The majority of rotational moulding polymers are thermoplastic. Thermoplastic materials have the characteristic that they can undergo a continual cycle of heating to soften and cool to solidify just like candle wax. The added benefit is that these materials maybe recycled.

Other materials have thermosetting characteristic such as cross linked polyethylene, once moulded these materials undergo an irreversible change. The primary requirements are that it should flow to coat the cavity evenly as the mould is rotated and secondly, its thermal characteristics should provide stability during the heating and cooling stages of the process.

The most commonly used material is polyethylene accounting for 80-90% of consumption depending upon who you talk to! LLDPE or linear low density polyethylene may be used for tanks, pots, containers, street furniture and playground equipment and most grades are available with a UV stabiliser additive.

The higher density HDPE provides additional rigidity and there is a cross-linking polyethylene which is suitable for low temperature applications, components requiring maximum toughness or higher weather resistance.