Natural Rubber Matrix Research Articles

Ultrasensitive and highly stretchable bilayer strain sensor based on bandage-assisted woven fabric with reduced graphene oxide and liquid metal

Flourishing flexible and wearable strain sensors still meet a challenge to realize ultrahigh sensitivity and wide working range simultaneously through a convenient strategy. Here, a strain sensor is designed based on natural rubber (NR) matrix and a bilayer structure composed of a highly stretchable liquid metal (LM) layer and a susceptible reduced graphene oxide (RGO)@carbonized bandage (CB) layer. By painting LM onto the surface of a graphene oxide (GO)-coated bandage template followed with a rapid flame pyrolysis, a dual conductive-layer woven fabric based on LM/RGO@CB was obtained. NR was then employed as an elastic substrate. Benefiting from the synergistic bilayer network and the high stretchability of the elastomer, the fabricated strain sensor exhibited ultrahigh sensitivity (gauge factor of up to 1.63 × 105), quite wide detection range (strain of 0 ∼ 515 %), low detection limit (0.25 %), fast response/recovery (135 ms/135 ms), and satisfactory durability (5700 cycles). The extraordinary strain-sensing performance allowed comprehensive monitoring of full-range (vigorous and subtle) human motions and physiological activities. This work provides a facile bilayer strategy for the preparation of high-performance strain sensors.

Effect of dispersants on the hydroxyapatite‐filled natural rubber biocomposites with enhanced functional properties

AbstractThe aim of this work was application of the hydroxyapatite (HAP) in various amounts by weight as a filler of natural rubber (NR) biocomposites. Innovatively, silanes, that is, (3‐aminopropyl)‐triethoxysilane (APTES) and bis[3‐(triethoxysilyl)propyl] tetrasulfide (TESPTS), surfactant, that is, cetyltrimethylammonium bromide (CTAB), and alkylimidazolium ionic liquids (ILs) with halide anions, that is, 1‐butyl‐3‐methylimidazolium chloride (BmiCl) and 1‐decyl‐3‐methylimidazolium bromide (DmiBr), were used to improve the dispersion of the HAP and curatives particles in the rubber matrix, and consequently the curing characteristics and properties of NR biocomposites. The influence of HAP and dispersants on the crosslink density, tensile properties, thermal stability, resistance to thermo‐oxidative aging, and ability to damp vibration of vulcanizates were investigated. It has been proven, that HAP can be efficiently used as a filler of NR biocomposites alternatively to commercial inactive or active fillers, for example, chalk, talc, or silica. The optimal HAP content is 30 phr. HAP did not detrimentally affect the curing characteristics of NR composites, crosslink density, and damping properties of the vulcanizates, while significantly raised their tensile strength, thermal stability, and resistance to thermo‐oxidative aging. Most importantly, CTAB and ILs considerably improved the dispersion of HAP and curatives particles in the NR matrix and consequently lowered the vulcanization temperature by approximately 25°C and enhanced by approximately 50% the crosslink density and tensile strength of the NR biocomposites.

Enhancing Natural Rubber Composites with Spent Coffee Ground: Physical Properties, Odor Absorption, and Processing

AbstractThis research aims to enhance natural rubber (NR) properties by incorporating spent coffee grounds (SCGs). Scanning electron microscope (SEM) reveals well‐dispersed SCG particles in the NR matrix without interaction. Shore A hardness notably increases by up to 49.90 (19% higher than unmodified), but tensile and tear strength decline with higher SCG levels. Optimal tear strength occurs at 10 phr of SCG due to uniform dispersion. The 300% modulus remains unchanged. The odor of composites (CO2 absorption) sees a 69.2% increase at 25 phr, while odor absorption efficiency peaks at 2%. Additionally, unmodified SCG affects scorch time (2.12%–23.40% increase from 1 to 20 phr) and cure time (3.12% to 76.82% improvement from 1 to 20 phr). These findings showcase improved hardness, enhanced CO2 absorption capacity, and effective odor control. Additionally, this study sheds light on the influence of SCG on processing times, contributing valuable insights for eco‐friendly applications.

Exploring the reinforcement and conductivity mechanism of K2FeO4‐modified multiwalled carbon nanotubes in carbon black/natural rubber composites

AbstractThis study employs potassium ferrate (K2FeO4) for the oxidation treatment of multi‐walled carbon nanotubes (MWNTs) under neutral and acidic conditions. A wet flash evaporation process is utilized to prepare natural rubber/MWNTs/carbon black composites, enhancing the performance of rubber composites. The increased oxidation level of MWNTs enhances their hydrophilicity, increases the quantity of oxygen‐containing hydroxyl groups on the surface, promotes dispersion within the natural rubber matrix, and ultimately improves the performance of the rubber products. The effective dispersion of MWNTs reduces electron transport resistance, forming a favorable electron transport channel in natural rubber. Experimental results indicate that K2FeO4 achieves the highest oxidation degree and optimal performance in an acidic environment. Compared to untreated MWNTs rubber composites, the oxidized MWNTs rubber composites exhibit a 34.9% reduction in the Payne effect, a 15.7% decrease in wear, a 12.7% reduction in rolling resistance, and a two‐order‐of‐magnitude increase in conductivity. This study provides a novel approach for preparing water‐dispersible MWNTs and high‐performance rubber composites, holding potential applications in premium rubber products and conductive rubber fields.Highlights The wet flash refining process improved the dispersion of MWNTs. K2FeO4 oxidation of MWNTs was enhanced under acidic conditions. Oxidized MWNTs combined with CB to form a CB‐MWNTs‐CB filler network. Oxidized MWNTs and CB increased the “ball‐chain” arrangement in NR.

Advancing mechanical performance in sustainable engineering: Synergistic effects of graphene oxide/nano‐silica hybrid nanofiller via latex coagulation in natural rubber composites

AbstractThis research investigates the utilization of a hybrid nanofiller comprising graphene oxide (GO) and amine‐modified nano silica in natural rubber matrix via the latex stage coagulation method. The resulting novel composite materials were characterized comprehensively for their static and dynamic mechanical properties. The hybrid nanofiller exhibited excellent dispersion within the rubber latex, facilitating the formation of a well‐interconnected network structure. The formed network resulted in remarkable improvements in tensile strength, elongation at break, and modulus of the composites. Dynamic mechanical analysis revealed that the hybrid filler (GO/nano‐silica hybrid (GO/NS)) could effectively reinforce the rubber matrix by constraining the mobility of rubber chains, leading to increased stiffness and mechanical strength. In fact, the confinement effect of the nanofillers has been carefully evaluated from dynamic mechanical spectroscopy. The increased glass transition temperature of the rubber nanocomposites specifies the restricted segmental mobility of the rubber chains. Moreover, the hybrid composites displayed significantly low rolling resistance, particularly GO/NS 2 (31% reduction), indicating their potential application as tire treads for fuel‐efficient and green tire manufacturing. The mechanical and rolling resistance properties achieved in these composites can be attributed to the efficient dispersion of the GO/nano‐silica hybrid(GO/NS) nanofiller and the resulting network formation within the rubber matrix. Findings emphasized the composites' viability as sustainable and eco‐friendly tire materials, potential for enhanced fuel efficiency, and reduced environmental footprint in tire manufacturing technology.Highlights The hybrid nanofiller (GO/nano silica hybrid) exhibited excellent dispersion within the rubber latex, leading to the formation of a well‐interconnected network structure. The resulting network structure significantly improved the tensile strength, elongation at break, and modulus of the composite materials. Dynamic mechanical analysis demonstrated that the hybrid filler effectively reinforced the rubber matrix, increasing stiffness and mechanical strength by constraining the mobility of rubber chains. Our hybrid composites displayed a remarkable reduction in rolling resistance, particularly GO/NS2, with a 31% reduction, indicating their potential application as tire treads for fuel‐efficient and green tire manufacturing. The study emphasized the composites viability as sustainable and eco‐friendly tire materials, offering potential benefits for enhanced fuel efficiency and reduced environmental footprint in tire manufacturing technology.

Acoustical, vibrational, and thermal investigations of pyrolytic carbon black reinforced natural rubber composites

The present study aims to utilize the carbonaceous filler (pyrolytic carbon black (PCB)) obtained from tire waste to fabricate composites for thermal, vibrational, and acoustical applications. Four composites were fabricated by increasing the PCB content (0, 10, 20, and 30 parts per hundred rubber (phr)) in the natural rubber (NR) matrix following ASTM D3182-21a standard. The optimum curing time was determined using a Moving Die Rheometer based on the ASTM D2084-19 standard. The physical, functional, microstructural, wettability, thermal, and mechanical properties of fabricated NR/PCB composites were comprehensively examined. Further, from an application standpoint, the study influence of increasing PCB content in a polymer matrix on thermal conductivity (TC), vibration damping, and sound transmission loss (STL) of the fabricated NR/PCB composites was investigated following ASTM E1530-19, ASTM E756-05, and ASTM E2611-17 standards, respectively. The study results indicate significant enhancement in the properties of the composites with increased PCB content. Specifically, the reinforcement of 30 phr of PCB in the polymer matrix led to a notable increase in TC (at 40 °C) by approximately 21.16% compared to NR/PCB0 composite. Also, the configuration mild steel (MS) + NR/PCB30 achieved the highest damping ratio, measuring 6.56 at the third vibration mode. Moreover, the average STL value of the NR/PCB30 composite showed a notable improvement of approximately 17.19% when compared to the NR/PCB0 composite, underscoring the effectiveness of PCB in enhancing the desired properties of the NR-based composites.

Dynamic Covalent Bonded Gradient Structured Actuators with Mechanical Robustness and Self-Healing Ability.

Flexible actuators with excellent adaptability and interaction safety have a wide range of application prospects in many fields. However, current flexible actuators have problems such as fragility and poor actuating ability. Here, inspired by the features of nacre structure, a gradient structured flexible actuator is proposed with mechanical robustness and self-healing ability. By introducing dynamic boronic ester bonds at the interface between MXene nanosheets and epoxy natural rubber matrix, the resulting nanocomposites with ordered micro-nano structures exhibit excellent tensile strength (25.03MPa) and satisfactory repair efficiency (81.2%). In addition, the gradient distribution structure of MXene nanosheets endows the actuator with stable photothermal conversion capability, which can quickly respond to near-infrared light stimulation. The interlayer dynamic covalent bond crosslinking enables good response speed after multiple bending and is capable of functional self-healing after damage. This work introduces gradient structure and dynamic covalent bonding into flexible actuators, which provides a reference for the fabrication of self-healing soft robots, wearable, and other healable functional materials.

Electrically Conductive Natural Rubber Composite Films Reinforced with Graphite Platelets.

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young's modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 × 10-4 S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates.

Analysis of static and dynamic mechanical properties of carbon black/carbon nanotubes hybrid filled natural rubber nanocomposites using coarse‐grained molecular dynamics

AbstractNanoparticle (NP)‐filled natural rubber (NR) has attracted much attention owing to their prominent mechanical strength, stiffness, and wear resistance. In this study, the static and dynamic mechanical properties of carbon black (CB)/carbon nanotubes (CNTs) hybrid filled NR nanocomposites are investigated using coarse‐grained molecular dynamics (CGMD) simulations. The non‐bonded coarse‐grained force fields for the CB/CNTs hybrid filled NR nanocomposites are constructed by combining several methods (i.e., effective force coarse‐graining, iterative Boltzmann inversion, and energy matching methods). The uniaxial tensile results indicate that the gradual replacement of CB by the same weight percentage of CNTs significantly improves the mechanical performances of the nanocomposites and increases the heterogeneity of the stress and strain distributions in the nanocomposites, which can be ascribed to the high mechanical strength of CNTs and the formation of the rigid interface networks between CNTs and the NR matrix due to the wrapping behavior of NR molecular chains on the surface of CNTs. Furthermore, the dynamic shear results demonstrate that the introduction of NPs significantly enhances the Payne effect of the nanocomposites, and the higher the CNT loading in hybrid NPs, the stronger the Payne effect. It is also found that the breakup of NP networks plays a dominant role for the Payne effect of filled rubber as compared to the interfacial separation between NPs and the rubber matrix. The present multiscale computational framework can be further extended to other polymer nanocomposites, and sheds new light on the design and exploration of polymer nanocomposites through bottom‐up prediction.

Investigation of Vibration Damping Characteristics of Natural Rubber Composites Reinforced with Waste Carbonaceous Fillers

The present work aims to utilize two different waste carbonaceous fillers, i.e., recycled carbon black (RCB) (industrial waste) and recycled graphite (RGP) (Battery waste), for the fabrication of vibration damping composites. Three types of composites were prepared, i.e., Neat NR, NR/RCB20, and NR/RGP20, using natural rubber (NR) matrix according to the standard ASTM D 3182-21a. The physical and mechanical properties of developed composites were investigated as per the standard ASTM D792-20 and ASTM D412-16. Moreover, the interfacial damping mechanism between polymer matrix, RCB, and RGP fillers was studied by determining vibration-damping properties as per standard ASTM E756-05. Furthermore, the influence of different parameters, such as particle size, carbon content, and surface area, of carbonaceous fillers on the resulting damping characteristics of developed composites was investigated through SEM, CHNS, and BET analysis. The result suggests that with the addition of 20 phr of RCB and RGP in the polymer matrix, the density of NR/RCB20 and NR/RGP20 composites were increased by ~ 7.08% and ~ 14.68%, respectively. Moreover, the mechanical and vibration damping properties of NR/RCB20 and NR/RGP20 composites show better performance than Neat NR composite.

Flexible lightweight Bi2O3-rubber based materials for X-ray protection

The flexible X-ray protective materials are commonly made of lead rubber. They have heavy weight, high biological toxicity, poor flexibility and aging resistance. The "weak absorption zone" in the energy range of 40–88 keV threaten environmental safety and human health. Bi2O3-rubber based flexible X-ray protective materials were prepared by rubber production process. The micromorphology, shore hardness, specific gravity, mechanical properties and radiation protective properties were characterized and analyzed. The results showed that Bi2O3 particles dispersed in natural rubber (R) matrix uniformly. The shore hardness of samples fluctuated between 41° and 46° with the increasing Bi2O3 content, lower than the Level 1 index requirement of the hardness (≤80°) of lead-free composite protective materials. The specific gravity increased from 1.35 g/cm3 to 2.38 g/cm3, which reduced approximately 34% comparing with the commercial protective materials containing Pb. The breaking strength and breaking elongation meet the index requirements in National standard GB 16757-2016. When Bi2O3 content reached 300 parts, the highest lead equivalent and maximum shielding ratio were 0.3012 mmPb and 52.95% respectively. It meets the index requirement of lead equivalent of 0.25 mmPb≤Pb≤0.35 mmPb for the front sheet of protective clothing. The effective shielding range of the protective material R/Bi2O3(100/300) was mainly in the range of incident energy of 65∼100 keV and 164–250 keV, which covered the “weak absorption zone” of lead.

Graphene rubber toward high content and energy saving enabled by spray drying

Graphene has always attracted widespread interest as a promising nano reinforcing filler for rubber. However, existing rubber preparation processes still difficult to find a balance between the high content of Graphene oxide (GO) addition and excellent dispersibility and interfacial interactions. And there are problems such as high energy consumption and long-time consumption in the production process. In this work, the content of GO in natural rubber (NR) was increased by spray drying, which effectively improved the performance of NR composites with high GO filler content. Compared with the NR composites filled with unmodified GO prepared by traditional latex blending method, the amount of GO added to the NR matrix was greatly increased to 30 phr without sacrificing excellent mechanical properties. More importantly, this process has the advantages of energy conservation and environmental protection. This means that users can add high content GO masterbatch with different ratios to mix with other rubbers to prepare rubber composites with the required GO content. This broadens the application of NR/GO composites and reduces production costs for the practical application of GO rubber in industry. Therefore, this work provides a new perspective for the preparation of energy-saving, environmentally friendly and high-performance graphene rubber tires.

Spherical CaCO3: Synthesis, Characterization, Surface Modification and Efficacy as a Reinforcing Filler in Natural Rubber Composites

Natural rubber (NR), an important natural polymer derived from the Hevea brasiliensis tree, has been widely used in the rubber industry owing to its excellent elastic properties. However, it requires reinforcing fillers to improve its mechanical properties for the manufacturing of rubber products. Generally, calcium carbonate (CaCO3) is employed as a non-reinforcing filler. This work aimed to synthesize spherical-shaped CaCO3 at a submicrometric scale without and with surface treatment and explore its utilization as a reinforcing filler in NR composites. The morphological shape and polymorphic phase of CaCO3 were investigated using SEM, TEM, XRD, ATR-FTIR and Raman techniques. The mechanical properties of various amounts (0 to 60 phr) of CaCO3-filled NR composites were explored. As a result, the NR/treated CaCO3 composites provided higher tensile strength than the NR/untreated CaCO3 composites and pure NR at all filler loadings. This may have been due to the improved interfacial interaction between NR and CaCO3 with the improved hydrophobicity of CaCO3 after treatment with olive soap. The optimal filler loading was 20 phr for the highest tensile strength of the rubber composites. In addition, the elongation at break of the NR/treated CaCO3 was slightly decreased. Evidence from SEM and FTIR revealed the vaterite polymorph and shape stability of CaCO3 particles in the NR matrix. The results demonstrate that the particle size and surface treatment of the filler have essential effects on the mechanical property enhancement of the rubber composites. Synthesized spherical CaCO3 could be a potential reinforcing filler with broader application in polymer composites.

Boosted Chemical Protective Properties Using Interface Constructed between Ti3C2Tx MXene and Natural Rubber.

Rubbers are extensively applied in chemical protective clothing (CPC) due to their eye-catching anti-penetration of chemicals. However, their impermeability, particularly that of natural rubber (NR), is unsatisfactory. In this work, we demonstrate the facile construction of Ti3C2Tx MXene/NR interface using a plant-scale and feasible method combining latex mixing, emulsion flocculation, and flat-plate vulcanisation. The above crafts achieved a homogeneous dispersion of Ti3C2Tx MXene in the NR matrix in a single layer, thereby constructing a strong interfacial interaction between Ti3C2Tx MXene and NR, which induced the formation of a robust three-dimensional (3D) network in the composite. The anti-swelling capacity of the 3D cross-linked network structure and the layered structure of Ti3C2Tx MXene effectively prolonged the permeation path of toxic chemicals. Compared with pure NR, the nanocomposite with 1 wt% of Ti3C2Tx MXene showed substantially enhanced breakthrough times of toluene, dichloromethane, and concentrated sulfuric acid (increased by 140%, 178.6%, and 92.5%, respectively). Furthermore, its tensile strength, elongation at break, and shore hardness increased by 7.847 MPa, 194%, and 12 HA, respectively. Taken together with the satisfactory anti-permeability, tensile strength, elongation at break, and shore hardness, the resulting Ti3C2Tx MXene/NR nanocomposites hold promise for application to long-term and high-strength CPC in the chemical industry and military fields.

Development of sansevieria trifasciata/natural rubber composites for a soft body armor application

Body armor is an indispensable material in the military and defense. The development of body armor nowadays has shifted to lower-cost material with comparable ballistic properties. This research studied the potential of sansevieria trifasciata (ST) fiber as a reinforcement in soft body armor composite. The ST fiber was treated with various NaOH concentrations to achieve the highest tensile strength. The result showed that the highest ST fiber strength was achieved at 1.2GPa by treating the fiber with 1 wt% NaOH solution. The rebound resilience properties of the natural rubber (NR) matrix were optimized by varying the accelerator and carbon black content and were tested according to ISO 4662. The optimum energy absorption of the NR matrix was obtained using 0.4 part per hundred rubber (phr) accelerator and 30 phr carbon black. The ballistic performance of ST/NR composites was evaluated through a simulation using LS-DYNA software. The ballistic simulation revealed that the minimum thickness of ST/NR composite was 15mm to stop a bullet with a velocity of 436m/s. The results of this study indicated that ST/NR green composite was a promising candidate for a soft body armor application.

Functionalization of mesoporous silica with oligoisoprene brushes: Application as charge for elastomers reinforcement

The interfacial interaction between mesoporous silica nanoparticles (MSN) and natural rubber was successfully improved by surface modification of hydrophilic silica using oligoisoprene brushes. This approach involved grafting 3-aminopropyltriethoxy silane (APTES) onto the silica surface, achieving a grafting efficiency of 13.22 % and generating amine groups. The long polyisoprene chains of natural rubber were selectively cleaved using an optimized oxidative reaction, resulting in the formation of short oligomers with carbonyl chain ends known as Carbonyl Telechelic Natural Rubber (CTNR), having a molecular weight of 4100 g/mol. The CTNR oligomers were subsequently linked to APTES-modified silica via a Schiff's base reaction, imparting hydrophobicity to the silica surface and enhancing its compatibility and dispersion within the natural rubber matrix. Two conditions, MSN@CTNR1 and MSN@CTNR2, were investigated, exhibiting grafting efficiencies of 10.66 % and 4.70 %, respectively. The functionalized silica particles from MSN@CTNR1 were examined and incorporated at varying proportions into rubber latex, leading to the formation of thin films. Surprisingly, films containing 1 part per hundred rubber (phr) functionalized silica had better mechanical and thermal properties than films containing unmodified silica. This study underscores the potential of MSN, whose surfaces are modified by grafting oligoisoprene brushes, to enhance the crosslinking points and serve as innovative additives in the formulation of composite rubber films. Furthermore, these findings highlight the prospects of utilizing modified silica nanoparticles as coating additive materials, enabling the enhancement of properties and performance in rubber-based composites, thereby paving the way for the development of advanced coating applications in diverse industries.

Pineapple fruit residue-based nanofibre composites: Preparation and characterizations

Abstract Natural fibre composites are widespread for being eco-friendly and having unique properties. This study prepared nanocomposites by water evaporation using cellulose nanofibres (CNFs) as fillers and natural rubber (NR) latex as the matrix. Here, CNFs were extracted from the “pineapple fruit residue,” a waste material in juice industries. These fibre-reinforced nanocomposites were prepared under three different weight/volume percentages (5%, 10%, and 15%) and analysed for their mechanical and thermal properties. Furthermore, the morphology and distribution of CNFs in the NR matrix were examined by scanning electron microscopy and Fourier transform-infrared (FT-IR) analysis. The study found that CNFs were randomly oriented and evenly distributed in the nanocomposite. CNFs were detected by FT-IR spectroscopy in the NR matrix, as indicated by absorption peaks at 1,033 and 1,057 cm−1. Thermogravimetric analysis reveals increased thermal stability with more CNFs. Tensile strength and elastic modulus also increase. Pineapple fruit residue-based CNFs enhance mechanical and thermal properties of NR composites and can be considered an ideal natural reinforcing material.

Three‐phase bio‐nanocomposite natural‐rubber‐based microfibers reinforced with cellulose nanowhiskers and 45S5 bioglass obtained by solution blow spinning

AbstractAiming at biomedical applications, the present work developed a new bio‐nanocomposite fibrous mat based on natural rubber (NR) reinforced with 45S5 bioglass particles (BG) and cellulose nanowhiskers (CNW), which reveals excellent mechanical properties, good biocompatibility and bioactivity properties. Analyses of the specimens were conducted by means of morphological observations (SEM) and thermal analysis (TG/DTG), as well as mechanical tests used to verify the effect of the incorporation of BG particles and CNW on the ultimate properties of these flexible NR‐CWN/BG fibrous membranes. An SEM analysis revealed that all filaments possessed a ribbon‐like morphology, with increasing diameters as the BG concentration increased. This likely results from an increased viscosity of the solution used for fiber blowing. In comparison with neat NR fibrous mats, the ultimate mechanical properties of bio‐nanocomposites were significantly improved due to the presence of CNW and BG particles dispersed in the NR matrix. According to the TG/DTG analysis, the specimens' thermal stability was unaffected by the high BG content, and the thermal profiles were similar, with isoprene chains decomposition of the NR occurring between 350 and 450°C. In‐vitro analysis on fibroblasts confirmed that the bio‐nanocomposite fibrous mats are noncytotoxic. It was found that fibrous mats enhanced cellular growth and hold great promise for tissue engineering applications.

Novel slag/natural rubber composite as flexible material for protecting workers against radiation hazards

This work is an attempt to employ the electric arc furnace (EAF) slag as a by-product material to develop an alternative and environmentally friendly material for gamma-radiation protection applications such as in medical and industrial areas. For this purpose, different concentrations of micro-sized EAF slag (0, 20, 40, 60, 80, 100, 500, and 800 phr) were incorporated as fillers in the natural rubber (NR) matrix to produce the shielding composites. In addition, nano-sized EAF slag particles were prepared by using a high-energy ball milling technique to investigate the effect of particle size on the gamma-radiation shielding properties. The synthesized micro and nano EAF/NR composites were tested as protective materials against gamma-radiation by employing NaI(Tl) scintillation detector and standard radioactive point sources (152Eu, 137Cs, 133Ba, and 60Co). Different shielding parameters such as linear and mass attenuation coefficient, half value layer (HVL), tenth value layer, mean free path, effective atomic number (Zeff), and effective electron density (Neff) were determined to assess the radiation shielding capability of the EAF/NR composites. Furthermore, equivalent atomic number (Zeq) and the exposure buildup factor values for photon energy in the range from 0.015 to 15 MeV were also computed by Geometric Progression method. The experimental results of micro EAF/NR composites showed that at 121.78 keV, EAF0 composite (without EAF slag content) had the lowest μ value of 0.1695 cm−1, while the EAF800 composite (which was loaded with 800 phr of micro EAF slag) had the highest μ value of 0.2939 cm−1 at the same energy, which in turn decreases the HVL from 4.09 to 2.36 cm, respectively. Therefore, increasing the filler weight fractions of EAF slag in the NR matrix, increases the shielding properties of the composites. Moreover, the NR composite reinforced with 800 phr of nano EAF slag has better gamma-radiation shielding efficiency compared to that filled with 800 phr of micro EAF slag. The success of this work was to prepare a flexible, lightweight, low-cost, and lead-free material with better shielding capability.

Effects of fiber loadings and lengths on mechanical properties of Sansevieria Cylindrica fiber reinforced natural rubber biocomposites

In this present investigation, Sansevieria cylindrica fiber was used as a reinforcement in a natural rubber matrix. Various biocomposite samples with different fiber contents (lengths and loadings) were fabricated, using compression molding process and vulcanizing technique by maintaining the temperature around 150 °C. From the results obtained, mechanical properties: tensile strength, modulus elongation at break and tear strength of 10.44 MPa, 2.36 MPa, 627.59% and 34.99 N respectively, were obtained from the optimum composite sample with length and loading of 6 mm and 20 wt% composition, respectively. The maximum hardness was observed at 76.85 Shore A from the composite sample of 6 mm and 40 wt%. The optimum properties can be attributed to the presence of strong interfacial adhesion between the Sansevieria cylindrica fiber and the natural rubber matrix. The mechanisms of failure of the biocomposites at their interfaces were examined and analyzed, using scanning electron microscopy (SEM). The micrographs obtained from SEM further confirmed that the Sansevieria cylindrica fibers were surrounded with more amount of natural rubber which can exhibit strong interfacial bonding between fiber and matrix. The optimal composites of this work can be used in general, abrasion resistant conveyor belt.