What types of mold release agents carry out these functions?
Release agents can be categorized in a variety of different ways. Here are a few examples of possible categorizations, and how they relate to the functions of high performance release agents:
Based on the type of carrier:
- Solvent-based release agents: The active principle(s) of the release agent formulation are dissolved or dispersed in a solvent or blend of solvents. The choice of solvent influences the dispersion quality, film formation and evaporation rate. This category of release agents lends itself not only to heated molds, but also to room temperature application.
- Water-based release agents: The release agent active components are emulsified into water as the active compounds generally are not water soluble. This category of release agent is more environmentally friendly due to having reduced or no VOC’s (volatile organic compounds). However, technology and manufacturing techniques are more complex in order to provide a stable emulsion and good film formation particularly at room temperature. Often times this category of release agent is presented in a form that can be diluted. Water-based release agents are also required to be biologically stable /robust.
- Carrier-free release agents: These are usually solid release agents in powder form. Application is often done using an electrostatic spray gun. Film is formed upon contact with the heated surface similar to powder coatings.
Based on how the mold release agent (MRA) interacts with the process:
- Sacrificial Release Agents: This category of release agent is applied in every molding cycle. The release agent film on the mold surface is in great part depleted after each molding cycle and needs to be replenished.
- Semi-Permanent Release Agents: This category of release agent is reactive with the mold surface, chemically adhering to it whereas it also provides a chemical and physical release barrier. Once applied onto the mold, semi-permanent release agents allow for multiple molding cycles before the release agent has to be reapplied to the mold.
- Internal Mold release agents: These are specialty chemicals which are embedded into the material being molded. Because they are generally chemically incompatible with the material, they tend to exude to the surface of the part during the molding process providing a release layer. Sometimes the release agent migration mechanism to the surface can also be accelerated by heat.