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Mechanical and radiation shielding properties of boron nitride reinforced high-density polyethylene

Herrman, Korey
In this study, the mechanical and radiation shielding properties of boron nitride (BN) reinforced high-density polyethylene (HDPE) were investigated. Pure polyethylene is considered the best material to use when shielding against galactic cosmic radiation in space; however, it lacks the mechanical properties necessary for structural applications. The effect of adding boron nitride to HDPE was evaluated by determining the mechanical and radiation shielding properties. The mechanical properties were investigated using varying amounts of BN by weight percent in the HDPE. The results for the flexural modulus showed little variation with changing the amount of BN present; however, the compressive modulus and tensile properties showed an increase when using above 5 wt.% BN. The results of these three tests were reinforced by the atomic force microscope (AFM). The storage modulus, loss modulus, and damping factor were found using dynamic mechanical analysis (DMA). The results of DMA showed higher values for storage modulus, loss modulus, and damping factor than for neat HDPE. The combination of these results led to the conclusion that higher amounts of boron nitride lead to better mechanical properties for the composite material. The number of extrusions the filament was exposed to was also considered during this study. This was investigated to determine if heating the sample multiple times would result in a negative effect on the mechanical properties. Performing multiple extrusions on the sample had little to no effect on the storage and loss modulus and resulted in a slight increase of the damping factor. The AFM results proved that by doing multiple extrusions, the BN would form agglomerates in HDPE. Two forms of radiation tests were also performed during this study: neutron exposure and heavy ion exposure. The neutron exposure tests were conducted on varying amounts of BN in the HDPE. For higher amounts of BN in HDPE, the shielding effectiveness increases. For the heavy-ion medical accelerator in Chiba, Japan (HIMAC) tests, a 30 wt.% BN-HDPE composite tank was tested using air and water as fillers. Compared to no shield, the tank proved to shield against the heavy ions when air and water were used as fillers, with water proving to be a better shield.