Overview of Plastisol Dip Molding

Plastisol dip molding a process whereby a dipping mandrel is dipped into a liquid polymer, typically plastisol, to eventually create a solid form on the mandrel’s external surface.

The cost of molding by dipping is always low.

Most molds are very simple and inexpensive. Dip molding, if automated, is competitive with most other molding processes.

Dip molding has its origin in candle making.
After the second world war, vinyl plastisol came on the market for non-military use. Plastisol dippings immediately became the standard for tool handles, and it still is. Piper was founded in 1958 as a chemical company, supplying a range of coating materials to the rapidly growing plastic coating industry. Piper completed its first dip molding job in 1959.

Plastisol is a vinyl compound that is liquid at room temperature and will keep for years.
When heated, it fuses into standard vinyl, never to liquefy again. Our suppliers can compound plastisols that produce parts in almost any durometer (hardness), clarity and color, and resistance to electricity, chemicals, and weathering. Surface appearance can range from shiny to matte.

Plastisol can also meet many standards, including FDA food contact, Non-Toxic, USP Class VI, UL, MIL-P-20689, and A-A-59464A.

Dip Molding examples by Piper Plastics Corp.
Dip Molded Examples by Piper Plastics Corp.

Plastisol dip molding is a thermal process. Metal mandrels (or other materials that can withstand the process temperatures) are preheated, dipped, and then post-heated. During dipping, heat in the mold transfers to the plastisol and gels the surrounding material.

  • The hotter the mold and the longer the dip, the thicker the gelled coating.

During the post-heat (or “cure,”) the plastisol fuses. Naturally, temperatures and dipping profiles are critical in determining the amount of plastisol buildup on the part. It’s amazing to see the shapes of parts that can be made by dipping.

Since they are elastic, we can easily strip complex parts from the dipping molds.

The parts made by dip molding are precise. Plastisol follows the details of the mandrel exactly.

The inside of the dipped part is an exact negative of the mold. It even has the same surface texture (shiny or matte) that the mold has. The outside dimensions of the parts are surprisingly controllable. Piper can hold wall thickness to very close tolerances. Using precisely controlled ovens, dip speeds, dip times, and withdraw speeds, a range of wall thickness configurations is achievable.

Piper Plastics has designed, developed, and built custom dipping machinery that is computer-controlled, precise, and efficient.

  • Our proprietary oven technology utilizes high velocity forced air and PID control accurate to ±1°F at 450 degrees.
  • Our dipping profiles are infinitely adjustable with resolution and accuracy of .005” and 0.1”/minute in position and velocity.
  • Piper’s technology results in lower costs because of low reject rates, fast setup time, and fast cycle times associated with computer-controlled equipment.

Currently, Piper operates 19 centrally networked dipping systems in both industrial and cleanroom environments.

We operate our systems 24 hours per day and are always adding capacity.

Piper can also formulate its own plastisols. Therefore we are very responsive to special requirements of properties and colors.