Motorsport Composite Fundamentals: Pigments, Fillers, Powders & Additives

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Pigments, Fillers, Powders & Additives

05.19

00:00	In this module we'll discuss the various materials we can add to our resins during construction or to our coatings to modify the appearance and properties of the final product.
00:10	Let's dive straight in and talk about pigments for colouring our resins and gel coats, which is done primarily for aesthetic purposes.
00:18	What's important to understand is that these are resin specific, meaning that if we're using an epoxy resin or gel coat, we need to use a pigment compatible with epoxy resin and similarly for polyester resin and gel coat.
00:32	These pigments are available in a range of colours and in concentrated liquid or powders, as well as metallic powders to give a pearl effect.
00:40	Past this, there's not really much to it.
00:42	We mix them thoroughly with our resins in the recommended ratios, which is usually under 10%, and progress through the work as we usually would.
00:51	These metal effect powders shouldn't be confused for genuine metal powders, which are also available as additives.
00:58	Typically we see aluminium, brass, copper and bronze powders, which are mostly used in resin casting, not something we're focusing on in this course.
01:07	They can be added to our resins and gel coats for aesthetic purposes, although they can also have functional uses.
01:14	For example, adding aluminium powder can help improve the dimensional stability of parts at high temperatures, so we might consider adding this to epoxy tooling gel coat for prepreg tooling.
01:25	Next, we'll discuss filler powders, not to be confused with body fillers that might be used on composite body panels, which we'll be looking at in the next module.
01:34	The point of a filler powder when added to our resin or coating is to enhance specific properties, modify processing characteristics or make the composite part cheaper by bulking out the resin.
01:46	In reality, this bulking out adds significant weight and is used mostly in casting resins, which again isn't the process we're focusing on in this course.
01:55	So, let's shift our focus back to some examples that can be used for laminates and their coatings.
02:01	Graphite powder is a filler that when added to our resins or gel coats will help produce a smooth, hard-wearing and low friction laminate.
02:09	Due to its colour, it'll also act as a dark grey pigment.
02:13	Next, is colloidal or fumed silica powder, commonly also known by its brand names aerosil or cabosil.
02:20	This is a super fine powder that we can use to thicken resins into a lightweight filler, sometimes called a resin filler or resin bulk.
02:29	Fumed silica can also be called thixotropic powder, and if this isn't a term you've heard before then you're probably not alone.
02:37	Thixotropy is a time-dependent, shear-thinning property that helps it cling to surfaces without running.
02:44	So, this is an example of using an additive to modify the processing characteristics.
02:49	Aluminium trihydroxide powder, or ATH for short, can be added for a range of reasons, like bulking out and adding weight in the rare occasions we want our parts to be heavier.
02:59	Perhaps more useful though is its ability to reduce shrinkage and act as a flame retardant.
03:05	When any of these powders are mixed with resin, we often describe the levels of consistency as ketchup, mayonnaise and peanut butter, in that order of ascending thickness, each suitable for different processes.
03:17	Another additive is glass bubbles, also called microspheres.
03:21	These are added to reduce the density of the cured part and make it more sandable, or in other words, easier to remove materials through sanding.
03:29	Chopped toe is also sometimes referred to as an additive, although it's a common structural reinforcement for forged compression moulded parts, and we've already covered this in the reinforcement section earlier in the course.
03:41	However, milled carbon powder, made from finely ground carbon fibres, can be used as an additive to resins to improve strength, dimensional stability and electrical conductivity.
03:52	It's unlikely we'll need to enhance the electrical conductivity in any of our applications, but a more common use would be adding milled carbon powder to an epoxy tooling resin, to improve its strength and dimensional stability with temperature for the likes of pre -preg construction.
04:08	Before wrapping up, it's worth noting that this hasn't been an exhaustive list, as there's an almost endless number of additives out there for all different purposes.
04:18	For example, something like Duratec high gloss gel coat additive, which as the name suggests, is added to increase the durability of the surface finish.
04:28	It will take hours to cover them all, but what we've discussed already will most likely cover our needs, and if not, a quick search and a review of the supplier's recommendations should answer your questions.
04:39	So, let's quickly go over what we've covered in this module.
04:42	Pigments and metal effect powders can be added to our resin and gel coat for aesthetic purposes.
04:48	Just remember that they're resin specific, so we need to use those that are compatible with our resin systems.
04:54	Genuine metal powders can be used for functional purposes.
04:58	For example, aluminium powders used in pre-preg tooling to provide dimensional stability with temperature.
05:04	Many other filler powders and additives are available to modify the density, thixotropy, sandability and friction properties, among other attributes of our resin and our coatings.