. The process improves flow and cohesion, reduces dust and crosscontamination, and permits the handling of powder blends without loss of homogeneity. 

The dry-blending operation is a critical process in case of low-dosage forms. In order to obtain a high degree of mixing, cohesive powder components have to be disagglomerated. For this purpose, it is often advantageous to proceed as follows ... 

Dry powders must be able to flow readily to leave the capsule or powder reservoir but also must generate a fine aerosol so that the patient can inhale a proper dose. These two requirements are often difficult to achieve simultaneously. Fine powders tend to be cohesive and have poor flow properties. Blending with a carrier phase, pelletization, and other approaches have been used to overcome these limitations. The use of blends and homogeneous powders is compared in Table 4 from a DPI device perspective. 

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