The Use of Positron Emission Pa Rticle Tracking ( Pep T ) to 1 Study Milling of Roll - Compacted Microcystalline 2 Cellulose Ribbons 3

13 Milling is a critical process for controlling the properties of the granules produced by roll 14 compaction. In the current study, the positron emission particle tracking (PEPT) technique was 15 used to examine the milling kinematics of roll compacted ribbons at various milling speeds. 16 Microcrystalline cellulose (MCC, Avicel PH-102) was used as the model feed material and a 17 radioactive particle (tracer) was mixed with the MCC powder and roll-compacted to form sample 18 ribbons. They were then milled using an oscillating mill at various speeds and the kinematics of 19 the ribbons (trajectory, velocity, and occupancy) were quantitatively determined using PEPT. A 20 close examination of the PEPT data reveals that, for milling MCC PH-102 ribbons using the 21 oscillating mill considered in this study, the milling speed plays an important role: at low values, 22 the milling process is dominated by cooperative motion of the ribbons with the blade (i.e. the 23 speeds of the ribbons and the blade are similar, and the ribbons move along with the blade) and 24 the ribbons are milled primarily by abrasion; as the speed increases the ribbons undergo more 25 random motion involving collisions that results in an increase in ribbon breakage and hence an 26 increase in the milling efficiency. It is shown that the PEPT technique is a useful technique for 27 examining milling kinematics of roll compacted ribbons. 28 * Corresponding author. Tel: +44 1384 683506 Fax: +44 1384 686581. Email: [email protected]