Every part of the process is critical to manufacturing success. At Chem-Trend, we leave nothing to chance. Our semi-permanent release systems come in liquid form and are designed to cross-link with humidity or heat and chemically bond to the mold, thus providing an inert, durable polymeric film that is resistant to wear, chemical and thermal attack. Because of the cross-linking nature of the semi-permanent, it often affords molders multiple molding cycles before the release agent must be reapplied and with minimal transfer to the molded part. Semi-permanent mold releases are versatile and will provide good release-ease for virtually all molding resins used in the composite fabrication process. Semi-permanent technology includes more than just a release agent and are used as a part of system to ensure best performance, typically consisting of a combination of the following components:
- Release agent
Delivering tailored solutions for the toughest composites molding challenges
Chem-Trend’s technical experts have hands-on insight into the toughest composite molding production challenges. Download our brochure to find out more about solutions that can improve your operating efficiency.
High Performance Release Systems for the Wind Energy Composites Industry
We are committed to bringing you premier Chemlease® mold release agents and ancillary products, download our product brochure to learn more about Chemlease®today.
Composites Europe 2019
Removal of semi-permanent releases can be more difficult due to the toughness of the cross-linked coating. The recommended procedure is to use a specially designed cleaner or a buffing compound to ensure that all of the coating is removed.
Many of the same factors that cause hazing also cause streaking. In our experience, streaking that occurs on application of release is most often the result of contamination, entrapped moisture, or improper application techniques. Presuming that the mold was cleaned properly, how you apply the release can have a big impact. Both sealer and release should be applied in a light even coating, using clean 100% cotton cloths. Do not use synthetic cloths because the solvent in the mold release can dissolve this type of cloth and cause streaking. DO NOT REUSE CLOTHS.
Shop environment and atmospheric conditions can play a major role in aggravating streaking. Hazing can occur when molds are cooler than air temperatures. This can result in condensation being trapped within the mold release coating as it cures.
Haze On The Mold After Applying Release (before molding): This can be caused by reaction of the release with contaminants on the mold surface; styrene in the mold blushing to the surface and becoming entrapped; entrapment of moisture in the curing release (particularly in very humid conditions); contaminated application cloths or wipes; condensation (particularly when molds are cooler than air temperature).
Haze That Appears After Molding: Heat as a catalyst can drive moisture, un-reacted styrene or other un-reacted materials up through the mold matrix during the molding process, entrapping them between the mold surface and the semi permanent film. Over several molding cycles the styrene can also polymerize leaving a tenacious film on the mold surface. Compounding is the preferred method of removing this buildup.
If you are evaluating any mold release, we suggest that you totally strip a test mold and prepare it according to the manufacturer’s instructions. This is the only way you can gauge performance and understand the specific application process. When testing any mold release, we always suggest that you select a test mold that is representative of your production, and one that is expendable in the event of a mishap occurring while testing. Always perform a tape test in several areas of the mold to assure that it is clean (tape should adhere well). Similarly, always perform a tape test on several areas of the mold after applying sealer and release (tape should release easier than on a clean surface).
Seasoned Test Mold Previously Prepared with Wax
This includes any kind of liquid wax, paste wax and waxed based sealers. Remove all foreign matter from the mold surface with a high quality mold cleaner and a cotton cloth. We do not recommend applying a semi-permanent directly over waxes, as this will compromise the bond of the semi-permanent mold release to the mold surface.
Seasoned Test Mold Previously Prepared with a Semi-Permanent Release
All semi-permanent mold releases are not the same. Many, however, are compatible with each other, which means one can be directly applied over a cured film of the other without stripping or compounding the mold. Test a small area with a high quality mold cleaner. Next, apply a coat of the new semi-permanent release. If the initial coat is difficult to apply (wets poorly), streaks or behaves unusually, STOP, and strip the mold. If everything appears as usual, follow this procedure for the entire mold.
Pre-releasing is another issue that has many contributing factors. Mold design, laminate schedule, resin formulation, gel coat formulation, improperly calibrated spray equipment, gel coat cure time, under or over catalization, shop temperature, humidity, and external heat sources – to name a few – can all lead to pre-release. Most semi-permanent mold releases have a lower surface coefficient of friction than conventional paste waxes, which is why they are more often implicated in pre-release. If all factors other than mold release have been addressed, you may be able to reduce the incidence of pre-release by lightly wiping areas where the mold is pre-releasing with a high quality mold cleaner to slightly alter the surface tension.
First, evaluate the area that is sticking. Perform a tape test in various spots on the mold to determine if the problem is related to application. Is it a consistent problem in one area or in one mold? Perhaps the sticking is related to abrasion, sheer edges, or draft angles. Is the area that is sticking a difficult area to reach when applying mold release? It may also be an area that simply requires more frequent touch ups of release, such as sheer edges or other areas of abrasion.
Gel Coat Over-Spray: Gel coat over-spray has been catalyzed. Even if the film over-sprayed on the mold is thin, it will eventually get hard. If the over-spray has not cured it can usually be wiped off with a cloth dampened with a high quality mold cleaner and then followed by a re-application of mold release. If the over-spray has cured, and the mold has release agent on it, it can sometimes be wiped off with a cloth saturated with a high quality mold cleaner and then followed with a re-application of the release. Or, simply let it totally cure and just peel it off the mold surface. If the mold surface has no release on it and the over-spray cures, in most cases it must be compounded off.
Raw or un-catalyzed resin: Dampen a cloth with a high quality mold cleaner and wipe the raw resin off the mold surface. Use as little mold cleaner as possible and as little pressure in removal as possible to avoid removing an excessive amount of release from the mold. However, you must ensure that you totally remove the un-catalyzed resin from the mold surface; since a thin uncured film of resin could lead to problems on the next de-molding. Having removed all of the uncured resin from the mold surface, reapply mold release and continue processing.
By taking a few precautions, you can achieve the same production from these types of surfaces as from a polished smooth surface. Buildup in non-skid areas generally can be seen as the same color as the spray-up gel coat. The cause of buildup in the grooves of the pattern usually result from either: 1) failure to apply the release into the tips of deep recesses in the pattern which causes small bits of gel coat or resin to bond in the tips with each cycle, or 2) excess release agent pooling in these areas because of poor application technique. When excess release is present, it does not have a chance to dry or cure thoroughly, or to develop full chemical resistance. The release films over on the surface and can attract free styrene from the gel coat or resin used to mold parts. This can occur because styrene in the resin acts as a solvent, penetrating the heavier areas of release and accelerating the buildup and sticking in these areas. To reduce the buildup and sticking concerns, care should be taken to thoroughly brush out and polish the release into these deep patterns without leaving a heavy residue.