•Thermal degradation of NR is an apparently exothermic and multistep reaction.•Tar yield reaches up to 96.59 wt%, along with a small quantity of char and gas.•Pyrolysis tar mainly consists of ...cycloolefin with a high proportion of D-limonene.•NR pyrolysis tar mainly consists of dimer (C10) or trimer (C15) of isoprene.•Cracking of NR molecular structure is mainly based on the β bond breakage.
Pyrolysis is a potential approach to treat post-consumer waste natural rubber (NR), however, unclear pyrolysis mechanism restricts its actual utilization. In this work, thermal degradation of NR was investigated combining dynamical method with pyrolysis on the infrared-heating fixed-bed reactor. Results show that thermal degradation of NR is an apparently exothermic and multistep reaction, tar yield reaches up to 96.59 wt%. Pyrolysis tar mainly consists of cycloolefin with a small quantity of chain olefins and mono-ring aromatic hydrocarbons. High temperature reduces the cycloolefin yield but promotes the generation of mono-ring aromatic hydrocarbons. Tar is mainly composed of dimer (C10) or trimer (C15) of isoprene with different structures. H type in tar is mainly aliphatic hydrogen. Besides, a possible pyrolysis mechanism based on the β bond breakage was proposed. The work can provide a theoretical basis for direct control of high value-added products during NR pyrolysis and achieve high efficiency pyrolysis of NR.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The special mechanical properties of natural rubber originate from the stretching of the network chains (i.e., cis‐1,4‐polyisoprene chains) in the rubber network. The chains with various lengths ...exhibit various relative extensions, leading to various normalized energy contributions to the mechanical properties of rubber. However, the stretching behaviors of cis‐1,4‐polyisoprene chains with different lengths are not studied clearly. Here, the stretching behavior, which is the basis for analyzing the normalized energy contribution, is obtained by the modified freely jointed chain model. Next, using a new statistical model, i.e., the two‐component quantum‐mechanics Gaussian (TCQMG) model, the relative extension–length relationship of network chains is determined. Combining the above results, the energy contributions of network chains with different lengths are analyzed. The results show that long and short chains show different stretching states. The following can be explained by these results: short chains play an important role in the mechanical properties of rubber. As the network chain density increases, the average length of the chains decreases, leading to the variation of the normalized extensions. It is found that the variation of the normalized extensions is responsible for both the effects of the network chain density and network chain length on the mechanical properties of rubber.
The elasticity of a single cis‐1,4‐polyisoprene chain (top) upon stretching is analyzed by the single‐chain mechanical model. When a natural rubber network (bottom) is stretched, the relative extensions of the network chains with different lengths are calculated by statistical mechanics. Combining the results, the normalized energy contribution of the network chains with various lengths is analyzed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Rubber promises to be an excellent matrix for heat dissipation composites due to its unique elasticity and flexibility. However, restricted by traditional processing approaches, it remains ...challenging to fabricate high-performance rubber nanocomposites with both good mechanical strength and high thermal conductivity (TC). Herein, we develop a novel GO-assisted gelation method to construct a 3D interconnected rGO@Al2O3 hybrid fillers network as efficient heat transfer path in natural rubber nanocomposite acquiring desirable performance. The as-prepared rubber nanocomposite, at a filler loading of 18.0 vol%, exhibits not only a largely increased tensile strength (25.6 MPa) but also a high TC (0.514 W/(m·K)). Owing to the construction of a highly interconnected filler network, the resulting 3D rGO@Al2O3-NR shows apparently higher TC than the nanocomposites prepared by conventional method at the same filler content. More promisingly, the filler network tends to orient perpendicular to the compressing direction at ultrahigh filler loading, causing surprisingly enhanced in-plane TC which is up to 3.233 W/(m·K) at 33.9 vol% filler content. Moreover, we can easily control electrical resistance by adjusting the mass ratio of GO to Al2O3, making the nanocomposites satisfy the use requirement of electrical insulation. This study provides a creative insight to the design of high-performance rubber nanocomposites with a bright application prospect in advanced heat dissipation materials.
•Alumina-coated graphene oxide hybrid fillers (GO@Al2O3) were fabricated by a facile electrostatic self-assembly method.•Interconnected filler network was constructed successfully in the NR nanocomposite via a novel and simple strategy.•The obtained NR nanocomposite exhibits a high thermal conductivity and excellent mechanical properties.•The volume resistivity of the resulting products is adjustable.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Developing mechanically strong and efficient self-healing rubbers is booming and shows great potential in a wide range of applications. Herein, by introducing pyridine ligands onto rubber chains via ...ring-opening reaction between epoxy groups and aminopyridine, we constructed dynamic Fe3+-pyridine coordination bonds in commercially available epoxidized natural rubber (ENR). The reversible nature of the coordination bonds endows the rubbers with efficient self-healing behavior under moderate conditions. Meanwhile, the coordination bonds can also serve as crosslinking points, which enhanced mechanical properties of the fabricated rubbers. When the molar ratio of Fe3+ to pyridine was 1 : 4, the tensile strength and 100% modulus reached 2.23 and 0.78 MPa, which are 18-times and 8-times that of the neat sample. Noteworthy, the sample also shows excellent self-healing capability with healing efficiency of 87% (tensile strength). Furthermore, by embedding conductive materials, we designed a conductive rubber with sandwich structure, which exhibits sensitive strain sensing behavior in detecting small strains.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Green biodegradable thermoplastic natural rubber (GB‐TPNR) based on simple blend of natural rubber (NR) and poly(butylene succinate) (PBS) was prepared using three NR alternatives: unmodified NR and ...epoxidized NR with 25‐ or 50‐mol% epoxide (ie, ENR‐25 or ENR‐50). It was found that ENR‐50/PBS blend showed the best compatibility, which resulted in superior mechanical and thermal properties with the highest crystallinity of the PBS phase, on comparing with the ENR‐25/PBS and NR/PBS blends. This might be attributed to stronger chemical interactions between the epoxide groups in ENR‐50 and the polar functional groups in PBS, which were confirmed by Fourier transform infrared (FTIR). Furthermore, scanning electron microscopy (SEM), atomic force microscopy (AFM), and polarizing optical microscopy (POM) micrographs of ENR‐50/PBS blend revealed phase separation with finer‐grained cocontinuous structure than in ENR‐25/PBS and NR/PBS simple blends. Furthermore, the chemical interactions in ENR‐50/PBS blend enhanced the resistance to accelerated weathering.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In this research, 3 different low degrees (4, 8, and 14 mol%) of epoxide functionalized natural rubber were prepared via chemical modification of natural rubber, which was then vulcanized. Each of ...them was mixed with silica (50 parts per hundred of rubber) without a silane coupling agent and investigated their properties. It was found that the tensile and tear properties, as well as abrasion resistance of the silica filled epoxide functionalized natural rubber vulcanizates were higher than the silica filled natural rubber vulcanizate. These properties improvements could be attributed to the interaction of the silanol groups of the silica with the epoxide groups of the modified rubber chains via chemical and physical interactions. This could be supported by the occurrence of tear parts from the morphology investigation of the tensile fractured surface of the modified rubber vulcanizates using a scanning electron microscope. The presence of silicon elements in the rubber matrix was evidenced by scanning electron microscopy and energy dispersive X-Ray spectrometer. Moreover, the silica filled epoxide functionalized natural rubber having 14 mol% epoxide content without a silane coupling agent exhibited low abrasion loss, low heat build-up and enhancement in loss tangent at 0 °C, hence improved wet skid resistance, compared to the silica filled natural rubber without a silane coupling agent. This work demonstrated that the prepared low degree of epoxide functionalized natural rubber could be potentially applied to the tire tread rubber application without the use of a silane coupling agent.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study investigates the incorporation of block natural rubber (NR) as a viscosity-inducing agent in NR oily liquids designed for drug delivery systems. A variety of liquids, encompassing natural ...oils, synthetic and non-oil liquids, and a eutectic mixture, were incorporated with NR using solvent displacement technique. Successful formulations were achieved for several oily liquids, with viscosity correlating to NR concentration. Particularly, a eutectic mixture of menthol and camphor exhibited optimal viscosity by direct dissolving enabling the development of transdermal ibuprofen delivery and injectable azithromycin for periodontitis treatment. NR prolonged the release of both drugs. The extended-release ibuprofen system holds promise for transdermal applications, while the azithromycin system displayed inhibitory effects against Staphylococcus aureus, Streptococcus mutans, and Porphyromonas gingivalis, suggesting potential for periodontitis treatment. Overall, this investigation advances the development of NR oily liquids as a versatile drug delivery system that can be applied both on the skin and for the local injection into the periodontal pocket, showcasing promise for various therapeutic applications.
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•NR oily liquids in eutectic mixture were successfully prepared by direct dissolving method.•Ibuprofen and azithromycin were incorporated into NR oily liquids.•Both NR and eutectic mixture could prolong drug release from the systems.•Azithromycin in the systems exhibited inhibitory effects against pathogens for periodontitis treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This research paper investigated the effects of the silica content and the sulfur vulcanization system on the mechanical properties of silica-filled natural rubber (NR) composite film and foam to be ...used in various applications. Three different sulfur vulcanization systems (conventional (CV), semi-efficient (Semi-EV), and efficient (EV)) were thoroughly studied to improve the quality of vulcanized NR and their composite with silica. The ground silica was treated with Silane 69. Scanning Electron Microscope demonstrated that the treated silica in NR was well dispersed. In addition, the treated silica resulted in better mechanical properties than for untreated silica. The optimum amount of silica in non-vulcanized rubber was 16 phr. Furthermore, the mechanical properties of vulcanized rubber from the CV system were better than those from the Semi-EV and EV systems due to the higher degree of crosslinking in the former. In addition, when the TSi/NR composite foam specimens at 8 phr had an applied load that was 4.41 times that of non-silica rubber foam.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
