Abstract. In the present work, the effect of polymer and fibre properties on sintering and densification of a rotationally moulded part was investigated. Previous researchers have concluded that polymer characterisation is fundamental to achieve optimum processing of the polymer powder. Nevertheless, the presence of a disperse phase during sintering has a direct impact on the current understanding of how sintering and densification works. Lack of pressurisation during the process of rotational moulding implies an absence of driving forces to strongly bond two materials together as necessary in composite structures. This means that sintering and densification are the fundamental phases in which two or more materials can create an interface together by which stresses can be transmitted. The present work focuses on the characterisation of the continuous and dispersed composite phases and how their properties affect the mechanisms of sintering and densification. The fibre and matrix characterisation study comprise of scanning electron microscopy (SEM), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) among other techniques. Effect of polymer-fibre interaction during sintering and densification was investigated by a Fibre-Particle Interaction Test (FPIT), a variation of Wilhemly technique (PenTest) and a Densification Test (DT). Sintering results showed that fibre treatment has a fundamental effect in the polymer sintering and adhesion can be optimised by the treatment chemistry. Densification test demonstrates that, although air trapped within the polymer bed is intrinsic to the sintering-densification mechanism, fibre content can be optimised so that normal bubble appearance can be achieved. Finally, results showed that polymer-fibre characterisation plays a key role in sintering and densification and work is ongoing to present conclusions as to how sintering and densification affect the full-scale manufacturing process.