State-of-the-art processes cannot achieve rubber/multi-walled carbon nanotube (MWCNT) composites with satisfactory performance by using pristine MWCNTs and conventional processing equipment. In this work, high performance rubber/MWCNT composites featuring a combination of good mechanical properties, electrical and thermal conductivities and damping capacity over a wide temperature range are fabricated based on a well-developed master batch process. It is demonstrated that the MWCNTs are dispersed homogeneously due to the disentanglement induced by well-wetting and shearing, and the elastic-resilience-induced dispersion of the MWCNTs by rubber chains via the novel processing method. To further enhance the efficacy of elastic-resilience-induced dispersion for MWCNTs, a slightly pre-crosslinked network is constructed in the master batch. Consequently, we obtain rubber/MWCNT composites with unprecedented performance by amplifying the reinforcing effect of relatively low MWCNT loading. This work provides a novel insight into the fabrication of high performance functional elastomeric composites with pristine CNTs by taking advantage of the unique elastic resilience of rubber chains as the driving force for the disentanglement of CNTs.
No abstract is provided for this article.
Sorbic acid (SA) was used to improve the performance of styrene-butadiene rubber (SBR)/halloysite nanotubes (HNTs) nanocomposites by direct blending. The detailed mechanisms for the largely improved performance were studied by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), differential scanning calorimetry (DSC), porosity analysis and crosslink density determination. The strong interfacial bonding between HNTs and rubber matrix is resulted through SA intermediated linkages. SA bonds SBR and HNTs through grafting copolymerization/hydrogen bonding mechanism. Significantly improved dispersion of HNTs in virtue of the interactions between HNTs and SA was achieved. Formation of zinc disorbate (ZDS) was revealed during the vulcanization of the composites. However, in the present systems, the contribution of ZDS to the reinforcement was limited. Effects of SA content on the vulcanization behavior, morphology and mechanical properties of the nanocomposites were investigated. Promising mechanical properties of SA modified SBR/HNTs nanocomposites were obtained. The changes in vulcanization behavior, mechanical properties and morphology were correlated with the interactions between HNTs and SA and the largely improved dispersion of HNTs.
This chapter focuses on heterogeneous network design in dynamic covalent polymer networks (especially rubbers). The design, performance, and mechanisms of heterogeneous networks from the perspectives of inhomogeneous crosslinking and hybrid multi-networks are briefly reviewed. The exchangeable functions of dynamic covalent bonds (DCBs) enable unique properties of the heterogeneous crosslinked polymer networks. Based on characteristics such as micro-phase separation, interlocking, or interconnection between the multiple sub-networks crosslinked by DCBs, the relative independence and synergistic effect between the heterogeneous networks are exploited to achieve the robustness, functionalization, and melt-processing ability of DCB crosslinked elastomers. This new approach is expected to open a new avenue for intelligent application and sustainable development of polymer networks.
Efficient and inexpensive electrocatalysts play an important role in electrolysis of water and hydrogen evolution reaction. The catalytic activity of electrocatalyst can be improved by adjusting the electronic structure and increasing the active center. In this study, Ni2P nanosheets were grown on carbon cloth through straightforward solvothermal, and tiny MoS2 nanosheets were uniformly covered on Ni2P nanosheets by in-situ growth method to form heterogeneous electrocatalyst (Ni2P @ MoS2/CC). The results show that Ni2P @ MoS2/CC had more active sites than Ni2P/CC and MoS2/CC catalysts. In addition, the interface interaction based on heterogeneous structure promotes its charge transfer kinetics. In alkaline electrolyte, Ni2P @ MoS2/CC electrocatalyst had good HER performance. At a current density of 10 mA cm−2, the overpotential was 99 mV, and the Tafel slope was 97 mV dec−1. In addition, the catalyst showed excellent electrochemical stability, with no significant loss of activity after 2000 cyclic voltammetry tests and 50 h i-t tests.
Reinforcing rubbers and expanding their application galleries are two important issues in material science and engineering. In this work, we demonstrate a bioinspired design of high-performance and macroscopically responsive diene-rubber by engineering sacrificial metal–ligand motifs into a chemically cross-linked architecture network. The metal–ligand bonds are formed through the coordination reaction between the pyridine groups in butadiene–styrene–vinylpyridine rubber (VPR) and metal ions. Under external load, the metal–ligand bonds serve as sacrificial bonds that preferentially rupture prior to the covalent network, which dissipates energy and facilitates rubber chain orientation. Based on the function mechanisms, the modulus, tensile strength, and toughness of the samples are simultaneously improved without sacrificing the extensibility, and these properties can be conveniently tuned by varying the structure parameters of the covalently cross-linked network and metal–ligand bonds. Moreover, the dissociation/re-formation of metal–ligand bonds upon heating/cooling can endow VPR with thermally triggered adaptive recovery for shape memory application.
Graphene has attracted a great deal of interest in recent years, illustrated by its potential in a variety of areas in physics, chemistry, and engineering. Specifically, graphene has opened up exciting possibilities for high-performance and functional rubber composites. Although copious literature deals with the fascinating properties related to graphene, its real (large scale) applications in rubber-based composites have not been approached. We discuss the state of the art in development in processing and the status in understanding of structure/performance relationships. Accordingly, the prospectives and challenges of some real applications of graphene-based rubber composites such as tires and sensors are surveyed and discussed.
Summary: Attempts were made to prepare thermoplastic elastomers (TPE) from scrap rubber powder (SRP) and linear low‐density polyethylene (LLDPE) as thermoplastic polymer matrix. The solid‐phase grafted copolymer of LLDPE (LLDPE‐g‐VM) and epoxidized natural rubber (ENR) were used as dual compatibilizers to improve the interfacial adhesion between SRP and LLDPE. The compatibilized SRP/LLDPE blends had obviously improved the interfacial properties between SRP particles and LLDPE. Using this method, thermoplastic elastomer was prepared successfully. The mechanical properties especially elongation at break was improved significantly. SEM and TEM studies showed that the ENR/LLDPE‐g‐VM dual compatibilizer improved the distribution state of SRP particles in LLDPE and the adhesion between SRP and LLDPE. DSC results showed a distinct glass transition at 74 °C of the interfacial region. The improvement in mechanical properties was attributed to the enhanced interfacial properties of the blend. Surface of SRP particles of the composites compatibilized by the dual compatibilizer. image Surface of SRP particles of the composites compatibilized by the dual compatibilizer.
It has been commonly acknowledged that particle dispersion and interfacial interactions are vital in determining the ultimate performance of polymer composites. However, the interplay between dispersibility and interfacial interaction in polymer composites has not been explicitly unraveled. In this contribution, a series of silica with controlled surface chemistry are prepared to reveal the effects of subtle change in surface property of filler on the structures and mechanical performance of the rubber composites. On the basis of thermodynamic theory, the dispersibility of modified silica in rubber is quantitatively evaluated by using surface energy. The modified silica was introduced into styrene-butadiene rubber (SBR) to investigate the effects of surface modification on the dispersion of silica and interfacial interaction of the rubber composites. It has been demonstrated that subtle change in surface chemistry of silica drastically improves its dispersibility in rubber matrix, leading to much improved accessible surfaces and hence much complete interfacial reaction. At very low grafting content (0.2 molecule/nm2), improved modulus (44%) and wet-traction (54%), together with reduced rolling-resistance (11%), are concurrently observed.
The reinforcement effects of halloysite nanotubes (HNTs) on styrene-butadiene rubber (SBR) and the modification effect of epoxidized natural rubber (ENR) on SBR/HNTs composites were studied. The structure, morphology and properties of SBR/HNTs composites before and after the incorporation of ENR were investigated. The results indicated that ENR can promote the dispersion and orientation of HNTs in SBR matrix at nanoscale and strengthen interfacial combination between HNTs and SBR by the formation of covalent bonds and hydrogen bonds between ENR and HNTs. Consequently ENR can improve the mechanical properties of the vulcanizates of SBR/HNTs composites. Besides ENR can decrease the rolling resistance of the vulcanizates and increase the wet grip property of the vulcanizates.
High performance light-colored rubber-inorganics nanocomposites were fabricated by the direct incorporation of sorbic acid (SA) in the filled rubber compounds. The mechanisms of largely improved performance were studied in details. The strong interfacial bonding between rubber matrix and the filler and significantly improved dispersion of the filler were resulted through SA intermediated linkages. Effect of SA on the vulcanization behavior, morphology and mechanical properties were studied. Formation of zinc disorbate (ZDS) and its reinforcing effect on rubber was investigated. High content of ZDS leaded to high ionic crosslink density and had a more significantly effect on enhancing the performance of rubber. The composites with high nanotubular clay content were found to be highly ionic crosslinked, optical transparent and exhibited high mechanical strength and heat resistance. The properties of the composites were ascribed to the strong interfacial interactions and the excellent dispersion of nanotubular clay.
