Release Agents for Rotational Molding

Q: How do I prevent warping?

Warping is often caused by pre-release, differential cooling rates, or venting issues. First, ensure the mold is venting properly. If pre-release occurs during the cycle, it may indicate excessive release agent application or using a release coating with too much slip. For thick-walled parts, investigate cooling both the inside and outside of the part to allow for even crystallization.

Q: How do I reduce buildup and stoppages for cleaning?

To prevent rapid mold dirtying, reapply release agents a cycle or two before parts become difficult to remove. Focus reapplication on difficult areas like legs, feet, or threads rather than the entire mold. Ensure semi-permanent coatings are fully cured and avoid overapplication, as both issues can lead to undue buildup on mold surfaces.

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Release agents and other process aids for rotomolding

Release agents for rotational molding, when properly selected and applied, can prevent prerelease, improve flow characteristics, and reduce or eliminate buildup. In short, the right release agent can give you more control over your process.

McLube® offers a full line of production-proven solvent-based and water-based release agents for rotational molding to suit any roto process. We also offer process aids for rotational molding, including flow promoters, mold cleaners, and specialty machine greases.

McLube® Technical Representatives have years of experience solving the most complex rotomolding challenges with programmed release technology and meticulously planned application methods. Contact McLube® today for process assistance and samples.

Supported Rotational Molding Materials

Our semi-permanent release agents for rotational molding are designed to work with a variety of thermoplastics.

Over 80% of the rotational molding industry uses one or more types of polyethylene (PE), also known as polythene, including:

Cross-linked polyethylene (PEX, XPE, XLPE),
Linear low-density polyethylene (LLDPE)
Low-density polyethylene (LDPE)
High-density polyethylene (HDPE).

We also offer rotomolding release agents for traditional PVC materials and newer materials to the rotomolding industry like Nylon 6, ECTFE, polycarbonate, and polypropylene.

Benefits of our Rotational Mold Release Agents

Controlled release of rotomolded parts
Custom slip characteristics (low, medium, high)
Tailored release and flow characteristics for complex parts
Preserve mold details
Protect expensive equipment from corrosion
Maintain product geometries
Chemically bond to the mold surface to prevent peeling, transfer, and flake-off
Durability and abrasion resistance for multiple releases per application
Easily diluted or delivered ready-to-spin
High temperature tolerance
Reduced need for touchup
Highly automatable with custom viscosities available

Featured Release Agents for Rotational Molding

Product	Base	Type	Description	Recommended for
McLube® 787	Water	Heat-cured	Semi-permanent with medium to low slip.	General rotomolding and flat-walled parts.
McLube® 841	Water	Heat-cured	Semi-permanent with medium to high slip.	All PE and PP, flanges and parting lines
McLube® 841X2	Water	Heat-cured	Semi-permanent w/ high slip. Versatile and dilutable.	All PE and PP
McLube® 916	Water	Heat-cured	Semi-permanent with low to medium slip.	Parts prone to pre-release, PP, PE
McLube® 973	Water	Heat-cured	Fast-cure, semi-permanent, dilutable	PE, PP, Nylon
McLube® 974	Water	Heat-cured	Faster cure with low slip.	Large parts prone to pre-release
McLube® 1039	Solvent	Fast drying	Highly durable, semi-permanent.	Cross-linked PE (XLPE), PP, Nylon
McLube® 1135X3	Water	Heat-cured	Semi-permanent and versatile	For most Roto processes
McLube® 3030	Water	Heat-cured	Semi-permanent with moderate slip.	All PE and PP

Other Process Aids for Rotational Molding

Product	Recommended for
McLube® Flow Promoters	Tailored to your material and process. Applied over release agents to ensure adequate resin flow to difficult areas.
McLube® MoS2 – 951A	Fortified, high-drop-point NLGI#2 machine grease. Apply to high wear areas up to 700F.
McLube® 1042B	A dilutable, water-based mold cleaner

* This is a list of featured products only. All McLube® products for rotomolding applications are not listed on this page. If you do not see the McLube® product you currently use listed above, this does not mean it has been discontinued. Contact Us to inquire about a product that is not listed above.

Common Issues Facing Rotomolders

Pre-Release and Warpage
McLube’s rotomolding release agents create a thin, even film along the mold wall delicate enough to mimic the substrate but durable enough to resist abrasion. We analyze the unique relationship that exists between every customer’s material and mold to provide a release agent that offers enough slip for effortless separation but not so much as to cause prerelease from the mold wall.

Surface Finish
The most important factor for excellent surface finish is the condition of the molding surface itself. McLube® release agents preserve mold details with thin, even coatings that compliment, but never diminish, the finest details. Our mold release technology also includes proprietary additives that help to protect your mold walls from corrosion, grime, and microscopic abrasions that lead to poorer surface finish over time and decrease the effective lifespan of rotational molds. Ask about our flow promoters to help prevent blemishes due to material starvation.

Color Swirl
“Swirling” is a result of excess static electricity buildup during rotational molding of dry, colored polymer resins. McLube’s line of rotational molding release agents reduce static buildup as resins wash over the mold surface during initial heating steps. Reduced static prevents particle separation, allowing for normal blending during the rotational molding process.

Is your rotomolding process experiencing pigmentation swirling?
Some rotational molders may simply be able to slow rotation during heating to prevent excess static. Contact McLube® and one of our experienced Technical Representatives will help you solve color consistency issues and, if necessary, seamlessly integrate our anti-static release agents into your existing process.

Optimizing the Release Agent for your Rotomolding Operation?

We are here to help from product selection to testing and ongoing support.

Rotomolding FAQs

How should release agents be applied to rotational molds?

Always start with a clean, dry mold. Release agents are best applied to rotational molds using a high-quality spray gun or automated system but can also be wiped on with a lint-free cotton cloth. When spraying on, select a nozzle that will ensure fine, atomized shots. Apply to preheated molds at 150°F (65°C) to facilitate drying, especially when using water-based release agents. Follow any cure instructions in the product’s TDS carefully and avoid overapplication.

Proper application of release agents is a crucial but often overlooked aspect of part quality and process efficiency

Consider taking the time to run a full “dry cycle” for optimal semi-permanent release agent curing. On a clean mold, apply the release agent to a heated tool according to the technical data sheet instructions, then close the mold and run it in the oven until peak internal temperature (PIAT) is reached (usually 300F-350F), and then remove after five to ten minutes. A dry cycle cure will ensure all of the release agent’s carrier is evaporated and the release agent is adequately cured. Taking a little extra time to properly apply mold release will keep molds running cleaner and longer and prevent part defects.

How do I prevent warping?

Warping refers to distortions of the part shape and can be caused by pre-release of the part from the mold wall, differential cooling rates, or venting issues. Warping is more common with flat part geometries. If warping occurs while the resin is laying down, then the cause is likely incorrect application of release agent or improper release agent selection.

Troubleshooting steps:

First, make sure your mold is venting properly and has enough vent area.
If the mold is venting correctly, then identify where and when in your process the warping/ pre-release is happening.
- If pre-release is happening during the molding cycle, it points to excessive application of mold release or using a release agent with too much slip.
- If the warping is happening during cooling and you have a thick-walled part, investigate cooling the inside and outside of the part to allow for even cooling (crystallization) of the polyethylene.
If the issue persists, contact us for process assistance.

How do I reduce buildup and stoppages for cleaning?

When parts start to get harder to release it is a sign that buildup is occurring on the mold. Rotomolders may push for a few more cycles at this point before reapplying release agents. This practice leads to dirtying of the mold surface more rapidly and more frequent cleaning. Consider reapplying release a cycle or two before that point to prevent buildup.

It may not be necessary to reapply to the entire mold. Focus first on legs, feet, threads, or other difficult areas.

Insufficient cure of semi-permanent release agents or overapplication of release agents can also lead to undue buildup of release on mold surfaces.