Degradation of silicone‐based materials as a driving force for recyclability

Abstract

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.

Closing the Carbon Loop in the Circular Plastics Economy

“…[ 559 ] Furthermore, ring‐closure depolymerization (Figure 12F) is the method of choice for regaining cyclic siloxane monomers from polydimethylsiloxane (PDMS), known as versatile silicone rubber. [ 560 ] As cyclic siloxane synthesis is capital‐, energy‐, and resource‐intensive, its molecular recycling via depolymerization of PDMS offers economic advantages. According to Albertsson switching back and forth between controlled ring‐opening polymerization (cROP) and controlled ring‐closing depolymerization (cRCDP) of cyclic carbonates enables reversible transition between monomeric and polymeric states by adjusting reaction parameters that determine T C .…”

Scanning Drop Friction Force Microscopy

“…Nonwetting coatings find a place in a variety of industrial applications, for instance, dirt-repellent surfaces, microfluidics, anti-icing, and antifogging surfaces, to name a few. − For their optimum performance, it is important to have a homogeneous hydrophobic coating. However, in reality, failure in the coating preparation process or harsh ambient conditions result in nonuniform or degraded coatings . Undesired localized variations in the wetting properties appear due to topographical or chemical surface imperfections.…”

Nurturing inclusivity: removing obstacles and valuing perspectives

“…Rupasinghe and Furgal point to the degradation mechanisms for siloxanes with impact on the fundamental understanding of siloxane durability but also on potential pathways for recyclability. 8 Fang and Guymon raise our awareness of dimensional shrinkage in polymeric materials that are prepared from free radical polymerization processes. 9 This perspective addresses a long-standing concern in traditional and rapidly emerging additive manufacturing processes, and suggests strategies to improve the mechanical properties of printed polymeric parts.…”

“…The theme of sustainability continues to resonate with early career scientists, and the recyclability of silicone‐based materials has received significantly less attention. Rupasinghe and Furgal point to the degradation mechanisms for siloxanes with impact on the fundamental understanding of siloxane durability but also on potential pathways for recyclability 8 . Fang and Guymon raise our awareness of dimensional shrinkage in polymeric materials that are prepared from free radical polymerization processes 9 .…”