Injection Molding

Injection molding involves heating resin (raw plastic material in the form of pellets) so it can flow under pressure. The molten resin is injected (pushed by a plunger or screw) into the mold, which consists of a core (male) and cavity (female) sections. Once the plastic cools in the mold, the mold opens and the part is ejected.

Polytainers uses a range of injection molding machines to manufacture both containers and lids. Machine capacities range from 200 to 600 Metric tons, which refers to the clamping pressure that the machines apply to the mold during the injection of resin.

Our process and molding research has led to continual refinements that include the types of resins we employ, the speed of the resin melt-flow, the introduction of anti-static additives to inhibit dust particles from attaching to containers on store shelves, and the conversion to high-density polypropylene to produce thinner, lighter and thereby more cost-effective packaging.

There are subtle advantages (and disadvantages) to using injection molding over thermoforming to create plastic containers. Polytainers closely examines the requirements of any container and our customer's objectives to select the most effective manufacturing method.

Some of our injection-molding processes include:

• Thermoplastic injection molding
• Hot runner injection molding
• Controlled part ejection (using swing chutes to remove parts from molds)
• Automatic part stacking