Powder Processing

Jim Throne on May 4th, 1999

Background Rotational molding focuses on the sinter-melting, densification and cooling of polymer, beginning with powder. Typically, polymer powder has a particle size range of -35 mesh to + 200 mesh. The powder is usually manually charged to the mold while the mold is in the open configuration in the servicing stage of the process cycle. […]

Continue reading about Powder Flow Characteristics

Jim Throne on September 9th, 1998

A Brief Review Rotational molding begins with -35 mesh polymer powder tumbling in a metal mold. It ends with a monolithic layer of solid polymer against the metal mold. In between, the powder tumbles against the mold until the mold temperature reaches the tack temperature of the powder, whereupon the powder begins to stick to […]

Continue reading about So… Where Does All the Air Go?

Jim Throne on September 1st, 1998

Thermoplastic structural foams have been around for several decades now. We all know that, at the same part weight, the stiffness of the structure increases in proportion to the reduction in plastic density. And that at the same part thickness, the weight decreases in proportion to that same reduction in plastic density. Injection molders and […]

Continue reading about Foaming in Rotational Molding I

Jim Throne on March 13th, 1998

In my Rotomolding Tech Minute I, I commented in general on model building for the heating and cooling process in rotational molding. And further, I remarked on the six technical papers presented at the 1997 SPE ANTEC that focused on this aspect of rotational molding. According to the 1998 SPE ANTEC advance program, there will […]

Continue reading about Boundaries on the Heating Process

Jim Throne on April 30th, 1997

Nine technical papers were presented on 29 April at the 1997 SPE ANTEC in Toronto. Six of the nine papers dealt with certain aspects of the rotational molding heating and cooling process. Nearly every one of these began with words of this type: Rotational molding is a simple process for making hollow plastic objects. Of course, […]

Continue reading about Some Observations on Model Building at 1997 SPE ANTEC