Understanding liquid silicone rubber properties will help you determine whether the product is good for a specific application or not.
Remember, liquid silicone rubber, also called LSR is known for its two-component feature. That is, the first component has the methylhydrogensiloxane while the second consist of a special curing agent called platinum.
But, what makes LSR unique?
Wide Temperature Range
LSR is stable in both cryogenic and high temperatures. For example, liquid silicone remains stable at 180°C. However, by adding specific additives, the LSR remains stable above 250°C.
At the same time, you can improve the cryogenic properties of LSR by adding special additives. Consequently, liquid silicone rubber will serve in extremely low-temperature conditions as low as -90°C.
Furthermore, the siloxane bonds have a 433 Kj/mol binding energy. This explains the superior thermal stability in LSR.
Additionally, it is worth noting:
- Electrical insulation of LSR varies from 1TΩ·m to 100TΩ·m depending on the temperature range
- The thermal conductivity is about 0.2 W/mΩ·K
Chemical Properties of LSR
Liquid silicone rubber has superior chemical resistance properties. LSR is considered a highly inert material due to its organic backbone. A reason it is popular in many applications.
This desirable liquid silicone rubber property is due to the unique siloxane bond.
Whenever are choosing liquid silicone rubber for any application, remember the material:
- Does not react with most chemicals
- Resist oxidation
- Resistant to both ozone and UV rays
- Moisture resistance (When exposed to an extended time, the rate remains low – about 1%)
- Resistant to unpressurized steam
Hypoallergenic and Biocompatibility
This is yet another important property of liquid silicone rubber in the medical or food industry. LSR does not cause any form of allergic reaction. Therefore LSR forms a perfect solution for most products in the healthcare and food industry.
Additionally, it has been approved by the FDA to be safe for most food and medical products.
High Degree of Elasticity
One of the main properties of LSR is its high degree of elasticity. This is contributed by the low molecular force. This allows the various chemical groups to rotate freely making it a highly elastic material.
Physical Properties of Liquid Silicone Rubber
In its pure form, liquid silicone rubber is distinctly known for its:
- Translucent color
- Smooth feeling
Furthermore, the average density varies from 0.0307 to 0.0650 lb/in³. On the other hand, the viscosity ranges between 15.0 and 1.30e+7 cP.
However, you cannot use these to conclusively ascertain that a particular material you are dealing with is liquid silicone rubber.
Mechanical Properties of Liquid Silicone Rubber
LSR is known for superior mechanical properties. It is also dimensionally stable. Besides, LSR is also tear resistant.
Although there are many LSR grades, some notable mechanical properties include:
- 400 to 1520 psi tensile strength
- 50 to 590 ppi tear strength
In addition to these, LSR is also:
- Flame retardant
- Exhibit low creep
- Show superior vibration resistance
Additionally, the unique properties make it perfect for fabrication using different techniques such as injection molding LSR, liquid silicone rubber Overmolding, or liquid silicone rubber compression molding.
Modifying Liquid Silicone Rubber Properties
At times, you may modify the molecular structure of the LSR. This can help you achieve specific properties for unique applications. That is, you can achieve this by altering the side groups.
For this reason, you will find many grades of liquid silicone rubber with varying properties.
These properties of liquid silicone rubber make the material the perfect choice for most applications today. Although the material is slightly expensive, it makes economic sense in specialized applications.