Predictive powder compaction models
Both roll and die compaction are cost-effective continuous manufacturing processes with low waste production. However, heat accumulation and subsequent degradation of heat-sensitive materials limit the application of compaction processes for manufacture of high value added products. EU-funded researchers on the THERMOPC (Thermomechanical modelling of powder compaction) project worked to develop innovative predictive models to represent the thermomechanical behaviour of heat-sensitive materials during powder compaction. They successfully developed a finite element method-based thermomechanical model for powder die compaction as well as roll compaction. Die punches of various shapes were then evaluated. Results revealed that punch shape, compression speed and die-wall friction significantly affect thermomechanical behaviour of powders during die compaction. Key factors that need to be controlled to reduce maximum temperature of the tablet include die-wall friction and compression speed. These findings have been published in two papers. For roll compaction, researchers investigated the effect of roll speed on temperature distribution in the material. They found that increasing the roll speed raised the temperature of the ribbon at the narrowest gap but decreased the density. Pharmaceutical powder formulations can undergo thermal degradation or crystallinity changes during compaction. As understanding such responses is critical, THERMOPC focused on experimentally studying the behaviour of different grades of microcrystalline cellulose powders during tableting. Test outcomes provided important information on how temperature changes depend on material properties, compression speed and tablet shape. A first, the THERMOPC study has developed predictive models to determine the thermal response of powders to process conditions during compaction. Such robust predictive models should prove invaluable for product development, particularly in the European particulate product manufacturing industries.
Keywords
Powder compaction, particulate products, heat-sensitive materials, thermomechanical, THERMOPC
