Powder flowability is essential upon handling and during the various unit operations used in the manufacturing of pharmaceutical products. Surface interactions such as cohesive- adhesive contribution depend on the surface composition and particle morphology. The materials used in this study are from different processing conditions having their specific physicochemical properties and surface composition. Various analytical tools were used for having a fundamental insight of the influence that the surface forces have on powder flow. It was found that there were differences in magnitude and extend of the measurable flow by dynamic and static methods. The results obtained on the agglomeration strength suggest that particle properties, material composition as well as microenvironment moisture and shelf life storage (ageing) are responsible for flow performance. These suggests that surface energetics responsible for agglomeration, start with particle adhesivecohesive interactions, with neck formation due to capillary bridges (moisture presence) and /or to “sintering” (consequence of temperature, glass viscosity, Tg). All contribute to the anisotropic forces that lead to microstructural evolution on the surface of particles that in turn affect powder flowability. The insights of this study at the nano-, micro- and macro-levels will show the relationship between surface anisotropic interactions and flowability of powders that ultimately will help to control and manipulate powder flow
Teresa Carvajal is a faculty member of the Agricultural and BiologicalEngineering department at Purdue University. Dr. Carvajal’s research focuses on surface science to assess issues and behavior of powders as a result of the inherent solid state structural, physicochemical, particle surface (interactions e.g. adhesion/cohesion and electrostatics) and mechanical properties. The effects of these properties on powder agglomeration, dispersion and flow could be detrimental on the final pharmaceuticalproduct. Her research interests are on probing surface and bulk properties at the microscopic level to be able to manipulate their characteristics at the macroscopic level and get involved in strategies for controlling behavior of powders. Her experimental approach is to use various techniques thermal, spectroscopic and surface characterization to interrogate materials. Her work on fundamental understanding of the systems extends to design, control and choose appropriate materials for formulation development of powders for inhalation and beverage. Prior to joining Purdue University, Dr. Carvajal worked in the pharmaceutical industry for 13 years. She worked at Hoffmann-LaRoche (Nutley, NJ) in the area of oral dosage form development. Working on the behavior of powders and powder blends, her activities expanded to research and development of formulations for pulmonary delivery of small molecules and peptides. She later joined Bayer Pharmaceuticals (West Haven, CT) where she was responsible for pre-formulation activities as well as early formulation development for lead compounds of drug discovery. She has been an invited and keynote speaker at various national and international conferences. Dr. Carvajal gives short courses to industry on a various topics in Powder Technology to the USA, Europe and Latin America.