Development of Lead-Free Radiation Shielding Material Utilizing Barium Sulfate and Magnesium Oxide as Fillers in Addition Cure Liquid Silicone Rubber

Abstract

The radiological protection has the purpose of safeguarding the physical well-being of the user, preventing exposure to detrimental levels of ionizing radiation. This study introduces a novel, cost-effective category of lead-free elastomeric material designed for radiation shielding. The filler compounds utilized are notably lighter than conventional lead-based materials, enhancing user ergonomics during application. They comprise of a blend of barium sulfate combined or not with magnesium oxide with addition-cure liquid silicone rubber. To ensure the effectiveness of the radiation shielding, X-ray transmission measurements were performed for the different thicknesses of the materials and the results compared with Monte Carlo simulations. Additionally, the physical properties of the new materials, such as density, homogeneity, tensile strength, viscosity, and wettability, were also evaluated. The findings indicate that both materials fulfill the requirement for application in radiation protection garments.

Keywords: Geant4 Monte Carlo toolkit; addition cure liquid silicone rubber; barium sulfate filler; ionizing radiation; lead-free elastomeric radiological protection; magnesium oxide filler; transmitted radiation.

Figure 1

(a) Top view and (b) 3D view of 3D printing custom-made molds manufactured according to ASTM D412 [40]. All the dimensions as expressed in mm. The internal volume of the mold amounts to 3.627 cm³.

Figure 2

X-ray exposure depicting the evaluation of shielding effectiveness using a 4 mm sample placed on the X-ray QA meter.

Figure 3

Viscosity values for different shear rate for the ALSR 6014.

Figure 4

Mean and standard deviation of the tensile strength (a) and Young’s modulus (b) for the three formulations studied: pure silicone, ALSR-Ba, and ALSR-Ba-Mg. The error bars displayed correspond to the standard deviation associated with measurements obtained from three identical test specimens. The means indicated by the same greek letter do not differ significantly from each other.

Figure 5

Homogeneity analysis with EDS in ALSR with varying proportions of BaSO₄ and MgO, using energy-dispersive spectroscopy (EDS). ALSR with: (a) 10% BaSO₄, (b) ALSR with 10% BaSO₄ (combined with 10% MgO), (c) 30% BaSO₄, (d) 10% MgO (combined with 10% BaSO₄), and (e) 50% BaSO₄. The scale bar in the lower right corner of the SEM image represents a length of 80 μm, and the image was magnified 500 times. The red arrows indicate clusters of barium.

Figure 6

The simulated geometry was visualized using HepRep visualizer, generating an illustration comprising two perspectives: (a) a lateral view and (b) a 30° angled view. Within this visualization, distinct elements were distinguished: the scatterer (ALSR-Ba or ALSR-Ba-Mg), depicted as a yellow rectangle; the sensitive volume, depicted as a red cylinder; the external cover of the ionization chamber, depicted as a pink cylinder; photons, represented by green lines; and secondary electrons, denoted as red dots.

Figure 7

Simulated spectra emitted by the source with no filter. The dotted green line, the dashed yellow line, and the solid blue line represent the polychromatic spectra at 50, 60, and 80 kVp, respectively.

Figure 8

The behavior of the normalized effective transmission against the sample thicknesses. The frames (a,c,e) represent the ALSR-Ba compound for peak tensions values of 50, 60, and 80 kVp, respectively. The frames (b,d,f), in that order, represent the compound ALSR-Ba-Mg for the same peak tension values. The solid blue line represents a bivariate fit of the experimental data, while the dashed red line represents a bivariate fit of the simulated data.