The importance of curing new and green moulds
It is impossible to accurately measure the amount of un-reacted styrene remaining in the gel-coat or laminates of a new mould. Therefore, there is no way of knowing if the residual styrene in the mould will affect the first release. In light of this, it is ideal to post-cure a new and green mould to minimize the free styrene, which comes through the gel-coat surface during the cure of a mould. New moulds can be simply placed outside to bake in the hot sun for two to three days. This allows the majority of the free styrene in the laminates and gel-coat surface to evaporate, giving better release properties to the first few parts during the break-in period of a new mould. However, new moulds that have rested inside for two weeks can potentially have residua l styrene remaining, leading to an array of problems.
And, even a new mould that has had ten coats of wax applied to it can still experience some form of sticking because of styrene monomer burn-through if the mould is not fully cured. Considering that we do not yet have the technology to conclusively determine whether or not a mould has been built under ideal conditions, we always advise using PVA for releasing the first few parts. PVA is generally resistant to the residual styrene, which is driven up through the mould surface during the first exposure to the curing part. PVA should be applied over the mould release, which has already been applied on the surface. After the first de-moulding, the PYA should be removed with a damp cloth and reapplied along with the mould release. This procedure should be continued until all of the PVA releases cleanly from the mould and sticks on the moulded part.

Mould release categories
PVA
One of the oldest release agents used by the reinforced plastics industry, PYA is still one of the safest, most efficient, and most reliable agents for breaking in new and green moulds. PYA’s advantageous quality is that it resists being dissolved by styrene monomer, which usually vaporizes in excessive amounts during the break-in period of a new and green mould. When the PVA film completely comes off on the part, it can be discontinued and subsequently replaced with another more convenient and easy to use mould release agent.
Waxes
These were the earliest mould release agents used by the composites industry. It is for this reason that many shops prefer to have a supply of cans of hard paste wax around the shop to use for release. These old fashioned release agents have been somewhat modernized for faster and easier application, by being manufactured in paste and liquid forms. While some still have low temperature resistance others are suitable for high temperature applications. Nevertheless, be aware that many waxes have silicone added to them to promote high luster and easy application, as this is usually the reason for “fish eyes” when you spray up gel-coat. Furthermore, there is the danger of pre-release.
Polymeric mould releases
Polymer mould releases are based on fluorocarbon chemistry and include polytetrafluorethylene (PTFE). Some suppliers formulate proprietary polymericbased releases, which do not contain fluorocarbons. These types generally have a strong bond to the mould, do not transfer and offer multiple releases from a single application. Parts moulded with polymeric release agents are the easiest to achieve secondary bonding or painting without adhesion problems.

Internal mould releases
These can either be based on vegetable oils or other refined types of proprietary polymer chemistry. They are used as additives mixed with resin or gel-coats in a range of0.5% to 1.0% by resin weight. In the case of vegetable oils, the release mechanism is achieved by exudation because of complete incompatibility of the oils with the resin.

Silicones
Silicones are rarely used in their pure state as mould releases. As mentioned in the discussion of waxes, liquid mould, release products containing high amounts of silicone can cause pre-release and fish eye formation

BASIC TROUBLESHOOTING

1. Problem: Poor release, and particles from moulding material remain on the mould. Cause: Microporosity in the mould. Solution: Thoroughly clean mould, apply sealer and reapply the release. Problem: Unable to achieve multiple release. Cause: Poor release in high draft areas. Solution: Apply one to two extra coats of release in high draft areas.

2. Problem: complete release failure. Cause: Poorly cleaned mould surface prevented release from adhering to the mould or release applied improperly. Solution: Strip part, thoroughly clean the mould and ensure that release is fully cured before moulding.

3. Problem: Poor release and white patches on parts Cause: poorly cleaned mould surface prevented release from adhering to the mould or excess styrene. Solution: Thoroughly clean the mould and reapply release, reduce styrene/adjust catalyst.

4. Problem: Build-up or release agent on the mould or transfer of release to the moulded part. Cause: Over application of the release agent Solution: Thoroughly clean the mould, reapply release and carefully follow application instructions.

In the future
In the fast-paced and competitive world of composites manufacturing, engineers need to use every advantage they can get on their competitors. Quality alone is no longer what customers demand, but rather higher quality along with the ability to produce in larger quantities and at great speeds. It is therefore essential to eliminate every factor than may be slowing down production, and one of the easiest ways to remove inefficiencies is by choosing the proper mould release agent.

Whether your application requires a wax, silicone or external or internal release agent, it is important to make sure that the most effective one is selected. It is for this reason that it is essential for those in the industry producing and engineering mould releases to be careful in their research and development, and in their respective manufacturing processes. Once aware of the needs of high performance composites, you can select from the many lines, types and varieties of mould release agents – especially from those manufacturers that are constantly coming up with the new and improved ways to achieve better, faster and more efficient release performance.