CALORIMETRIC ANALYSIS OF POWDER COMPRESSION .1. DESIGN AND DEVELOPMENT OF A COMPRESSION CALORIMETER

The heat of compression and work of compression of three common pharmaceutical excipients (Avicel PH-101, anhydrous lactose, and Starch 1500) were determined using experimental instrumentation of original design. The heat of compression was independently determined using two different temperature sensors: a tungsten wire temperature sensor positioned within the powder sample and a two-thermistor system positioned behind thin metal plates in the lower surface of the upper punch. The effective heat capacity of the sample when contained within the punch and die apparatus was determined by a simultaneous heating and compression method. An energy correction method was used to account for system heat effects. Upper and lower punch force transducers and a displacement transducer were used to determine the work of compression. In the materials studied, exothermic powder compression subprocesses outweighed the endothermic subprocesses and an overall net exotherm was observed. The rank orders of the heats of compression determined from the in-sample and in-punch temperature sensors were in agreement. This instrumentation and approach, while still being developed, is proposed as a discriminating method to characterize and quantitate fundamental powder compression behavior.