Synthetic silicas is an efficient reinforcing filler using elastomers and plastomers to modify mechanical properties such as
- Tensile modulus
- Tensile strength
- Abrasion resistance
- Cut growth resistance
- Tear resistance
Silica fillers are also used in reducing the rolling resistance of tyres thereby improving the fuel economy of the vehicle "green tyre".
The ability of the silica to impart the desired features to an elastomer or plastomer compound depends on chemical structure, surface chemistry and particle size. The surface of a silica particle carries a concentration of hydroxyl groups. These readily absorb a wide range of materials such as accelerators. Addition of a glycol will inhibit this adsorption thus controlling cure rate. In green tyre silicas the addition of a silane inhibits adsorption.
Rubber compounds which require a semi-reinforcing filler with no need for transparency can utilise Alusil ET or Microcal ET. These give good ie fast, controllable cure rates and can also enhance colour intensity. Classed as semi-reinforcing fillers, they give a lower tensile strength and lower elongation at break than silicas do, at equivalent loading.