Tooling & Vacuum Bagging Processing

Fillers
Filler powders are designed to modify the properties of liquid epoxy resins to create a variety of semi-liquid products such as filling and fairing compounds and adhesives. The fillers form three distinct categories: hollow spheres, short fibres, and flow modifiers.

Phenolic microballoons are hollow phenolic resin spheres which have a distinctive reddish/brown colouration.  Although not as waterproof as glass bubbles, microballoons are often preferred for their excellent sanding characteristics. Microballoons are not normally used with polyester or vinylester resins because they can be subject to styrene attack which may cause the spheres to collapse. When storing microballoons, it is particularly important to exclude air as they readily absorb atmospheric moisture which will affect the performance of the filled mix.

Glass Bubbles are hollow glass spheres with a more variable particle size than microballoons. Being composed chemically of glass, they are physically harder than microballoons and filled resin mixes are noticeably more difficult to sand. However, glass bubbles produce a more waterproof filler mix and are often used on below-waterline applications on boats. Being significantly less expensive than microballoons they are often preferred if easy sanding performance is not of prime importance.

Short Fibres, such as cotton flock adds strength to a resin and hardener mix used as a structural adhesive. Short reinforcing fibres are often added which act in a similar strengthening way to the long reinforcing fibres used in composite construction. The fibres also help to prevent resin starvation when bonding porous surfaces.

Colloidal Silica is an agent which is used to control the thixotropy or ‘sag’ characteristics of a resin system. By adding colloidal silica powder in varying amounts to a resin mix containing the other filler types mentioned, the handling and flow characteristics can be controlled. Relatively small quantities added to a resin mix containing glass bubbles or microballoons will give non-sag properties and impart easier handling. The inclusion of colloidal silica has the effect of increasing the hardness of the resulting mix which will create more difficulty when sanding. For this reason colloidal silica is usually added in the minimum quantities to any mix for which sanding is anticipated. In some applications this feature can be used to an advantage, for example to create a hard wearing edge or surface.

Glass Chips - Chopped 6mm glass

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