Applications of Some Spectroscopic Techniques on Silicones and Precursor to Silicones

Tiwari, Atul

doi:10.1002/9781118938478.ch12

Cited by 4 publications

(5 citation statements)

References 44 publications

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“…Chemical structure of siloxanes caused that they are distinguished by many features that allowed their dynamic development, diversity and wide application. Especially significant is an unusual static flexibility of siloxane chain manifested by a huge number of available conformations, as well as dynamic flexibility related to the ease of rapid conformational changes ( Tiwari and Soucek, 2014 ). The extraordinary flexibility of polysiloxanes chain results from relatively long Si-O (about 1.64 Å) and Si-C bonds (about 1.88 Å), and the lack of substituents at every second atom of the chain.…”

Section: Characteristics Of Siloxanes (Silicones)mentioning

confidence: 99%

“…Table 2 presents the most important properties of siloxanes, which cause their common application as an active compound or auxiliary substance in medicinal products, medical devices, and cosmetics ( Kuo, 1999 ; De Buyl, 2001 ; Clarson, 2003 ; Lin et al, 2009 ; Mojsiewicz-Pieńkowska, 2011 , 2014 , 2015 ; Tiwari and Soucek, 2014 ).…”

Section: Characteristics Of Siloxanes (Silicones)mentioning

confidence: 99%

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Direct Human Contact with Siloxanes (Silicones) – Safety or Risk Part 1. Characteristics of Siloxanes (Silicones)

Mojsiewicz‐Pieńkowska

et al. 2016

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Siloxanes are commonly known as silicones. They belong to the organosilicon compounds and are exclusively obtained by synthesis. Their chemical structure determines a range of physicochemical properties which were recognized as unique. Due to the susceptibility to chemical modifications, ability to create short, long or complex polymer particles, siloxanes found an application in many areas of human life. Siloxanes differ in particle size, molecular weight, shape and chemical groups. As a result, this determines the different physico-chemical properties, that directly affect the safety or the risk of their use. The areas that can be a source of danger to human health will be commented in this paper.

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Section: Characteristics Of Siloxanes (Silicones)mentioning

confidence: 99%

Section: Characteristics Of Siloxanes (Silicones)mentioning

confidence: 99%

Direct Human Contact with Siloxanes (Silicones) – Safety or Risk Part 1. Characteristics of Siloxanes (Silicones)

Mojsiewicz‐Pieńkowska

et al. 2016

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“…Usually, it is preceded by branching of the polymer. These two processes are very important in silicone technology [ 1 , 2 , 3 , 4 , 5 ]. There are many methods for the formation of a cross-linked siloxane network.…”

Section: Introductionmentioning

confidence: 99%

Self-Restructuring of Polyhydromethylsiloxanes by the Hydride Transfer Process: A New Approach to the Cross-Linking of Polysiloxanes and to the Fabrication of Thin Polysiloxane Coatings

et al. 2022

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The branching and cross-linking of siloxane polymers are important processes in silicone technology. A new type of such a process has been developed, which is a self-restructuring of linear polyhydromethylsiloxane (PHMS). This process involves the reorganization of the PHMS to form a highly branched siloxane polymer or finally a cross-linked siloxane network. It occurs through the transfer of a hydride ion between silicon atoms catalyzed by tris(pentafluoromethyl)borane. Its advantage over existing branching and cross-linking reactions is that it runs at room temperature without a low-molecular-weight cross-linker in the absence of water, silanol groups, or other protic compounds and it does not use metal catalysts. The study of this process was carried out in toluene solution. Its course was followed by 1H NMR, 29Si NMR and FTIR, SEC, and gas chromatography. A general mechanism of this new self-restructuring process supported by quantum calculations is proposed. It has been shown that a linear PHMS self-restructured to a highly branched polymer can serve as a pure methylsiloxane film precursor.

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“…Elastomers represent a multibillion dollar industry and enjoy widespread use due to their exceptional properties including elasticity and durability. As a substitute for natural rubber, synthetic elastomers are critical constituents of automotive parts, sealing systems in construction and consumer applications, soft electronics, and biomaterials. , Typically, elastomers serve on applications where they would deform at low strain rates around room temperature, and under these conditions, their mechanical properties have been well characterized. Like most polymeric materials, elastomer performance is strongly affected by temperature and the strain rate, where often high-frequency oscillatory response is correlated with low-temperature or high-strain rate service conditions.…”

Section: Introductionmentioning

confidence: 99%

Quantifying Chemical Composition and Cross-link Effects on EPDM Elastomer Viscoelasticity with Molecular Dynamics

et al. 2021

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To understand the effect of chemical composition, cross-link density, and microstructure on the linear and nonlinear viscoelasticity of ethylene propylene diene monomer (EPDM) rubber, we carried out high-frequency oscillatory shear molecular dynamics simulations at varying shear strain rates. Sweeping through different EPDM compositions with varying ethylene, propylene, and diene ratios, a positive correlation was observed between the ratio of the propylene monomer and the complex shear modulus of EPDM in the high-frequency glassy regime. For small deformations in this regime, we found that the simplest measure of local molecular stiffness, namely, the Debye–Waller factor, is predictive of the complex shear modulus and loss modulus of 20 unique systems with distinct compositions and cross-link densities. Polymer design parameters that reduce the Debye–Waller factor, including cross-linking or increased propylene content generally, result in higher moduli. Remarkably, large-amplitude oscillatory shear simulations revealed that dissipation becomes strongly influenced by polymer entanglements, which results in divergent optimal compositions for small-strain vs large-strain applications of EPDM. Utilizing time–temperature superposition and varying strain rates in simulations, we were able to capture rheological properties over 6 orders of magnitude in frequency. The data was captured well using a Rouse model superposed with a stretched exponential function, which was used to predict key constants that determine the mechanical behavior in these regimes. Our findings establish a chemistry-specific molecular simulation approach for capturing the constitutive behavior of elastomers and pave the way for multiscale analyses linking composition and microstructure to performance.

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Applications of Some Spectroscopic Techniques on Silicones and Precursor to Silicones

Cited by 4 publications

References 44 publications

Direct Human Contact with Siloxanes (Silicones) – Safety or Risk Part 1. Characteristics of Siloxanes (Silicones)

Direct Human Contact with Siloxanes (Silicones) – Safety or Risk Part 1. Characteristics of Siloxanes (Silicones)

Self-Restructuring of Polyhydromethylsiloxanes by the Hydride Transfer Process: A New Approach to the Cross-Linking of Polysiloxanes and to the Fabrication of Thin Polysiloxane Coatings

Quantifying Chemical Composition and Cross-link Effects on EPDM Elastomer Viscoelasticity with Molecular Dynamics

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