Technical Report 132, c4e-Preprint Series, Cambridge
Multivariate characterisation of lactose powder and granules of a wet granulation process
ref: Technical Report 132, c4e-Preprint Series, Cambridge
Associated Theme: Particle Processes
In this work, α-lactose monohydrate powder and the granules produced from this powder by a high-shear granulation process are characterized with respect to size, shape, porosity and strength using various analytical methods. The multivariate data set includes an assessment of the applicability and reproducibility of each measurement technique. Particle size distributions are obtained by static image analysis (SIA), laser scattering (LS) analysis and sieving. Granule porosities are determined using individually developed procedures for X-ray computed tomography (μCT) and mercury intrusion porosimetry (MIP). Lactose granules show absolute porosities increasing from 30% to 40% along the size classes. Filling pressure adjustment for granules smaller than 600 is required to overcome the limit for interstitial void intrusion at the standard mercury filling pressure of 1 psia. The μCT derived visual information of larger granules shows internal pore structures with denser cores and porous shell parts. Particle surface roughness is approached using atomic force microscopy (AFM), scanning electron microscopy (SEM) and μCT. A reasonable range to estimate heights of asperities on lactose powder particles may feature values up to about 800 nm. The strength of the product granules is measured via uniaxial compression testing. The compression strength of the granules, derived from the largest failure peaks at low displacement, follows a logarithmic decrease with size from 1.2 to 0.2 MPa.
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