Why only Hollow LSR parts Float on Water

Hollow liquid silicone rubber floats on water because its density is usually lower than water. Generally, this contributes the hollow LSR buoyancy.

If you want to learn more about this phenomenon on silicone rubber parts, read this guide.

Liquid Silicone Rubber Parts Density

Hollow Liquid Silicone Rubber Parts
Hollow Liquid Silicone Rubber Parts

In most cases, you will realize the density of liquid silicone rubber ranges from 1.0-1.2 grams per cubic centimeter (g/cm3). Liquid silicone rubber density varies on the materials based on the materials used.

Some of the factors that influence the density of liquid silicone rubber include:

  • Formulation
  • Curing process
  • Fillers
  • Additives

LSR Buoyancy

Liquid silicone rubber buoyancy depends on a specific gravity that usually causes the objects to rise in areas such as air and water.

The principle of buoyancy includes the density of water and density of liquid silicone rubber.

But again, you should note that it is affected by factors such as air entrapment, density of the LSR material, and the hollow design.

As a result, you can use LSR products in many applications such as marine and aquatic, medical devices, and consumer goods.

Quality Standards Relating to LSR Parts Floating on Water

When examining liquid silicone rubber parts floating on water, there are other quality standards you must consider. Generally, they all relate to:

Liquid Silicone Rubber Injection Molding
Liquid Silicone Rubber Injection Molding


Mainly used in medical devices and material applications and ensures they reach the required standards and are safe for use.


ASTMD 1418 helps to identify and group material grades and properties for certain applications.


It ensures that quality management system standards are applied to the manufacturing process resulting in consistency.


Mostly used in the medical device industry ensuring they meet quality management requirement


Used to determine the density and specific gravity of plastics by displacement


This method is used for testing the tensile properties of rubber


Used in testing the hardness of rubber materials.

Specific Volume of Hollow LSR Structure

The specific volume of the hollow liquid silicone rubber structure is mainly influenced by the material properties of the liquid silicone rubber. Of course, the design of the hollow structure plays an important role too.

To determine the specific volume of the LSR one should consider the following.

  • Material specific volume
  • Design volume calculation

Hollow Structure of LSR Parts

Hollow structure of liquid silicone rubber has different advantages. For example, you can use them in different applications like reducing weight and increasing buoyancy among others.

It can be created using different methods such as;

Injection Molding with Core Insert

This method is usually created from metal or other materials. The core is placed inside the mold cavity to create the hollow section enabling the LSR to be injected to fill the space around the mold.

Blow Molding

Liquid silicone rubber is forced out into a tube which is then clamped into a mold and then blown into the tube causing it to expand.

Dip Molding

In this method, a mold is dipped into a bath of liquid silicone rubber forming a layer of silicone around the mold.


Hollow liquid silicone parts float on water due to various reasons and principles of buoyancy. From our discussion above, you will realize the variables include additives, fillers, air entrapments, floating or sinking, density, and buoyancy among others.


More resources:

Step-by-step Liquid Silicone Rubber Injection Molding Process – Source: LEGENDAY

Top 10 Liquid Silicone Rubber Manufacturers in the World – Source: LEGENDAY

What Is Medical Grade Liquid Silicone Rubber? – Source: LEGENDAY

Liquid Silicone Rubber Properties – Source: LEGENDAY

Why only Hollow LSR parts Float on Water – Source: LEGENDAY


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