Capping Mechanisms during Pharmaceutical Powder Compaction
Wednesday, 26 April 2006 - 2:40 PM197f
Capping Mechanisms during Pharmaceutical Powder Compaction
Chuan-Yu Wu, Department of Chemical Engineering, Formulation Engineering Research Centre, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom
Pharmaceutical tablets are the most popular dosage form for drug delivery. The tablets are generally produced by compacting dry powders. During pharmaceutical powder compaction, the tablets produced need to sustain their integrity during the process and have to be strong enough to sustain any possible load experienced during the post-compaction processes, such as coating, packing and handling. Hence, any defects, such as chipping, capping and laminating, are not tolerable during pharmaceutical powder compaction. However, such defects are common problems during the tabletting process. Therefore, understanding the failure mechanisms of these defects has attracted considerable attention.
In this paper, only the mechanisms of capping were considered. Previous studies on capping during pharmaceutical powder compaction have been reviewed. capping mechanisms have been further explored by conducting a combined experimental and computational study on pharmaceutical powder compaction. An instrumented hydraulic press (also known as compaction simulator) has been used to investigate the powder behaviour during the compaction. In addition, an instrumented die has also been used, which enable the material properties to be extracted for some real pharmaceutical powders. Close attentions have been paid to the occurrence of capping during tabletting. An X-ray Computed Microtomography system has also used to examine the internal failure patterns of the tablets produced using the compactions simulator. Furthermore, pharmaceutical powder compaction has also been analysed using finite element (FE) methods, in which the powder was modelled as an elastic-plastic continuum medium following Drucker-Prager-Cap yield criteria and the material properties were determined from the uniaxial compaction with an instrumented die. In both experimental and numerical studies, cylindrical tablets with different surface curvatures, including Flat-face round tablets and convex tablets, were considered.
From the experimental observation, it is clear that different capping patterns were obtained for different shaped tablets: cone-shaped capping for flat-faced tablets and normal capping with essentially horizontal failure surface for convex tablets. It was also observed in the experiments that capping takes place at the early stage of decompression (unloading), i.e., the top punch begins to withdraw. Close examination of FEA results reveals that the capping is associated with an intensive shear band developed at the early stage of unloading for all cases considered. Therefore, the combined experimental and numerical studies demonstrated that the intensive shear bands developed at the early stage of unloading are responsible for the occurrence of capping.
See more of #197 - Compaction and Sintering (TWC16)See more of Topical W: Fifth World Congress on Particle TechnologySee more of The 2006 Spring National Meeting
Wednesday, August 29, 2007
Freeze Dryer Characterization using Water Sublimation Tests and Applications for Lyocycle Scale-Up
Conference Module
Description:
Purpose: To compare lab, pilot, and production-scale freeze dryers using water sublimation tests. Sublimation tests will be used to (i) identify shelf to shelf variation and map the lyophilizer with respect to sublimation rate (ii) evaluate the maximum sublimation rate attainable without overloading the freeze dryer (iii) calculate the vial heat transfer coefficient for various locations in the freeze dryer.
Methods: Using Water for Injection (WFI), the sublimation rate, determined gravimetrically, was evaluated for lab, pilot, and production-scale freeze dryers. Steady-state heat and mass transfer relationships relevant to freeze drying were used to calculate the heat transfer coefficients and overloading conditions for each freeze dryer evaluated. The heat transfer coefficient was used to model primary drying using PassageÒ Freeze Drying software.
Results: The sublimation tests in trays demonstrated that failure of the freeze dryer (e.g. loss of pressure control) might occur if the sublimation rate exceeds the thermal load capacity. The sublimation tests also demonstrated that the sublimation rate in vials increased towards the rear of the freeze drying chamber (closest to the pipe separating chamber and condenser) and typically the lowest sublimation rates were observed on the middle shelf, indication of the “coldest zone” of the lyophilizer. The heat transfer coefficient for various locations on a shelf is also dependent on the scale of the freeze dryer. For example the heat transfer coefficient for center vials in a pilot-scale freeze dryer was approximately half of the heat transfer coefficient calculated for center vials in a lab-scale freeze dryer. The PassageÒ Freeze Drying software predicted relative drying times that were consistent with experimental data for sublimation endpoint for various size lyophilizers.
Conclusion: Data acquired from water sublimation tests can be used to ensure the freeze dryer can sustain a thermal load for specified lyocycle conditions. Sublimation test data is also used to determine hot/cold zones in the lyophilizer that should be identified as areas interest for post-lyophilization testing such as water content and reconstitution time. Sublimation test data can be also be used to compare equivalence of various capacity dryers and the PassageÒ Freeze Drying software can be used to predict the endpoint of ice sublimation which is extremely valuable for lyocycle scale-up.
Description:
Purpose: To compare lab, pilot, and production-scale freeze dryers using water sublimation tests. Sublimation tests will be used to (i) identify shelf to shelf variation and map the lyophilizer with respect to sublimation rate (ii) evaluate the maximum sublimation rate attainable without overloading the freeze dryer (iii) calculate the vial heat transfer coefficient for various locations in the freeze dryer.
Methods: Using Water for Injection (WFI), the sublimation rate, determined gravimetrically, was evaluated for lab, pilot, and production-scale freeze dryers. Steady-state heat and mass transfer relationships relevant to freeze drying were used to calculate the heat transfer coefficients and overloading conditions for each freeze dryer evaluated. The heat transfer coefficient was used to model primary drying using PassageÒ Freeze Drying software.
Results: The sublimation tests in trays demonstrated that failure of the freeze dryer (e.g. loss of pressure control) might occur if the sublimation rate exceeds the thermal load capacity. The sublimation tests also demonstrated that the sublimation rate in vials increased towards the rear of the freeze drying chamber (closest to the pipe separating chamber and condenser) and typically the lowest sublimation rates were observed on the middle shelf, indication of the “coldest zone” of the lyophilizer. The heat transfer coefficient for various locations on a shelf is also dependent on the scale of the freeze dryer. For example the heat transfer coefficient for center vials in a pilot-scale freeze dryer was approximately half of the heat transfer coefficient calculated for center vials in a lab-scale freeze dryer. The PassageÒ Freeze Drying software predicted relative drying times that were consistent with experimental data for sublimation endpoint for various size lyophilizers.
Conclusion: Data acquired from water sublimation tests can be used to ensure the freeze dryer can sustain a thermal load for specified lyocycle conditions. Sublimation test data is also used to determine hot/cold zones in the lyophilizer that should be identified as areas interest for post-lyophilization testing such as water content and reconstitution time. Sublimation test data can be also be used to compare equivalence of various capacity dryers and the PassageÒ Freeze Drying software can be used to predict the endpoint of ice sublimation which is extremely valuable for lyocycle scale-up.
Friday, August 24, 2007
Casting Simulation Software
Casting Simulation Software - Engineering Services - PASSAGE®/PowerCAST by Technalysis
Benefits
Better understanding of process parameters, cold shuts, porosity, and misruns
Ability to improve casting by design changes of mold geometry, gating, risering, chills, paddings
perform filling and solidification analyses and graphically visualize results and model conditions.
Better castings, faster results and less costly than experimental methods
Powerful design tool coupling with foundry engineer's experience
Some Application Areas
Sand castings
Permanent mold castings
Die castings
Lost foam casting
Automotive parts
Appliances
more on Passage/PowerCAST and CFD consulting services by Technalysis
Benefits
Better understanding of process parameters, cold shuts, porosity, and misruns
Ability to improve casting by design changes of mold geometry, gating, risering, chills, paddings
perform filling and solidification analyses and graphically visualize results and model conditions.
Better castings, faster results and less costly than experimental methods
Powerful design tool coupling with foundry engineer's experience
Some Application Areas
Sand castings
Permanent mold castings
Die castings
Lost foam casting
Automotive parts
Appliances
more on Passage/PowerCAST and CFD consulting services by Technalysis
Process and Analytical Technology (PAT) Initiative
Process and Analytical Technology (PAT) Initiative
CFD Process Modeling Software and Consulting for Pharmaceutical and Chemical Industry
Computer-aided Engineering (CAE) in process modeling and equipment design has become an important factor for Pharmaceutical applications and Process Analytical Technology (PAT).
CAE complements existing testing methods by reducing costs and improving quality. CAE can also be used for scale-up studies.
Since 1985, Technalysis has been providing CAE engineering services and software and accumulated considerable experience using CAE for Pharmaceutical, Chemical and Food process modeling and equipment design.
Technalysis' CFD consulting and Passage® Software can be used within wide range of application areas such as:
Processes
Chromatography
Particle flows
Filtration - Micro and Ultra filtration
Mixing - Bin mixer, bladed mixer, stirrer, V-Mixer and ribbon mixer
Agitation - Vibro-mixer, vial plunger blade, stirred tank reactor
Fermentation - Tank design, perfusion tube, jacketed reactor
Drying - Freeze drying, spray drying, vacuum shelf drying, tray and fluidized bed drying
System analysis - Flow fume collection systems, purified water distribution, filling line
Flow with particle tracking
Barrier technology - Room flow, hood and box flow
Cleanroom design
High speed filing
Drug delivery devices
Melting and freezing phase changes
Passage Software can be used with many other applications or can be customized for specific need.
CFD Process Modeling Software and Consulting for Pharmaceutical and Chemical Industry
Computer-aided Engineering (CAE) in process modeling and equipment design has become an important factor for Pharmaceutical applications and Process Analytical Technology (PAT).
CAE complements existing testing methods by reducing costs and improving quality. CAE can also be used for scale-up studies.
Since 1985, Technalysis has been providing CAE engineering services and software and accumulated considerable experience using CAE for Pharmaceutical, Chemical and Food process modeling and equipment design.
Technalysis' CFD consulting and Passage® Software can be used within wide range of application areas such as:
Processes
Chromatography
Particle flows
Filtration - Micro and Ultra filtration
Mixing - Bin mixer, bladed mixer, stirrer, V-Mixer and ribbon mixer
Agitation - Vibro-mixer, vial plunger blade, stirred tank reactor
Fermentation - Tank design, perfusion tube, jacketed reactor
Drying - Freeze drying, spray drying, vacuum shelf drying, tray and fluidized bed drying
System analysis - Flow fume collection systems, purified water distribution, filling line
Flow with particle tracking
Barrier technology - Room flow, hood and box flow
Cleanroom design
High speed filing
Drug delivery devices
Melting and freezing phase changes
Passage Software can be used with many other applications or can be customized for specific need.
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