SP Colloidal Silica is an agent which is
used to control the thixotropy or ‘sag’ characteristics of a resin
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.
Colloidal silica is also used with
microfibres to produce a mix suitable for use as a high strength,
non-sagging structural adhesive, particularly for non-absorbent
materials such as grp. 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.