Properties of lead-free gamma-ray shielding materials from metal oxide/EPDM rubber composites

Enhancing electromagnetic interference shielding effectiveness for radiation vulcanized natural rubber latex composites containing multiwalled carbon nanotubes and silk textile

“…This behavior was observed due to the increase in crosslinks between NR molecular chains caused by gamma rays that restrict the mobility of intercross‐linking chains, leading to the increase in overall strength of the samples. [ 29–32 ] The evidences of the effects of gamma irradiation on the increase of crosslinks could be seen by the subsequent decrease in swelling ratios from 3600% to 749% in nonirradiated NRL and RVNRL samples, respectively. The lower swelling ratios also implied a higher degree of crosslinking network in the sample, resulting from higher numbers of chemical bonds and crosslinks, which limited the water uptake.…”

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

“…However, as technologies relying on the use of high-energy photons are rapidly expanded, development in novel and better radiation-shielding equipment is constantly pursued with specific added-on properties such as flexibility, transparency, environmental friendliness, and self-healing ability. Examples of newly developed high-energy photon-shielding materials are self-healing gamma-shielding hydrogels from nano-bismuth oxide (nano-Bi 2 O 3 )/poly(vinyl) alcohol (PVA) [ 10 ], flexible ethylene propylene diene monomer (EPDM) and natural rubber (NR) composites containing metal oxides [ 13 , 14 ], biocompatible polyaniline reinforced with hybrid graphene oxide-iron tungsten nitride flakes [ 15 ], and environmental-friendly Bi 2 O 3 -filled concrete [ 16 ].…”

“…However, despite its advantages, Pb is highly toxic and hazardous to humans, animals, plants, and the environment as it could damage the brain and blood systems of living organisms, causing abdominal pain, constipation, headaches, irritability, and even death [ 21 ]. Therefore, alternative heavy-metal-containing compounds such as bismuth compounds, especially Bi 2 O 3 and Bi 2 S 3 , which are considered safer for producers and users than Pb, has gained much attention from researchers [ 13 , 14 ]. For example, the report from Poltabtim et al showed that EPDM composites containing 500 phr Bi 2 O 3 had a linear attenuation coefficient ( µ ) of 24.3 ± 2.2 m −1 at a gamma energy of 1.25 MeV [ 13 ], which was comparable with NR composites containing the same Pb content that had a µ value of 26.0 m −1 [ 22 ].…”

“…Therefore, alternative heavy-metal-containing compounds such as bismuth compounds, especially Bi 2 O 3 and Bi 2 S 3 , which are considered safer for producers and users than Pb, has gained much attention from researchers [ 13 , 14 ]. For example, the report from Poltabtim et al showed that EPDM composites containing 500 phr Bi 2 O 3 had a linear attenuation coefficient ( µ ) of 24.3 ± 2.2 m −1 at a gamma energy of 1.25 MeV [ 13 ], which was comparable with NR composites containing the same Pb content that had a µ value of 26.0 m −1 [ 22 ]. This comparison implied the high potential of Bi 2 O 3 and Bi 2 S 3 to replace Pb as effective and safe protective fillers.…”

“…Consequently, these effects lowered the overall strength and flexibility of the materials. Examples of the effects from high filler contents are a decrease in the tensile strength of Bi 2 O 3 /NR composites from ~13 MPa in a sample with 100-phr Bi 2 O 3 to ~8 MPa and ~6 MPa for samples with 300-phr and 500-phr Bi 2 O 3 , respectively [ 13 ]. Thus, the effects of radiation protective fillers in improving shielding properties but also lowering the overall mechanical properties of the composites are two competing factors which researchers and product developers must pay close attention to in order to produce NR composites that are effective, safe, and usable for all the intended applications.…”