Issue link: https://www.e-digitaleditions.com/i/1138630
Tablets & Capsules July 2019 37 A compaction emulator, also referred to as a compaction simulator, is a good technology for studying a material's deformation properties, because the machine mimics the manufacturing compaction process while collecting data that a standard, rotary tablet press does not. The Presster is a single-station machine in which the punches travel through cams and rollers as in a produc- tion-scale rotary tablet press, but in a linear fashion. The machine is instrumented to measure dosing height, upper and lower pre- and main compression force, ejection force, radial die-wall force, and take-off sticking force. The punch holders are equipped with linear displacement sensors allowing real-time punch position measurements during the compaction process. This enables users to study work curves, elastic recovery, Heckel plots for prod- uct yield pressure, and other characterizing data. Material deformation characteristics All solid materials change in shape and volume when subjected to mechanical forces. The force per unit area, or pressure, applied to the material is referred to as stress, and the material's relative change in geometry is referred to as strain. When upper and lower punches travel through the compression rollers of a tablet press, they apply a load to the tablet formulation, which repacks and deaerates the particles, resulting in a higher bulk density. With continued increased pressure, the particles will deform via one or more of the following mechanisms: Brittle fracture. With brittle fracture, the particle structure fails and breaks into two or more pieces. A com- monly used excipient that exhibits this behavior is dical- cium phosphate. Elastic deformation. Elastic deformation resembles the action of a spring. The applied stress causes a matching strain response, but when the stress is removed, the mate- rial immediately recovers and returns to its original shape. Pregelatinized starch and some active ingredients behave in this manner. Tablet manufacturing poses many challenges. It's common to develop what appears to be a robust formu- lation on an R&D tablet press but then find that the for- mulation performs poorly when transferred to produc- tion-scale equipment. This article discusses ways to improve the tableting scale-up process at the develop- ment stage where materials may be costly and difficult to come by. It is important to understand what developers and scientists need to research about a formulation for successful production. If the goal is to manufacture the product on a high-speed tablet press, you must under- stand the process dynamics at high speed and anticipate the production conditions during development. A material's deformation properties are key attributes to evaluate when developing a product for high-speed production. To study these properties in the lab, Natoli Scientific uses a Presster compaction emulator (Photo 1). Photo 1: A compaction emulator such as the Presster shown here mimics the manufacturing compaction process while collecting data that a standard, rotary tablet press does not. Figure 1 Heckel plots for four commonly used excipients 0.0 20.0 40.0 60.0 80.0 100.0 120.0 2 1.5 1 0.5 0 -Ln Porosity Emcocel 90M Compression pressure (MPa) yppl 98.8959 ypel 935.3803 0.0 20.0 40.0 60.0 80.0 100.0 120.0 2 1.5 1 0.5 0 -Ln Porosity Parteck M 200 Compression pressure (MPa) yppl 149.3521 ypel 1814.292 0.0 20.0 40.0 60.0 80.0 100.0 120.0 2 1.5 1 0.5 0 -Ln Porosity Starch 1500 Compression pressure (MPa) yppl 115.8658 ypel 760.7016 0.0 20.0 40.0 60.0 80.0 100.0 120.0 2 1.5 1 0.5 0 -Ln Porosity Emcompress Compression pressure (MPa) yppl 138.8195 ypel 1560.813