What is the main function of the release agent (the importance of the release agent for composite materials)

2022-08-18 17:03:02

What is the main function of the release agent (the importance of the release agent for composite materials)

Regardless of the mold material, the importance of mold release agents cannot be overstated. Release agents form a barrier between the mold and part, preventing part/mold adhesion and facilitating part removal.

For open molds (such as the FRP hand lay-up process), most mold release agents are either waxes or based on polymer chemistry. In some cases, release paper is applied to the mold. Of these, most are polymers in solvent-borne carrier solutions, such as aliphatic hydrocarbon mixtures. Some manufacturers prefer naphtha-based release agents, which have longer shelf life and faster evaporation rates, and are believed to be less damaging to composite tool surfaces. Increasingly stringent emissions regulations have encouraged the development of water-based release agents that do not generate volatile organic compounds (VOCs), are easier to clean, and pose less risk of skin irritation.

Semi-permanent polymer release systems enable multiple parts to be formed and released in one application, while pasty waxes require reapplication for each part. Semi-permanent release agents—the first choice for better control of VOC emissions—are specially formulated to meet the needs of resin transfer molding (RTM) and other closed mold processes.

Internal mold release agents added to resins or gel coats, in place of or in conjunction with external mold release agents on mold surfaces, can further reduce emissions and have a negligible impact on part physical properties and surface finish.

The pultrusion process requires an internal release agent because the part is continuously pulled through the die and does not allow for the intermittent application of an external release agent on the die surface.

In addition, the specification of the release agent is as important as the correct selection. The details affect the difference in the final surface quality of the composite part. A complete release system should also include necessary procedures such as mold surface cleaning and hole sealing.