How Foam Expands

Tempo is a sophisticated popcorn popper. We control foam bead size and density with batch pre-expanders. We offer a variety of puff bead granulations and raw feedstocks to meet customer needs. Flame retardant and ESD grades of materials are available.

How Foam Expands

Expandable foams look like table sugar, small granules of white or dark resin. The resin is referred to as “beads” and it arrives in vapor sealed containers.

The raw material has a hydrocarbon blowing agent dissolved inside each bead. The natural blowing agent inside your everyday popcorn is water, and it works in a similar way. When heated, the blowing agent softens the bead, when boiling temperature is reached the blowing agent begins to gasify, causing the softened bead to expand.

The beads are first processed much like popcorn, in pre-expanding the beads to a desired size. By controlling the time and temperature of this "pre-expansion" process, the bead size can be controlled to achieve various performance characteristics of the final molded part.

After pre-expanding and ageing the beads, they are blown into an aluminum mold which is heated with steam, this bakes the beads so that they expand further until contained by the mold wall, further heating causes the beads to fuse together until they lose their individuality and become part of a solid mass of foam. If not provided enough heat, the result is poorly fused beads with a "crumbly" appearance, a condition often seen in the competing "wet molding" process.

Once the surface finish is optimized with the proper amount of heating, the mold temperature is reduced to stop the internal vapor pressure of the blowing agent inside the molded part. The mold is finally opened after the part stops expanding. The part is warm on removal from the mold and begins a shrinkage which is built into the mold design so your molded part “shrinks to fit.”