SMC (Sheet Moulding Composite) and BMC (Bulk Moulding Composite) both refer to a material and to a process in which an article (e.g. a sheet) is made through moulding.
A composite used in a SMC or BMC process is combination of two materials:
- the matrix (formulation containing the polymer/resin)
- a fibrous material (in case of pultrusion continuous glass-fibres or even textiles).
The main reason to make composites is to get mechanically stronger (reinforcement) materials by establishing a strong interaction between the resin and the fibre.
To get the best properties for the composite the matrix needs to be fully wetted (impregnated to saturation) with the formulation containing the polymer.
For the above reason composites are sometimes also referred to as FRP’s (Fibre Reinforced Plastics). While the resin can be of any kind, most often they are thermoset resins (like polyester, vinyl-esters and epoxies). What sets composites aside from “compounds” is the fact that unlike “compounds” the individual components (matrix and fibrous material) remain separate and visibly distinct within the finished structure/composite.
Composites are often used as a replacement of metal to reduce the overall weight of e.g. a car or plane leading to better fuel economics.
Fillers are added to the composite and Sibelco offers mineral fillers that can further improve the properties (beyond reinforcement) of the article made by the SMC or BMC process, by providing
- Flame-retardancy (ATH)
- Dimensional Stability (Silica)
- Lower cost (Silica)
- Sound deadening (Baryte)
- Better heat conductivity (ATH)
The combination of two different (coarse and fine) ATH-grades offered by Sibelco can lower the viscosity of the formulation and improve processing and final product properties.