Polymer sintering plays a major role in processes such as rotational molding, governing the heating cycle and the properties of the final parts. There is evidence to suggest that the material molecular structure, molecular order and morphology are of importance in the sintering process. To date, however there has been no satisfactory explanation as for their role in polymer sintering. One objective of this work is to examine the sintering behavior of ethylene copolymers under conditions related to the rotational molding process and to determine the relative effects of the polymer molecular structure and morphology on the sintering process. Sintering experiments were conducted under isothermal and non-isothermal conditions using both powder and cylindrical particles. It was found that the trends observed for the sintering of powder were consistent with the predictions of Newtonian sintering models. Sintering results obtained using cylindrical particles, however showed significant differences not seen when using powder particles. These were attributed to the differences in the surface area between the two types of particles. It is speculated that the effect of material properties other than viscosity and elasticity are enhanced when cylindrical particles are used.