Finishing of RTM part

Resin Transfer Molding (RTM): Release Agents & Molding Aids

Resin Transfer Molding (RTM) is a closed-mold process that holds many challenges. Dry reinforcement textiles are set in place before bringing two matching halves of a mold together and latching them shut. A resin is then transferred, or injected, to fill all of the voids in the laminate, as well as to chemically adhere to the inside surface of the gel-coat, which is normally applied to the “A” side of the mold only. Chem-Trend’s many years of experience working with composite molders has allowed for the development of products to address the challenges of releasing parts made through RTM.

The RTM technique is gaining popularity for several reasons. Extremely accurate dimension control can be guaranteed, as well as ensuring that solvent emissions are kept to a minimum. Since the process involves “two-sided” molds, the release system needs to perform two separate functions. The “displayed” (cosmetic) side of the molding is often required to be a class “A” finish – thus the “A” side designation. The back side of the mold most often does not need to be a class “A” finish and the laminate will shrink tightly onto its surface, meaning that the release system will need to provide excellent release ease as its prime attribute. This side of the mold is often referred to as the “B” side.

Chem-Trend’s Chemlease® Products

Chem-Trend’s Chemlease® products have been specially formulated to withstand the rigors of the RTM process. Release systems consisting of cleaners, primers, sealers and top-coats have been developed to ensure that the mold is fully protected to provide multiple releases. The Chemlease® release system will not be disturbed by the ‘washing action” of the transferred/injected resin in applications where no gel-coat is used. In some cases, the system can also be augmented with a Chemlease® internal release agent.

Chemlease® system components include:

  • Cleaner – In a resin transfer molding application it is absolutely essential that both sides of the mold be clean before attempting to mold. Any imperfections, especially on the A-side, will most likely result in a scrapped part. If necessary, the mold should be treated with cleaning abrasives designed specifically for the application to remove resin residues or previously-used release agents. A Chemlease® cleaner should then be used to remove all remaining contaminants on the mold surface.
  • Primer – This part of this system allows the sealer and top-coat to perform their roles flawlessly in the release process. The primer provides the ultimate mold protection from the “ground up” to keep build-up or “scumming” to an absolute minimum. This is particularly important for the mold B-side, which is most often not laid up with a gel-coat and is therefore subjected to very high levels of abrasion during the mold opening process.
  • Sealer – This component performs the role of a “tie-layer” between primer and top-coat in RTM applications.
  • Top-coat – Chemlease® semi-permanent top-coats can be selected from a range of options designed to provide the molder some degree of flexibility in both application technique and release characteristics.
    • High or low slip depending upon the shape of the molded part
    • Wipe-on, wipe-off application method
    • Wipe-on, leave-on application method
    • Spray-on, leave-on application method

Click here to watch the Chemlease® video on our RTM system of products.

Fish eye paint defect in composite partOnce the mold has been cleaned, primed and sealed, the choice of top-coat can be made to address a particular need. Correct preparation ensures that the mold will give the maximum number of releases between re-applications of the top-coat, while ensuring that build-up on the mold surface is minimized. These top-coats allow any applicable gel-coat to be applied without fear of fish-eyes occurring. Parts that require a cosmetic finish will reflect the appearance of the treated mold for an extended number of de-moldings, with little or no build-up, if timely re-application of the top-coat is applied.

A Lot More than Release Systems

When you purchase Chem-Trend’s Chemlease® products for composites molding you get a lot more than just products. You gain access to a worldwide support network of industry professionals committed to developing the right solutions for your application. Our long history in the industry, combined with our many years of experience on composite shop production floors, means that we can help you optimize your mold release application and cleaning processes to improve your bottom line. Our sales and technical service experts are available locally to support our customers, and their distributors, through a global network of offices. We also support our customers through our technical service and development laboratories located around the globe. It’s all part of our commitment to providing our customers with greater value, performance and dependability.

Learn more about how you can leverage our expertise and products to increase your efficiency and lower the costs of your composite molding operations, or contact us directly.

Want to find out what Chem-Trend can do to help you? Contact us and give us a chance to improve your molding, casting and forming operations.

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