Solid State NMR Measurements for Preliminary Lifetime Assessments in gamma-Irradiated and Thermally Aged Siloxane Elastomers

Chinn, S C ; Herberg, J L ; Sawvel, A M ; Maxwell, R S

Lawrence Livermore National Laboratory

关键词: Aerospace Industry;    Coupling Constants;    37 Inorganic, Organic, Physical And Analytical Chemistry;    36 Materials Science;    38 Radiation Chemistry, Radiochemistry, And Nuclear Chemistry;   

DOI  :  10.2172/15014707
RP-ID  :  UCRL-TR-208387
RP-ID  :  W-7405-ENG-48
RP-ID  :  15014707

美国|英语

来源: UNT Digital Library

【 摘 要 】

Siloxanes have a wide variety of applications throughout the aerospace industry which take advantage of their exceptional insulating and adhesive properties and general resilience. They also offer a wide range of tailorable engineering properties with changes in composition and filler content. They are, however, subject to degradation in radiatively and thermally harsh environments. We are using solid state nuclear magnetic resonance techniques to investigate changes in network and interfacial structure in siloxane elastomers and their correlations to changes in engineering performance in a series of degraded materials. NMR parameters such as transverse ( T{sub 2}) relaxation times, cross relaxation rates, and residual dipolar coupling constants provide excellent probes of changes crosslink density and motional dynamics of the polymers caused by multi-mechanism degradation. The results of NMR studies on aged siloxanes are being used in conjunction with other mechanical tests to provide insight into component failure and degradation kinetics necessary for preliminary lifetime assessments of these materials as well as into the structure-property relationships of the polymers. NMR and MRI results obtained both from high resolution NMR spectrometers as well as low resolution benchtop NMR screening tools will be presented.