What Is Liquid Silicone Rubber(LSR)?

Since liquid silicone rubber (LSR) is an elastomer, it has a high degree of elasticity (ability to resume its normal shape after stretching). Key LSR attributes include hardness, tensile strength (resistance to break under tension) and compression set. Other LSR characteristics include excellent bacteria resistance and hydrophobicity, meaning that it acts as a water repellent. There are two different kinds of liquid silicone rubber: food grade and medical grade.

Types of LSR Injection Molding

There are many types of LSR materials. Some include:

  • medical levels

The ability to be extracted for medical applications, which have extremely delicate criteria to prevent interfering with tissues, will be removed from an LSR in subsequent phases. The strength of the material is also increased by removing the extractables. Restrictive (implant for fewer than 30 days) and unrestricted are the usual classifications for these grades (implant greater than 30 days). The only difference between these classes typically is the degree of biocompatibility testing that was done on the substance. To assist clients in obtaining FDA clearance for their medical device, several suppliers create FDA master files.

  • Self-lubricating:

It is possible to combine incompatible fluids with the parts. This substance will bloom to the surface to provide a slick surface when the silicone has dried and hardened. Then, depending on the pace at which the consumer wants the fluid to bloom, 1.5 to 3 percent of a phenyl fluid is added to the silicone.

  • Conductive:

To the LSR components is put conductive-grade carbon black. In comparison to silicones packed with metal particles, these grades have very high mechanical qualities and may achieve volume resistivity as low as 9 ohm-cm.

  • Self-bonding:

The addition of adhesion promoters. It provides primer-free adherence to a range of surfaces. The substance adheres nicely to polysulfones, stainless steel, aluminum, and nylons with glass filler. For composite seals, it provides the ideal means of reducing assembly components or achieving even greater sealing between two mating components.

  • Radio Obscure

In order to make the silicone component visible under X-Ray, barium sulfate is applied. This works nicely for medical uses like catheters and wound drains.

  • Flame Resistant

Without any additions, the majority of LSR rubber will satisfy a UL 94 HB grade. Higher grades, such V1 or VO, need for chemicals that break down and release water.

  • Quick Cure:

A maker of LSRs can regulate the quantity of functional groups added as cure sites in the material, just like with ethylene propylene, where a terpolymer with double bonds is added, to adjust the degree of crosslinking of the elastomer. Higher reactivity is the outcome, which leads to extremely short cycle times for the mass manufacture of silicone components.

Liquid silicone rubber applications

Consumer electronics to high-strength industrial uses are all included in the vast variety of applications for liquid silicone rubber.

  • Molding using liquid silicone rubber
  • Molding using liquid silicone rubber (Source: DOW)
  • Outdoor, automobile, and professional lighting all use optics.
  • Lenses, LED illumination, Light guides, Optical connection, O-rings, buttons, parts, gaskets, and wire harness components for automobiles
  • Electronics: Light guides, LED lenses, and protective sleeves
  • Consumer products: Headsets, Googles, earplugs, and nose pads
  • Healthcare and Medical - Syringe stoppers, UV LED lights, flow control valves, catheters, lenses, and medical tubing

About Frank

With a background as an injection molding engineer at Kaysun, Frank brings unique depth and insight to his role as Business Development Engineer. His ability to synthesize information and pair need with opportunity is a benefit to prospects and customers alike.

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