A process for the production of virtually full density polyolefin suitable for further processing by drawing to form a high tenacity, highly oriented polyolefin sheet comprising: a) feeding a metered amount of polyolefin powder into the nip between two heated calender rolls initially set at a gap smaller than the size of the smallest polyolefin powder particle and at a temperature above the melting point of the powder; b) rolling the powder through the nip under these conditions until a coherent sheet of polyolefin is produced: and c) once a coherent sheet of polyolefin exits the nip lowering the temperature in the nip to a temperature below the melting point of the polyolefin powder and increasing the gap to a desired level above the thickness of the largest powder particle. Apparatus for the performance of such a process is also described.