NR Composites Research Articles

A chemical modification-free strategy for fabricating tough and tear-resistant natural rubber/polysaccharide material

Natural rubber latex (NRL) is widely used in a variety of products, including gloves, balloons, condoms, and foamed items like pillows and footwear components. However, the limitations of traditional NRL materials in terms of tear resistance and toughness restrict their use in high-end applications. Hence, developing tough and tear-resistant NRL materials using eco-friendly and user-friendly methods remains highly desirable. In this work, a chemical modification-free method is reported for the fabrication of tough and tear-resistant vulcanized natural rubber/carrageenan material (SNR/KC). KC is introduced into NRL via a modified latex mixing strategy, which can form hydrogen bonds with the non-rubber components (NRC) such as proteins on the surface of natural rubber latex particles. As a result, KC can be well dispersed and form a segregated network structure within the rubber matrix. The rigid filler network created by KC effectively impedes crack propagation and enhances energy dissipation during deformation. Furthermore, the presence of KC in the NR matrix fosters the strain-induced crystallization (SIC) of NR. All these contribute to the superior tear resistance and toughness of composite materials. With only 0.1 phr of KC, the composite exhibits a fracture toughness of 208.4 kJ/m2 and a tear strength of 50 kN/m. This work demonstrated that the interaction between polysaccharide and NRC of NRL can be leveraged to fabricate tough and tear-resistant NR composites without any chemical modification and tedious process, favoring a green development and high-quality pursuit of NRL materials.

High-value application of kaolin by wet mixing method in low heat generation and high wear-resistant natural rubber composites

In this study, a silane coupling agent and kaolin, a natural mineral resource, were introduced into the wet mixing process of natural rubber latex, the high wear-resistant and low-generation heat natural rubber composites were prepared. The sputtering, collision, and deposition of coupling agent/fillers/natural rubber latex mixed emulsion onto the roller effectively could break up the filler aggregates, enable fillers to be better infiltrated, distributed, and dispersed in the rubber. The effects of dry/wet mixing processes and the ratio of kaolin to silica on the crosslinking density, filler dispersion, extrusion rheological properties, gas barrier properties, dynamic mechanical properties and thermal stability of NR composites were investigated, and the silanization mechanism was summarized by FTIR and XRD. The experimental results showed that kaolin improved the crosslinking density and failure temperature, reduced the Payne effect, extrusion swell, and rolling resistance. Compared with 60 phr silica-filled natural rubber, the gas barrier property and wear resistance of 60 phr kaolin-filled natural rubber were improved by 64 % and 27 %, respectively, and the rolling resistance was reduced by 57 %. When the ratios of silica to kaolin were both 20:40, the crosslinking density, gas barrier property, and wear resistance of wet mixing were improved by 24 %, 45 %, and 9 %, respectively, compared with dry mixing. This study provided a new method for the high-value application of kaolin in wet mixing and green tires.

Preparation of low‐rolling resistance natural rubber composites from pyrolysis carbon black by plasma treatment

AbstractIn this study, the surface of pyrolysis carbon black (CBp) is modified by integrating the ball milling process with plasma treatment. High‐energy mechanical ball milling enabled more uniform contact and sufficient reaction temperature for the silane coupling agent and CBp. In addition, the impact of plasma activated the ash and surface deposits of CBp, reducing its inertness. Herein, the filler dispersion grade, Payne effect, vulcanization characteristics, and mechanical and dynamic mechanical properties are investigated by considering modified CBp/natural rubber (NR) composites. The ball milling plasma process can reduce the polarity of CBp. Compared with untreated CBp/NR composites, the plasma‐treated SCA‐CBp/NR composites exhibited increased CBp dispersion grades, higher processing safety, better processing fluidity, and improved mechanical properties. The reduced Payne effect ensured more filler‐rubber network structure, resulting in a reduction in rolling resistance.HighlightsThe coupling agent and CBp are treated by low‐temperature plasma and ball milling.The process promotes the formation of the filler‐rubber network.The dispersion grade of composites increased by 26.29%.The tensile strength increased by 5.57%, and the rolling resistance decreased by 19.44%.

Effect of multi-walled carbon nanotubes reinforcement on self-healing performance of natural rubber

Abstract This work is motivated by the desire to restore the quality of rubber-based product properties with the intention of prolonging the service life period, thus helping create a sustainable environment by proposing effective rubber waste management. This study experimentally investigated an intrinsically self-healing zinc thiolate grafted natural rubber (NRZT) compound filled with multi-walled carbon nanotubes (MWCNT) to assess its influence on mechanical properties and self-healing performance. The MWCNT loading varied to 0, 2, 4, 6, and 8 phr. The Equilibrium swelling test was used to quantify the amount of ionic and covalent crosslinks formed. Fourier Transform Infrared (FTIR) spectra were used to detect the presence of MWCNT in the compound. The mechanical properties computed by the tensile and tear strength tests showed that the incorporation of MWCNT increased both properties up to three and twofold, respectively. However, as expected, the elongation at break (Eb) value was reduced. The unfilled sample showed that it can heal up to ∼98 %, measured from the tensile strength. However, the healing efficiency obtained from tensile strength reduces to ∼88 % by incorporating 2 phr MWCNT. The Eb and its self-healing efficiency gradually decreased as the MWCNT amount increased. All samples showed outstanding properties under the tearing mode, where the healed samples produced higher tear strength (>100 % healing) than the initial value. Scanning Electron Microscopy (SEM) micrographs revealed a noticeable gap along the healed cut line with increased MWCNT numbers, possibly due to the lower reaction between polymerized zinc thiolate (PZTh) radicals with zinc thiolate (ZT) and rubber molecules. The work aims to investigate the influence of MWCNTs on the mechanical and healing performance of self-healing NR composites by comparing them to their unfilled sample.

Simultaneously Improved Curing, Mechanical, Antioxidative Properties and Reduced ZnO Loading of Silica Filled NR Composites by Incorporation of Low-cost Crude Carbon Dots via Conventional Melt-milling Method

Simultaneously Improved Curing, Mechanical, Antioxidative Properties and Reduced ZnO Loading of Silica Filled NR Composites by Incorporation of Low-cost Crude Carbon Dots via Conventional Melt-milling Method

Molecular Insights into Antioxidant Efficiency of Melanin: A Sustainable Antioxidant for Natural Rubber Formulations.

N-(1,3-Dimethyl butyl)-N'-phenyl-p-phenylenediamine (6-PPD) is a worldwide antioxidant commonly added to delay the thermo-oxidative degradation of tire rubbers. Unfortunately, 6PPD and its transformation product 6PPD-quinone are toxic to aquatic organisms (e.g., coho salmon). Herein, we explore the free radical scavenging activity and protective mechanism of melanin (MLN) on natural rubber's (NR's) oxidative resistance using molecular dynamics (MD) and quantum mechanical (QM) calculations. The relationship between the molecular structure and the chemical nature of the antioxidant molecules via transition state calculations is explored to unravel the reaction mechanisms of antioxidants interacting with peroxy radicals (ROO·) of NR with the estimation of reaction barriers. Following this, the radical scavenging activity of antioxidants was quantified via a hydrogen atom transfer mechanism and bond dissociation energy calculations. Parallel MD simulations were considered to study the interfacial interactions of antioxidant molecules with polymer chains and fillers with a quantifiable structure-property correlation. Given these results, the nanocomposite (NR-MLN-SiO2) with natural antioxidant melanin manifested outstanding antioxidant properties by preferentially bagging the ROO· radicals, thus improving NR's thermal-oxidative aging relative to 6-PPD. The MD results revealed that the intermolecular interactions at the NR/antioxidant interface benefited the antioxidant MLN to bind tightly to the NR in NR-MLN-SiO2 composite, thus exhibiting improved dispersion, O2 barrier properties, and thermo-oxidative stability, which could extend the service life of NR products (e.g., tires). In addition, as a sustainable antioxidant, MLN could replace toxic antioxidants like 6-PPD. More importantly, the QM/MD simulations provided a fundamental understanding of the mechanistic pathways of antioxidant molecules in NR composites, which are conducive to designing high-performance and sustainable green elastomers.

Improved interfacial interactions of modified graphene oxide/natural rubber composites with the low heat build‐up and good mechanical property for the green tire application

AbstractWith the rapid development of transportation system, the safety, reliability, and durability of green tires play an important role in modern transportation. While for the material preparation, the poor dispersion ability of reinforced filler and the weak interfacial interactions with polymer matrix seriously restricted the further application in the green tire field. Meanwhile, avoiding the use of organic solvents is also an environmental issue that needs to be considered in the preparation process. Herein, water‐soluble 2‐mercapto‐1‐methylimidazole (MMI) functionalized graphene oxide (GO‐MMI) was obtained through a simple, green and one‐step hydrothermal method. Additionally, the modified graphene oxide/natural rubber composites (GO‐MMI/NR) with different GO‐MMI content were prepared by the latex coprecipitation approach. As a result, the modified GO‐MMI could be evenly dispersed in the NR matrix through the mechanical blending and the obtained GO‐MMI/NR composites possessed the good comprehensive properties after vulcanization. Specifically, the tensile strength (26.8 MPa), elongation at break (801%), low heat build‐up (6.2°C), Deutsches Institute for Normung (DIN) abrasion loss volume (71.31 mm3) and heat resistance index (162.1°C) were synchronic‐lifting when compared with the GO/NR composites. The results demonstrated that obtained GO‐MMI/NR composites owned the promising application for the industrial‐scale green tires.

Significant Influence of Bound Rubber Thickness on the Rubber Reinforcement Effect.

In this work, the contribution of different types of carbon blacks (N115, N330, N550, N660) and their primary and secondary thermally cracked recovered carbon blacks to the mechanical properties of NR composites was evaluated. The thermally cracked recovered carbon blacks were prepared by cracking the rubber composites at 500 °C and de-hybridizing them at 900 °C. The characterization of the thermally cracked recovered carbon blacks by scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that carbon blacks after primary and secondary thermal cracking recovery were more prone to aggregation and exhibited a higher degree of carbon defects. The number and type of functional groups on the surface of these carbon blacks were significantly reduced. For NR composites with pristine samples added, the mechanical properties and the bound rubber content tests showed that the mechanical properties of the NR composites became weaker with the increase in carbon black particle size. The bound rubber content also decreased with increased carbon black particle size. The mechanical properties of the NR composites reinforced with carbon black recovered by primary and secondary thermal cracking would therefore decrease. The results of AFM and DSC tests further confirmed the decreasing trend of bound rubber. The present work demonstrates the effect of bound rubber content variation on the mechanical properties of rubber, demonstrates the morphology of bound rubber more visually, and provides new insights into the reinforcement theory of CB.

Multifunctional role of tannic acid in improving the mechanical, thermal and antimicrobial properties of natural rubber-molybdenum disulfide nanocomposites

Natural rubber is the only biosynthesized rubber and the most prominent of all the elastomers. Insertion of nanofillers into natural rubber matrix has received much research interest because of the enhanced mechanical, thermal, electrical, antibacterial, etc. properties of the final natural rubber nanocomposite. Molybdenum disulfide (MoS2), an important member in transition metal dichalcogenides (TMD) is having excellent optical, thermal, mechanical, electronic and antibacterial properties. The inherent properties of this novel filler was exploited through the preparation of natural rubber-MoS2 nanocomposites via latex dipping method in which tannic acid (TA), naturally occurring macromolecule was used as an exfoliating agent for MoS2. MoS2:TA dispersions were prepared in 1:2, 1:4 and 1:6 ratios by mechanical stirring followed by sonication method for analyzing the optimum amount of exfoliating agent for the preparation of NR-MoS2 nanocomposite. MoS2:TA in 1:4 ratio was found to be the optimum loading for the NR nanocomposite preparation with improved mechanical, thermal and antibacterial properties. The enhanced properties of the NR composites could be attributed to the synergistic effect of both MoS2 and TA. The current study shows the role of TA in tuning the properties of NR/MoS2 nanocomposites that enable their potential utilization in various biomedical applications.

Improving actuation strain and breakdown strength of natural rubber dielectric elastomers incorporated with AlN with silane grafting

In this study, dielectric elastomers offering intrinsically good integrated performances are achieved by introducing AlN particles grafted with γ-methacryloxypropyl trimethoxy silane (KH570). The C=C of KH570 participated in the vulcanization of NR, which could increase the dispersions and interfacial interactions. By incorporating 10 phr AlN-KH570 fillers, the dielectric and mechanical properties of the composite are increased compared with the pristine DEA, and the breakdown strength remains above 93.9 kV/mm. Correspondingly, the actuation strain of 10 phr AlN-KH570/NR composite is 7 times higher than that of pristine DEA under the same driving voltage. Consequently, the AlN particles developed here are promising candidates as dielectric in actuators, and their excellent electromechanical properties could be applied in future industrial applications of DEs.

Comparative study on the synergistic reinforcement of lignin between carbon black/lignin and silica/lignin hybrid filled natural rubber composites

When the content of carbon black (CB)/silica is constant, the combination of lignin and CB/silica offers obvious advantages over previously reported partial replacement of carbon black/silica by lignin. Considering the distinction between CB/lignin and silica/lignin interactions, the effects of lignin concentration on the vulcanization behavior, crosslink density, filler dispersion, and physical and mechanical properties of the NR composites were investigated. The results showed that the incorporated lignin extended the scorch time (ts1) and optimum vulcanization time (tc90) of the sulfur-cured NR/CB/lignin compounds. The addition of lignin was beneficial for reducing the networking of CB. Although the moduli at 100% and 300% elongation decreased, the NR/CB/lignin composites still exhibited good tensile strength and elongation at break, especially with the addition of lignin at less than 30 phr. For the silica-filled NR composites, the extent of vulcanization of the NR/silica/lignin compounds slightly increased, and the vulcanization rate showed little change. The introduction of lignin plays a significant role in the reinforcement effect of silica-filled NR composites. The strengthened interaction between silica/lignin and NR and the improved filler dispersion significantly contributed to improved reinforcement. However, severe filler networking was observed when the lignin concentration was too high (up to 50 phr), resulting in decreased tensile strength. It is worth mentioning that due to significant reinforcement and the little changes in the hardness of the silica-filled NR vulcanizates by the addition of lignin, the combination of lignin and silica becomes more practical and potential for the formulation optimization of industrial rubber products.

Physical-Mechanical Properties of Chartwell® Coupling Agent-Treated Calcium Carbonate and Silica-Reinforced Hybrid Natural Rubber Composites

In this work investigated the possibility of applying a superficial treatment to ultra-fine calcium carbonate aiming to improve its interaction with the polymer chains of natural rubber so it does not act just as a filler. Commercial processes commonly use 40 phr of Silica as reinforcement filler. Here, we have evaluated the partial replacement of Silica by two types of calcium carbonate into hybrid natural rubber composites, untreated ultra-fine calcium carbonate and with ultra-fine calcium carbonate treated with 2% Chartwell C-515.71HR®. We added calcium carbonate fillers to the composite mixtures (as replacements for commercial silica treated with silane) and studied their influence on the vulcanization process. According to our findings, between 25% and 75% of the silica can be replaced with treated calcium carbonate, and up to 30 parts of CaCO3 can be combined with 100 parts of NR without compromising the properties of the polymer matrix (NR), which generates economic advantages for this industry. Treated calcium carbonate was able to link the inorganic and organic parts of the composite due to its bifunctionality; hence, it can be used as a filler to partially replace silica in hybrid NR composites.

Strengthened self-healable natural rubber composites based on carboxylated cellulose nanofibers participated in ionic supramolecular network

Cellulose, as a green reinforcing agent for rubber, has excellent improvement on the tensile strength but usually accompany with a deterioration of extensibility and self-healing property. Herein, we report an efficient method to prepare robust and self-healable natural rubber/zinc dimethacrylate/carboxylated cellulose nanofibers (NR/ZDMA/CNC) composites which are constructed by a CNC participated ionic supramolecular network. Ionic supramolecular network in NR is generated by the polymerization of ZDMA during a controlled peroxide-initiated vulcanization of NR. Interestingly, NR with massive ion clusters has strong affinity with CNC, which facilitates the uniform dispersion of CNC and the compatibility between CNC and NR. Meanwhile, CNC participates into the supramolecular network via non-covalent interaction with NR chains equipped with ionic crosslinks. This greatly reduces the adverse effect of CNC on the dynamic characteristics of supramolecular network. As a result, the tensile strength of NR/ZDMA composite with 20 phr CNC could reach 4.13 MPa, while its self-healing efficiency still maintains at >80 %. Thus, NR composites with non-covalent interaction between CNC and supramolecular network display improved strength, maintained extensibility, and excellent self-healing capability. This study thus demonstrates a feasible approach to reduce the negative effect of reinforcing fillers on a self-healing rubber based on supramolecular networks.

In situ growth of ZnO on carbon nanospheres and its properties in natural rubber

AbstractCarbon Nanospheres (CNs) are nano‐carbon materials. In order to expand their application fields, this study applies them to rubber fillers. In this study, CNs were prepared by vapor deposition method in a high temperature tube furnace. After acidification of CNs, ZnO was grown in situ on the surface of CNs. CNs@ZnO/NR composite was prepared by traditional mechanical blending method. The experimental results showed that the ZnO nanoparticles were adsorbed on the surface of CNs, resulting in a strong interfacial interaction with the CNs. In the composite material, the hybrid is uniformly dispersed in the rubber matrix under the influence of its own many factors, thereby improving the cross‐linking effect of the composite material. Compared with the ZnO/NR composite, the modulus at 100%, 200%, and 300% elongation of NR composites are increased by 40.3%, 30.6%, 23.3%, and 9.6% respectively, maintaining the elongation at break of the composites. At the same time, the rigidity of the composite material is increased, the cross‐linking efficiency is improved, and the crosslinking density of the composite material is greatly improved. Compared with ZnOC/NR composite, CNs@ZnO/NR composite maintained better wet‐skid properties. The CNs in the CNs@ZnO can inhibit the agglomeration of ZnO nanoparticles, which can better improve the vulcanization rate and crosslinking density, and is an efficient vulcanization activator. This study provides a simple synthetic route for ZnO nanofillers for the preparation of high‐performance natural rubber composites.

Synergistic effect of cuttlebone particles and non‐rubber components on reinforcing ability of natural rubber and synthetic isoprene rubber composites

AbstractThe comparison of the reinforcing ability of cuttlebone (CTBO) particles in natural and synthetic isoprene rubber (NR and IR, respectively) composites were investigated. The CTBO particles could reinforce in both NR and IR composites. However, the improvement of tensile properties in CTBO‐filled NR composites was higher than that of IR composites due to the presence of non‐rubber components in NR. The non‐rubber components promoted the strong interfacial adhesions with filler and rubbery matrix to increase the bound rubber content. These results affected the increase of the stress softening degree, hysteresis loss, residual strain during cyclic deformation and the volume fraction of constrained rubber region (immobilized area of rubber) in CTBO‐filled NR composites. The atomic force microscopy evidently revealed good compatibility between the CTBO particles and the NR matrix due to the presence of organic components from CTBO particles and from non‐rubber components in NR. Accordingly, the CTBO particles and non‐rubber components play important roles in improving the properties of green rubber composite materials.

Effect of Lanthanum Cerium Cysteine on Cure Characteristics, Mechanical Properties, and Thermooxidative Aging for Natural Rubber

In this work, a novel additive lanthanum cerium cysteine (LC-Cys), with the molecular formula La0.35Ce0.65(Cys)3Cl3·3H2O, was successfully synthesized through complex decomposition reaction of L-Cysteine and chlorinated rare earths. The effects of additive LC-Cys on cure characteristics, mechanical properties, and thermooxidative aging were investigated. LC-Cys as a multifunctional additive was applied to increase the curing rate and reduce the content of zinc oxide in the presence of the sulfur vulcanization system. It was found that the vulcanizates filled with (5ZnO/2LC-Cys) exhibited the highest modulus, which indirectly indicated the high crosslink and stiffness of the vulcanizates. Moreover, the vulcanizates with LC-Cys showed excellent mechanical properties and resistance to thermooxidative aging. Compared to NR composites filled with normal ZnO, LC-Cys even enhanced the mechanical strength and thermooxidative aging properties with 40% lower ZnO addition.

Bioinspired modification strategy to improve thermal conductivity and dielectric constant of natural rubber composite for thermal management applications

AbstractNatural rubber (NR) composites filled with modified aluminum nitride (AlN) particles were successfully fabricated with high thermal conductivity and dielectric constant. To boost the interfacial interactions form thermal conductive networks between AlN and NR matrix, a mussel‐inspired polydopamine and γ‐(2,3‐epoxypropoxy)propy trimethoxysilane (KH560) grafting were combined to yield AlN‐PDA‐KH560. The double‐layer structure led to good filler dispersion of AlN‐PDA‐KH560 with decreased interfacial thermal resistances. As a result, the largest thermal conductivity in 30 phr AlN‐PDA‐KH560/NR was reached to 0.48 W/m K, which was 2.28 times larger than pure NR. Furthermore, the 30 phr AlN‐PDA‐KH560/NR composite also had relatively high dielectric constant (3.95 at 103 Hz) and low dielectric loss (~0.01 at 103 Hz), benefiting for long time operation and thermal diffusion. This strategy provides a facile, low‐cost, and scalable method to fabricate high electrical and thermal conducting composites for strong potential in thermal management for electronic devices.

Facile fabrication of chrome-tanned leather wastes/natural rubber composite: Mechanochemical de-crosslinking effect on collagen fibers and chrome complexation enabled in-situ compatibilization

With the growth of leather industry, plenty of leather solid wastes (LSW) have been generated annually but economic and ecological solution to utilize LSW is lacking because the crosslinked structure inhibits the reprocessing at macromolecular level to attain high performance materials. Herein, we present a facile route to realize physically de-bundling and de-crosslinking of chrome tanned collagen fibers as well as the preparation of LSW/natural rubber (NR) composite featuring remarkable tensile properties via mechanochemistry effect exerted by solid-state shear milling (S3M) equipment. It is found that original coordination between chrome and carboxylic group can be cleaved and the released chrome enables the in-situ compatibilization between LSW and natural rubber via the complexation between chrome and sulfur, which enables dual excellence in toughness and tensile strength compared with non-chromium containing composite. The improved dispersion and interfacial interaction enable the incorporation of 40 wt% LSW to afford respective NR composites with exceptional stress at 100 % strain (S100) and modulus, which are 5.07 MPa and 27.33 MPa, respectively, as well as superior tear strength and thermal stability. The S3M technology not only highlights a facile and green route to turn chrome containing LSW into high performance bio-based NR material, but also spurs the devising of innovative materials comprising leather collagen fibers.

SYNERGISTIC MAGNETORHEOLOGICAL NR–NBR ELASTOMER BLEND WITH ELECTROLYTIC IRON PARTICLES

ABSTRACT This article presents the development of a new kind of magnetorheological elastomer blend made with natural rubber, acrylonitrile–butadiene rubber (NR-NBR), and electrolytic iron particles through solution mixing. The compressive stress and elastic modulus of the composites in the isotropic and anisotropic states of the filler were studied. A unique study of the filler distribution and filler orientation mechanism was proposed from the compressive properties and scanning electron microscopy. A strong improvement in the elastic modulus of the NR–NBR blend from isotropic to anisotropic change was achieved as compared with NR and NBR in single-rubber composites. The filler content in the anisotropic magnetorheological elastomers was optimized by measuring the field-dependent elastic modulus in the presence of an externally applied magnetic field. The blend rubber composites showed better sensitivity in the presence of a magnetic field than the NR and NBR composites did. The improvement might be due to the better filler orientation and strong adhesion of filler particles by the NR phase in the blend matrix. The new elastomer blends may have applications in active dampers, vibrational absorption, and automotive bushings.

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

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 (µm), linear attenuation coefficient (µ), and half value layer (HVL) of the composites, determined at varying photon energies of 0.001–5 MeV and varying filler contents of 0–1000 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 µm 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 Bi2S3 contents 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.