Knowledge Base

Knowledge Base

Choosing Between Semi-Permanent and Sacrificial Mold Release Agents

May 7, 2020, 17:53 PM

Worker removing rubber part from a moldIt’s a fact. For molders within the specific industries we serve here at Stoner Molding Solutions, the priority is typically getting as many releases as possible out of every release agent application for less downtime and less waste.

Notably, this means that many of our valued customers today tend to prefer semi-permanent mold release agents versus conventional sacrificial mold release coatings, especially as formulation advancements have been made. Of course, there are still molding operations in which sacrificial mold release coatings make sense—perhaps most significantly in composites molding.

This Knowledge Base article gives a bit of background into sacrificial mold release agents and insight for when those still might be preferable. We’ll also introduce a few semi-permanent mold release agents, including an example from our TraSys® system that our customers rave about.

What are Sacrificial Mold Release Agents?

Back in the earliest days of molding operations, sacrificial release agents were the only category available, which is why they’re referred to as “conventional” mold release agents. Paste waxes were the first mold releases, and a few other types—including polyvinyl alcohol (PVA), silicone oils, and more—joined the category later. It should be noted here that paste waxes are still quite popular, like our Honey Wax® and Miracle Gloss® products. In fact, Honey Wax Liquid applies rapidly and also cleans the mold.

The main point to know about sacrificial coatings is that while they get applied directly to the mold itself, they do not bond to its surface. As the newly molded part is removed from the mold, these release coatings transfer from the mold to the surface of the part.

At this stage in the process, the release agent has been “sacrificed” and must be reapplied to the mold before the next molding cycle can begin.

When Might Sacrificial Release Agents Still Be Preferred?

As mentioned above, sacrificial release agents are particularly useful in molding operations in the composites industry. Some plastics and rubber part manufacturers may also find sacrificial coatings work best for their individual needs depending on the products they mold.

Often, when manufacturers are in the business of fabricating massive, one, or few-of-a-kind parts or components—like boat hulls—sacrificial coatings are a cost-effective solution. Wax release agents especially can also improve an imperfect mold’s surface by filling in small pits or flaws, so those imperfections do not transfer to the molded part.

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Additional Sacrificial Release Agent Advantages to Consider

       Relatively low cost
       Little training needed by the applicator
       Visual cues as to proper coverage (hazing)
       Gloss enhancement
       Thickness of dried film resists abrasion (can be walked on)
       Consistently reliable and repeatable
       Can often obtain more than one pull
       Can be applied in a wide range of temperatures (cold to hot)
       Generally DO NOT contribute to Gel Coat Pre Release
       Excellent for rough surfaces, cracked gel coats

Sacrificial Release Agent Drawbacks

Problems with sacrificial coatings arise in many other molding operations. For instance, in some rubber molding processes, sacrificial release agents tend to inhibit proper bonding when rubber-to-rubber bonds or rubber-to-metal bonding are desired during the curing stage, resulting in defects.

Using sacrificial mold release agents in high-volume parts manufacturing also results in a lot of downtime for the reapplication of coatings to molds. It often adds a need for cleaning parts after they’ve been molded, too.

Additionally, consider the following disadvantages of sacrificial release agents:

       Wax will build up over repeated molding cycles requiring stripping (unless Honey Wax Liquid is used)
       Generally not recommended for post-cure applications above 100° C
       Can transfer to a finished part, potentially causing post-painting issues
       Paste wax will build up in non-skid areas

Why Choose Semi-Permanent Mold Releases?

Unlike sacrificial release agents, semi-permanent mold releases bond to the mold surface itself instead of the part. The main advantage of this property is that many molding cycles can take place before the release agent must be reapplied.

It is important to note that over-application of semi-permanent mold releases is always possible, especially when molders are working with the coatings in a non-aerosol format and have not been adequately trained in application techniques.

When semi-permanent release agents are properly applied as a thin film, they will not transfer to parts. This means that they will not interfere with secondary adhesive bonds—a noted problem with sacrificial coatings in some processes—or application of paint or other coatings post-mold.

Additional Semi-Permanent Release Agent Advantages to Consider

       Able to achieve many (4-30+) molding cycles before a reapplication is required
       Very fast to apply, can be wiped or sprayed on
       Provides good gloss
       Handles molding temperatures from RT to 400° C
       Formulas can be tailored for gloss, slip, and resin chemistry

But What About Safety Concerns with Semi-Permanent Mold Releases?

Once upon a time, semi-permanent release agents were solvent-based, which did make some molding operations a bit wary of their use. However, changing environmental regulations and a growing global concern over the use of solvents has led solutions manufacturers like us here at Stoner to formulate many water-based semi-permanent mold release options.

At Stoner Molding Solutions, we have a wide range of water-based semi-permanent mold releases available, including our TraSys 3000 mold release coating, which is an excellent release agent for molded rubber, molded fluoropolymer, molded plastic, epoxy, and plastic laminates. Check out our case study document on how TraSys 3000 is ideal in the manufacture of tires, O-rings, and seals.

You may also be interested in our best-selling TraSys 9825 product—documented in this case study—or TraSys 818, which is excellent for hot mold applications in rubber, fluoropolymer, plastic, epoxy, and plastic laminates.

Not sure whether water-based releases are right for your process? We are always happy to work with customers to find the best mold release agents for their unique molding operation. And, if we don’t already have a solution, our chemists can work with you to formulate new solutions, too!

Are There Any Other Disadvantages of Semi-Permanent Mold Releases?

In short, yes. Cost is one disadvantage, as semi-permanent release agents are significantly higher in price than sacrificial release agents. You’ll also want to weigh these factors of semi-permanent options against your needs as you think about your release agent choice:

       Prone to spillage, contamination, and waste during application
       Requires testing and a learning curve
       Requires significantly more skill to apply
       No visual indicator of application
       Very poor abrasion resistance, easily scratched off mold during part de-molding
       A complete stripping of the mold is usually required when switching formulas

Stoner Can Help You Choose the Best Mold Release Agents for Your Operations

In the end, there is never one best mold release for any given material or manufacturing process. Working with an experienced molding solutions producer to determine which release agent and other molding systems are best for your unique operation is a must-do to optimize your ROI.

Ready to get started on the road to better results from your molding processes? Contact our experts today for expert guidance and advice!

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Unlike many mold release brands, Stoner Molding Solutions formulates, manufactures, and distributes our own products. Check out our full line of mold releases, sealers, cleaners, rust preventives, and lubricants. In stock products are ready to ship now!

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