Influence of degree of disorder on the Heckel yield pressure: a comparison between milled and physical mixtures of lactose
(English)Manuscript (preprint) (Other academic)
The purpose of this study was to investigate the effect of degree of amorphisation of a series of lactose powders, prepared by milling α-lactose monohydrate powders for different time periods, on the plastic stiffness of the particles. As references, a series of physical mixtures consisting of original crystalline particles and amorphous particles obtained by spray-drying was used. In addition, the effect of powder pre-storage humidity on the mechanical properties was investigated. The particle plastic stiffness was assessed by the Heckel yield pressure derived from the relationship between porosity of the powder column and the applied compression pressure during confined powder compression.
For milled particles of a low degree of disorder, a decreased particle size increased the particle plastic stiffness. For milled particles of constant particle size, the plastic stiffness decreased with an increased degree of disorder while the elastic stiffness seemed independent of the degree of disorder. The presence of moisture caused a recrystallization of milled particles with low degree of disorder which increased their plastic stiffness.
For the physical mixtures of crystalline and amorphous particles, similar relationships between plastic stiffness and amorphous content as for the milled powders were obtained. A reasonable explanation is that the nature of the milled particles is represented by a two-state system with crystalline and amorphous domains.
Milling-induced disorder, plasticity, elasticity, compression, amorphous lactose, Raman spectroscopy
IdentifiersURN: urn:nbn:se:uu:diva-317799OAI: oai:DiVA.org:uu-317799DiVA: diva2:1082882