Siloxane-based polymeric materials are widely used all over the world because of their chemical, mechanical, and thermal stability and due to their low toxicity. Despite their usefulness, the high energy cost used to make them is lost when they are discarded, wasting resources and energy. Practical and simple methods of recycling these materials are therefore required. However, the simplification of these methods is underdeveloped. The present techniques used to recycle silicone-based materials, such as polydimethylsiloxanes, often involve high temperatures/pressures and complicated setups. To address this issue, we have established an efficient room-temperature technique for the depolymerization of silicone-based polymers, elastomers, and resins in the presence of low catalytic amounts of fluoride in specific high swell organic solvents. The products primarily contain cyclic siloxane units (D 4 , D 5 , and D 6 ) as verified by GCMS and 29 Si nuclear magnetic resonance. Nearly any silicone resin can be depolymerized rapidly using these methods. Silicone-rich systems result in the best conversions and the highest quantity of identifiable cyclics, while complex resins resulted in complicated products alongside discernible cyclics. We have also repolymerized the products from this process to reform silicones via acid, base, and fluoride catalysis. This process has the potential for large-scale industrial processing because of the use of mild conditions and solvent recycling ability.

Siloxane polymers are an important industrial commodity based on the structure –(R2–Si–O)–. Scission of the siloxane bond is essential, as it is the first step leading to polymerization or the depolymerization of polymers into smaller units for potential recycling. These highly condition‐specific reactions selectively trigger whether polymerization or breakdowns occur and have been extensively studied over the past 80 years. However, studies to recycle siloxanes are still in their infancy. Traditional methods to synthesize silicones involve high capital‐intensive and environmental costs using carbothermal reduction. These reactions cause the excessive release of global warming gases such as CO2 and other pollutants into the environment. Therefore, being able to reuse and recycle them in a meaningful manner is highly sought. As a result, ways to controllably rupture the siloxane bond into known products have been a goal of siloxane researchers since the 1950s. Hydrolysis, catalytic depolymerization, thermal depolymerization and radical extractions are the main approaches to imbue the scission of the siloxane bond, resulting in a slew of products, including new polymers, cyclics or monomeric silanes. The present review summarizes the available published data on the degradation and depolymerization of polysiloxanes published up to July 2021. © 2021 Society of Industrial Chemistry.

Since the early 1800s, siloxane has been an industrial staple due to its remarkable structure, but even though there are many benefits for using siloxanes, there are significant environmental implications, one of which being the lack of recyclability. As the first step to polymerization or the depolymerization of polymers, the scission of the silicone bond is essential. While condition-specific reactions investigating what triggers polymerization have been extensively studied, traditional synthesis methods are unfortunately not ideal due to their high cost and detrimental release of greenhouse gases. Since the 1950s, several studies have related to rupturing the siloxane bond, including hydrolysis, catalytic depolymerization, thermal depolymerization, and radical extractions. This work has resulted in new polymers, cyclics, and monomeric silanes. However, only a few studies have focused on how to build new silicone-based materials from the primary siloxane cyclic forms. Thus, more investigation into better methods for recycling siloxanes is needed. This chapter summarizes and categorizes the published data on the degradation and depolymerization of polysiloxanes based on their reaction temperature up to July 2021.