If applying by hand, always use a fresh, clean set of cloths for each coat of release. A 100% bleached, white cotton cloth is preferred. As you continue to use the cloth, it can become loaded with dust, start to breakdown or the release agent can begin to gel in the cloth. All of these flaws can cause streaking on the surface, which is a tell-tale sign that it’s time to replace the applicator cloths with clean ones.
Some releases’ production processes lend themselves to spray application of the release agent. When using these products, high-quality spray guns are the best choice of equipment. High-quality spray guns provide a better spray pattern/adjustability, controlled throughout and good atomization. Plastic spray bottles should be avoided. Because many solvent-based, semi-permanent mold releases are sensitive to moisture, it is important to use a dry air source when spraying; this is easily accomplished by equipping air lines with moisture traps.
- Know your product
There are many different types of semi-permanent mold releases available. Information about the product’s benefits, limitations, cure times, proper uses and more should be documented and well understood by the workforce. Key instructions from the supplier of the release system regarding use, handling, storage, etc. should be easily seen and/or available to workers and supervisors. It sounds simple, but the majority of composites manufacturing shops have no visible procedures for mold cleaners, sealers, releases, etc. How are operators and supervisors to perform their job adequately when procedures and data sheets are in an office drawer?
- Treat it right
Properly preparing and storing your products for future use will extend their lifespan. A tightly closed container can make all the difference with products sensitive to air and moisture. Also, semi-permanents need to be properly rotated while stored according to the mold release manufacturer’s recommendations to prevent old, out-of-shelf-life product from accidentally being used. Using products beyond their shelf life can lead to poor performance, as well as damage the parts or the molds.
Solvent-based semi-permanent mold releases are often very sensitive to moisture. Leaving these products open or repeatedly exposing them to the atmosphere can cause polymerization in the can. This degradation may be invisible, but can compromise the performance.
One way to reduce risks when using moisture-sensitive mold releases is to dispense the release into heavy duty HDPE bottles with flip-top caps. Siphon-type bottles are not suitable, as they draw in air each time they are squeezed. Low density or other plastics should be avoided. Open cans, (paint) trays, buckets, etc. of release should definitely be avoided. Large containers of release can be conserved with a desiccant drum drier or by purging with nitrogen after dispensing.
Remember that these are general guidelines. Each molder should assess the materials they are working with and decide which combination of mold strippers, cleaners, sealers and release agents are most appropriate in their situation. Contact your supplier if you have any questions about your mold release programs. Your supplier should work with you to establish the right care and handling procedures.
Scott Waterman is director of global sales at AXEL Plastics. Email comments to swaterman@axelplastics.com.
Disclaimer: Opinions, statements and technical information within the Tech Talk column are that of the authors. ACMA makes no warranty of any kinds, expressed or implied, with respect to information in the column, including fitness for a particular purpose. Persons using the information within the column assume all risk and liability for any losses, damages, claims or expenses resulting from such use.
