Powder Flow Characteristics of Excipients

Nowadays, direct compression (DC) remains the preferred pharmaceutical manufacturing technology. Compared to wet-granulation  method, DC offers the advantages of good product stability, simple manufacturing process, and low process cost. DC technology requires the excipients and APIs to form a compressible mixture. Therefore, a series of excipients with the function of enhancing flow and compressibility are added in this process. The powder flow properties of excipients will affect the final disintegration effect of the drug product, which will further affects the release of the drug. Understanding the powder properties of excipients can help to create stable dosage forms.

Figure 1. Powder flow properties and compactability of selected active pharmaceutical ingredients, excipients. (Worku, A. A.; et al. 2017)

Factors Affecting the Flow Characteristics of Powders

The flow characteristics of powders are essentially mechanical properties. Due to their plastic flow and dilatancy, particle iterations are influenced by a series of attractive forces, including:

• Particle size

Very fine particles have attractive forces, which can result in poor cohesion and flow characteristics of the powder. As particle size increases, flow of the powder increases.

• Surface texture

Smooth surface of particles increases the flow characteristics, and high density and low porosity provide good flow characteristic.

• Moisture content

The higher the moisture content, the greater the risk of cohesion and adhesion. Therefore, some flow additives are often added during the drug manufacturing to improve the flowability of drug powders.

Application of Powder Flow Characteristics Studies

• Helps to prevent agglomeration of excipients during transportation or due to vibration
• Compaction kinetics study of pharmaceutical tableting processes
• Batch to batch identification
• Effect of environmental conditions (humidity, temperature) on the behavior of excipient powders

Figure 2. Flow properties of starch, pregelatinised starch (P.starch), MCC, ergocalciferol (Erg.) and micronised ergocalciferol (Mic Erg.). (Alyami, H.; et al. 2017)

BOC Sciences’ Assessment of Powder Flow Characteristics

Understanding the flow propensity and compression behavior of powders is essential for the development of oral solid dosage forms. BOC Sciences has introduced the latest new technology for measuring flow properties. Combined with advanced testing equipment, we can carry out an evaluation of the following flow properties of primary excipients of tablets:

• Angel of repose

The repose angle measurement is an essential test in the pharmaceutical field. We provide repeatable, fast and user-independent testing service that is simple, fast and intuitive.

• Mass flow

We measure the flow rate for a set of aperture sizes to obtain a flow curve, and then fit the whole flow curve to the Beverloo theoretical model to obtain the flow index (Cb, related to the powder flowability) and the minimum aperture size to obtain the flow rate (D_min). All the measurements and analysis of the results are assisted by software.

• Flow time
• Compaction capacity
• Compression index

We can provide compression index for each rpm, which ranges from 2-70 rpm.

• Carr index & Hausner ratio

In order to understand the compressibility of different excipients powders, we are able to measure the bulk density, the tapped density, the Hausner ratio and the Carr index for the characterization of the rheological properties of the powder. In addition, BOC Sciences can help you classify your excipient powders based on the flowability and processability by providing the full packing curve and the characteristic tap number to measure the packing kinetics of the powder.

Our Capabilities

• We were able to characterize the flow properties of different types of excipient products in order to improve the suitability of modified starch products for continuous production.
• Our experts are skilled in the use of powder flow testers to provide sensitive, reliable and process-relevant analysis
• Simulate powder processing conditions to ensure process-relevant data
• We provide multiple aspects of powder flow properties characterization: assessment of dynamic flow, bulk and shear properties