Motorsport Composite Fundamentals: Applying Release Agents
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Applying Release Agents
04.11
| 00:00 | So, far we've discussed materials used during the construction of our composites that make up the structure of the part, like resins, reinforcements and core materials. |
| 00:09 | But there are other materials used in the construction and finishing of composite parts outside of these, specifically coatings applied for aesthetic and functional purposes. |
| 00:19 | Arguably the most important and one that you've likely already heard used around composite discussions is gel coat. |
| 00:26 | This term encompasses quite a wide range of products, but the main idea is to provide a high quality, protective finish on the visual surfaces of our composite parts. |
| 00:37 | These are most commonly thermosetting polymers which are based on the same chemistry as the resins we use in our construction. |
| 00:44 | Generally, if we're using epoxy resin, we'll use an epoxy-based gel coat, and likewise for polyester products. |
| 00:52 | Usually, a polyester gel coat won't be compatible with an epoxy resin, and if used together they won't bond and will delaminate. |
| 01:00 | However, there are polyester gel coats that are compatible with epoxy resins and will provide a strong bond, so it's just important here to review the supplier's recommendations for whatever we're buying. |
| 01:12 | It's important to understand that they're not usually applied like normal coatings to the surface of finished parts. |
| 01:19 | Rather gel coats are usually mixed with an MEKP catalyst or a hardener, just like our resins, and then applied directly to the mold in a liquid state using a large soft paintbrush or a spray gun before lamination. |
| 01:33 | We'll be covering the practical skills for this later in the course, so don't stress too much on these details for now. |
| 01:40 | The gel coat is then cured into a solid, although it will still be tacky, also referred to as the gel state. |
| 01:47 | Following this we will complete a typical layout for the composite part, and in practice a tacky surface can help to hold the reinforcement in place. |
| 01:56 | As the part cures, the gel coat bonds to the surface, so as the part is removed, the gel coat is already applied to it. |
| 02:04 | The outer surface is of course the mold surface, so it'll generally be nice and smooth. |
| 02:09 | Most gel coats are designed to be very durable, helping to protect the part and also providing resistance to the degradation caused by UV light. |
| 02:18 | This durability is well suited to use on composite tooling. |
| 02:22 | Keep this in mind and we'll come back to tooling gel coats shortly. |
| 02:25 | Probably the most common use of gel coats on composite parts is on boathouse, but in motorsport applications, these are the typically white or grazed finishes that we'd see on aftermarket fiberglass body kits. |
| 02:39 | On this note, it's common to color gel coats with the use of dyes, which we'll be discussing more in a coming module. |
| 02:45 | We often see tooling gel coat come pre-dyed in bright colors like greens or oranges, where gel coats for parts are more often white. |
| 02:54 | Most chop strand matte fiberglass based automotive parts are finished with a dyed gel coat to hide the reinforcement, where clear gel coats are used on carbon parts like hoods for example, which naturally have more acidic value and are typically something to be shown off. |
| 03:11 | On parts like this, the gel coat not only prevents wear and tear and also UV degradation, but also provides some material thickness that can be polished flat, like the clear coat over the paint on our cars. |
| 03:24 | Tooling gel coats, as we mentioned earlier, are designed specifically for the mold surface. |
| 03:29 | These require higher levels of durability to hold up to the mechanical stresses from demolding and the thermal stresses from curing. |
| 03:37 | As you might have guessed, these are applied to the pattern or the plug prior to mold construction, so the idea for pattern to mold is similar to what we discussed for mold to part. |
| 03:48 | Using a thicker layer also helps prevent what's known as print through, where the texture of the subsequent layers of reinforcement in the tooling will imprint through into the surface of the parts. |
| 04:00 | We often see vinylester resins used as tooling gel coats, especially on molds for composite parts that will use epoxy resins. |
| 04:08 | These can be polished to provide a great mold surface finish and also provide a lower resistance release compared to polyester tooling resins. |
| 04:17 | To summarise this module, gel coats are protective coatings that are usually applied to the mold before construction of our composite parts. |
| 04:25 | As the part cures, they form a strong bond to the surface. |
| 04:29 | Gel coats provide added durability and UV protection and they can also be polished for a smooth surface and a high gloss. |
| 04:37 | It's important to understand the compatibility of the gel coat we want to use with the resin used for the construction of the part. |
| 04:44 | Typically this will be epoxy with epoxy and polyester with polyester, although there are some exceptions. |
| 04:50 | Tooling gel coats are formulated to be more durable and applied to the pattern before the mold construction, again providing a highly durable surface finish on the tooling. |
| 05:00 | Tooling gel coats are also often vinylester based. |
