Exploring Silicone Rubber “Blooming”

Providing a unique balance of the chemical and mechanical properties required by many of today’s more demanding industrial requirements; Silicone Rubber continues to excel in many applications from architecture to healthcare.

An example of Blooming of Silicone Extrusions with Jehbco“Blooming” refers to the milky discoloration or white powder caused by the migration of compounds to the surface of the rubber. The presence of by-products or excess compounds can cause blooming, affecting both the functionality and aesthetics of the silicone rubber. Depending on the application, utmost purity and cleanliness of materials are essential, i.e. healthcare applications, or material aesthetics become a major material selection driving force, i.e. architecture design applications.

Most silicone rubber, among other silicone products, are derived from the same chemical starting material and are later differentiated. Depending on the application, tailored silicone rubber properties can be achieved through various mechanisms, such as the addition of fillers, functional fluids, and curing agents.

Curing; an essential process as to convert silicone rubber to solid from its highly-adhesive gel or liquid uncured state, is normally achieved in a catalyst-driven two-stage process; at the point of manufacture into the desired shape, and further in a prolonged post-cure process.

The choice of the catalyst system, either addition or peroxide, significantly affects the production of by-products. Addition curing system, i.e. platinum-based catalyst, the curing occurs with no byproducts, while peroxide-based curing system leaves behind byproducts, which can be an issue in food and medical applications. Both the solubility of any added fillers or agents, along with the presence of byproducts developed during curing, influence what is known as ‘Blooming’. Generally, each curing method has its own advantages and disadvantages, and based on the required end-product material properties, an optimised design selection is selected.

Accordingly, it is essential to select a reputable silicone manufacturer known for their high grades of raw materials and silicone expertise (we meet these requirements at Jehbco). By tailoring the process design per application, silicone can meet and exceed blooming and other requirements.

Overall, blooming can be influenced by the presence of added-materials to the silicone for enhanced properties and/or processability, along with the byproducts developed during the curing process.

For any help with your application, please review the Jehbco website www.jehbco.com.au, and contact us with any questions