Executive Summary
The aim of the project is to establish a relationship between the product properties and feed material and the mill functions for milling of organic solids. The specific objectives are:
a) To characterise the physical, mechanical, and thermal properties of organic feed materials (material function) at the single particle level, and to examine the effects of temperature and humidity on these properties,
b) To investigate the breakage behaviour of single organic particles at quasi-static and dynamic conditions under the influences of temperature and humidity,
c) To investigate the bulk milling behaviour of model organic solids and mill hydrodynamics (mill function),
d) To characterise the properties of milled product, and to correlate the product properties to material and mill functions.
Model materials used in the work include aspirin, α-lactose monohydrate (α-LM), sucrose, sorbitol, starch, and microcrystalline cellulose (MCC). These materials cover a fairly wide range of physical, mechanical and thermal properties, hence ensuring generality of the results to be achieved. This report summarises the work done over the past three years, including the single particle breakage studies using the impact tester under both ambient and sub-ambient conditions, measurements of Young’s modulus, hardness and fracture toughness of single particles of some model materials using the nano-indentation method, characterisation of some product particles using the Dynamic Vapour Sortion (DVS), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD), analysis of the bulk milling behaviour of the model materials in a single ball simulating mill under both ambient and sub-ambient conditions, theoretical analysis of the mill dynamics, distinct element modelling of particle and milling ball motion to establish the mill function, investigation into the use of a flow aid (Aerosil) on the bulk milling, and population balance modelling of the milling of aspirin in collaboration with Du Pont. The main findings are summarised in the following: