PHAR2823 Lecture Notes - Lecture 5: Van Der Waals Force, Opposing Force
Document Summary
Van der waals force, electrostatic force, capillary force, frictional force. Driving force can be there but resistance force stopping it from flowing. (below 50um) As weight increases flow increases because driving force overcomes resistance force. Effect of fine particles: glidant reduces resitance force and improves flow. Increase amount of fine particles, increase flow but to a threshold only. Fine particles fill the void between normal particles, increasing the bulk density thus improving flow. When all the void is over filled and coating in excess, a lot of resistance force accumulates. *** learn how to calculate powder flow rate *** Expensive excipients are required (e. g. spray dried lactose) Simplest, fewer processing steps, less variables (faster production time) Does not require solvent or heat (reduce risk of instability of api. Lubrication is added to the same vessel as powder mixing (reduce loss during transfer)
