Rotational molding, also known as rotomolding, is a popular plastic processing method that has been in use for many decades. It involves pouring plastic powder into a mold, which is then heated and rotated until the powder melts and builds up to the desired thickness. The mold is then cooled and opened to remove the finished part. California Plastics now offers rotomolding as a new service.
Compared to other plastic processing methods, rotomolding has several advantages. Firstly, mold and tooling costs are low, making it a cost-effective option for small volume or short production runs. Additionally, it is able to produce very large and hollow parts, and is a low-pressure process that results in parts that are virtually stress-free. There is also little to no resin waste or scrap generated during the process.
Rotomolded parts can be found in a variety of industries and markets, with applications ranging from kayaks to traffic barriers to large storage tanks. Although polyethylene is the most commonly used resin for rotomolding, other resins such as polypropylene, nylon, acetal, and polyester are also used.
Customers will have access to this versatile and cost-effective plastic processing method. Whether producing small or large parts, rotomolding can be a great option for those looking for high-quality and low-waste production.
Rotomolded parts can be found in virtually every industry and market. Common rotomolded applications include:
- Playground Equipment
- Traffic Barriers
- Large Trash Cans
- Tote Bins
- Storage Tanks
- Portable Outhouses
Choosing the Right Resin
The selection of the base resin is a crucial step in the rotational molding process, as it serves as the foundation and must be chosen based on the specific performance requirements of the application. Several factors should be considered when selecting the resin, including strength, rigidity or flexibility, temperature resistance, intended use (indoor or outdoor), color, and any special requirements.
Polyethylene is the most commonly used material in rotational molding, but other resins such as polypropylene, polycarbonate, nylon, acetal, and polyesters are also utilized. While a few other plastic resins have been used in rotational molding, their use is limited.
Because of the longer cycle times involved in rotational molding, resins used in the process typically contain additional antioxidants and UV stabilizers to ensure longevity and durability in outdoor applications. Polyethylene, in particular, is an excellent choice for rotational molding due to its melting characteristics and heat stability, which allows it to withstand the high temperatures and prolonged heating cycles of the process. Parts produced from polyethylene possess exceptional strength, toughness, and other mechanical properties, making it a highly desirable material for a wide range of applications.
Polyethylene is available in several types depending on the desired end properties needed:
- Low Density Polyethylene (LDPE): Tough and flexible
- Medium Density Polyethylene (MDPE): Better properties than LDPE, but not as high as HDPE
- High Density Polyethylene (HDPE): Highest mechanical properties and chemical resistance
- Polyolefin Elastomer (POE): These are high flexibility, high impact polyethylene elastomers
- Cross-Linkable Polyethylene (XLPE): Contains a crosslinking agent that reacts during molding and provides a product with higher thermal and chemical resistance and environmental stress crack resistance