Comprehensive Comparison: Solid Silicone Rubber (SSR) vs. Liquid Silicone Rubber (LSR)


You could be mistaken in thinking that all rubber is the same. A particular type of rubber can perform tasks that standard rubber cannot. Silicone rubber is composed of silicon and other elements. It can be used for various due to its exceptional properties, including gaskets, electronic potting, medical devices, and formed parts. It exists in both liquid and solid states, so called Solid Silicone Rubber (SSR) and Liquid Silicone Rubber (LSR). While they share the base material, their physical states, processing methods, and material properties differ significantly.

In this comprehensive comparison, we delve into the distinctions between SSR and LSR, exploring their manufacturing processes, material properties, and applications. We will explain in this article why silicone rubber is the best option for your needs and how to choose between liquid and solid forms.

Note: Solid Silicone Rubber (SSR), also known as High Consistency Rubber (HCR), is cured at high temperatures with either organic peroxides or a platinum catalyst. SSR contains long polymer chains with a high molecular weight, which provides the rubber with a solid consistency.


Physical State of Solid Silicone Rubber and Liquid Silicone Materials


1. Solid Silicone Rubber (SSR)

SSR is inherently solid at room temperature. Solid Silicone Rubber (SSR), also known as High Consistency Rubber (HCR), is cured at high temperatures with either organic peroxides or a platinum catalyst. It is typically supplied in the form of sheets, strips, or preformed molded components. This solid state is achieved through a process called vulcanization, which involves curing the silicone with heat and a curing agent. SSR, once cured, maintains its solidity, flexibility, and shape over a wide temperature range.

2. Liquid Silicone Rubber (LSR)

LSR, in contrast, is a liquid or highly viscous material at room temperature. It is a thermoset rubber supplied as a two-part, colorless, translucent paste that yields good clarity and excellent mechanical strength. This material offers unique characteristics that are not obtainable with conventional thermoplastic elastomers (TPEs). The mixing initiates a cross-linking reaction, transforming the liquid into a solid rubber within the mold. Once LSRs are heated and crosslinked, their chemical and physical properties can no longer be altered. This means that they will maintain their physical and chemical properties over a broad range of temperatures and environmental conditions.

What’s the Difference in Manufacturing Processes between SSR and LSR?


1. Solid Silicone Rubber (SSR)

Manufacturing with SSR primarily involves processes such as compression molding, transfer molding, and extrusion:

  • Compression Molding: In compression molding, preformed solid silicone material is placed in a mold cavity. The material is then subjected to both heat and pressure, causing it to take the shape of the mold. After curing, the finished part is removed from the mold.
  • Transfer Molding: Transfer molding is similar to compression molding, but it uses a plunger to force the material into the mold cavity.
  • Extrusion: Extrusion involves heating the solid silicone and forcing it through a shaped die to create continuous lengths of specific profiles or cross-sectional shapes.

2. Liquid Silicone Rubber (LSR)

LSR processing is primarily carried out through injection molding:

  • Injection Molding: LSR is processed through injection molding, where the two liquid components (silicone polymer and cross-linking agent) are mixed in precise ratios. The mixed liquid is then injected directly into a mold cavity. Inside the mold, the material cures, taking on the shape of the mold. Injection molding with LSR is known for its precision and design flexibility, making it ideal for creating intricate and highly detailed parts.

How to Distinguish Between Liquid Silicone and Solid Silicone from Material Properties?


1. Material Properties of Solid Silicone Rubber (SSR):

  • Heat Resistance: SSR exhibits excellent heat resistance, making it ideal for applications exposed to high temperatures. It remains stable within a broad temperature range, typically from -50°C to 232°C (-58°F to 450°F).
  • Flexibility: SSR maintains its flexibility over a wide temperature range. It can withstand bending, stretching, and compression without losing its shape.
  • Aging Resistance: SSR is highly resistant to aging, which is essential for parts with long lifespans.
  • UV Resistance: SSR can endure exposure to ultraviolet (UV) radiation without degrading or losing its physical properties.

2. Material Properties of Liquid Silicone Rubber (LSR):

  • Biocompatibility: LSR is biocompatible, making it suitable for medical and healthcare applications. It complies with stringent medical standards and is used in implants and other medical devices.
  • Intricate Detailing: LSR’s low viscosity allows for intricate detailing in parts. It is used in applications where precision is crucial, such as medical, electronics, and automotive.
  • Consistency: LSR offers consistent dimensions and uniformity in part production, reducing the need for post-processing.
  • Wide Temperature Range: LSR has a wide temperature range for applications, typically from -50°C to 232°C (-58°F to 450°F).

Which Silicone Rubber Should You Get for Your Product Application?



1. Solid Silicone Rubber (SSR)

Applications of SSR:

  • Gaskets: SSR’s heat resistance and flexibility make it ideal for gaskets, ensuring effective sealing even in high-temperature environments.
  • Seals and O-Rings: SSR is used in applications where airtight or watertight seals are essential.
  • Automotive Components: SSR is employed in automotive components exposed to engine heat and environmental stress.

2. Liquid Silicone Rubber (LSR)

Applications of LSR:

  • Medical Devices: LSR’s biocompatibility and precision make it suitable for medical implants, seals, and devices.
  • Electronics: LSR is used in applications like connectors, keypads, and electronic enclosures where precision and biocompatibility are vital.
  • Automotive Components: LSR is employed in automotive parts requiring intricate detailing, such as grommets and seals.

Curing and Vulcanization for Solid Silicone Rubber and Liquid Silicone Products


1. Solid Silicone Rubber (SSR)

Curing of SSR: The curing of SSR involves vulcanization, a chemical process that transforms the material from a rubber compound into a durable solid. Vulcanization typically occurs at higher temperatures.

2. Liquid Silicone Rubber (LSR)

Curing of LSR: LSR cures at lower temperatures compared to SSR. This characteristic is advantageous for heat-sensitive materials and allows for shorter cycle times in the injection molding process.

Your Silicone Rubber Product Forming Partner @GEMS-MFG


In conclusion, both Solid Silicone Rubber (SSR) and Liquid Silicone Rubber (LSR) have their unique advantages and are chosen for specific applications based on their distinct material properties and manufacturing processes. SSR excels in heat resistance and durability, making it suitable for applications that require stability in extreme conditions. LSR is valued for its biocompatibility, precision, and consistent performance across varying temperatures, making it ideal for intricate detailing and medical applications. The choice between SSR and LSR depends on the specific needs and requirements of the application, with each material offering a range of benefits to diverse industries.

Therefore, in the world of Silicone Rubber Products, your business partner like GEMS-MFG can be the key to unlocking your company’s full potential. We can bring expertise, custom solutions, quality assurance, cost efficiency, and timely delivery to the table. With a collaborative and sustainable approach, we help you succeed in today’s competitive manufacturing landscape, ensuring a long-lasting partnership built on trust and excellence. Choose your business partner for Solid Silicone Rubber and Liquid Silicone Materials wisely, and watch your manufacturing endeavors reach new heights of success. To get started, please request a quote through our convenient online form or call us.



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