Epoxy resins composites for X-ray shielding materials additivated by coated barium sulfate with improved dispersibility

Epoxy resins additivated by barium sulfate proved to be promising low cost, easy workable and environmentally friendly alternative to lead and steel as X-ray shielding materials, but the composites tends to be stratified, with the additive accumulating in the bottom side of the sample. This sedimentation process has been, at first, studied by in situ X-ray powder diffraction, thermogravimetric techniques and X-ray tomography and then inhibited by exploiting finer barite sources, implementing a grinding procedure, combined to a surface modification of the inorganic additives. Stearic acid and sodium dodecyl sulfate were used to coat barite surface, using a liquid assisted grinding (LAG) approach. The functionalized additives resulted more compatible with the resin and their dispersion within the polymer resulted much improved. The produced composite samples were then studied by optical and electron microscopy, X-ray radiography, X-ray diffraction, thermogravimetric analysis and tensile strength test. The use of a finer additive and the grinding procedure allowed to limit the sedimentation and induced a marked hardening of the samples, with the drawback of a reduction of their plasticity. Stearic acid coating was able to eliminate sedimentation maintaining good mechanical properties.