Degradative Thermal Analysis of Engineering Silicones

Lewicki, James P.; Maxwell, Robert S.

doi:10.1002/9781118938478.ch13

Cited by 9 publications

(13 citation statements)

References 60 publications

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“…Thermal degradation studies of siloxanes have shown that the polymers can degrade through a back biting mechanism where the silanol end group of the polymer chain can attack a silicon atom several repeat units back on the chain with formation of a cyclic siloxane oligomer and a shorter polymer chain as products . A schematic representation of this type of degradation is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Determination of cyclic volatile methylsiloxanes in personal care products by gas chromatography

Boehmer

Campbell

Dorn

et al. 2017

Intern J of Cosmetic Sci

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OBJECTIVE: Organosiloxanes are prevalent in personal care products (PCPs) due to the desired properties they impart in the usage and application of such products. However, the European Chemical Agency (ECHA) has recently published restriction proposals on the amount of two cyclic siloxanes, octamethylcyclotetrasiloxane (D4) and decamethylcyclotetrasiloxane (D5), allowed in wash off products such as shampoos and conditioners which are discharged down the drain during consumer use. This legislation will require that reliable analytical methods are available for manufacturers and government agencies to use in documenting compliance with the restrictions. This article proposes a simple analytical method to enable accurate measurement of these compounds down to the circa 0.1 weight per cent level in PCPs. METHODS: Although gas chromatography methods are reported in the literature for quantitation of D4 and D5 in several matrices including PCPs, the potential for generation of false positives due to contamination, co-elution and in situ generation of cyclic volatile methylsiloxanes (cVMS) is always present and needs to be controlled. This report demonstrates the applicability of using a combination of emulsion break, liquid-liquid extraction and silylation sample preparation followed by GC-FID analysis as a suitable means of analysing PCPs for specific cVMS. RESULTS: The reliability and limitations of such methodology were demonstrated through several round-robin studies conducted in the laboratories of a consortium of silicone manufacturers. In addition, this report presents examples of false positives encountered during development of the method and presents a comparative analysis between this method and a published QuEChERS sample preparation procedure to illustrate the potential for generation of false positives when an inappropriate approach is applied to determination of cVMS in personal care products. CONCLUSION: This report demonstrates that an approach to determine cVMS levels in personal care products is to perform an emulsion break on the sample, isolate the non-polar phase from the emulsion break and treat with a silylation reagent to abate potential in situ formation of cyclics during the course of GC-FID analysis. Round-robin studies conducted in laboratories representing multiple siloxane manufacturers demonstrated the reliability of the GC-FID method when measuring cVMS in PCPs down to circa 0.1%.R esum e OBJECTIF: Les organosiloxanes sont des compos es utilis es essentiellement dans les produits de soins corporels (PSC) en raison des propri et es recherch ees qu'ils conf erent quant a l'utilisation et application de tels produits. Cependant, l'Agence europ eenne des produits chimiques (AEPC) a r ecemment emis des propositions de restriction en quantit es pour deux des siloxanes cycliques -l'octam ethylcyclot etrasiloxane (D4) et le d ecam ethylcyclot etrasiloxane (D5)-qui sont autoris es dans les produits cosm etiques de type « wash off » tels que les shampoings et pr eparateurs capillaires e...

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Section: Resultsmentioning

confidence: 99%

Determination of cyclic volatile methylsiloxanes in personal care products by gas chromatography

Boehmer

Campbell

Dorn

et al. 2017

Intern J of Cosmetic Sci

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“…However, when the siloxane polymers have a 3D network structure, it is essential to n = 0 , 1, …. 24 rupture from two or more points for degradation. 68,80,82,129 Hydrolysis and catalytic depolymerization reactions are explained by using backbiting reaction mechanisms.…”

Section: Degradation Of Polysiloxanesmentioning

confidence: 99%

“…Filler type/level are the main characteristics of the structural architecture, and oxidative (or reductive) atmospheres also define the degradation rate. 24,80,132,135,139,[199][200][201][202][203][204][205][206][207][208][209] It is noted that polysiloxane types -Si-R-(Si-O) xwhere the R end group is a phenyl are more thermally stable than when R is an aliphatic group (Fig. 5).…”

Section: Thermal Degradation and Radical Scission Reactions Over 350 °Cmentioning

confidence: 99%

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

Rupasinghe

Furgal

2021

Polymer International

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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.

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“…Some knowledge of the original structure and components of engineered silicones can be understood from destructive techniques, such as pyrolysis, which allows for the interpretation of the thermal degradation products of the engineered silicones . Other techniques such as solid state nuclear magnetic resonance (NMR), attenuation total reflectance Fourier transform infrared (ATR-FTIR), and Raman spectroscopy are limited to bulk or surface analysis which generates broadly averaged data , and limited structural resolution.…”

Section: Introductionmentioning

confidence: 99%

NMR Methodologies for the Detection and Quantification of Nanostructural Defects in Silicone Networks

et al. 2018

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We present and discuss a sensitive spectroscopic means of detecting and quantifying network defects within a series of polysiloxane elastomers through a novel application of 19F solution state nuclear magnetic resonance (NMR). Polysiloxanes are the most utilized non-carbon polymeric material today. Their final network structure is complex, hierarchical, and often ill-defined due to modification. Characterization of these materials with respect to starting and age-dependent network structure is obfuscated by the intractable nature of polysiloxane network elastomers. We report a synthetic strategy for selectively tagging chain-end silanols with an organofluorine compound, which may then be conveniently and quantitatively measured as a function of structure and environment by means of 19F NMR. This study represents a new and sensitive means of directly quantifying aspects of network architecture in polysiloxane materials and has the potential to be a powerful new tool for the spectroscopic assessment of structural dynamic response in polysiloxane networks.

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Degradative Thermal Analysis of Engineering Silicones

Cited by 9 publications

References 60 publications

Determination of cyclic volatile methylsiloxanes in personal care products by gas chromatography

Determination of cyclic volatile methylsiloxanes in personal care products by gas chromatography

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

NMR Methodologies for the Detection and Quantification of Nanostructural Defects in Silicone Networks

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