Semi-Permanent Technology for Greater Efficiency and Reduced Costs

Semi-permanent mold release technology is primarily used in all composite molding applications. Semi-permanent release agents are designed to bond to the mold surface, providing a durable polymeric layer that is resistant to both chemical and mechanical attack. Every Chemlease® semi-permanent mold release will provide excellent release-ease for all materials commonly used in the composite fabrication process. If a combination of release agent plus a sealer is used in preparing a mold, or more than one coat of release agent is used, this is often referred to as a “release system”.

The Chemlease® semi-permanent release system consists of:

  • Cleaner
  • Primer
  • Sealer
  • Top-coat

This system is developed to be flexible depending on the specific release situation. Not all components are always required – such as the need for a primer. However, because of the very aggressive molding environment of most closed molding situations, use of the primer is always recommended for these processes. As well, the top coat of a semi-permanent system is always required because it is the special properties of the top coat that provide the fabricator with options. For example:

  • Traditional semi-permanent products were designed to be wiped on to a mold surface and then buffed off in order to maintain the surface finish of the mold surface.
  • High slip varieties of this type of product are available for use on molds with deep draft angles in order to make the de-molding operation easier. These products are particularly suitable for the “B” sides of RTM molds where the laminate often shrinks tightly on this part of the mold.
  • A wipe-apply product is available that does not need the mold to be buffed after application, even on the most glossy mold surface. The product will dry to a streak-free finish. This product can also be spray-applied to provide a similar effect.
  • If you want to have the security of knowing exactly where your top-coat has been applied (since most semi-permanents are crystal clear formulations), you can select a wax-containing semi-permanent that forms a hazy layer on the mold surface when wipe-applied. The hazy layer can then be buffed to a brilliant shine after a short wait.

Since composites processing is usually a “cold mold” process, the above options would normally have been addressed by solvent-based formulations. However, Chem-Trend has developed a strong portfolio of water-based options that are also available. Water-based top coats can either be wipe-applied, allowed to dry and then buffed off in the case of a glossy mold surface or wipe-applied and allowed to dry should the surface required be non-cosmetic.

Semi-permanent release systems provide special attributes to the molder, such as:

  • Repetitive Imitation of Surface Finish
  • Modification of Gloss Level
  • Reduction of Pre-release
  • Low Transfer/High Film Durability

Surface finish

The surface of the prepared mold will usually dictate the surface finish that is seen on the molded part. A low gloss finish mold will turn out a low gloss part and vice-versa for a high gloss mold. A mold that is either high or low gloss can be prepared with a cleaner, sealer and a choice of semi-permanent top-coat, which will maintain the level of gloss through many de-moldings. A timely touch-up with the top-coat from time to time will maintain this performance

High or low gloss – mold surface modification

Chem-Trend can provide special mold primers that offer the option of preparing molds with either a low gloss or high gloss surface finish, regardless of the state of the actual mold surface. These primers can be regarded more as a “surface-modifiers”. In special cases where the same mold sometimes needs to be used to produce parts with high gloss and, at other times, low gloss, these primers are ideal. Since Chem-Trend mold primers adhere strongly to the mold surface and form a very tough film, the release system that is used will exhibit greater durability

Low pre-release

The manufacture of very large moldings can be susceptible to pre-release, due to the sheer weight of the article being molded. The mold release must hold the laminate in place until the part is fully cured – otherwise the part will be misshapen and possibly need to be scrapped. Chem-Trend has developed unique Chemlease® products in order to handle this specific issue.

Low transfer/film durability

Since the semi-permanent system fully cures to the mold surface, there is very little mold release transfer to the molded article. This means that the amount of preparation for painting or gluing after molding is kept to a minimum. Since only a very small amount of the mold release transfers to the molded part, one can expect the top coat to provide many releases before there is the need to re-coat the mold.

Although Semi-Permanent technologies offer great benefits to the molder, they are not right for every composite application. For some applications only a conventional release system will work. If you want to learn more about the trade-offs between conventional and semi-permenant technologies and which might be best for your process contact us to meet with one of our composite industry experts.

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