We report the synthesis and properties of solvent-filled silica microcapsules to be used in thermoplastic extrinsic self-healing polymeric systems processed via conventional extrusion processing. The silica microcapsules were produced via hydrolysis and condensation of tetraethyl orthosilicate (TEOS) using an aqueous glycerol microemulsion as the template. The effect of the solvent/TEOS ratio on the dimensions and wall thickness of the microcapsules was studied. Pre-hydrolysis of TEOS was found to be essential to obtain isolated free-flowing silica microcapsules. Microcapsule compression loads of up to 350 mN were obtained. Full details of the work have been reported elsewhere [1].