The 400-MHz nuclear magnetic resonance spectrometer is used in studying the aging of polymer materials, using both solid and liquid samples.
Polymer Performance and Aging
Understanding polymer degradation mechanisms is often an important part of being able to predict the long-term reliability of individual components and systems. For this reason, Sandia National Laboratories has developed extensive technical expertise in polymer aging. Our polymer characterization facilities allow us to monitor and interpret degradation effects in diverse environments.We
- Follow various properties of polymers as they age to determine the characteristics most useful for monitoring degradation;
- Design and build unique experimental devices useful for monitoring polymer aging;
- Interpret property changes to determine the chemical and physical mechanisms underlying degradation;
- Design and conduct accelerated-aging experiments in various environments (including thermal, high-energy radiation, ultraviolet, humidity, mechanical stress, and electrical stress); and
- Interpret accelerated-aging results and develop models for extrapolating to make long-term polymer lifetime predictions.
Capabilities
- Age polymer samples for long time periods in diverse environments, including high-energy radiation, thermal, oxygen, ultraviolet, humidity, aggressive chemical, mechanical, and electrical stresses.
- Utilize a full complement of standard polymer analysis techniques to follow and interpret changes caused by degradation.
- Obtain maps of polymer modulus values with 50-µm resolution with unique modulus-profiling apparatus.
- Design efficient accelerated-aging experiments that maximize reliability of predictions.
- Interpret/model accelerated-aging studies of polymers in thermal, radiation, and humidity environments.
- Measure parameters necessary for modeling/understanding degradation effects, such as oxygen permeability coefficients from room temperature to 150°C.
- Measure oxygen consumption rates and identify/quantify gaseous degradation products during aging.
- Determine oxidative degradation mechanisms in polymers using spectroscopic techniques.
- Perform long-term compression stress-relaxation measurements versus time and temperature to predict long-term o-ring behavior.
- Develop stabilizers for polymers.
- Increase the wear resistance of polymers by plasma treatment.
- Extend the lifetime of adhesive bonding by plasma surface modification.
- Perform fundamental studies of electrical breakdown and conceive innovative real-time and post-mortem techniques to identify the location and cause of electrical-breakdown failures.
- Model electric-field distributions and electrically induced stress in dielectrics.
- Develop specific chemical sensors for monitoring degradation.
- Perform gaseous-atmosphere analyses for monitoring degradation products inside closed containers.
- Develop specialized scavenging devices for passive uptake of unwanted gaseous products (such as hydrogen).
- Profile composition, density, and cross-link density with nanometer resolution within thin polymer films.
- Extend the lifetime of adhesive bonds by chemical coupling strategies.
- Extend the lifetime of adhesive bonds by applying thin films that inhibit corrosion as well as enhance chemical bonding.
Major Resources
- Cobalt-60 gamma-ray facility that allows long-term radiation aging at numerous dose rates (1 krad/h to 600 krad/h) in combination with selected temperature (ambient to 250°C), surrounding atmosphere (air or nitrogen) and, if desired, electrical or mechanical loading.
- Continuously monitored, multi-temperature, long-term aging facility. Fully equipped polymer characterization facilities.
- Unique modulus profiling apparatus for mapping modulus values with 50-µm resolution.
- Oxygen-permeability coefficient apparatus modified for measurements to be made up to 150°C.
- Radio frequency plasma reactors with advanced in-situ diagnostics.
- State-of-the-art facility dedicated to ultrasensitive oxygen consumption measurements.
- Access to national neutron scattering facilities and extensive expertise in neutron scattering and reflection.
- X-ray reflection, x-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry (SIMS).
Recent Accomplishments
- Developed predictive aging methodologies for long-term, combined radiation plus elevated-temperature environments for the nuclear industry. Information is being used to predict the condition of nuclear power plant safety cables.
- Developed micromodulus profiling technique allowing identification of diffusion-related, oxidation degradation effects in aged polymers and derived theories that quantitatively explain these effects.
- Demonstrated accelerated aging methodologies (i.e., radiation, thermal and humidity environments) resulting in improved predictive capabilities for long-term applications.
- Developed first-and-only approach (ultrasensitive oxygen consumption) for quantitatively testing the often-used, but unsubstantiated low-temperature extrapolation of higher-temperature Arrhenius results.
- Developed superior methods of predicting the lifetimes of seal materials based on combining finite-element modeling of oxygen-diffusion anomalies and our ultrasensitive oxygen-consumption extrapolation approach.
- Demonstrated the power of 17O nuclear magnetic resonance for obtaining unique degradation information for materials oxidized or hydrolyzed in 17O enriched oxygen or water environments.
- Developed new method for profiling the cross-link density within thin thermosetting polymer films and primer/coupling agent films.
Humidity conditioning degrades interface strength but also modifies the adhesive's mechanical properties. Both must be understood to model the effects of aging. This test examined the beneficial effects of a hydrophobic monolayer between the epoxy and aluminum.- Established quantitative relationship between the extent of chemical bonding and engineering fracture quantities in shear and tensile loading.
Contacts: Robert Bernstein, (505) 284-3690, rbernst@sandia.gov
Jim Aubert, (505)844-4481, jhauber@sandia.gov
