Comminution of polymers - An example of product engineering

Investigations into the processes of grinding and classification are presen ted. It is shown how the properties of filled polymer products like powder coatings or toner can be tailored through grinding and classification. A sy stematic approach to describe the process by a machine and a material funct ion is introduced. Single particle comminution tests allow the determinatio n of the material function. The breakage probability curves of different or ganic and inorganic materials can be transferred to one single master curve . The transfer of single particle tests to production mills seems to be pos sible, at least for the given example that of powder coatings. This compari son shows that the width of the final size distribution is determined in th is example by the material function and not by the operation of the mill. S ignificant improvements were achieved for both powder quality, i.e. the amo unt of fines below 10 mum, and the yield by employing two new classifiers f or the removal of fines. The classifiers were operated inline, directly aft er a classifying mill.