In the present work, the development and characterization of an intrinsically self-healable material based on butyl imidazole modified bromobutyl rubber (BIIR)/natural rubber (NR) blends, which are ...filled with carbon nanotubes (CNTs) are reported. It was found that the addition of CNTs and the blending with NR significantly enhance the tensile strength of the BIIR composites. The use of butyl imidazole as physical cross-linker for the BIIR phase provides the blend composites the non-covalent bondings, which are responsible for their self-healing properties. Owing to the increase of the viscosity of the BIIR phase upon its physical crosslinking the island-matrix morphology of the blend changes over to a co-continuous structure. The preferential wetting of the CNT surface by the low-loading NR phase in the NR/BIIR blends can be explained by the good rubber-filler interaction between the linked phospholipids of the NR molecules and the π-electrons of the CNT surface. As a result, the favored localization of the CNTs in the NR phase strongly improves the electrical properties of the blends according to the double percolation theory. On the other hand it does not deteriorate the self-healing of the BIIR phase. The high electrical conductivity provides us a possibility to heat the blend by application of an electrical voltage in order to accelerate the self-healing process.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The aim of this work was to study the effect of the ionic liquids (ILs) with respect to their anion type and the length of alkyl chain as dispersing and coupling agent in carbon nanotube (CNT) filled ...styrene butadiene rubber (SBR)/natural rubber (NR) blends. We characterized the ILs by their surface tensions whereupon their different values explain the different compatibilities of ILs with the rubber components and the filler. The wetting concept was further developed in order to experimentally characterize the effect of the rubber-IL and CNT-IL compatibility on the selective wetting of CNTs in rubber blends. It was found that all the used ILs improved the dispersion of CNTs in rubber blends significantly. During the mixing process the IL layer pre-bound to the CNT surface was replaced mainly by the NR phase and, partly, by the SBR phase. Thus, ILs cannot be used as coupling agent in this rubber blend. For the ILs with surface tension similar to that of CNTs the filler was partly wetted by IL that imparts the mixture a high electrical conductivity directly after the mixing process. This high conductivity can be used for triggering the vulcanization of the blend by means of the Joule heating. The preferential localization of ILs in the rubber matrix - but not in rubber-filler interphase - considerably influences the cross-link behavior of the vulcanizates and thus their final mechanical properties significantly.
Display omitted
•Effect of the rubber-ionic liquid and filler-ionic liquid interaction on the CNT dispersion.•Prediction and experimental determination of the selective wetting of CNTs in rubber blends.•Replacement of pre-bound ionic liquid layer on the CNT surface mostly by NR and, partly by SBR.•Improved network formation of CNTs partly wetted by IL.•Joule heating triggered vulcanization of rubber blend by application of an electrical voltage.
We report about the successful ‘expanded organoclay’ (EMt) assisted dispersion of multiwall carbon nanotubes (MWCNT) and the subsequent synergy of both fillers in non-polar natural rubber (NR) ...compounds. Higher upward shifting of G band and substantial reduction of ID/IG ratio of MWCNT in the Raman spectroscopy in the presence of EMt was an indication of strong interactions between MWCNT and EMt particles which further improved the dispersion of MWCNT in the NR matrix. Attributed to the strong affinity of MWCNT with EMt we find significantly exfoliated EMt and homogeneously networked in these composites. The EMt driven dispersion of MWCNT, particularly at high content in the NR, was evidenced from transmission electron microscopy (TEM). The fractal dimension (df) of the MWCNT clusters in NR matrix both in the presence and absence of EMt was predicted utilizing the phenomenological Huber–Vilgis model. Interestingly, a lower value of df of MWCNT clusters was documented in the presence of EMt. Additionally, both the electrical and mechanical percolation threshold of MWCNT was reduced marginally with the addition of EMt.
A novel homogenisation method for heterogeneous structures containing a twist symmetry by means of RVEs with twisted-periodic boundary conditions is introduced. The method considers finite ...deformations and is applied to hybrid-yarn reinforced elastomers in order to compute the macroscopic elastic behaviour and the failure surface. The excellent numerical efficiency and parallelisability are shown in comparison to two classical homogenisation methods.
The yarn is modelled by a modified approach of Criscione et al. (2001) in terms of an alternative set of physically based strain invariants. Its definition preserves the advantages of physically based invariants while allowing for a straight forward derivation of the stress and material tangent within the framework of the finite element method.
The performance of elastomeric materials,
i.e.
in car tires, is substantially determined by the used reinforcing filler system. In particular, the flocculation tendency of filler particles to form ...clusters and even network-like structures significantly determines the mechanical properties of these elastomer materials and enhances especially their energy dissipation under periodic mechanical deformations. In a simplified thermodynamic model, inspired by a segregation model from game theory, we describe fundamental mechanisms of filler structure formation. As the final goal of this paper we want to demonstrate how similar structures in society, nature or materials like rubbers emerge when supposing obvious cardinal mechanisms of structure formation in complex systems.
A novel simple model for filler flocculation in polymers, inspired from Schelling's segregation model from game theory and social sciences.
Display omitted
•Super TPV based on XNBR and PA12 via the application of novel cyclic peroxide.•Highest mechanical properties and thermal stability of TPV of 50:50 XNBR-PA12.•Superior performance ...behaviour with reference to heat and oil aging study.
Thermoplastic vulcanizates (TPVs) are special classes of thermoplastic elastomers, in which dynamic vulcanization of the rubber phase takes place during melt mixing with a semi-crystalline thermoplastic matrix phase at elevated temperature. TPV is characterized by processing behaviour like thermoplastic at elevated temperature and performance properties of vulcanized rubber at ambient temperature. High performance TPVs or super TPVs are new generation TPVs which exhibit high heat resistance as well as excellent oil resistance property suitable for automotive under-the-hood applications. In the present work, a new super TPV based on carboxylated acrylonitrile butadiene rubber (XNBR) and polyamide (PA12) has been developed. (XNBR:PA12) TPVs of different blend ratios have been prepared by using a fixed concentration of novel cyclic monofunctional peroxide. Final morphology of TPVs varies from either a co-continuous to a dispersed one depending on the blend ratio. TPV of 50:50 XNBR-PA12 shows the highest mechanical properties as well as superior thermal stability among all other TPVs. From differential scanning calorimetric (DSC) study, it can be clearly seen that the glass transition temperature (Tg) of XNBR has shifted to high temperature range in case of all TPVs as compared to that of uncrosslinked blend system. Dynamic mechanical analysis (DMA) also demonstrates that tanδ values of all the TPVs are lower and the storage moduli are higher than the uncrosslinked blend system. Lowest tanδ peak of TPV of 50:50 blend ratio of XNBR:PA12 indicates the highest degree of crosslinking and this is also supported by the swelling studies. The highest level of mechanical properties and superior thermal stability support that phenomenon. Heat aging and oil resistance study have also been carried out in details to understand the performance behaviour of these super TPVs at service condition.
•Electrical response of CNT-NR composite to the external mechanical stimuli is investigated in a wide range of CNT concentrations and crosslinking degrees of NR.•Based on the obtained results, the ...possibilities of using the investigated CNT-NR composite as a strain sensor are explored quantitatively.•Theoretical scaling model has been developed, which gives an adequate description of the observed dependance of the piezoresististance of the composite on the applied stress.
We explore, both experimentally and theoretically, the possibility to use a composite of natural rubber (NR) and multiwall carbon nanotubes (MWCNT) as a piezoresistive tensile sensor. As an essentially new feature relative to the previous work, we have performed a systematic study of the mechanism of the piezoresistance at large deformations in a wide range of MWCNT concentrations and crosslinking degrees of the host rubber material. In qualitative agreement with the previous work, the conductivity of the unstrained NR/MWCNT nanocomposite is shown to be adequately described by the percolation theory with the critical exponent evaluated to ∼2.31. Varying tensile stress-induced strains in the composite has been shown to results in a non-linear electrical response that cannot be described by simple modifications of the percolation theory. In order to explain the observed non-linear dependence of the resistance R of the composite on the strain ε, we have developed a scaling theory that relates this resistance to the structural changes in the conducting MWCNT network caused by deforming the host NR. Based on the obtained results, we discuss the ways of using the highly stretchable conductive elastomer composites as an efficient piezoresistive tensile sensor.
Novel thermoplastic vulcanizates (TPVs) based on silicone rubber (PDMS) and polyamide (PA12) have been prepared by dynamic vulcanization process. The effect of dynamic vulcanization and influence of ...various types of peroxides as cross-linking agents were studied in detail. All the TPVs were prepared at a ratio of 50/50 wt% of silicone rubber and polyamide. Three structurally different peroxides, namely dicumyl peroxide (DCP), 3,3,5,7,7-pentamethyl 1,2,4-trioxepane (PMTO) and cumyl hydroperoxide (CHP) were taken for investigation. Though DCP was the best option for curing the silicone rubber, at high temperature it suffers from scorch safety. An inhibitor 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) was added with DCP to stabilize the radicals in order to increase the scorch time. Though CHP (hydroperoxide) had higher half life time than DCP at higher temperature, it has no significant effect on cross-linking of silicone rubber. PMTO showed prolonged scorch safety and better cross-linking efficiency rather than the other two. TPVs of DCP and PMTO were made up to 11 minutes of mixing. Increased values of tensile strength and elongation at break of PMTO cross-linked TPV indicate the superiority of PMTO. Scanning electron micrographs correlate with mechanical properties of the TPVs. High storage modulus (E') and lower loss tangent value of the PMTO cross-linked TPV indicate the higher degree of cross-linking which is also well supported by the overall cross-link density value. Thus PMTO was found to be the superior peroxide for cross-linking of silicone rubber at high temperature.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The phase specific localization of the reinforcing fillers like carbon black (CB), which has been known to influence the physical and mechanical performance of the rubber blends, can be determined by ...different characterization techniques, however, only for binary rubber blends. They have been failed so far when applied for more complicated systems like filled ternary rubber blends. In the present work we introduced a new technique using the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with germanium crystal for characterization of the specific localization of CB in a ternary blend of solution styrene butadiene rubber (SBR), butadiene rubber (BR) and natural rubber (NR). It is the first time we could follow the change of the amount of CB localized in each phase of this blend along the mixing time. CB firstly is incorporated into the NR phase and then it obviously migrates from the NR phase to the SBR phase as a function of mixing time that corresponds very well with the theoretical prediction based on the Z-model using the surface tension values of the filler and rubber blend components. The interaction between CB and rubber components can be qualitatively proved by the shift of the FTIR peak. Thermogravimetric analysis (TGA) was used to support the results obtained by the FTIR method. The study was further extended to follow the CB distribution in multi-step mixing.
Display omitted
•A new method for experimental characterization of CB localization in ternary rubber blend.•Prediction of the selective wetting of CB in rubber blends using the Z-model.•Kinetics of CB localization in SBR/BR/NR blend during the mixing process.•Migration of CB in ternary rubber blend during masterbatch mixing.
In the present work, the development of morphology and selective wetting of nanoclay and carbon nanotubes (CNTs) in rubber nanocomposites were characterized qualitatively by means of the optical ...microscopy, TEM and AFM and quantitatively by means of the wetting concept. Carboxylated hydrogenated nitrile butadiene rubber (XHNBR), ionic liquid and ethanol were used as dispersing agent and they show very good effect on the macro- and microdispersion of nanofillers in different rubbers. It was found that the selective wetting of filler surface by the dispersing agent and rubber matrix is controlled by thermodynamic and kinetic factors. A model basing on surface energy data of polymer components (rubber and dispersing agent) and filler was introduced in order to determine the thermodynamic equilibrium state of filler wetting, which is found to be simultaneously determined by the filler–polymer affinity and the rubber/dispersing agent mass ratio. During the mixing process a replacement process of bound polymer components takes place on the filler surface until the predicted state is reached.
Display omitted
PDF
