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Rotational Molding

process

A hollow plastic forming process where polymer powder is placed in a mold, heated while rotating on multiple axes, allowing material to coat mold walls and fuse into seamless parts.

In Simple Terms

Think of rotational molding like coating the inside of a rotating container with melted plastic. Polymer powder is put in a mold, then heated and spun around until the powder melts and sticks to all the mold surfaces, creating hollow products without seams or joints.

Why It Matters

Critical process knowledge for resin traders as it requires specific polymer grades with controlled particle size and melt flow properties. Understanding rotomolding helps traders match the right HDPE, LDPE, or specialty grades to customer applications and processing requirements.

Technical Details

Process involves loading polymer powder (typically 35-500 mesh) into a split mold, sealing, then heating to 200-350°C while rotating biaxially at 4-20 RPM. Material melts and adheres to mold walls through centrifugal force and gravity. Cooling while rotating prevents sagging and maintains uniform wall thickness of 3-25mm.

Real-World Examples

HDPE Grade Selection

A trader recommends rotomolding-grade HDPE with 3-5 MFI and controlled particle size distribution for water tank manufacturing, ensuring proper flow and surface quality.

Material Certification

Providing FDA-compliant rotomolding resins with certificates of analysis showing particle size, density, and melt flow properties for food-grade storage container production.

Color Matching Requirements

Supplying pre-colored LLDPE powder with UV stabilizers for outdoor playground equipment, matching customer color specifications and weatherability standards.

Related Terms