Rotomolding commonly uses a variety of commodity based thermoplastic materials. The most commonly used for the rotomolding process is Polyethylene (PE). PE is offered in a number of grades and classifications, such as Linear Low Density Polyethylene (LLDPE), Medium Density Polyethylene (MDPE), High Density Polyethylene (HDPE) and Cross Linked Polyethylene (XLPE). While other materials are offered for rotomolding, the selection is not as fast in comparison to other processes, such as injection molding or blow molding. Rotomolding requires that the materials be pulverized to a fine powder, typically around a 35 mesh. While some improvements have been discovered such as the ability to mold micropellets, a smaller version of a pelletized material, rotomolding is still limited in the arena of engineered resins. Some of the other materials available for rotational molding include Polypropylene, Nylons, PVC, Vinyls, Polycarbonate and some less other processed materials. Because of the requirements of powder or micropellets, many of these materials come at a premium due to processing requirements such as cryogenic grinding to get the materials reduced to powder form.
Raw materials for rotomolding vary tremendously across physical properties and their intended use for applications. Additives and colors can be blended into materials to achieve different colors or different characteristics and properties. Learn more about materials for rotomolding below!
To understand polyethyle for rotomolding, it is imperative to understand thermoplastic materials. Thermoplastics or thermosoftening plastics are a plastic material, a polymer, that becomes soft, pliable or moldable when the material is heated beyond a specific temperature. The material also hardens and solidifies upon cooling. The polymer chain of thermoplastic materials weaken rapidly when exposed to increased temperatures, turning the material into a thick, viscous liquid. Thermoplastics are more forgiving than thermosetting polymers, as thermoplastics may be reshaped by heating and are used by a number of plastics processes from rotomolding, injection molding and even compression molding. Thermosetting polymers function in an entirely different manner, by forming irreversible chemcia bonds during the curing process. Thermoset materials typically do not melt when heated, they generally decompose and will not reform when cooled.
A 2D example of a PE molecule chain
Polyethylene is a thermoplastic material that is a part of the polylefin family. PE is further broken down into groups according to its density as indicated in the following abbreviations: