Document Abstract
ANTEC Papers: 2002
Powder Flow During Rotational Molding
James L. Throne, Sherwood Technologies, Inc., Dunedin FL 34698-3347
For about the first-third of the rotational molding heating cycle, the polymer free of the mold surface flows as a powder. Although it appears that the powder is cohesionless at room temperature, there is strong evidence that there is increasing cohesion during heating. This changes the nature of powder flow from avalanche to block flow with frictional or shear flow occurring between the mold surface and the powder layer against it. Stress analyses on the powder bed show that shear forces between powder particles and between the particles and the mold surface are linearly proportional to the normal force on the powder, and yield two fundamental powder properties, powder cohesiveness and particle-to-particle coefficient of friction. The parameters that affect these relationships and methods of measuring them are discussed.