Polyurethane Release Agents

There are some concrete release agents that are low or zero VOC. This needs to be investigated when discussing the characteristics and attributes of different release agents with potential suppliers.

This is an area of growing concern and interest and there are products available that have low and zero VOC materials.

Depending on the production set up a wide variety of configurations can be utilized. From manual HVLP guns to automated spray systems, assistance with determining the best selection to efficiently apply concrete release agents should be provided by the release agent supplier.

Materials may be diluted through very reliable wall mounted or floor model proportioners. These units provide a consistent water to concentrate ration that allows for a dependable mix without the use of valuable manpower.

By using a piece of cardboard a spray pattern may be tested. First make sure the spray equipment nozzle and air cap are clean and unrestricted. Hold the spray gun a distance from the cardboard that is a normal distance from the spray gun to the molding surface. Spray the mold release onto the cardboard in a sideways sweeping motion. The pattern should be solid yet dry quickly. Any splotches will show areas that may be under sprayed or unevenly applied. Liquid running down the surface means the liquid is being applied too heavily.

When applying a release agent with manual spray it is important to establish a baseline throughput to maintain a consistent spray. Required throughput amounts will vary based on the tooling grain, part complexity, and the speed of the line. When a proper spray amount is determined the throughput in grams or milliliters per second should be recorded. This should be checked each shift to make sure there is consistency between operators. This information will help to train new operators to correctly apply the release agent. Consistent fluid and atomizing air pressures are also a must for repeatable application.

The key is to have a dry mold surface before the foam is poured. A liquid carrier is used to deliver the release agent to all surfaces of the tooling. This carrier should be evaporated before the foam is poured or injected into the tool.

Key selection factors are:

• Type of foam being produced (rigid, seating, RIM, etc.)
• Molding temperature range
• Mold material (aluminum, steel, etc.)
• Time between mold release application and foam pour
• Cure time
• Foam density
• Post molding requirements (bonding, painting, etc.)

The more information on the process the easier it is to determine the perfect release agent.

Hybrid products provide the benefits of a solvent based material, such as an open surface and faster film formation and evaporation, but they utilize a waterborne carrier with a small amount of solvent to provide these benefits. This technology significantly minimizes VOC emissions.

Various release agents can be used with many forms of spray equipment. While HVLP systems are the most common method of application, many other methods can be used based on equipment and plant configurations.

Release agents for veneer/masonry stone applications and other specific concrete applications should be designed to allow pigments to wet out on the surface and to keep molds clean through improved color transfer. Maintaining a proper application amount and/or dilution is important in achieving these goals and the effectiveness of the release agent should be fully evaluated in a field trial prior to full scale adoption.