Fillers

Fillers are added to epoxy or polyester resin to modify properties such as viscosity, workability, sandability or the structure of the mixture. Depending on the filler you choose, you can thicken a liquid resin or create your own adhesive, fairing compound or filling compound.

At Polyestershoppen, you will find various fillers for epoxy and polyester, including glass fibres, cotton fibres, Stewathix, Microdol and microballoons. The filler you need mainly depends on what you want to achieve with the resin mixture.

Why add a filler to epoxy or polyester?

Epoxy and polyester resins are relatively fluid without additives. For applications such as bonding, fairing, making fillets or filling holes, you often need a thicker mixture with different processing properties.

With a filler, you can adjust these properties for a specific application. For example, you can:

• Thicken the resin so that it flows less easily;
• Make it suitable for bonding or fillet joints;
• Turn it into an easily sandable fairing compound;
• Add more structure for filling holes and cracks;
• Modify it for specific casting applications.

The result depends on the type of filler and the amount you add. Add the filler gradually until you achieve the desired consistency for your application.

Which filler do you need?

Not every filler has the same function. Some fillers are mainly used to thicken a resin mixture, while others are used for bonding, filling or making an easily sandable fairing compound.

Glass fibres

Glass fibres are short fibres that can be added to resin to create a fibre-reinforced compound. This filler is used for applications such as bonding GRP and filling or repairing holes and cracks.

The fibre structure creates a different mixture compared with fine, powdered fillers. Glass fibres are therefore particularly useful when you need a resin mixture with fibre reinforcement.

Cotton fibres

Cotton fibres are used to thicken epoxy or polyester resin and create a fibre-rich compound. With epoxy, cotton fibres are used for applications such as bonding wood, making fillet joints and filling holes and cracks.

Cotton fibres are particularly suitable when you need a thicker resin mixture that stays in place during application.

Stewathix

Stewathix is a thickening agent used to increase the viscosity of resin. It makes a liquid resin thicker, so that it is less likely to run on surfaces such as vertical sections.

Stewathix is used for applications including adhesive mixtures and fillet joints. It can also be combined with other fillers to achieve the desired consistency.

Microballoons

White microballoons and red microballoons are mainly used for making fairing and filling compounds. They are particularly useful when the cured mixture needs to be easy to sand.

Microballoons are used, for example, to level surfaces before applying the next finishing layer. Which type is most suitable depends on the resin system and application.

Microdol

Microdol is a mineral filler that can be used for certain casting applications. In combination with resin, Microdol is used, for example, for embedding metals or gravel.

Fillers for polyester

Use the table below as a practical guide when choosing a filler for polyester resin.

Fillers for epoxy

With epoxy, you can use different fillers to create an adhesive, fairing compound, fillet compound or filling compound. The table below will help you choose a filler for your application.

How much filler should you add to epoxy or polyester?

The amount of filler required varies depending on the product and application. For a slightly thickened resin, for example, you will need less filler than for a thick adhesive or fairing compound.

With a two-component resin, first mix the resin and hardener according to the specified mixing ratio. Then gradually add the filler and mix thoroughly until you achieve the desired consistency. Always follow the specific processing instructions for the resin and filler you are using.

Make your own adhesive or fairing compound with fillers

With the right combination of resin and filler, you can create your own mixture for different applications. For an adhesive mixture or fillet, you generally need a mixture that is thick enough to stay in place. For fairing, a filler that makes the cured material easy to sand is more suitable.

First determine what you want to use the mixture for and then choose the appropriate filler. Also consider the substrate, such as wood or GRP, and the resin system you are using.

Which filler should you choose for your project?

The right choice depends on the resin system and the desired result. Do you want to thicken epoxy, make an adhesive mixture, fill holes or create an easily sandable fairing compound? Each application requires different properties from the mixture.

Use the tables above as a guide and always check the product information for the filler before use. Not sure which filler is suitable for your epoxy or polyester project? Please contact the Polyestershoppen specialists. We will be happy to help you choose the right combination.