Mineral fillers for composite

Mineral fillers are a fundamental component in the formulations for polymeric matrix composites. The selection of the appropriate composite fillers, as well as their proportion to the resin, will have a direct influence on the properties of the final product. Composite fillers will also condition how the production process should be carried out as they determine the viscosity, the gel time, the curing time, etc… Below we show you all you need to know about mineral fillers for polymeric matrix composites. Further on, we give you the keys to be able to select the appropriate mineral fillers according to the characteristics of the composite to be manufactured.

Mineral fillers for composite

Mineral fillers are solid, organic or inorganic particles, which are added to the resin or gel coat. The purpose of the use of mineral fillers in the production of polymeric matrix composites is basically:

  • provide the physical and mechanical properties required for the final product. The mineral composition and the optimum proportion of the mineral fillers with respect to the resin shall be determined by the requirements and standards to be fulfilled by the final product. Thanks to the combination of different minerals, we can, among other things:
    • modify the mechanical properties: hardness, abrasion, bending, etc…
    • lighten or increase the weight of the final product
    • improve conductive or anti-static properties
    • improve fire resistance
  • lower the cost of the mixture as mineral fillers are cheaper than the resin itself

Both the mineral composition and the proportion with respect to the resin, will affect directly in the way the production process is carried out since the composite fillers:

  • determine the viscosity of the mixture
  • affect the catalysis
  • can cause contractions during the curing of the part
  • may affect the color of the final product as well as other aesthetic aspects
  • determine the mechanical and superficial properties of the final product

Mineral fillers therefore have a large influence on how to face and organise the polymer matrix composites manufacture.

Choosing the right composite fillers for our project

In the choice of the mineral fillers for our project we will have to analyse the following aspects:
  • particle size (grading). Very thick particles will tend to go to the bottom of the mixture. On the contrary, the particles that are too thin may not disperse in the mixture. We will have to choose the optimum particle size for our formulation.
  • particle shape (milling). If the particle is like a golf ball, the resin will stick easily. If on the contrary, the particle is like a ping pong ball, it will be much more complicated its perfect bond with the resin.
  • purity of the particles. In the case of homogeneous pigmented mass products such as solid surface, it is essential to avoid the presence of polluting particles that can generate black dots on the surface of the finished piece.
  • silanization

The contribution of the silane to a mineral fillers is:

  • greater translucency
  • better resistance to thermal shock of the finished part
  • reduction of thermal dispersion
  • lower viscosity
  • shorter gel and curing time
  • better water vapor resistance
  • excellent surface properties
  • greater mechanical and chemical resistance
In the case of polymeric matrix composites where the outer layer is a gel coat, the choice of the appropriate mineral fillers shall be reduced only to:
  • fulfil the physical-mechanical properties required by the final product
  • reduce the cost of the mixture as much as possible

Use of aluminium trihydrate (ATH)

Aluminium trihydrate (ATH) is a mineral filler obtained by the digestion of bauxite through the Bayer process. It is chemically combined with three water molecules and has a high melting temperature. Due to the physical properties of this mineral, it has become a basic raw material in the formulation of a multitude of composite materials: rubbers, polyurethanes, polyester, silicones, thermoplastics, cables, etc… The advantages of using aluminium trihydrate are:
  • important properties such as fire retardant and smoke suppressor. In fire conditions, the water vapour is released through an endothermic reaction that acts to cool the surface and displace the oxygen required for combustion. The resulting aluminum oxide carbon barrier makes combustion even more difficult and reduces the density of smoke. The aluminium trihydrate is becoming the most widely used flame retardant in the market. It is a friendly- environment mineral. Its thermal decomposition occurs at about 200 °c, making it suitable for a wide range of plastics and rubber applications.
  • excelent chemical resistance and physical properties. In combination with boehmite allows us to improve the resistance to scratching, shine and stains. It is especially resistant against acids attacks. Due to these high performance, it has become a fundamental raw material for the manufacture of solid surface-type products. If you want to know more about solid surface production, click here.

Last generation composites formulation

With the proliferation of polymeric matrix composites designed for new applications, the formulation of specific mineral fillers has become a science. Depending on the requirements to be fulfilled by these new polymeric compounds it is advisable to select the appropriate mineral fillers. Thanks to our close cooperation with strategic partners, we can offer our clients a technical department specializing in the formulation and combination of mineral fillers. By taking part in the development of specific composites we have acquired a recognized and valued experience in the sector. If you need to improve the performance of your product or want to create a new composite, do not hesitate to contact us.

A good example of our developments in the field of polymeric matrix composites are our low weight filler. These special fillers are based on different minerals that manage to reduce the weight of a composite up to 40% without diminishing the physical-mechanical properties of the final product. This represents lower transport costs and other advantages in handling, mounting times, etc.

Conclusions on mineral fillers for composite

The selection of the appropriate mineral fillers and their proportion to the resin will have a direct influence on both the properties of the final product and the production process. In the case of composite materials coated with gel coat, we will simply look for cheaper mineral fillers to ensure the physical-mechanical requirements of the final product. In case you need to provide fireproof properties to our composites, ATH is then the ideal solution. Thanks to our close cooperation with strategic partners, we can offer our clients a technical department specializing in the formulation and combination of mineral fillers. We specialize in the formulation of mineral fillers adapted to specific projects.

If you want to be permanently informed about everything related to mineral fillers, read our latest articles on this topic here.