RTV silicone

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RTV silicone (room-temperature-

lens applications for some optically clear grades.[2] It is also used widely in the automotive industry as an adhesive and sealant, for example to create gaskets
in place.

Chemistry

RTV silicones are made from a mixtures of silicone polymers, fillers, and organoreactive silane catalysts. Silicones are formed from a Si–O bond, but can have a wide variety of side chains.[3] The silicone polymers are often made by reacting dimethyl dichlorosilane with water.[4]

dimethylpolysiloxane
polymer reaction

Fillers such as acetic acid can provide a fast cure time, while oxides and nitrides can provide better thermal conductivity. Tack-free times are typically on the order of minutes, with cure times on the order of hours.[3]

One-component silicone

One-part silicones make use of moisture in the atmosphere to cure from the outside towards the center.[4] The time to cure will decrease with an increase in temperature, humidity and surface-area-to-volume ratio.

Two-component silicone

Two-part silicones use moisture in the second component as well as a cross-linker such as active alkoxy to cure the silicone in a process called condensation curing. Two-part silicones can also be platinum catylized in a "addition" reaction.[3] Other reactive species to facilitate cross-linking include acetoxy, amine, octoate, and ketoxime.[4]

Applications

To produce the material, a user mixes silicone rubber with the

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 (without using a release agent). A more recent innovation is the ability to 3D print[5] 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.[2]

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 (polyurethane, polyester, and epoxy). No release agent is required, obviating post-production cleanup. Silicones also exhibit good chemical resistance and high-temperature resistance (205 °C, 400 °F and higher). For this reason, silicone molds are suitable for casting low-melt metals and alloys (e.g. zinc, tin, pewter, and Wood's metal).

RTV silicone rubbers are, however, generally expensive--especially platinum-cure. They are also sensitive to substances (

copper wire
.

References

  1. doi:10.1002/aoc.2832
  2. ^
    doi:10.1002/14356007.a24_057
  3. ^ a b c Lorenz, Günter, and Andreas Kandelbauer. “14 - Silicones.” Handbook of Thermoset Plastics. Third Edition. Elsevier Inc, 2014. 555–575. Web.
  4. ^
    OCLC 1061100690
    .
  5. ^ "picsima-ii". picsima-ii. Retrieved 2017-01-05.
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