Dose effects in the crosslinking of irradiated polysiloxane

Delides, C.G.; Shepherd, I.W.

doi:10.1016/0146-5724(77)90047-4

Cited by 30 publications

(14 citation statements)

References 14 publications

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“…These are likely the result of radiation induced backbiting reactions observed in previous studies of radiation induced degradation of siloxane polymers [5,6,[26][27][28][29][30][31][32][33][34][35][36][37][38][39]. It has been postulated that recombination of the two types of polymer radicals pSi and pSiCH 2 can lead to three types of crosslinks [5].…”

Section: Resultsmentioning

confidence: 94%

“…Gel-permeation chromatography and solution state NMR methods, for example, will only provide insight into the changes occurring in the soluble sol fraction. FTIR and standard magic angle spinning 13 C, 29 Si, or 1 H NMR can provide insight into the chemical speciation changes in the bulk materials if they are significant enough to produce signatures in sufficient quantity. Headspace analysis by various mass spectrometry based methods can provide insight into volatile or semi-volatile degradation by products, but provides no insight into the remaining polymer network topology.…”

Section: Introductionmentioning

confidence: 99%

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Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Maxwell¹,

Chinn

Alviso

et al. 2009

Polymer Degradation and Stability

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a b s t r a c tRadiation induced degradation in a commercial, filled silicone composite has been studied by SPME/GC-MS, DMA, DSC, swelling, and multiple quantum NMR. Analysis of volatile and semi-volatile species indicates degradation via decomposition of the peroxide curing catalyst and radiation induced backbiting reactions. DMA, swelling, and spin-echo NMR analysis indicate an increase in crosslink density of near 100% upon exposure to a cumulative dose of 250 kGray. Analysis of the sol fraction via Charlesby-Pinner analysis indicates a ratio of chain scission to crosslinking yields of 0.38, consistent with the dominance of the crosslinking observed by DMA, swelling and spin-echo NMR and the chain scissioning reactions observed by MS analysis. Multiple quantum NMR has revealed a bimodal distribution of residual dipolar couplings near 1 krad/s and 5 krad/s in an approximately 90:10 ratio, consistent with bulk network chains and chains associated with the filler surface. Upon exposure to radiation, the mean CU d D for both domains and the width of both domains increased. The MQ-NMR analysis provided increased insight into the effects of ionizing radiation on the network structure of silicone polymers.

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Section: Resultsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Maxwell¹,

Chinn

Alviso

et al. 2009

Polymer Degradation and Stability

View full text Add to dashboard Cite

show abstract

“…It has been shown earlier (Charlesby, 1991;Delides and Shepherd, 1977) that on radiolysis of PDMS at ambient temperature the main chain scission and crosslinking reactions occur simultaneously, although crosslinking reaction is predominant.…”

Section: Effect Of Radiation Dose On Mechanical Propertiesmentioning

confidence: 94%

“…PDMS can be regarded as a cross-linked polymer since the probability of cross-linking is much higher than the probability of chain scission. It may be concluded from the literature data that for PDMS the degree of cross-linking is proportional to the irradiation dose (Delides and Shepherd, 1977).…”

Section: Introductionmentioning

confidence: 99%

In vitro progesterone release from γ-irradiated cross-linked polydimethylsiloxane

Mashak¹,

Taghizadeh²

2006

Radiation Physics and Chemistry

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“…The relative contributions of these competing reactions can be a function of polymer sequence, the chain length (or mobility), the temperature, and the type of incident radiation. Because these dependencies may be interconnected or non-linear with dose or time, their effects are thus generally difficult to predict [6,[14][15].…”

Section: Introductionmentioning

confidence: 99%

Molecular weight distributions of irradiated siloxane-based elastomers: A complementary study by statistical modeling and multiple quantum nuclear magnetic resonance

Dinh

Mayer

Maiti

et al. 2011

Journal of Applied Physics

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ABSTRACT:The statistical methodology of population balance (PB) has been applied to predict the effects of cross-linking and chain-scissioning induced by ionizing radiation on the distribution of molecular weight between cross-links (MWBC) of a siloxane-based elastomer. Effective molecular weight distributions were extracted from the quantification of residual dipolar couplings by multiple quantum nuclear magnetic resonance (MQ-NMR) measurements and are taken to reflect actual MWBC distributions. The PB methodology is then applied to the unirradiated MWBC distribution and considers both chain-scissioning and the possibility of formation of three types of cross-links: random recombination of scissioned-chain ends (endlinking), random covalent bonds of free radicals on scissioned-chain ends (Y-cross-linking), and formation of random cross-links from free radicals on side groups (H-cross-linking). The qualitative agreement between the statistical modeling approach and NMR data confirms that it is possible to predict trends for the evolution of the distribution of MWBC of polymers under irradiation. The approach described herein can also discern heterogeneities in radiation effects in different structural motifs in the polymer network.--

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Dose effects in the crosslinking of irradiated polysiloxane

Cited by 30 publications

References 14 publications

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

Quantification of radiation induced crosslinking in a commercial, toughened silicone rubber, TR55 by 1H MQ-NMR

In vitro progesterone release from γ-irradiated cross-linked polydimethylsiloxane

Molecular weight distributions of irradiated siloxane-based elastomers: A complementary study by statistical modeling and multiple quantum nuclear magnetic resonance

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