Solutions to Molding Challenges of Pre-impregnated Composite Fibers
Commonly referred to as “advanced composites” – since high strength fibers are often used – pre-impregnated (pre-preg) composite materials can pose challenges to composite molding processes. Pre-pregs are laid on a mold surface, consolidated with bagging materials under vacuum and then heat-cured, most often by autoclave. The mold release system must ensure that the pre-preg remains in place during the lay-up procedure while, at the same time, provide sufficient slip in the release agent to allow for easy fiber placement. These two characteristics of the release agent are opposed, so the choice of a release agent that offers the right balance to match with both the pre-preg, and the mold being used, is important. Often, tackifiers are used to keep the pre-preg in place. When that occurs then the mold release system selected should not be affected by these materials. Chem-Trend’s many years of experience in working with molders of advanced composites helps assure that our solutions to these challenges add value to your operations.
The Role of Mold Release Agents
The selection of the mold release should take into consideration any post molding operations or requirements. For example;
- Will the part be painted? Most advanced composite parts are painted, so the surface of the part will need to be cleaned and abraded. If this is the case, then the release agent should have very minimal transfer to the finished part, and any transfer that does occur should be easily removable.
- Is a cosmetic finish on the molded part required? For most parts formed using the pre-preg method a cosmetic finish is not required, however should one be required, then a release agent should be selected that supports the necessary finish requirement.
- If a semi-permanent release agent is being utilized, and the fabricator is applying a touch-up to the top coat to the mold every cure, then a top-coat should be chosen that will ensure that rapid buildup does not become a concern.
Chem-Trend has been in the business of helping composite molders produce higher quality parts, more efficiently and with lower scrap for about three decades now. We understand the multiple challenges that you face in molding advanced composites parts. To further aid us in supporting our customers in the constantly evolving composites industry, we acquired the Chemlease® brand of high performance release agents and related products in 1998. With the additional products, technology and expertise that we gained through that acquisition, we were able to expand our range of mold release system technology to further support the composites industry around the world.
The Chemlease® Brand, Globally Recognized for Quality and Performance
In a composite molding operation, one of the top considerations is to protect the mold surface! The mold very often is a significant investment and, if damaged, may require extensive repairs or the creation of an whole new mold. Either scenario involves large costs as well as loss of operational efficiency. Our Chemlease® release systems have been developed to protect the significant investment you have in your molds. The systems consist of cleaners, primers, sealers and top-coats;
- Cleaner – Chemlease® cleaners are designed to remove all contaminants on a mold surface – even those remaining, should the mold have been treated with a purpose-designed abrasive to remove any resin residues or previously used release agents. It is absolutely essential that a mold be properly cleaned before attempting to apply a primer so that the primer can chemically bond to the mold surface.
- Primer – Priming the mold surface is a key to ensuring that subsequent release materials can perform to their true potential. A mold in good condition requires just one coat of primer, but if the mold is highly porous, subsequent coats of primer can be added to ensure that the surface is properly sealed.
- Sealer (if selected) – The sealer performs the role of an interlayer between the primer and the top-coat, aiding in the bonding of the top coat and the primer. A sealer is not always necessary.
Top-coat – Chemlease® semi-permanent top-coats have been designed to provide the molder with flexibility in both application technique and release characteristics to best suit their operational requirements:
- 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
A Lot More than Release Agents
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.