What Is Clear Liquid Silicone Rubber (LSR) and Why Is It a Good Choice for Injection Molding?

With Contributing Expertise From: Luis Marrero

Clear liquid silicone rubber — also known as optical silicone — is a transparent thermoplastic that is increasingly replacing glass in a range of applications. In this article, we discuss why and how so many manufacturers are incorporating clear silicone into their processes.


Clear liquid silicone can enhance the performance of a product in many ways. It is:

  • Lighter than glass and many other plastics, keeping the overall weight of a product down.
  • More flexible than glass but stiffer than other plastics, which reduces the risk of breaking, particularly when exposed to continuous vibrations or other stresses.
  • Optically and mechanically stable at extremes of heat and cold and capable of withstanding rapid shifts in temperature, making it ideal for indoor and outdoor use.
  • Long-lasting, as it will not fade or lose transparency with long-term exposure to UV rays.


Clear liquid silicone is more than just a strong, long-lasting material. It also has a number of properties that make it easy to work with and offer expanded design potential. For example:

  • Its low viscosity makes it ideal for injection molding, as it can fill a mold easily, allowing for more complex shapes and finer details than would be possible when working with another material.
  • It remains dimensionally stable as it cools, which makes it possible to design products with tighter tolerances.
  • It may not require additional polishing once molded, which speeds up production times and reduces secondary costs.
  • It is suitable for multishot and overmolding processes and can support undercutting and negative draft.

In short, clear silicone compares favorably to glass in almost all dimensional, mechanical and thermal properties. It is highly versatile, making it a good choice for any manufacturer that must meet strict production requirements while keeping costs down.


Potential uses for clear liquid silicone include:

  • Lighting: Lighting is an ideal application for clear liquid silicone. Manufacturers use clear silicone in bulbs, lenses and other optical components that would traditionally use glass.
  • Automotive: Thanks to its ability to withstand impacts, vibrations and extreme weather conditions, clear silicone is also excellent for automotive use. Manufacturers use it primarily for headlight casings and related parts.
  • Consumer goods: Clear silicone can be found in a number of consumer goods, ranging from electronics to novelty items.

Wondering if clear liquid silicone is the right choice for your project? SIMTEC can help. As a pioneer in injection molding, we regularly work with optical-grade silicone to manufacture items for businesses of any size. Call our office to learn more about the benefits of clear liquid silicone or to request a quote.



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