There are a couple of different ways to make the base polymer for an LSR. Like all elastomeric materials, there needs to a polymerization reaction to create molecular chains. Vinyl and methyl siloxane groups are polymerized to form polydimethylsiloxane chains. These chains provide strength and flexibility to the material. This process will change it from the liquid, almost watery starting components, to the more viscous basic form of the LSR. It’s in here that a lot of other properties can also be designed into the material, as well.
Once that main polymer gets created, the material gets reinforced normally with fumed silica. Unlike the organic materials where the filler of choice is carbon black or clays (pigmented materials), LSR materials use other silicates to reinforce the polymer chains and add tensile strength to the material.
From here, the material is split into two halves and the catalyst (platinum) and crosslinker are added to separate halves. This greatly increases the shelf life of these materials. When blended together, there’s a short working life of LSRs, averaging around eight hours. By splitting these halves, the material can potentially be stored for years with little worry of it curing during that time.