RTV silicone


RTV silicone is a type of silicone rubber that cures at room temperature. It is available as a one-component product, or mixed from two-components. Manufacturers provide it in a range of hardnesses from very soft to medium—usually from 15 to 40 Shore. RTV silicones can be cured with a catalyst consisting of either platinum or a tin compound such as dibutyltin dilaurate. Applications include low-temperature over-molding, making molds for reproducing, and lens applications for some optically clear grades.

Applications

To produce the material, a use mixes silicone rubber with the curing agent or vulcanizing agent. Usually, the mixing ratio is a few percent. For RTV silicone to reproduce surface textures, the original must be clean. Vacuum de-airing removes entrained air bubbles from the mixed silicone and catalyst to ensure optimal tensile strength, which affects reproduction times. In casting and mold-making, RTV silicone rubber reproduces fine details and is suitable for a variety of industrial and art-related applications including prototypes, furniture, sculpture, and architectural elements. RTV silicone rubber can be used to cast materials including wax, gypsum, low melt alloys/metals and urethane, epoxy or polyester resins. A more recent innovation is the ability to 3D print RTV silicones. RTV silicones' industrial applications include aviation, aerospace, consumer electronics, and microelectronics. Some aviation and aerospace product applications are cockpit instruments, engine electronics potting, and engine gasketing. RTV silicones are used for their ability to withstand mechanical and thermal stress.

Features

  1. Good characteristics of easy operation
  2. Light viscosity and good flow-ability
  3. Low shrinkage
  4. Favorable tension
  5. No deformation
  6. Favorable hardness
  7. High-temperature resistance, acid and alkali resistance, and ageing resistance

    Advantages and disadvantages

RTV silicone rubber has excellent release properties compared to mold rubbers, which is especially an advantage when doing production casting of resins. No release agent is required, obviating post-production cleanup. Silicones also exhibit good chemical resistance and high-temperature resistance. For this reason, silicone molds are suitable for casting low-melt metals and alloys.
RTV silicone rubbers are, however, generally expensive--especially platinum-cure. They are also sensitive to substances that may prevent the silicone from curing. Silicones are usually very thick, and must be vacuum degassed prior to pouring, to minimize bubble entrapment. If making a brush-on rubber mold, the curing time factor between coats is long. Silicone components must be mixed accurately by weight or they do not work. Tin catalyst silicone shrinks somewhat and does not have a long shelf life. Acetoxysilane-based RTV releases acetic acid during the curing process, and this can attack solder joints, detaching the solder from the copper wire.