Wednesday  |  Carnegie III  |  04:40 PM–05:00 PM

#13857, Unintended Consequences: Radiation Damage in Vinyl Nitrile Polymer Foams During Micro-Computed Tomography

Micro-computed x-ray tomography (µCT) is an important tool for quantifying the internal structure of heterogeneous materials. Integration of imaging and mechanical testing, in situ µCT, has improved the ability to connect strain-induced structural changes to mechanical responses, i.e., structure-property relationships. The effects of long-term exposure to ionizing radiation and its impact on polymer properties, in particular the mechanical response, is often not under characterized. Typically, for foams, each volume image collected on lab-scale µCT equipment requires total exposure time between 12 h and 24 h depending on resolution, and a given polymer specimen might be exposed for several days to generate an image series with incrementally increasing load or strain. Here, we describe the effects of radiation dosage on the mechanical and chemical properties of a vinyl nitrile-based closed cell polymer foam. We investigate these over 0 d, 1 d, and 2 d exposures to an x-ray tomography source at 4 W and 50 kV. Changes in the viscoelastic response were measured with dynamic mechanical analysis using a single frequency sweep (10 rad/s) over a range of temperatures (ca. -30 °C to 60 °C). Longer radiation exposure is associated with stiffening of the matrix. Thermal transitions were assessed using differential scanning calorimetry (DSC) from -80 °C to 100 °C. Thus, the matrix material of vinyl nitrile foams, and thus bulk properties, is sensitive to radiation exposure.

Alexander Landauer   National Institute of Standards and Technology
Orion Kafka   National Institute of Standards and Technology
Newell Moser   National Institute of Standards and Technology
Aaron Forster   National Institute of Standards and Technology