What are the advantages and disadvantages of each type of release agent?
Each type of agent has its own particular strengths (S) and limitations (L). Here is a brief overview by type of release agent:
- Solvent-based release agents:
- S: Easier to apply. The solvent carrier also helps with the film formation. The evaporation rate can be adjusted based on the solvent blend. The choice of solvent may ease the dissolution / dispersion of the release agent active ingredients.
- L: Not highly environmentally friendly. Offer higher health (VOC’s) and safety concerns (fire hazards) than non-solvent based products.
- Water-based release agents:
- S: Environmentally friendly and presents no fire hazards. May sometimes be dilutable (can be shipped as concentrates). They can be used to cool the die if necessary. May be developed with a level of technology that ensures mold release agent performance equivalent with solvent based release agents.
- L: Require more complex technology to manufacture. Proper film formation can be more challenging. This category of release agents may be more prone to stability issues and biological attack. Water-based release agents have slower evaporation rates than their solvent based counterparts and may not be appropriate for some room temperature molding operations or operations with short cycle times. Residual water onto the mold may affect molding performance (entrapped steam) or even chemically react with the material being molded. The latter is particularly an issue when molding polyurethane parts.
- Carrier-free Release Agents:
- S: Can be applied “as is” due to the absence of carrier. No vapors emission. Less noisy application is observed. Do not require dilution or tank storage. No waste stream.
- L: Can create a dust hazard if not applied properly. Require special application equipment (often being electrostatic spray guns), which may require expensive investment. The use of carrier-free release agents may also require additional modifications to the molding equipment to ensure thermal balancing of the mold. These factors often limit the application of this category of release agents.
- Sacrificial Release Agents:
- S: Easy to apply. Require less application technique and offer more tolerance of work (less dependent on trained operators).
- L: Tend to build up on the mold if over applied. In general, the release coating is partly transferred to the molded part, which may cause negative side effects on post molding operations (painting, adhesion, etc.) if applied in excess or if the release agent chemistry is not compatible with the post molding operation. If water-based, tend to cool the mold, removing heat & energy from the system (this may represent a disadvantage if the process is not designed for that).
- Semi-Permanent Release Agents:
- S: Require significantly lower application frequency than sacrificial release agents because the release agent film lasts for multiple molding cycles (frequency depends on the process conditions). Allow for a more steady and continued production without interruption for release agent application. There is very little transfer to the molded part, which allows for better post molding operations (coating, adhesion). The release agent can be reapplied regularly on the coated mold refreshing the release agent film. This category of release agents provides an excellent combination of chemical and physical barriers, preventing build up and providing the desired release performance.
- L: Requires more training of operators to ensure the right touch up frequency is observed. Molds need to be clean to allow for good interaction between the release agent and the mold surface during the initial application of the release agent.
- Internal Mold Release Agents:
- S: Reduce the need for external mold release agents.
- L: May continue to exude to the surface over time compromising post molding operations (coating and adhesion) or the surface cosmetics of the part. Often do not eliminate the need for external releasants as the internal mold release agents do not always migrate to the mold interface or may not ensure 100% release efficiency. Limited in their capability of performing high performance release agent functions such as affecting part surface characteristics.