Particle Engineering in Pharmaceutical Solids Processing: Surface Energy Considerations

Abstract

During the past 10 years particle engineering in the pharmaceutical industry has become a topic of increasing importance. Engineers and pharmacists need to understand and control a range of key unit manufacturing operations such as milling, granulation, crystallisation, powder mixing and dry powder inhaled drugs which can be very challenging. It has now become very clear that in many of these particle processing operations, the surface energy of the starting, intermediate or final products is a key factor in understanding the processing operation and or the final product performance. This review will consider the surface energy and surface energy heterogeneity of crystalline solids, methods for the measurement of surface energy, effects of milling on powder surface energy, adhesion and cohesion on powder mixtures, crystal habits and surface energy, surface energy and powder granulation processes, performance of DPI systems and finally crystallisation conditions and surface energy. This review will conclude that the importance of surface energy as a significant factor in understanding the performance of many particulate pharmaceutical products and processes has now been clearly established. It is still nevertheless, work in progress both in terms of development of methods and establishing the limits for when surface energy is the key variable of relevance.

An overview of powder granulometry on feedstock and part performance in the selective laser melting process

“…It would also be useful to study the surface free energy of powder particles associated with surface chemistry changes (E.g. moisture contamination) through techniques including the sessile drop method, Inverse gas chromatography (IGC) as well as Atomic force microscopy (AFM) [86]. The sessile drop method probes powder particle surfaces using a wetting liquid with known surface tension and derives surface free energy of the solid particle using Young's equation [87].…”

Interplay between Ethanol Adsorption to High-Energy Sites and Clustering on Graphene and Graphite Alters the Measured Isosteric Adsorption Enthalpies

“…The net-retention time of ethanol was therefore negligible in those measurements (see bottom panel of the Figure 1), leading to high uncertainty in the measured quantities. 23,24 We thus decided to discard the peaks with net-retention time lower than 3σ from further data fitting, where σ stands for the standard deviation of the methane Gaussian peak. In other words, we only kept the measurements where ethanol had a significant retention time.…”

A digital workflow from crystallographic structure to single crystal particle attributes for predicting the formulation properties of terbutaline sulfate

“…18 Accurate characterization of particle surface-energies can be challenging. [19][20][21] For example, sessile-drop contact angle measurements on the individual facets of macroscopic single-crystals and/or powder compacts via the capillary rise method have not always been found to provide reliable results. 22,23 Surface energy measurements from inverse gas chromatography (IGC) using both polar and apolar probes 17,[24][25][26][27] have, however, been found to be particularly useful in studies of the crystallinity, surface energy and surface properties of particles.…”