Compression Behaviour Of Powders Research Articles

Experimental research on the compression behavior of ultrafine alumina powders under gas pressurization

The compression behavior of powder bed under gas pressurization plays a crucial role in the performance of pressurized powder pneumatic conveying systems. The compression behavior of ultrafine powder, especially nanoscale powder, is more complicated. In this study, a visualization method was employed to compare the compression behaviors of alumina powders with different particle sizes ranging from the microscale to the nanoscale. The experimental results revealed that the strong agglomeration led to a higher compressibility percentage of about 58% for the nanoscale powders compared to the microscale powders with the percentage of about 44% under gas pressurization. However, the compression degree of powders shows a non-monotonic relationship with particle size. In particular, the most compressible nanoscale powder exhibited the ability to significantly reduce the compressibility at a lower gas pressurization rate. This finding provides a new optimization method for the pressurized pneumatic conveying and feeding systems of ultrafine powder.

Mechanism of "unification of drugs and excipients" for Chinese medicine semi-extract based on powder compression behavior analysis

In this paper, five representative Chinese herbal decoction pieces of Scutellariae Radix, Paeoniae Radix Alba, vinegar-processed Corydalis Rhizoma, Polygoni Multiflori Radix Praeparata and Lonicerae Japonicae Flos were selected to prepare the corresponding fine powder of pieces, extract powder, semi-extract powder and physical mixed powder. The physical properties of 20 kinds of powders, such as related parameters of particle size, density, stability and flowability, were evaluated comprehensively. The compression curves of powder porosity and tensile strength changing with pressure were plotted, and the Heckel equation and the Kawakita equation were used to describe the powder compression behavior. The results showed that compared with the fine powder of pieces, the compressibility of the semi-extract powder and the extract powder was significantly improved. Compared with the extract powder, the particle size and relative uniformity of the semi-extract powder were increased, indicating that the uniformity of the powder was improved. Besides, the semi-extract powder could reduce the hygroscopicity of the powder. Particularly, the semi-extract powder of Scutellariae Radix, Paeoniae Radix Alba and vinegar-processed Corydalis Rhizoma could maintain the porous structure of the tablet even under a high tableting pressure, which was beneficial to tablet disintegration. For some traditional Chinese medicines(such as Lonicerae Japonicae Flos), the semi-extract powder could reduce the viscosity, which avoided the sticking in the die compression. The semi-extract powder and the physical mixture powder prepared by the same Chinese herbal decoction pieces had similar physical properties and compression behaviors. Principal component analysis(PCA) was carried out on the 17 physical attributes and 5 compression parameters of the powder. It was found that the first principal component mainly reflected the differences among the material sources, while the second principal component could reflect the differences among fine powder of pieces, extract powder, semi-extract powder and physical mixed powder originating from the same Chinese herbal decoction pieces. In this paper, the mechanism of "unification of drugs and excipients" of Chinese medicine semi-extract powder was explained in terms of physical properties and compression behavior of powders, which provided reference for the formulation design and process development of Chinese medicine tablets.

Roller compaction of moist pharmaceutical powders

The compression behaviour of powders during roller compaction is dominated by a number of factors, such as process conditions (roll speed, roll gap, feeding mechanisms and feeding speed) and powder properties (particle size, shape, moisture content). The moisture content affects the powder properties, such as the flowability and cohesion, but it is not clear how the moisture content will influence the powder compression behaviour during roller compaction. In this study, the effect of moisture contents on roller compaction behaviour of microcrystalline cellulose (MCC, Avicel PH102) was investigated experimentally. MCC samples of different moisture contents were prepared by mixing as-received MCC powder with different amount of water that was sprayed onto the powder bed being agitated in a rotary mixer. The flowability of these samples were evaluated in terms of the poured angle of repose and flow functions. The moist powders were then compacted using the instrumented roller compactor developed at the University of Birmingham. The flow and compression behaviour during roller compaction and the properties of produced ribbons were examined. It has been found that, as the moisture content increases, the flowability of moist MCC powders decreases and the powder becomes more cohesive. As a consequence of non-uniform flow of powder into the compaction zone induced by the friction between powder and side cheek plates, all produced ribbons have a higher density in the middle and lower densities at the edges. For the ribbons made of powders with high moisture contents, different hydration states across the ribbon width were also identified from SEM images. Moreover, it was interesting to find that these ribbons were split into two halves. This is attributed to the reduction in the mechanical strength of moist powder compacts with high moisture contents produced at high compression pressures.

Single and bulk compression of pharmaceutical excipients: Evaluation of mechanical properties

The compaction of powders into tablets is widely used in the pharmaceutical industry to convert drugs, in the form of small particles, into coherent and robust metered solid dosage forms. In order to produce robust tablets with the required properties, it is essential to understand the elastic, viscoelastic and plastic properties and rupture strength of the feed particles, which can be as small as a few microns in diameter. The objective of this work is to characterise the mechanical properties of single particles using a micromanipulation diametrical compression technique and relate the parameters to the compression behaviour of powders. Mechanical parameters, such as the Young's modulus, hardness and nominal rupture stress, were thus determined for each sample. The bulk compression data of the powders were analysed to calculate the parameters of the Heckel (Heckel, R.W., 1961a An analysis of powder compaction phenomena, Trans Metal Soc. AIME, 221, 1001–1008; Heckel, R.W., 1961b Density–pressure relationships in powder compaction, Trans Metal Soc. AIME 671–675), Kawakita (Kawakita, K. and Ludde, K.H., 1971 Some considerations on powder compression equations, Powder Technology, 4, 61–68) and Adams (Adams, M.J., Mullier, M.A. and Seville, J.P.K., 1994 Agglomerate strength measurement using a uniaxial confined compression test, Powder Technology, 78, 5–13.) models. These parameters will be compared with each other, and with the mechanical properties of the individual component particles. A correlation has been found between the nominal rupture stress of single particles and the apparent strength derived from the Kawakita and Adams models.

Continuous matrix formation for controlled drug release: Compression of isotropic polymeric system

The compaction of a powdered solid within the confines of a die between two punches is complex, and numerous simultaneous internal processes lead to consolidation and bonding. These events include particle r~rr~gement, fracture and plastic deformation (Hiestand et al., 1977; Carstensen, 1973; Fell and Newton, 1971). With materials of low melting point, localized melting at the asperities of contact points occurs (Rankell and Higuchi, 1968; York and Pilpel, 1973). Compression behaviour of powders is conveniently characterized by Heckel plots (Heckel, 1961) and various authors have successfully applied Heckel’s equation to pharmaceutical powders to identify the types of mechanism occurring during compression (Hou and Carstensen, 1985; Roberts and Rowe, 1985; Hersey and Rees, 1971; York and Pilpel, 1973). Considerable efforts in research are under way to adapt polymeric systems for drug delivery and release. The purpose of the present work is to report the compression behaviour of polymers and their mixtures with active drug material in relation to tabletting.