Powder injection moulding (PIM) is an important and accepted industrial technique for net shaping of precision components which can have a rather complex geometry. In order to meet the imposed, often rather strict, requirements with regard to dimensional accuracy, it is important to have an adequate knowledge and control of the rheological behaviour and the related processing properties of the powder/polymer melt (feedstock). Such a knowledge is furthermore of crucial importance in numerical simulations of the PIM-process. In the present work, a model system, consisting of steel powder, poly(ethylene glycol) and wax, is used in order to illustrate how the viscometric properties as well as thermal properties, such as the conductivity and the specific heat, of the system can be related to the corresponding properties of the polymeric binder system. In a similar way, the pvT (pressure-volume-temperature)-behaviour of the model system is analysed and discussed. The pvT-behaviour, which has not been extensively reported on for PIM-feedstocks, is considered to be of significant relevance for controlling the outcome of the injection moulding process.