How can we choose the appropriate hardness of Liquid Silicone Rubber

Liquid Silicone Rubber (LSR) are available in a wide range of hardnesses, from 0°A to 100°A, and are differentiated by units every 5 degrees. The different hardnesses of liquid silicone rubber have their own specific uses in applications. Next, we will focus on additive silicone, which is an important type of liquid silicone. Typically, the hardness of molded liquid silicone can be categorized as high, medium, or soft. Now, let's explore what each hardness level is used for.

What is the hardness of Liquid Silicone Rubber:

For liquid silicone rubber, the common hardness ranges from Shore 0°A to 70°A. Solid silicone rubber has a hardness range of Shore 30°A to 70°A. Liquid silicone rubber with a hardness below Shore 0°A is available but is rarely used and requires custom manufacturing. Its hardness must be measured using a Shore C hardness tester!Liquid silicone rubber can also be produced with hardness levels as high as 80°A to 90°A, but it becomes more brittle and is not commonly used. For hardness levels above 90°A, a Shore D hardness tester is used for measurement. This type of silicone rubber has very high hardness but little elasticity.

• Very soft silicone (0°A): Its elongation is extremely high, while its tensile strength is relatively low. Molded silicone also has a low tear strength but a significant elongation.

• Flexible silicone (5-10°A): The elongation and tensile strength of this type of silicone are at moderate levels and are adaptable to a wide variety of applications.

• Medium-hard silicone (20-30°A): Compared to soft silicone, medium-hard silicone is harder, while still retaining a certain degree of elasticity and compressibility.

• Hard silicone (40-50°A): This type of silicone is moderately hard and has both elasticity and compressibility for specific needs.

• Hard Silicone (60-90°A): Hard silicone is very hard and exhibits excellent abrasion and heat resistance properties for harsh environmental conditions.  
  

Application Areas

• Very Soft Silicone: This type of silicone is ideal for soft, bendable, stretchable or wobbly applications, such as the manufacture of children's toys and modeling.

• Soft Silicone: Its soft nature makes it ideal for soft gaskets, sealing gaskets and automotive parts.

• Medium Hardness Silicone: This type of silicone is often used to make electronic product shells, protective cases, etc., to provide the necessary protection with its moderate hardness.

• Hard silicone: In the automotive industry, hard silicone is often used for seals, molds, and anti-slip mats, etc. Its moderate hardness ensures elasticity and provides stability.

• Hard silicone: This type of silicone has a high degree of hardness and is ideally suited for the production of injection molds, various joints, seals, and wear parts, etc. Its excellent abrasion resistance and high temperature resistance properties allow it to perform well in harsh environmental conditions.

• Ultra-hard silicone: This type of silicone is usually used in applications that require high temperature, acid and alkali resistance, as well as abrasion resistance, such as seals for high-temperature environments and the manufacture of wear-resistant parts.
   
  

Product Characteristics

• Squeeze strength: low hardness silicone will gradually weaken when subjected to force, while high hardness will, on the contrary, gradually strengthen.

• Tear resistance: As the hardness of silicone increases, its tear resistance decreases, while lower hardness silicone exhibits better tear resistance.

• Tensile force: The hardness of silicone is closely related to its tensile force, and the level of hardness will directly affect the degree of deformation of the product.

• Wear resistance and fatigue: After long term use and break-in, high hardness silicone may suffer from insufficient wear resistance and reduced fatigue.

• Elasticity: Silicone with different hardness has different elasticity, which directly affects the use of the product and comfort.

In general, silicone hardness classifications, measurement methods and their areas of application vary. High-hardness silicone, with a hardness range of 40-100°A, is ideally suited for jig molds and precision parts. This type of silicone is hard, inelastic and resistant to deformation, and is capable of reproducing fine grain patterns precisely. Medium hard silicone, with a hardness of 10-30°A, is widely used for simple molds such as soap, candle and food molds. This type of silicone not only has good tear resistance, but also offers excellent reusability. Low-hardness silicone, with a hardness of around 0°A, is ideal for use in drip DIY molds and mannequins. Due to its low hardness, good elasticity and easy foam removal, it is possible to reproduce very fine patterns.

When choosing the hardness of silicone, the decision must be made according to the specific requirements of the mold and the use of the scene, in order to ensure the effect and quality of the mold production. Therefore, picking the right hardness of silicone products according to the actual needs is the key to meet the needs of different fields.