The most important detail in achieving the best possible release agent treatment results is the mould cleaning. Only a properly cleaned mould surface will produce the desired outcome of release agents and product surface quality. Cleaning new moulds is not usually a problem, but with older ones, and the different release agents types and qualities they have been exposed to, may prove more challenging.
It is very important and common for the entire mould to be cleaned of all visible, old release agents, adhering resins, and contaminants. Underneath may be thin, hard to see remnants of layers that will inhibit the functionality of newly added layers.Consequences of old release agents left on the mould’s surface include:
- New release agent layers do not produce the same number of releases as they should.
- The manufactured product’s surface is not clean and doesn’t shine evenly due to old sections of release agents adhere to the product surface.
- Otherwise the agent does what it is supposed to do and releases.
The release agent’s purpose is also to protect the mould’s surface, reduce the mould’s servicing needs, and preserve it’s longevity.
The mould cleaning system to be used depends on the mould’s material, the contaminants to be removed, and how dirty the mould is. The different cleaning systems include:
- A diluted, water-base detergent solvent
- Glass bead/ball pressure cleaner
- Light hand or machine sanding
- Silicone release agent with toluene or White Spirit
- Waxes with methylene chloride or tetrachloroethylene
- Petroleum ether
- Cleaning detergents for alternative manufacturing
After cleaning, an old, heavily used mould will virtually always be either more or less porous. The pores are then sealed with a suitable mold surface sealer before the actual treatment of the surface with a release agent.
Using release agents
Polymerized release agents strongly adhere to moulds surfaces after curing as a hard, dense, thin layer (1 layer < 1 µm), that does not stick to the manufactured product..
Release agents polymerize by means of air humidity, which is why it must be at a minimum level of 30 %. In drier environments, the curing time could be increased tenfold. The surrounding temperature should be around 17 – 25 ºC. Release agents generally have good chemical resistance.
The release agent can be applied by spray, brush, or a clean cotton cloth. Release agent layers are then spread onto the mould’s surface according to instruction; thinly and evenly. In fact, one layer of release agent is all that is needed for good results as long as it is properly spread to all areas of the mould. Additional layers are needed to ensure a completely uniform, stable release film. Both the release agent and the mould surface need to be completely dried before further application. it is essential for each release agent to be used according to it’s manufacturer’s instructions. The best results arise from allowing lower layers of release agent to fully cure before adding additional layers.