Ageing and structural changes in PDMS rubber investigated by time domain NMR

1H Double Quantum (1H DQ) and Dipolar Filtered Magic Sandwich Echo (DF-MSE) methods were used to characterize the structural and dynamic modifications taking place during degradation of PDMS elastomeric networks. The samples were collected from an insulator extracted directly from the electrical wir...

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Bibliographic Details
Published in:	Polymer degradation and stability Vol. 166; pp. 300 - 306
Main Authors:	Munaro, Ana P., da Cunha, Giovanni P., Filgueiras, Jefferson G., Pinto, José M., Munaro, Marilda, de Azevedo, Eduardo R., Akcelrud, Leni C.
Format:	Journal Article
Language:	English
Published:	London Elsevier Ltd 01-08-2019 Elsevier BV
Subjects:	Biodegradation Chain entanglement Chain mobility Chains Crosslinking Crosslinking polymerization Degradation Elastomers Electrical junctions Entanglement Exposure Materials elasticity Molecular chemistry Networks NMR NMR spectroscopy Nuclear magnetic resonance Polydimethylsiloxane Polymers Rubber Silicone resins Silicone rubber insulator Thermal analysis Wiring Degradation Crosslinking NMR spectroscopy Polydimethylsiloxane Silicone rubber insulator
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Summary:	1H Double Quantum (1H DQ) and Dipolar Filtered Magic Sandwich Echo (DF-MSE) methods were used to characterize the structural and dynamic modifications taking place during degradation of PDMS elastomeric networks. The samples were collected from an insulator extracted directly from the electrical wiring that was exposed during 12 years to harsh atmospheric conditions. Information obtained included soft to hard ratio, dynamics of soft mobile chains, crosslink/entanglement density. Measurements were made at various depths, from the surface to bulk and at various distances from the core of the equipment. Molecular relaxations were also accessed by Dynamical Mechanical Thermal Analysis (DMTA). More exposed regions tended to have a higher content of dynamically restricted regions, suggesting a higher degree of junctions due to crosslinking and/or chain entanglements. The heterogeneity of the networks was significantly larger at the insulator's surface, suggesting that the atmospheric exposure induces not only cross-link formation but also defects on the networks. •Degradation of PDMS directly collected from the electrical wiring system was studied.•1H NMR methods were used to probe structural and dynamic features of PDMS networks.•Dipolar Filtered-Magic Sandwich Echo, Double Quantum and Low Field Time Domain applied.•Degradation along thickness and exposure level was explored.•Degradation pathways proposed.
ISSN:	0141-3910 1873-2321
DOI:	10.1016/j.polymdegradstab.2019.06.008