Characterization and transport properties of ceramic filler incorporated natural rubber composites

Crystalline glass–ceramic fillers were prepared from calcium carbonate, silica, alumina, and calcium fluoride by heating and subsequent quenching in cold water. The fillers were incorporated into natural rubber (1,4-cis-polyisoprene) and the filled rubber composites were crosslinked with sulfur in the presence of different rubber additives. The unfilled and filled rubber composites were characterized. The transport properties of benzene, toluene, and p-xylene (BTX) through the rubber composites were studied in terms of sorption, diffusion, permeation, and mass transfer coefficients. The effect of the ceramic fillers on the mechanical, thermal and transport properties were studied. The sorption data at different temperatures were used for calculating activation energy of diffusion, permeation, free energy, and enthalpy of sorption. The BTX remained in the liquid state within the composite matrix as evident from negative ΔS. The diffusion coefficient (D) and mass transfer coefficient (k_mtc) of BTX decreased with the increase in filler loading. Accordingly, for the transport of BTX the unfilled rubber showed a D (D × 10⁷ cm²/s) and mass transfer coefficient (k_mtc × 10⁴ cm/s) of 5.67/3.97/2.96 and 7.71/7.08/7.04, respectively which decreased to 5.06/2.95/2.57 and 7.53/6.95/6.90, respectively for the composite containing 50 wt.% ceramic filler.     

Styrene–butadiene rubber/graphite powder composites: Rheometrical,physicomechanical, and morphological properties

The physicomechanical properties, curing characteristics, and morphological behaviors of styrene–butadiene rubber/graphite powder composites were evaluated. Different weight fractions and particle sizes of graphite powder were used. An increase in the graphite content increased the maximum torque, reinforcing factor, and tensile strength and decreased the elongation at break and equilibrium swelling. Also, a decrease in the particle size of the graphite increased the tensile strength and decreased the equilibrium swelling. Moreover, the dielectric properties were measured at about 30°C and 100 Hz. The values of permittivity and dielectric loss were found to increase with increasing graphite content. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Swelling behavior of butyl and chloroprene rubber composites with poly(sodium acrylate) showing high water uptake

Water-swellable rubber (WSR) comprises super absorbent polymer (SAP) embedded in a rubber matrix and has been commonly used as sealants and caulks, in which high water uptake and sufficient mechanical strength are required. In this work, we investigated the swelling behavior and mechanical properties of rubber composites comprising SAP powders. A reinforcement effect is caused by the SAP particles, which are described using a modified Guth–Gold equation up to the semi-dilute region. The complex modulus shows upper deviation at high SAP content owing to network formation between SAP particles. The swelling force of the WSR is explained by the amount of SAP particles in the surface layer of the matrix up to the semi-dilute region. The formation of the SAP network leads to an appreciable increase in the swelling force of WSR, as SAP particles embedded in the matrix also contribute to the swelling of WSR. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48535.     

Preparation of epoxidized acrylonitrile butadiene rubber and its compatibilization effect on water-swellable rubber composites

In this research, water-swellable rubbers (WSRs) were prepared by the blending of acrylonitrile butadiene rubber (NBR) with epoxidized acrylonitrile butadiene rubber (ENBR), precipitated silica, vulcanizing agents, and polyacrylic acid sodium (PAAS) as superabsorbent polymers (SAPs). ENBR was prepared with a molybdenum trioxide catalyst and a tert-butyl hydroperoxide oxidant through a free-radical reaction under specific conditions and was used as a compatibilizer to improve the interfacial adhesion of the NBR matrix and hydrophilic components of the WSRs. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to analyze the structure and properties of ENBR. The dispersion of silica and SAPs in the rubber matrix was investigated by transmission electron microscopy. The presence of ENBR enhanced the water-absorption properties of the WSRs. The NBR–ENBR composites exhibited a higher mechanical performance after water absorption than that without ENBR. Both the swelling ratio and the absorption rate increased with the ENBR content. When the weight ratio of NBR–ENBR was 25/75, an equilibrium swelling ratio of 172% (13% higher than that of the sample without ENBR) was obtained. Scanning electron microscopy analysis revealed that the addition of ENBR improved the compatibility between the SAPs and the NBR matrix. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47694.     

Effect of carbon black on the mechanical and dielectric properties of rubber ferrite composites containing barium ferrite

Fine particles of barium ferrite (BaFe₁₂O₁₉) were synthesized by the conventional ceramic technique. These materials were then characterized by the X‐ray diffraction method and incorporated in the natural rubber matrix according to a specific receipe for various loadings of ferrite. The rubber ferrite composites (RFC) thus obtained have several applications, and have the advantage of molding into complex shapes. For applications such as microwave absorbers, these composites should have an appropriate dielectric strength with the required mechanical and magnetic properties. The N330 (HAF) carbon black has been added to these RFCs for various loadings to modify the dielectric and mechanical properties. In this article we report the effect of carbon black on the mechanical and dielectric properties of these RFCs. Both the mechanical and dielectric properties can be enhanced by the addition of an appropriate amount of carbon black. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 769–778, 2003     

有机蒙脱土/丁基橡胶/聚丙烯热塑性硫化胶的制备与性能

采用动态硫化法制备了有机蒙脱土(OMMT)/丁基橡胶(IIR)/聚丙烯(PP)热塑性硫化胶(TPV),考察了OMMT的用量和IIR/PP的质量比对TPV的物理机械性能、动态力学性能及热性能的影响.结果表明,当OMMT的用量为20份时,TPV的物理机械性能较佳,Payne效应最弱,OMMT均匀地分布在基体中,阻尼性能较好...     

Mechanical,thermal, and transport properties of nitrile rubber–nanocalcium carbonate composites

The article describes the properties of acrylonitrile butadiene copolymer (NBR)–nanocalcium carbonate (NCC) nanocomposites prepared by a two‐step method. The amount of NCC was varied from 2 phr to 10 phr. Cure characteristics, mechanical properties, dynamic mechanical properties, thermal behavior, and transport properties of NBR–NCC composites were evaluated. For preparing NBR nanocomposites, a master batch of NBR and NCC was initially made using internal mixer. Neat NBR and the NBR–NCC masterbatch was compounded with other compounding ingredients on a two roll mill. NCC activated cure reaction upto 5 phr. The tensile strength increased with the nanofiller content, whereas NBR–NCC containing 7.5 phr exhibited the highest modulus. The storage modulus (E′) increased up to 5 phr NCC loading; the reinforcing effect of NCC was seen in the increase of modulus which was more significant at temperatures above T_g. The effect of nanofiller content and temperature on transport properties was evaluated. The solvent uptake decreased with NCC content. The mechanism of diffusion of solvent through the nanocomposites was found to be Fickian. Transport parameters like diffusion, sorption, and permeation constants were determined and found to decrease with nanofiller content, the minimum value being at 7.5 phr. Thermodynamic constants such as enthalpy and activation energy were also evaluated. The dependence of various properties on NCC was supported by morphological analysis using transmission electron microscopy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical properties and reinforcement mechanisms of hydrogenated acrylonitrile butadiene rubber composites containing fibrillar silicate nanofibers and short aramid microfibers

Short‐fiber‐reinforced rubber composites (SFRCs) with hydrogenated acrylonitrile butadiene rubber (HNBR) as the matrix and fibrillar silicate (FS) nanofibers and short aramid microfibers (DCAFs) as the fillers were developed, and their tensile properties, compression moduli, and mechanical anisotropies were investigated. The results indicated that the properties of the HNBR/DCAF/FS composites were determined by the loadings of the FS nanofibers and DCAF microfibers. A small amount of the microfibers combined with an appropriate amount of the nanofibers resulted in synergetic reinforcement and imparted to the SFRCs significantly improved mechanical properties without substantially compromising the rubbery characteristics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of some properties of waste LDPE/waste butyl rubber blends using different compatibilizing agents and gamma irradiation

Blends of waste low‐density polyethylene with waste butyl rubber of equal quantities containing reactive compatibilizing agents, namely: maliec anhydride; glycidyle methacrylate, divinyl benzene, tetraethyleneglycoldimethacrylate and diethyleneglycoldimethacrylate were preparedand exposed to different γ‐irradiation doses up to 400 kGy. The swelling behavior in organic solvent of the gel and soluble fractions and the degree of crosslinking were investigated. The mechanical properties, namely tensile strength and elongation at break were also studied. Thermal properties using thermo gravimetric analysis and differential scanning calorimetry analysis follow analyses have been followed up to follow the change of the structure for the irradiated and nonradiated blends. Results obtained indicated improvement in physical, mechanical and thermal properties on irradiation of the prepared blends which incorporate compatibilizing agents, but with varying degrees. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Natural rubber-graft-poly(2-hydroxyethyl acrylate) on cure characteristics and mechanical properties of silica-filled natural rubber composites

The grafting of poly(2-hydroxyethyl acrylate) onto natural rubber (NR-g-PHEA) was used to compatibilize NR composites with silica filler. The NR/silica compounds were prepared with various grafting percentages of NR-g-PHEA (0, 6.5, 10.5, and 14.5%) and fixed amounts of 3 parts per hundred of rubber (phr) NR-g-PHEA and 20 phr silica. The cure characteristics were examined using a moving die rheometer. The physicomechanical properties of NR/silica composites were determined in terms of tensile strength, bound rubber content, and dynamic mechanical analysis. Thermal properties were assessed with thermogravimetric analysis. The results showed that scorch time and cure time tend to decrease with the level of grafting in NR-g-PHEA. The NR-g-PHEA decreased tan δ, whereas bound rubber content in NR/silica compounds increased, which indicates improved silica dispersion in the NR matrix. The mechanical properties improved with level of grafting in NR-g-PHEA. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48738.     

Synthesis and properties of conductive B4C ceramic composites with TiB2 grain network

High electrical resistance and low fracture toughness of B₄C ceramics are 2 of the primary challenges for further machining of B₄C ceramics. This report illustrates that these 2 challenges can be overcome simultaneously using core‐shell B₄C‐TiB₂&TiC powder composites, which were prepared by molten‐salt method using B₄C (10 ± 0.6 μm) and Ti powders as raw materials without co‐ball milling. Finally, the near completely dense (98%) B₄C‐TiB₂ interlayer ceramic composites were successfully fabricated by subsequent pulsed electric current sintering (PECS). The uniform conductive coating on the surface of B₄C particles improved the mass transport by electro‐migration in PECS and thus enhanced the sinterability of the composites at a comparatively low temperature of 1700°C. The mechanical, electrical and thermal properties of the ceramic composites were investigated. The interconnected conductive TiB₂ phase at the grain boundary of B₄C significantly improved the properties of B₄C‐TiB₂ ceramic composites: in the case of B₄C‐29.8 vol% TiB₂ composite, the fracture toughness of 4.38 MPa·m^1/2, the electrical conductivity of 4.06 × 10⁵ S/m, and a high thermal conductivity of 33 W/mK were achieved.     

Effect of hollow glass beads on density and mechanical properties of silicone rubber composites

In this work, low density hollow glass beads (HGB)/silicon rubber (SR) composites were prepared by solution method and flocculation process. The prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, tensile test, and friction test. The results show that the densities of SR composites decrease from 1.140 to 0.792 g/cm³ with the addition of HGB. By comparing theoretical density with true density, it can be estimated that the ratio of shattered HGB increase from 8.79% to 24.76%. Especially, the mechanical properties of SR composites were improved by surface modification of HGB. By adding surface-modified HGB at 5 and 10 wt%, the tensile strengths of SR composites were enhanced by 17.8% and 28.2%, respectively. In addition, tear strength, shore A hardness, compression set, and friction property were significantly ameliorated. Furthermore, the mechanism of surface-modified HGB in mechanical properties was analyzed.     

Microstructure and mechanical property of (TiB2-SiC) agglomerate-toughened B4C-TiB2-SiC composites

B₄C-TiB₂-SiC composites toughened by (TiB₂-SiC) agglomerates were prepared via reactive hot pressing with B₄C and TiSi₂ as raw materials. Phase composition, microstructure, and mechanical properties of the fabricated composites were investigated. The function of (TiB₂-SiC) agglomerates was analyzed, and the strengthening and toughening mechanism were also discussed. Results indicated that some of the in situ formed TiB₂ and SiC were interlocked to form special (TiB₂-SiC) agglomerates in the matrix. The good comprehensive performances of 510 MPa flexural strength, 5.84 MPa·m^1/2 fracture toughness, and 31.93 GPa hardness were obtained in the composites fabricated with 30 wt% TiSi₂. The in situ introduced fine TiB₂ and SiC grains refined the grains of B₄C due to the pinning effect, which enhanced the strength. The special (TiB₂-SiC) agglomerates and the existing toughening phenomena such as crack deflection, branching, and microcrack regions induced by the mismatch of thermal expansion coefficients, had cumulative effects on improving the fracture toughness.     

Cure characteristics,mechanical, thermal,and coloring properties of natural rubber/dye‐loaded shell powder composites

To explore the application of shell powder (SP) in rubber, a dye‐loaded SP (DSP) bio‐filler based on SP and Congo red was incorporated into natural rubber (NR). The adsorption experiments demonstrated that the maximum monolayer adsorption capacity of Congo red onto SP was 69.3 mg/g. The effect of aluminate coupling agent and DSP was investigated by evaluating the cure characteristics, mechanical, thermal, and coloring properties of NR/DSP composites. It was suggested that the optimum amount of aluminate coupling agent was 2 wt %, and the best tensile strength (24.80 MPa) of vulcanizates was achieved at the DSP content of 20 phr, while other mechanical properties such as tear strength kept increasing with the addition of DSP. Furthermore, the improved thermal stability and uniform color distribution of the NR composites was obtained. The results indicate that DSP is promising to become a low‐cost filler and pigment for rubber materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45750.     

Synergistic effects of carbon nanotubes and carbon black on the fracture and fatigue resistance of natural rubber composites

The quasi‐static fracture and dynamic fatigue behaviors of natural rubber composites reinforced with hybrid carbon nanotube bundles (CNTBs) and carbon black (CB) at similar hardness values were investigated on the basis of fracture mechanical methods. Mechanical measurement and J‐integral tests were carried out to characterize the quasi‐static fracture resistance. Dynamic fatigue tests were performed under cyclic constant strain conditions with single‐edged notched test pieces. The results indicate that synergistic effects between CNTBs and CB on the mechanical properties, fracture, and fatigue resistance were obtained. The composite reinforced with 3‐phr CNTBs displayed the strongest fatigue resistance. The synergistic mechanisms and dominating factors of quasi‐static and dynamic failure, such as the dispersion state of nanotubes, hybrid filler network structure, strain‐induced crystallization, tearing energy input, and viscoelastic hysteresis loss, were examined. The weakest fatigue resistance of the composite filled with 5‐phr CNTBs was ascribed to its strikingly high hysteresis, which resulted in marked heat generation under dynamic fatigue conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42075.     

Poly(vinylidene fluoride)/halloysite nanotubes nanocomposites: The structures,properties, and tensile fracture behaviors

Poly(vinylidene fluoride)/halloysite nanotubes (HNTs) nanocomposites with good dispersion were prepared. The effect of HNTs on the crystalline structure, dynamic rheological properties, dynamic mechanical properties, and tensile properties was investigated. Results showed that at low concentration, the effect of HNTs on the modulus was minor. However, at high concentration, improvement of the modulus can be observed. The tensile fracture behaviors were investigated, which showed that the addition of HNTs changed the fracture mode. When the concentration of HNTs was 20 phr, a fracture mode change from microductility/brittle to brittle/fibrillation occurred. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Powder characteristics,sinterability, and mechanical properties of TiB2 prepared by three reduction methods

Reaction processes, powder characteristics, sinterability, and mechanical properties of TiB₂ prepared by borothermal reduction, B₄C reduction, and boro/carbothermal reduction were compared. Results showed that TiBO₃ and Ti₂O₃ as the intermediate phases existed in the three reduction processes. The temperature where TiB₂ became major phase was lowest during borothermal reduction, resulting in the finest TiB₂ particle size, in contrast to the other two methods, especially boro/carbothermal reduction. However, TiB₂ powders prepared by B₄C reduction and boro/carbothermal reduction after pressureless sintering at 1800°C for 2 hours showed the relatively higher sinterability, due to the lower oxygen content and higher carbon content. Finally, using 5 wt% Ni as sintering additive, hot-pressed TiB₂ ceramics from B₄C reduction demonstrated higher densification, more fine-grained microstructure and higher mechanical properties, due to the better balance of oxygen/carbon content.     

Effects of substitution for carbon black with graphene oxide or graphene on the morphology and performance of natural rubber/carbon black composites

In this study, nanosheets including graphene oxide (GO) and reduced graphene oxide (rGO), were incorporated into natural rubber (NR), to study the effects of substituting GO or rGO for carbon black (CB) on the structure and performance of NR/CB composites. The morphological observations revealed the dispersion of CB was improved by partially substituting nanosheets for CB. The improvements in static and dynamic mechanical properties were achieved at small substitution content of GO or rGO nanosheets. With substitution of rGO nanosheets, significant improvement in flex cracking resistance was achieved. NR/CB/rGO (NRG) composites has a much lower heat build‐up value compared with NR/CB/GO (NG) composites at a high load of nanosheets. However, both GO and rGO tended to aggregate at a high concentration, which led to the poor efficiency on enhancing the dynamic properties, or even deteriorate the performance of rubber composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41832.     

Microstructure and Mechanical Properties of (TiB2 + SiC) Reinforced Ti3SiC2 Composites Synthesized by In Situ Hot Pressing

Fully dense (TiB₂ + SiC) reinforced Ti₃SiC₂ composites with 15 vol% TiB₂ and 0–15 vol% SiC were designed and synthesized by in situ reaction hot pressing. The increase in SiC content promoted densification and significantly inhibited the growth of Ti₃SiC₂ grains. The in situ incorporated TiB₂ and SiC reinforcements showed columnar and equiaxed grains, respectively, providing a strengthening–toughening effect by the synergistic action of particulate reinforcement, grain's pulling out, “self‐reinforcement,” crack deflection, and grain refining. A maximum bending strength of 881 MPa and a fracture toughness of 9.24 MPam^1/2 were obtained at 10 vol% SiC. The Vickers hardness of the composites increased monotonously from 9.6 to 12.5 GPa.     

Mechanical and tribological behaviors of PVA/PAAm double network hydrogels under varied strains as cartilage replacement

The strain change of double network (DN) hydrogels during compressive mechanical and frictional tests is crucial for their performances. The positive effect of the sacrificed network for prohibiting crack in DN hydrogel is likely to be initiated by large strain. In this study, the mechanical and tribological properties of polyvinyl alcohol/polyacrylamide (PVA/PAAm) DN hydrogels are investigated from the viewpoint of strain. The compressive tangent modulus of PVA/PAAm DN hydrogel with 15 wt% AAm shows a sudden increase in the strain of 60% due to the sacrificed PAAm network. The optimized friction behavior is obtained from PVA/PAAm hydrogel with 5 wt% of AAm content, which is not consistent with the optimal compressive modulus at 15 wt% of AAm content. The variation of frictional coefficient of PVA/PAAm DN hydrogels with load is quite different for migrating and stationary contact configurations. The biphasic lubrication mechanism transited to solid–solid contact dominant mechanism is also induced by the high strain at heavy load.