Mold release agent treatment with Chemlease release agent
Note! This instruction applies only to Chemlease release agents - not to waxes or similar products.
The release capability of Chemlease release agents is based on a thin polymer film formed on the mold surface. These release agents are known as semi-permanent release agents. The film cures through exposure to moisture in the air. The effectiveness of such an extremely thin polymer release agent relies on its strong adhesion to the mold surface. Once cured, the outer surface of the polymer film is suitably slick: it holds the manufactured part firmly during curing but allows the part to release from the mold with minimal force afterward. It is essential that the film is intact and fully cured—the thinner the applied layer, the faster and more reliably it cures. Release effectiveness is ensured by repeating the treatment multiple times so that a uniform film forms everywhere. With proper release agent treatment, countless releases can be made from the mold.
For handling composite molds, the manufacturer recommends:
- Mold Cleaner EZ solvent for mold cleaning. This solvent remains and acts longer on the mold surface than, for example, acetone, so it cleans the mold better.
- Chemlease 15 Sealer – a pore sealer for mold sealing. The pore sealer improves release effectiveness by smoothing out small pores and the “roughness” on the mold surface. Although these irregularities are microscopic, they affect the release result.
- The choice of Chemlease release agent depends on the manufacturing technique, the product being produced, and possibly other requirements, such as the mold surface gloss or slipperiness.
In all treatments, it is recommended to use 100% cotton, washed cotton cloths (Chemtrend cleaning cloth). If clean cotton fabric is not available, it is better to use clean paper towels than recycled mixed cotton fabric. For polyester resin lamination, Chemlease 75 or Chemlease PMR release agents are suitable. For epoxy manufacturing, Chemlease PMR MS release agent is recommended. Both are available in smaller containers. Additionally, there is a wide range of Chemlease products available for industrial use (Zyvax Composite Shield, Flex-Z, Chemlease PMR HS, PMR LS, 41-90, Zyvax Watershield, etc.), but these are only available in larger containers.
Recommended handling for a composite mold used to produce composite products (using polyester, vinyl ester, or epoxy resin - short basic guideline):
1. Clean the mold thoroughly with Mold Cleaner EZ solvent
2. Treat 1–2 times with Chemlease 15 Sealer (apply and let dry). Wait at least 15–30 minutes between applications. After the second treatment, wait at least 1 hour
3. Treat 4–5 times with Chemlease release agent (apply and let dry). Wait at least 15–30 minutes between layers. After the final treatment, wait 1 hour before starting production of the part
Before you start, make sure you have the following supplies: clean cloth made of 100% cotton, a clock, eye and respiratory protection, skin and protective gloves.
The mold and its cleaning
Important! If the mold is made of fiber-reinforced plastic, you must ensure that it is fully cured before starting the release agent treatment. In fresh (poorly cured) mold laminate, free styrene easily reacts with the polyester resin of the composite part. This creates a chemical bond, meaning the mold and the product become “one piece,” and the part adheres firmly to the mold. The thin polymer layer of the release agent cannot separate chemically active molecules from each other.
Once the mold is fully cured, the release treatment can be started. Cleaning the mold surface before applying the release agent is essential. A poorly cleaned surface (dirty, greasy, styrene residues on the surface) prevents the release agent from bonding to the mold surface.
For cleaning, Chemlease Mold Cleaner EZ mold cleaning solvent is recommended. Mold Cleaner EZ remains and acts on the mold surface longer than, for example, acetone, so it cleans the mold more effectively. Cleaning is performed with a cotton cloth moistened with the solvent. Cleaning is repeated as many times as needed to remove all grease and other impurities.
When refurbishing an old mold, mechanical polishing before solvent cleaning may be necessary. This is especially important if some polymer release agent (semi-permanent) has previously been used on the mold surface.
Release agent treatment – apply and dry (wipe on/wipe off)
1. Using a well-moistened (not dripping wet) cotton cloth, apply the Chemlease 15 pore sealer to one mold area at a time (0.5 x 0.5 m) with continuous strokes from the outside toward the center, so that the entire area is covered with an evenly wet layer
- After a short drying period (the surface gets some light color), the treated area is wiped with a clean dry cotton cloth in continuous motions until glossy.
- Wait at least 15–30 minutes for the layer to cure until the pore sealer film has hardened
2. Apply the second layer in the same way as the first layer and lightly wipe it with a clean dry cotton cloth.
3. Before the actual release agent treatment, wait at least 1 hour.
4. Apply the first layer of Chemlease release agent with a wet cotton cloth to one mold section (0.5 x 0.5 m) at a time.
- Wait for a short time as instructed (a few tens of seconds) until the release agent layer begins to dry starting from the edges, and then lightly wipe the surface clean with a clean dry cotton cloth so that an even glossy surface remains. Take care not to rub the surface too hard.
- Wait at least 15–30 minutes for the layer to cure.
5. Apply the second and subsequent layers of release agent in the same way as the first layer and lightly wipe dry with a clean cotton cloth.
6. Allow the mold release agent to cure for at least one hour before starting part production (be sure to also read the instructions for release agent treatment in winter conditions).
The necessity of sealing the mold
The pore sealer (Chemlease 15 Sealer) forms a tight film on the mold surface and seals any pores or surface roughness. One of its purposes is to prevent gases or solvents from moving between the part and the mold during production in a way that would change the release properties.
Sealing is especially important if the mold is visibly porous or rough. The sealer acts as a base for the actual release agent film.
The pore sealer treatment only needs to be renewed if the mold undergoes full maintenance and cleaning. This is usually necessary only after producing several dozen parts.
Verifying the effectiveness of the release agent treatment
Tape test: The result of the release agent treatment can be tested with the so-called tape test, in which masking tape is pulled off the treated surface at a 90-degree angle – the tape must release clearly more easily than in a test performed on a clean, untreated surface (the tape test should not be done on an unfinished treatment).
In the same way, you can test whether the release agent has properly bonded to the surface. If the release agent film has not cured, the release agent will stick to the tape – and the tape will no longer adhere to any surface. If this phenomenon is observed, it is possible that the initial cleaning of the mold was not thorough or that some of the release agent layers did not cure. As a result, the release agent will not remain on the mold surface, and even slight mechanical abrasion will remove the entire layer.
Water drop test: Pour or spray a little lukewarm water onto the mold surface. Spread the water film by hand and observe how it behaves: if the water film breaks up into so-called “fish eyes” with dry areas between them, there is still grease and/or dirt on the mold surface. When the mold is completely clean, the water film should form a uniform thin layer without ridge-like edges created by surface tension. Due to surface tension effects, this test does not always work on polyester mold surfaces. In such cases, the test described earlier is sufficient.
Release agent treatment in winter
Problems with release agent treatment can arise when the outdoor temperature drops and the production space is heated. The indoor air temperature also decreases, and typically there is no humidity control in production area. In this case, the relative humidity is likely to be well below 30% (in the middle of the heating season, the relative humidity is often only 15–20%), which is the generally stated lower limit for release agent treatment.
It is advisable to follow the manufacturer’s recommended 30% relative humidity limit, but in Finland this is not always possible. The best solution is to equip the production area with automatic humidity control. One method is to introduce moisture into the surrounding air, for example by wetting the floor - however, care must always be taken to ensure that no water or droplets come into contact with the mold surfaces being treated.
The most important way to improve the success of release agent treatment is to allow much longer curing times for the sealer and the release agent so that the humidity has time to take effect. In other words, after each application layer, extend the curing time from 15–30 minutes to several hours (even overnight).
If you proceed too quickly between layers, the new release agent layer will dissolve the previous one, and you will simply be “rubbing” the same release agent layer again and again. As a result, multiple overlapping layers will not form on the surface as intended.
When to renew the release agent treatment?
In general, the aim is to monitor the release performance between demoldings. At a certain point, when demolding becomes more difficult or the mold surface starts to become dull, the release agent treatment is renewed. Only the release agent treatment is renewed; the sealer treatment is renewed only when performing thorough mold maintenance (e.g., annual maintenance). In the event of damage, the pore sealer treatment should also be repaired. Under normal conditions, one release treatment can typically last for several dozen demoldings before reapplication is needed. The exact number depends on the release agent used and the shape of the part being produced—if the mold has tight shapes, mold surface wear is greater.