Natural Rubber Nanocomposites Research Articles

Bismuth oxyiodide nanorods towards improvements in fire safety and mechanical properties of natural rubber

Fire safety represents an enduring challenge in the realm of polymer-based nanocomposites, significantly limiting their application. The utilization of bismuth oxyiodide in flame retardant applications offers advantages such as increased surface area for improved interaction with combustible materials, the formation of a uniform flame retardant layer at the interface, and enhanced thermal stability. Hence, this work explored a facile strategy to synthesize bismuth oxyiodide nanorods by hydrothermal method combined with ball milling in anticipation of constructing an efficient flame retardant system. The bismuth oxyiodide nanorods dispersed relatively uniformly in the natural rubber matrix and endowed natural rubber nanocomposites with enhanced mechanical properties and fire-safety. The resultant natural rubber nanocomposite containing 5 wt% of bismuth oxyiodide showed a 36 % improvement in the tensile strength and a 39 % increase in the tear strength compared to those of the neat natural rubber. Cone calorimeter tests revealed that the introduction of 5 wt% bismuth oxyiodide to natural rubber matrix remarkably reduced the peak of heat release rate and peak smoke production release by 22 % and 25 %, respectively. A rational flame retardant mode of action for bismuth oxyiodide nanorods was proposed based on the analysis of pyrolysis fragments and char residues. Hence, this work provides a green and feasible method to prepare bismuth oxyiodide nanorods for flame retardant natural rubber products.

Fabrication and evaluation of organoclay-reinforced epoxidized natural rubber nanocomposites: A comprehensive study

The objective of this study is to assess the impact of incorporating a dual-functionalized organoclay with amine groups on the morphology and thermal characteristics of nanocomposites based on epoxidized natural rubber (ENR). To achieve this, organomodified montmorillonite clay (Cloisite30B) underwent treatment with 3-aminopropyltriethoxysilane (APS) via a silanization reaction, aiming to promote better interaction and compatibility between the two components. The structural and thermal properties of the resulting amine-functionalized Cloisite30B (f-C30B) were analyzed using infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Subsequently, various amounts of f-C30B (0, 1, 2.5, 5, 7.5, or 10 phr) were dispersed successfully in the ENR matrix using a solvent blending technique to create ENR/f-C30B nanocomposites. Standard techniques, including XRD, transmission electron microscopy (TEM), and TGA, were employed to analyze the nanocomposites for their structure and morphology. The morphological analysis revealed a uniform distribution of f-C30B throughout the ENR matrix. Moreover, TGA analysis indicated higher decomposition temperatures for ENR with f-C30B: 341 °C, 339 °C, 341 °C, 348 °C, and 352 °C for 1, 2.5, 5, 7.5, and 10 phr f-C30B, respectively, enhancing thermal stability. Char residues also rose accordingly: 2.3%, 1.9%, 3.7%, 4.9%, and 7.8%, respectively.Overall, this study highlights the potential of f-C30B as effective reinforcing agents in ENR-based nanocomposites, offering enhanced thermal stability, homogeneity, and valuable insights for the development of advanced ENR nanocomposites.

Enhanced Performance of Epoxidized Natural Rubber Nanocomposites for Strain Sensor Application

In this study, the major objective was to investigate the mechanical and electrical properties, and strain sensibility of the carbon nanotube (CNT) filled epoxidized natural rubber (ENR) nanocomposite. The second filler, cellulose nanofibers (CNFs), at various proportions was incorporated into the CNT-filled ENR nanocomposites. The preparation of ENR nanocomposite was carried out using a latex mixing process. The CNT:CNF hybrid filler was pre-dispersed in deionized water before being added to the ENR latex. The ratios of CNTs to CNFs varied from 1:0 to 1:0.05, 1:0.5, 1:1, 1:1.25, and 1:1.5. Although the presence of CNFs enhanced the stiffness of the substance, its negative effect on the tensile strength was noted. From the evaluated electrical properties, the outcomes demonstrated that the presence of CNFs with suitable proportions can have a positive effect on the performance of the substance when used as a stain-sensitive substance. The electrical conductivity of the hybrid ENR nanocomposite initially increased with the increase of CNF proportion up to 0.5. Beyond this proportion, the conductivity declined gradually. Moreover, the CNT:CNF1:0.5 filled ENR nanocomposite had the highest recoverable piezoresistive property. From this finding, it can be inferred that the CNT:CNF1:0.5 filled ENR nanocomposite is suitable to be used as a strain sensor device.

Preparation of deep eutectic solvents based on metal ions and their influences on reinforcement and strain softening behaviors of silica filled natural rubber nanocomposites

Deep eutectic solvents (DESs) are used as green additives to reduce zinc oxide (ZnO) activator usages and prepare volatile organic compounds-free nanocomposites. Herein highly active DESs containing different metal ions (Zn2+, Sn2+, Mg2+ and Fe3+) are introduced into silica filled natural rubber (NR) nanocomposites for regulating the network structure of rubber matrix and tailoring elasticity, strength and softening behaviors of the nanocomposites. The results show that DESs react with proteins in NR, which introduces hydrogen bonding between DESs and non-rubber components in the crosslinked network. DES can improve dispersion of silica and enhance the interfacial interaction between silica and NR. In comparison with NR nanocomposites containing 2 phr (part per hundred parts of rubber) ZnO, the partial replacement of ZnO with DESs can not only improve vulcanization rate, tensile strength and crosslinking density but also weaken the Mullins effect by reducing dissipation and softening energy densities. Normalization of tensile deformation energy density reveals that stress and softening behaviors are related to crosslinking density of NR and strain amplification effect induced by silica. The investigation is enlightening for mediating the reinforcement and strain softening behaviors and paving the way for manufacture high-performance NR nanocomposites in an energy-saving efficient and ecofriendly approach.

γ-radiation for improved reinforcement effect of single and hybrid nano-clay and cellulose nanofiber in thermoplastic natural rubber nanocomposite

The present research aims to investigate the effect of organoclay (OMMT) and cellulose nanofiber (CNF) filler loading exposed to different gamma irradiation dosages on the thermoplastic natural rubber (TPNR) of linear low-density polyethylene (LLDPE)/natural rubber (NR) and liquid natural rubber (LNR) as compatibilizer. The melt-blending method was used to prepare single nanofillers (3 wt % and 6 wt % filler loading) and hybrid nanofillers (same filler loadings with 1:1, 1:2 and 2:1 ratios) of OMMT and CNF incorporated into TPNR nanocomposites. The tensile results showed that 6 wt % CNF exhibited better tensile strength and elongation than OMMT with an increment of 77 % and 82 %, respectively. At 3 wt % filler loading, the hybrid nanocomposite at a ratio of 1:1 (OMMT:CNF) showed the best tensile properties. Upon gamma radiation, tensile properties increased from 5 kGy to 10 kGy until a dropping trend was observed at 15 kGy. The optimized tensile properties with 10 kGy irradiation aligned with the improved TPNR-nanofiller interface interaction, as observed from SEM morphology. The FTIR demonstrated the TPNR-filler interface interaction in single filler and hybrid nanocomposites, irrespective of gamma radiation. The obtained results reveal that OMMT/CNF in TPNR matrix is a suitable alternative for advanced lightweight structural and non-structural applications.

Compatibilization of Cellulose Nanocrystal-Reinforced Natural Rubber Nanocomposite by Modified Natural Rubber.

Due to global warming and environmental concerns, developing a fully bio-based nanocomposite is an attractive issue. In this work, the cellulose nanocrystals (CNCs) extracted from Luffa cylindrica, a renewable resource, were explored as a bio-based reinforcing filler in natural rubber (NR) nanocomposites. In addition, modified natural rubber was explored as a potential compatibilizer to assist the filler dispersion in the rubber nanocomposite. The effect of the CNC content (0-15 phr) on cure characteristics and the mechanical, dynamic, and thermal properties of NR/CNC nanocomposites was investigated. The results showed that the scorch time and cure time of the nanocomposites increased with increased CNC contents. The optimum tensile strength of NR nanocomposites having 5 phr of the CNC (NR-CNC5) was 20.60% higher than the corresponding unfilled NR vulcanizate, which was related to the increased crosslink density of the rubber nanocomposite. The incorporation of oxidized-degraded NR (ODNR) as a compatibilizer in the NR-CNC5 nanocomposite exhibited a considerably reduced cure time, which will lead to energy conservation during production. Moreover, the cure rate index of NR-CNC5-ODNR is much higher than using a petroleum-based silane coupling agent (Si69) as a compatibilizer in the NR-CNC5 nanocomposite. The good filler dispersion in the NR-CNC5 nanocomposite compatibilized by ODNR is comparable to the use of Si69, evidenced by scanning electron microscopy. There is, therefore, a good potential for the use of modified NR as a bio-based compatibilizer for rubber nanocomposites.

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.

Thermo-elasticity of multi walled carbon nanotube- natural rubber/acrylonitrile butadiene rubber blends

Natural rubber nano-composites are emerging as one of the key players in the industry and research due to its novel material properties and nano functionalities. In order to create high performance natural rubber nano-composites, new multifunctional nano-fillers can be created using a various approaches due to the advances of nanotechnology. Blends of natural rubber (NR) and acrylonitrile butadiene rubber (NBR) were used to evaluate the effects of various constitutional ratios between the two substances of fixed weight of multi walled carbon nanotubes (MWCNTs). The increase in the frequency of alternating extension (fatigue deformation) for samples (B2, B3) causes an increase in the thermo-elastic temperature change. The breakdown of the structure is thought to be prevailing at high strain amplitude and consequently may account for the observed effect. The thermo-elastic measurements also involve the determination of the thermo-elastic coefficient, change in entropy, internal energy per unit length, and Gruneisen constant. All these parameters were found to be highly dependent on both fatigue parameters and NR/NBR polymer ratios in the composite. The prepared sample (50/50 phr) can be used as thermo-elastic sensors.

Achieving ultra-tear resistant high-performance natural rubber nanocomposite via bio-inspired lignocellulosic compatibilization

Elastomers which are strong, tough, and resistant to tearing, are highly attractive for engineering applications such as conveyer belts, high-performance seals, tires, and soft robotics. Enhancing these properties for natural rubber materials is possible by utilizing nanoscale fillers, however the nanocomposite approach remains challenging because (a) nanofillers can impede latex molecular crosslinking, and (b) reduce the material’s inherent elasticity and compliance. This study demonstrates an approach to prepare ultra-strong, tear-resistant natural rubber nanocomposites using cellulose nanofibers decorated with nanoscale lignin. The reinforcement of latex with 0.1 wt% cellulose nanofibre compatibilized with 0.5 wt% lignin resulted in a 256% improvement in tear strength, 95% in tensile strength, and 50% in toughness, while retaining the elongation at break. Such a simultaneous improvement in tensile and tear properties has not been previously achieved through the latex casting method with any other fillers, and herein it is attributed to the nanoscale reinforcement efficiency of nanofibre coupled with enhanced interfacial adhesion between nanofibers and NR latex with the introduction of nanoscale lignin. This compatibilization approach has also resulted in improved resilience in the nanocomposites, as evidenced by the cycling loading and unloading analysis.

Exploring the suitability of psyllium husk nano-ash as green nano-filler for development of natural rubber nanocomposite

Exploring the suitability of psyllium husk nano-ash as green nano-filler for development of natural rubber nanocomposite

Structure–Property Correlation in Natural Rubber Nanocomposite Foams: A Comparison between Nanoclay and Cellulose Nanofiber Used as Nanofillers

Nanocomposite foams of natural rubber (NR) with 5 phr of two kinds of nanofillers, nanoclay (NC) and cellulose nanofiber (CNF), were produced using the latex mixing method and foaming with azodicarbonamide. The effect of the nanofiller on the structure and mechanical properties of NR foams was investigated through SEM, TEM, tensile tests, WAXD, and compression set measurements. Smaller cells with a narrower distribution were attained in the NC/NR foam when compared to the NR and CNF/NR foams, and the expansion ratio was larger due to the suppression of the shrinkage in the NC/NR foam. The foaming of the NR nanocomposites reduced the size of the filler aggregates and improved the dispersion and alignment of nanofillers in the cell walls. The addition of NC and CNF enhanced the tensile strength of the NR foam by 139% and 62%, respectively, without sacrificing the excellent strain of the NR, due to the acceleration of the strain-induced crystallization and small size of the filler aggregates. The compression set of the NR foam could also be reduced in the NC/NR foam compared with the NR and CNF/NR foams.

Synergistic effects of graphite and carbon nanotube hybrid fillers on key properties of epoxidized natural rubber nanocomposites

Synergistic effects of graphite and carbon nanotube hybrid fillers on key properties of epoxidized natural rubber nanocomposites

Enhancing curing, mechanical and electrical properties of epoxidized natural rubber nanocomposites with graphene and carbon nanotubes hybrid fillers

Enhancing curing, mechanical and electrical properties of epoxidized natural rubber nanocomposites with graphene and carbon nanotubes hybrid fillers

Physical property characterizations of natural rubber nanocomposites through experimental techniques, models and CRR concept

AbstractIn this research, the combinations of silica (SiO2), with either graphite (GR) or graphene oxide (GO), are studied as hybrid reinforcements of natural rubber (NR). Whereas individual improvements of rigidity, strength or ductility can be obtained depending on the composition, a synergistic reinforcement is specifically evidenced after addition of GO/SiO2 with a 3:1 ratio. For this formulation, both strength and modulus drastically increase while keeping the strain at break at a decent level. From the confrontation of all tensile tests results with theoretical reinforcement models, a good correlation between the experimental data and the Guth Gold model is observed, which reveals that the mechanical properties should essentially be governed by the filler/matrix interactions. This assumption has been discussed through the cooperative rearranging region (CRR) concept, by analyzing the calorimetric response of the nanocomposites at the glass transition. Not only the 3:1 GO/SiO2 composition is the only one for which the glass transition clearly shifts to higher temperatures, its CRR average size is also the lowest in comparison with reference NR. This result, interpreted as the signature of the most efficient intercalation of the fillers, matches well with the steep strain hardening recorded for this nanocomposite.

Fabrication and characterization of epoxidized natural rubber nanocomposites reinforced with mercapto‐functionalized nanozirconia filler

AbstractThe objective of this study was to develop a new type of nanocomposite material by reinforcing epoxidized natural rubber (ENR) through the integration of mercapto‐functionalized nanozirconia (SH‐ZrO2 NPs) synthesized using a ring‐opening reaction. The ENR was prepared through the epoxidation of natural rubber (NR) using in situ generated performic acid from formic acid and hydrogen peroxide. The SH‐ZrO2 NPs were pretreated and systematically embedded into the ENR matrix via a latex‐casting process, resulting in ENR/SH‐ZrO2 nanocomposites with enhanced properties. To prevent the accumulation of nanofillers in the ENR matrix, the surface of the nanozirconia was treated with 3‐(mercaptopropyl)trimethoxysilane (MTS) to create mercapto‐terminated ZrO2 NPs (SH‐ZrO2 NPs) that were covalently attached to the ENR chains. The presence of MTS on the surface of the nanozirconia was confirmed by FTIR and thermogravimetric analysis (TGA) analyses. Structural and morphological characterization of the resulting nanocomposites was performed using standard techniques such as x‐ray diffraction (XRD), scanning electron microscopy (SEM), and TGA. The morphological studies indicated a uniform distribution of SH‐ZrO2 NPs throughout the ENR matrix. Furthermore, TGA analysis revealed that the thermal stability of the nanocomposites was improved, as evidenced by a shift in the decomposition temperature to a higher value compared to neat ENR. Overall, this work demonstrates the potential of SH‐ZrO2 NPs as an effective reinforcing agent in ENR‐based nanocomposites, with improved thermal stability and homogeneity.Highlights Enhanced nanocomposite properties: Integration of mercapto‐functionalized nanozirconia improves the performance of epoxidized natural rubber (ENR) materials. Innovative synthesis approach: SH‐ZrO2 NPs synthesized via ring‐opening reaction offer a novel method for reinforcing ENR matrices. Improved thermal stability: ENR/SH‐ZrO2 nanocomposites exhibit higher decomposition temperatures, indicating enhanced thermal stability. Uniform dispersion: Morphological studies confirm the uniform distribution of SH‐ZrO2 NPs throughout the ENR matrix. Promising reinforcing agent: SH‐ZrO2 NPs demonstrate their potential as an effective filler for ENR‐based nanocomposites, enhancing homogeneity and performance.

Recyclable, Self-Healing, and Highly Thermal Conductive Natural Rubber Nanocomposites Enabled by a Dynamic Covalent Network with Carboxylated Boron Nitride Nanosheets

It is of great significance for saving resources and protecting the environment to endow rubber with excellent recycling ability. Recyclable and self-healing ENR/BN-COOH/GO nanocomposites were prepared through dynamic covalent crosslinking between epoxidized natural rubber (ENR) and carboxylated boron nitride (BN-COOH), and graphene oxide (GO) was used as a reinforcing filler. The constructed dynamic β-hydroxyl ester bond between ENR and BN-COOH resulted in the remarkable enhancement of interfacial interaction and effective energy dissipation, which contributed to good mechanical properties of the nanocomposites, increasing by 116 and 79% in comparison with ENR and ENR/GO, respectively. An exchangeable β-hydroxyl ester bond could regulate a network topology structure via a transesterification reaction at the interface, endowing ENR with desirable recycling and self-healing ability. Moreover, the significant improvement of thermal conductivity for ENR/BN-COOH/GO nanocomposites was achieved, reaching 2.853 W/(m·K) at only 6 wt % BN-COOH content, indicating the formation of effective thermal conductive paths via the β-hydroxyl ester bond and hybrid thermal conductive network of BN-COOH/GO. Meanwhile, the thermal conductivity of recycled samples still maintained a high level due to the construction of the stable thermal conductive network. Such a facile strategy exhibits a promising perspective in preparing recyclable and highly thermal conductive rubber nanocomposites for applications in efficient thermal management fields.

Molecular-Level Understanding of the Network Structural Changes of Thermo-oxidatively Aged Natural Rubber Nanocomposites

A combination of different macroscopic and microscopic methods is proposed to characterize the evolution of the network topology of natural rubber nanocomposites subjected to prolonged thermo-oxidative aging at 100 °C. The distribution of the elastically active chain density and the apparent dangling chain fraction of the aged specimens were monitored using solid-state 1H homonuclear dipolar double-quantum (DQ) nuclear magnetic resonance (NMR) spectroscopy. Both the evolution of the mechanical properties determined through dynamic tensile testing and the network structural changes highlight distinct aging mechanisms depending on the compound formulation. 1H DQ experiments reveal a gradual increase of the heterogeneities of the network over the aging duration and the formation of highly crosslinked domains. These domains are promoted by an autocatalytic thermo-oxidation process and correlated to specific oxidation products such as ether groups. On the other hand, the broadening of the residual dipolar coupling distribution, P(Dres), toward low Dres values is associated with the formation of highly mobile defect fractions induced by chain scission. Finally, the complex relationships between the evolution of stress–strain data and the network structural changes over aging emphasize the lack of a model of rubber elasticity that considers the crosslink density distribution and dangling chain fraction parameters determined through 1H DQ NMR.

Green Approaches for Functionalized Silica-Based Natural Rubber Nanocomposites Using Eco-friendly Sodium Alginate Biopolymers for Superior Static and Dynamic Behaviors

Green Approaches for Functionalized Silica-Based Natural Rubber Nanocomposites Using Eco-friendly Sodium Alginate Biopolymers for Superior Static and Dynamic Behaviors

Preparation and investigation of properties of deproteinized natural rubber nanocomposites incorporating functionalized nano‐alumina by in situ emulsion polymerization

AbstractThe present study reports the preparation, characterization, and investigation of properties of DNR/f‐Al2O3 nanocomposites through an in situ emulsion polymerization technique. The method consists of the dispersion of pretreated nano‐alumina (f‐Al2O3 NPs) onto deproteinized natural rubber (DNR) latex, followed by the polymerization reaction with the K2S2O8/K2S2O5 redox initiation system, after deproteinization of natural rubber using urea in the presence of a surfactant. To improve the compatibility and reactivity of the nanofillers with DNR latex, the nano‐alumina surface was treated with 3‐methacryloxypropyltrimethoxysilane (MPS) to produce f‐Al2O3 NPs. The thermo‐gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy approved that the MPS was bound onto the surface of Al2O3 NP. The resulting nanocomposites were characterized using standard techniques for physical properties and structural morphology, including X‐ray diffraction (XRD) analysis, FTIR spectroscopy, scanning electron microscopy (SEM), and TGA. The SEM images showed a homogeneous distribution of f‐Al2O3 NPs throughout DNR matrix. Due to such monodisperse particles, the DNR/f‐Al2O3 nanocomposite films revealed significant enhancement in thermal stability with increasing nano‐alumina loading as compared with the neat DNR.

Microstructure and Performance of Green Tire Tread Based on Epoxidized Solution Polymerized Styrene Butadiene Rubber and Epoxidized Natural Rubber

Blending a solution of polymerized styrene–butadiene rubber (SSBR) with natural rubber (NR) as a matrix and silane coupling agent (SCA) modified silica as filler is widely used to prepare green tire tread. However, it is difficult to adjust the distribution of silica in different phases of a rubber blend by SCA. Moreover, the coupling reaction between silica and SCA emits volatile organic compounds. In this work, we use a new strategy to improve the distribution of silica in two phases without a SCA. Epoxidized SSBR (ESSBR) and epoxidized NR (ENR) are synthesized, and the performance of silica-filled ESSBR/ENR nanocomposite (S-ESSBR12/ENR) is investigated and compared with that of silica-filled SSBR/NR nanocomposite (S-Si75-SSBR/NR) using Si75 as the SCA. The S-ESSBR12/ENR nanocomposites have stronger interfacial interaction that results in better silica dispersion than the S-Si75-SSBR/NR nanocomposite. The epoxy groups can effectively adjust the phase selective distribution of silica. The S-ESSBR12/ENR18 nanocomposite shows homogeneous distribution, leading to the best performance. Compared with S-Si75-SSBR/NR nanocomposite, S-ESSBR12/ENR18 nanocomposite increases wet-skid resistance by 118%, reinforcing index by 38%, and abrasion resistance by 40% and decreases rolling resistance by 23%. Moreover, S-ESSBR12/ENR nanocomposites are eco-friendly and have potential application in the production of green tire treads.