Abstract
Granulation of natural rubber (NR) after breaking of blocks in an oval-type twinrotor mixer is analyzed based on the flow behavior of model materials in a parallel plate rheometer. The surface of NR sheet was coated with a film of styrene-butadiene rubber (SBR) to simulate the effect of a thin layer of melted NR. In the parallel plate rheometer, the NR sheet was granulated first in a ring region along the periphery on the surface in contact with SBR. The granulated region increased its thickness and finally filled the gap from one surface to the other of the rheometer. The inner radius of the ring depended on thickness of the film. The melt fracture zone in the parallel plate rheometer formed also a ring. Radii of the two types of rings were the same and so granulation of NR is related to the melt fracture of film. The result was used in the analysis of NR mixing in the mixer, and it was clarified that granulation of NR is originated from the melt fracture in a thin layer of NR melted by higher temperature on the inner surface of the mixing chamber.
