Theoretical Determination of High-Energy Photon Attenuation and Recommended Protective Filler Contents for Flexible and Enhanced Dimensionally Stable Wood/NR and NR Composites

• Main Authors: Worawat Poltabtim, Donruedee Toyen, Kiadtisak Saenboonruang
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Polymers
• Subjects: natural rubber; wood particles; Bi₂O₃; Bi₂S₃; Pb; photon
• Online Access: https://www.mdpi.com/2073-4360/13/6/869

This work aimed to theoretically determine the high-energy-photon-shielding properties of flexible wood/natural rubber (NR) and NR composites containing photon protective fillers, namely Pb, Bi₂O₃, or Bi₂S₃, using XCOM. The properties investigated were the mass attenuation coefficient (<i>µ_m</i>), linear attenuation coefficient (<i>µ</i>), and half value layer (<i>HVL</i>) of the composites, determined at varying photon energies of 0.001–5 MeV and varying filler contents of 0–1,000 parts per hundred parts of rubber by weight (phr). The simulated results, which were in good agreement with previously reported experimental values (average difference was 5.3%), indicated that overall shielding properties increased with increasing filler contents but decreased with increasing incident photon energies. The results implied the potential of bismuth compounds, especially Bi₂O₃, to replace effective but highly toxic Pb as a safer high-energy-photon protective filler, evidenced by just a slight reduction in <i>µ_m</i> values compared with Pb fillers at the same filler content and photon energy. Furthermore, the results suggested that the addition of 20 phr wood particles, primarily aimed to enhance the rigidity and dimensional stability of Pb/NR, Bi₂O₃/NR, and Bi₂S₃/NR composites, did not greatly reduce shielding abilities; hence, they could be used as dimensional reinforcers for NR composites. Lastly, this work also reported the optimum Pb, Bi₂O₃, or Bi₂S₃contents in NR and wood/NR composites at photon energies of 0.1, 0.5, 1, and 5 MeV, with 316–624 phr of filler being the recommended contents, of which the values depended on filler type and photon energy of interest.