Rotational Moulding


Using rotational moulding to produce components can bring unique challenges. Common and costly problems include pinholes, abrasion marks and poor surface finish, resulting in excessive scrap rates and extended downtimes.

Numerous factors affect process efficiency and component quality, for example mould condition, thermoplastic resin flow patterns and finding the correct release agent for the process parameters deployed. Chem-Trend can bring you the benefit of their comprehensive experience to help optimise your rotational moulding – whether you are manufacturing children’s play equipment or fuel tanks.

Chem-Trend can assist you to improve your processes and overcome process issues such as interference from static charges and pigment swirls. At the same time, they can also help to minimise pre-release and enhance material flow using Mono-Coat® release agents and moulding process aids. Using the Chem-Trend® Flow Promoter augments these products, helping to optimise the final appearance of parts manufactured via rotational moulding.

Rotational Moulding Process Aids

A wide range of production issues can impact rotational moulding processes, including static electrical charge. Once removed from the mould, parts produced may also require additional work due to a surface finish which does not meet the specifications. Such problems can lead to increased scrap rates, reduced production efficiency, and more work.

Our moulding process aid range includes:

  • Anti-static coatings
  • Primers

Advantages for rotational molding:

Surface optimisation: when applied before each moulding operation, Mono-Coat® anti-static coating disperses electrical charge and solves pigment swirl issues.

Better gloss finish: Mono-Coat® primer imparts a high-gloss finish to components, meaning that flame-polishing is no longer required, or only to a limited extent.

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Mono-Coat® Mould Release Agents for Rotational Moulding

Rotational moulding processes often experience surface abrasion, discolouration and poor mould release. The correct mould release agent allows operational efficiency to be improved. Designed and produced specially for roto-moulding machines, the wide range of Chem-Trend solvent- and water-based semi-permanent mould release agents allow consistent release performance in all situations – even at elevated temperatures.

The Mono-Coat® release agents, which are safe and simple to use, are designed for use with a variety of polymers used within roto moulding processes, including PVC, HDPE, MDPE, LDPE, and LLDPE.

The Chem-Trend mould release range for roto-moulding covers:

  • Solvent-based mould release agents
  • Concentrated mould release agents
  • Semi-permanent mould release agents
  • Conventional mould release agents

Advantages for rotational moulding:

Less pre-release: with Mono-Coat® products components keep their intended geometry, since the agents are designed to enable plastics to contact the mould for a longer period, thereby minimising pre-release.

Better releasing around flanges and vent-tubes: Specially designed to allow correct plastic formation around flange and vent tubes, Mono-Coat® release agents give finished components an exceptionally smooth surface. By adding Chem-Trend Flow Promoter to the process, the flow of material to difficult areas can be improved.

Double-skin parts: The mould core can be removed more easily when using Mono-Coat® release agents.

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Flow Promoter for Rotational Moulding

Pinholes and other surface defects arising during the initial stages of the roto-moulding process can lead to components with a poor surface finish. Areas where such surface defects are present indicate that tumbling resins have not flowed correctly and were absent at critical points in the mould.

One way to address this typical problem is to use Chem-Trend Flow Promoter, specially formulated to enable the moulding resin to reach these problematic areas, making sure that the as-moulded surface of the component is smooth and free of blemishes. Although Flow Promoter is not a replacement for the release agent, it allows the appearance of finished components to be optimised.

Advantages for rotational moulding:

Optimum improvement of surfaces: enhanced coverage, no visible fouling or build-up on the mould.

Minimised pinholing and no blemishes: the Flow Promoter enables mould surfaces to be fully covered with powder, even in the most difficult areas. Forming is also highly reliable due to the reduced drying time.

Highly repeatable components: improved consistency with better thread moulding, enhanced insert encapsulation, complete edges and formation of letters.

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