Mineral fillers for composite
Mineral fillers consist of a set of mineral matter, homogeneous or made of different compounds, of the same or different granulometries, which respond to a specific formulation. They are an essential component in formulations for polymer 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 mineral fillers will also condition how the production process will be carried out as they determine the viscosity, the gel time, the curing time, etc…
If you want to know more about mineral fillers for polymer matrix composites, read on how to select the most suitable one for your project.
Table of contents
Mineral fillers for composite production
Mineral fillers are solid, organic or inorganic particles, which are added to the resin or gel coat. The aim of using mineral fillers in the polymeric matrix composites production is basically:
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- provide the physical and mechanical properties required for the final product. The mineral composition and the optimum ratio of mineral fillers to resin depends on the requirements and standards to be met 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
- in the particular case of dolomites, lowering the cost of the mixture as these are generally the cheapest component of the formulation
- provide the physical and mechanical properties required for the final product. The mineral composition and the optimum ratio of mineral fillers to resin depends on the requirements and standards to be met by the final product. Thanks to the combination of different minerals, we can, among other things:
Both the mineral composition and and the ratio of mineral fillers to resin, will affect directly in the way the production process is carried out since the composite fillers:
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- 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 are therefore largely responsible for the way in which the manufacture of polymer composites is organised.
Choosing the right composite mineral fillers for our project
When choosing the most suitable mineral fillers for our project, the following aspects should be taken into account:
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- 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 to avoid mass settling.
- 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:
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- 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 coating is a gel coat, the choice of the appropriate mineral fillers shall be reduced only to:
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- 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… when it comes to improving fire resistance.
The advantages of using aluminium trihydrate are:
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- important properties as fire retardant and smoke suppressor. Under fire conditions, 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 smoke density. That is the reason why aluminium trihydrate is becoming the most widely used flame retardant on the market. It is an environmentally friendly 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 it allows us to improve scratch, gloss and stain resistance. It is especially resistant to acids. Due to these high performance properties, it has become an essential raw material for the manufacture of solid surface products. If you want to know more about solid surface production, click here.
New generation composites formulation
With the proliferation of polymer matrix composites for new applications, the formulation of specific mineral fillers has become a science. Depending on the requirements to be met by these new polymer materials, we must select the right mineral fillers. Building on our close collaboration with our strategic partners over recent years, we are able to offer our customers a technical department specialised in the formulation and combination of mineral fillers. Our participation in the development of specific composites has enabled us to acquire an expertise that is recognised and valued 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 mineral filler developments in the field of polymer matrix composites is our low weight filler. These are formulations based on different minerals that manage to reduce the weight of a composite by up to 40% without reducing the physical-mechanical properties of the final product. This represents lower transport costs and other advantages in handling, assembly times, etc.
Conclusions on mineral fillers for composite
The selection of the appropriate mineral fillers, as well as their proportion in relation to the resin, will have a direct influence both on the properties of the final product and on the production process itself. In the case of gel-coated composites, we will simply look for economical mineral fillers that ensure the physical-mechanical requirements that the final product should meet. In the case we need to provide fireproof properties to our composites, ATH is the ideal solution. AITANA CHEMICALS offers its customers a technical department specialised in the formulation and combination of mineral fillers. Thanks to the experience acquired over the years, and the support of our technological partner, we can develop mineral fillers for specific projects.
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