Difference Between Silicone and Siloxane

The key difference between silicone and siloxane is that silicone is a polymer material whereas siloxane is a functional group.

Although we use the terms silicone and siloxane interchangeably, they are very different from each other; a siloxane is a functional group while silicone is a substance containing this functional group.

CONTENTS

1. Overview and Key Difference
2. What is Silicone
3. What is Siloxane 
4. Side by Side Comparison – Silicone vs Siloxane in Tabular Form
5. Summary

What is Silicone?

Silicone is a polymer material containing many siloxane functional groups throughout its structure. Therefore, we can call this material polysiloxane. It is a synthetic polymer that does not appear in nature. This material contains a backbone, consisting of Si-O bonds. Moreover, there are side chains attached to this backbone. We usually consider this as an inorganic polymer because it has no carbon in its backbone.

Since the bond between Si-O is more strong, the backbone is very stronger than carbon-containing backbones. Due to the same reason, this material is highly resistant to heat.

What is Siloxane?

Siloxane is a functional group having the Si-O-Si linkage. This functional group is present in organosilicon compounds. The siloxane compounds can be either straight chain compounds or branched compounds. These linkages form the backbone of the silicone polymer, i.e. polymethylsiloxane.

The major route of forming a siloxane linkage is by condensation of two silanols. We can produce silanol by hydrolysis of silyl chloride. This compound is important in making silicon carbide upon ignition in an inert atmosphere. Moreover, siloxane polymers are useful as sealers for waterproofing surfaces.

What is the Difference Between Silicone and Siloxane?

Silicone and siloxane are not the same. The key difference between silicone and siloxane is that silicone is a polymer material whereas siloxane is a functional group. Furthermore, silicone has a number of siloxane groups repeating throughout the structure while the structure of siloxane is Si—O-Si bond. When considering the stability, silicone is very stable because of the Si-O-Si backbone which has no carbon-carbon bonds and Siloxane is unstable because it is a functional group and tends to react to form either a molecule or a polymer.

Summary – Silicone vs Siloxane

There is a distinct difference between silicone and siloxane although we use the terms silicone and siloxane interchangeably. Silicone is a polymer material whereas siloxane is a functional group.

Reference:

1. Lim, Alane. “What Is Silicone?” ThoughtCo, Jan. 11, 2019, thoughtco.com/what-is-silicone-4164214.

Image Courtesy:

1. “PDMS” By SeiThis W3C-unspecified vector image was created with Inkscape. – Own work (CC BY-SA 3.0) via Commons Wikimedia

2. “SiloxaneFxnlGp” By Smokefoot – Own work (CC BY-SA 3.0) via Commons Wikimedia