Structure–property relationships of silica/silane formulations in natural rubber,isoprene rubber and styrene–butadiene rubber composites

The mechanical performance of natural rubber (NR), synthetic poly-isoprene rubber (IR), and styrene–butadiene rubber (SBR) composites filled with various silica/silane systems is investigated. The results are analyzed by referring to micro-mechanical material parameters, which quantify the morphological and structural properties of the polymer and filler network. These are obtained from fits with the dynamic flocculation model (DFM) describing the strongly nonlinear quasi-static stress–strain response of filler-reinforced elastomers as found from multihysteresis measurements of the investigated compounds. We focus on the reinforcement mechanisms of silica compounds with coupling and covering silane, respectively. The fitted material parameters give hints that the coupling silane provides a strong chemical polymer–filler coupling, which is accompanied by improved strength of filler–filler bonds for all three rubbers types. This may result also from the chemical coupling of short chains bridging adjacent silica particles. It implies larger stress values for the coupling silane and, in the case of NR and IR, a more pronounced “Payne effect” compared to the covering silane. In contrast, for SBR, the coupling silane delivers a lower Payne effect, which is explained by differences in the compatibility between rubber type and silane-grafted silica surface. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48435.     

Effect of epoxidised natural rubber latex oncarbon black–natural rubber interaction inbead masterbatch

Abstract

Epoxidised natural rubber has been synthesised and used to improve carbon black–natural rubber in the bead masterbatch prepared according to the acid precipitation technique. Scanning electron microscopy showed that carbon black (40 pphr) was well incorporated in the spherical beads. The presence of epoxidised natural rubber latex caused an increase in the amount of unextracted rubber (or bound rubber content) of carbon black–epoxidised natural rubber–natural rubber beads     

Preparation of powdered adhesiVe type chloroprene rubber

研究了包覆剂对黏接型氯丁胶乳(CR 244)包覆性能的影响,并通过扫描电子显微镜研究了所得粉末橡胶的微观结构.结果表明,包覆剂用量大于15份(质量)时,粒径不大于0.9 mm的试样质量分数大于99%.粉末CR 244中存在许多孔洞,使得试样易于干燥和溶解.     

Properties of natural rubber/recycled ethylene–propylene–diene rubber blends prepared using various vulcanizing systems

The role of various vulcanizing systems on the curing characteristics, mechanical properties, morphology and dynamic mechanical analysis of natural rubber and recycled ethylene–propylene–diene rubber blends was investigated. Accelerated sulfur-vulcanizing systems (semi-EV and EV), peroxide, and mixed sulfur/peroxide-vulcanizing systems (semi-EV/peroxide and EV/peroxide) were observed and compared. The blends were processed on a two-roll mill, and a fixed amount of carbon black was also incorporated. Amongst the blends, accelerated sulfur-vulcanizing systems exhibited higher torques, state of cure, tensile strength and elongation-at-break, in comparison with the peroxide-vulcanizing system, whereas the tensile modulus, hardness and cross-link density showed lower trend. In the mixed sulfur/peroxide-vulcanizing systems, it showed intermediate behavior to the individual sulfur- or peroxide-vulcanizing systems. This was associated to the interference of peroxide during the cross-linking formation. SEM micrographs of semi-EV-vulcanizing system exhibited more roughness and cracking path indicating that higher energy was required towards the fractured surface. The high cross-link density observed from the swelling study could be verified from the storage modulus (E′) where peroxide vulcanized blends provided a predominant degree of cross-linking followed by semi-EV, semi-EV/peroxide, EV and EV/peroxide-vulcanizing systems, respectively. The glass transition temperature (T _g) depicted at maximum peak of mechanical loss factor (tanδ _max), indicating that semi-EV-vulcanizing system showed highest T _g value. The T _g values can be ordered as semi-EV > peroxide > semi-EV/peroxide > EV > EV/peroxide-vulcanizing systems. The T _g of rubber vulcanizates can be increased due to the restriction of molecular movement such as cross-link density.     

Structure of carboxylated acrylonitrile-butadiene rubber (CNBR)–clay nanocomposites by co-coagulating rubber latex and clay aqueous suspension

Carboxylated acrylonitrile-butadiene rubber (CNBR)–clay mixtures were prepared by co-coagulating rubber latex and clay aqueous suspension, then combining the mixtures with a rubber ingredient and vulcanizing by a traditional rubber mixing processing procedure. Transmission electron microscopy (TEM) showed that the silicate layers of clay were delaminated or intercalated with CNBR and dispersed in the CNBR matrix at a nanometer level during co-coagulating. X-ray diffraction indicated that the amount of CNBR intercalating between the layers increased with the increase of content of clay in CNBR, which is in contrast with the results of other studies. Some reasons were put forward for this discrepency. The aspect ratio (width/thickness) of the platelet inclusions was reduced and the silicate layers were aligned more orderly during the compounding operation on an open mill. The intercalated CNBR, on co-coagulating, still remained within the interlayer space after curing. In these nanocomposites, the particles of silicate layers were dispersed at the nanometer level and the structure was a combination of delaminated and intercalated silicate layers dispersed in the continuous CNBR matrix. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2842–2848, 2001     

Effect of silica reinforcement on natural rubber and butadiene rubber vulcanizates by a sol–gel reaction with tetraethoxysilane

The effect of silica reinforcement was studied for natural rubber (NR) and butadiene rubber (BR) vulcanizates by a sol–gel reaction with tetraethoxysilane at different temperatures. The formation of silica in the rubber vulcanizates was investigated analytically with Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis. The variations of the mechanical and dynamic properties were measured in the NR and BR vulcanizates with silica filling. The hardness of the rubber vulcanizates increased with silica filling in the rubber matrix. The tensile strength and elongation at break decreased with silica filling in the NR vulcanizates. The moduli at 50, 100, and 300% elongation increased with silica filling in the rubber matrix. The storage modulus of silica-filled rubber vulcanizates became higher than that of pure rubber vulcanizates. The temperature dependence of the loss modulus also increased with silica filling. The temperature dependence of the loss tangent was maintained, regardless of silica filling in the BR vulcanizates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Effects of modified silica on the co-vulcanization kinetics and mechanical performances of natural rubber/styrene–butadiene rubber blends

Rubber blends are widely used for combining the advantages of each rubber component. However, to date, how to determine and distinguish the vulcanization kinetics for each single rubber phase in rubber blends during the co-vulcanization process is still a challenge. Herein, high-resolution pyrolysis gas chromatography–mass spectrometry (HR PyGC-MS) was employed for the first time to investigate the vulcanization kinetics of natural rubber (NR) and styrene–butadiene rubber (SBR) in NR/SBR blends filled with modified silica (SiO₂). The reaction rates of crosslinking of each rubber phase in NR/SBR were calculated, which showed that the crosslinking rates of NR were much lower than those of SBR phase in the unfilled blends and blends filled with unmodified and silane modified silica. Interestingly, the vulcanization rates of NR and SBR phase were approximately same in the vulcanization accelerator modified silica filled blends, showing better co-vulcanization. In addition, the vulcanization accelerator modified silica was uniformly dispersed and endowed rubber blends with higher mechanical strength compared to the untreated silica. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48838.     

Natural rubber–cassava starch foam by compression moulding

Abstract

The foaming processes of mixtures of cassava starch–water and cassava starch–natural rubber latex blends have been carried out by compression moulding. The appropriate conditions under which to produce expanded foam are as follows: a temperature of 150°C, 10·8 MPa pressure, and a 2 min moulding time. For the foam from the cassava starch with water as a blowing agent, it was found that water levels in the range of 150–200% by weight of the dry starch gave good conditions for foaming. The resulting foamed material has a uniform closed cell structure. Regarding blending of cassava starch with natural rubber, the natural rubber could not be dispersed in the gelatinised starch when blended at a temperature of 70°C. To stabilise and prevent the coagulation of natural rubber in the blending process, Nonidet P40, a nonionic surfactant, was used. A suitable amount of Nonidet P40 was 1·5% by weight of natural rubber latex. The compressive stress and the storage modulus of the foam obtained increased (42–233%) with increasing natural rubber content owing to the high elasticity of the natural rubber and its promotion of more elasticity to the foams. When 2–5% of benzoyl peroxide by weight of natural rubber was added to the rubber latex, the compressive stress of the foam was further increased (20–118%) owing to vulcanisation of the natural rubber. Furthermore, an addition of 15–30% of calcium carbonate by weight of the dry starch of the blends was found to increase the compressive stress and storage modulus of the foams (69–148%) and the hardness and brittleness of the foams.     

Foaming conditions of high density polyethylene–natural rubber blends

Abstract

Foams made from high density polyethylene (HDPE) and natural rubber (NR) blends, using azodicarbonamide as a chemical blowing agent, have been investigated to establish a relationship between the structure and physical properties. The blends of HDPE, NR, epolene wax, chemical blowing agent, and necessary ingredients were prepared on a two roll mill. Subsequently, foamed structures of the blends were obtained by a single stage compression moulding. Results indicate that foaming process variables, i.e. heating time, blowing agent loading, ratio of HDPE/NR, crosslinking agent loading, and ratio of HDPE/NR at a fixed crosslinking agent loading, affect the physical properties of the foams. Attempts were made to relate such properties as foam density, hardness, tensile strength, elongation at break, tear strength, flexural strength, elastic modulus, and gel content to the foam structure. The foam structure was investigated using optical microscopy, in terms of the average cell size and its distribution.     

Changes in morphology and properties of NR–NBR blends. Effect of viscosity ratio modified by liquid natural rubber and epoxidised liquid natural rubber

Abstract

Changes in rheological properties, morphology, and oil resistance in NR–NBR blends by viscosity ratio have been investigated. In this study, the viscosity ratio was modified by mechanical mastication and addition of liquid natural rubber (LNR) and epoxidised liquid natural rubber (ELNR). The results reveal that as viscosity ratio increased from 0·5 to 1·0, Mooney viscosity of the blends increased, and then decreased sharply as the viscosity ratio further increased from 1·0 to 2·0. The addition of LNR and ELNR for plasticising NR and NBR, respectively, does not significantly affect cure properties of the blends. The phase size of the NR dispersed phase depends strongly on the viscosity ratio. The high viscosity of the matrix and/or the low viscosity of the dispersed phase promote breaking up of the dispersed phase. Unexpectedly, a decrease in size of the dispersed phase by the modification of viscosity ratio via the use of low molecular weight rubber (i.e. LNR and ELNR) did not result in an improvement in oil resistance.     

Effect of bonding agents on natural rubber–aluminium powder composites

The effects of various bonding agents, namely the hexamethylene tetramine-resorcinol system (HR), bis[3-(triethoxysilyl)propyl]tetrasulphide (Si-69), cobalt naphthenate (CoN), and toluene diisocyanate (TDI), on the mechanical properties of aluminium powder-filled natural rubber composites have been investigated. Studies were done both as a function of the bonding agent by keeping the loading of aluminium powder constant and as a function of the aluminium powder loading along with the bonding agents. Shore A hardness, rebound resilience, heat build-up, etc., are increased by the use of bonding agents, due to the improved adhesion between the natural rubber and aluminium powder. The addition of a bonding agent minimizes the DIN abrasion loss and percentage of compression set. The tensile properties can also be improved by adding bonding agents. Of the various bonding agents used in this study, the silane coupling agent (Si-69) and the hexamethylene tetramine-resorcinol (HR) system were found to be better for natural rubber-aluminium powder composites.     

Study on aging of clay–rubber masterbatch from modified clay

Clay was modified by using a polymeric coating agent, a silicane coupling agent, and a titanate coupling agent together with the antioxidant for preparing the clay–rubber masterbatch. After the thermooxidative, photooxidative, and ozone aging, the properties of the masterbatch were also determined. The results indicate that, under the synergistic actions of the polymeric coating agent, antioxidant, and coupling agent, the thermooxidative and photooxidative aging resistances of the masterbatch were greatly improved. The properties of ozone aging resistance of the masterbatch can be increased by 50% under the combined action of a new kind of amine antioxidant with a titanate coupling agent. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 338–342, 2001     

Preparation of carbon nanotubes/hydrogenated nitrile rubber composite by ultrasonic technique

将低相对分子质量的液体氢化丁腈橡胶(HNBR)溶于丙酮溶剂中,加入碳纳米管,用超声波技术制备了液体HNBR与碳纳米管的复合母料,然后再与HNBR混炼、硫化,获得碳纳米管/HNBR复合材料.结果表明,碳纳米管在HNBR中分散性好,对HNBR有较好的增强性,但在后期机械加工中产生了断裂.     

Quantitative study of photocatalyzed oxidation of ethylene–propylene rubber and atactic polypropylene

The effect of photoactive pigments such as ZnO, CdS, and TiO₂ on the photooxidation (with and without water vapor) of ethylene–propylene rubber and atactic polypropylene were examined. The effects of surface treatment (passivation) and low granulometry (nanopigments) were also studied for TiO₂. A drastic increase of ketone and an inhibition of carboxylic acid formation for ZnO filled polymers were revealed and quantitatively measured by using derivatization reactions. Such a phenomenon, as well as a small decrease of average molecular weight, were explained by a modification of the ZnO decomposition mechanism of tertiary hydroperoxides. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1681–1689, 1998     

Buckling instability during the 180°-peeling of brass shim from polychloroprene rubber

The 180°-peel adhesion of brass shim firmly bonded to a steel plate with a rubber interlayer has been studied as a function of rubber thickness, t, and test temperature. At low temperatures, peeling occurs via 'normal' interfacial detachment and the peel force increases to a plateau with rubber thickness. At higher temperatures and with larger values of t, compressive forces during peeling become sufficient to cause buckling of the bonded shim behind the major peel front. This causes a segment of predetachment and results in a unique type of stick-slip peeling pattern, in which alternate bands of cohesive and interfacial failure are formed. The instability is in approximate accord with a model assuming the buckling of a column on an elastic foundation.     

Weak boundary layers on vulcanized styrene–butadiene rubber treated with sulfuric acid

A synthetic vulcanized styrene-butadiene rubber (R2) was used in this study. The presence of paraffin wax and zinc stearate in the rubber composition prevented the adhesion of R2 rubber to solvent-based polyester-urethane adhesive. To increase the adhesion properties of R2 rubber, a surface treatment with sulfuric acid (cyclization) was applied, and the length of the immersion in sulfuric acid and the time between the immersion time and the neutralization were varied. The treated R2 rubber surfaces were characterized using ATR-IR spectroscopy, contact angle measurements (water, ethanediol), and scanning electron microscopy (SEM). The mechanical properties of the treated rubber were obtained from stress-strain experiments. The joint strength was obtained from the T-peel test on treated R2 rubber/polyurethane adhesive joints. Due to the penetration of the sulfuric acid into the R2 rubber bulk, the mechanical properties decreased. The treatment with sulfuric acid produced several chemical modifications on the rubber surface: sulfonation of the butadiene and the creation of C C and C O bonds. Furthermore, the surface treatment of the R2 rubber with sulfuric acid removes paraffin wax from the rubber surface, which had a beneficial effect on adhesion to the polyurethane adhesive. To remove the wax layer, the surface was wiped with petroleum ether solvent after treating the R2 rubber with sulfuric acid. However, in some experiments a progressive migration of wax from the R2 rubber bulk to the surface with time happened. The migration of wax was prevented by increasing the immersion time in H₂SO₄ by more than 5 min.     

On the magnetic, mechanical and rheological properties of rubber–nickel nanocomposites

Rubber–nickel nanocomposites were synthesized by incorporating freshly prepared nanometric nickel particles in two different matrices namely natural rubber and neoprene rubber according to specific recipes for various loadings of nano nickel and the cure characteristics of these composites were evaluated. The maximum torque values register an increase with the increase in loading of nickel in both composites and this is attributed to the non-interacting nature of nickel nanoparticles with rubber matrices. The cure time of natural rubber composites decreases with increase in the content of nickel, and in neoprene rubber cure, time increases with increase in filler content. In natural rubber, the curing reaction seems to be activated by the presence of nickel particles. The magnetization studies of the composites reveal that the magnetic properties of nickel are retained in the composite samples. The elastic modulus of natural rubber and neoprene rubber are largely improved by the incorporation of nickel particles.     

Microton irradiation induced tuning of dielectric properties of nano ZnO–natural rubber disks

The effect of electron beam irradiation of dielectric and conductivity properties of nano ZnO–natural rubber (NR) disks was investigated here. It is revealed that electric properties such as AC conductivity, dielectric constant, and loss tangent of the irradiated samples were improved significantly as compared to the non-irradiated samples, which have been associated with defects in the composites. The total number of dipoles was generated inside the polymer matrix upon irradiation depends on the dislocations formed inside the matrix. From the experiments, we observe that in the amorphous region electron beam irradiation fetches crosslinking and breakdown at the same time. The enhancement of the dielectric and conductivity properties demonstrates that nano ZnO–NR disks will be a promising candidate for the optoelectronic industry. Finally, we also examined the influences of temperature on the electrical conductivity of irradiated samples.     

Mechanical, thermal and transport properties of nitrile rubber (NBR)—nanoclay composites

The article describes the properties of nitrile rubber (NBR)??nanoclay composites prepared by a two-step method. viz. preparation of a 3:1 [by weight] masterbatch of NBR and nanoclay followed by compounding on a two roll mill and molding at 150?°C and 20?MPa pressure. The tensile strength, elongation at break, modulus, storage modulus (E??) and loss modulus (E??) increased with the nanofiller content, reached the maximum value at 5 phr and decreased thereafter. The solvent uptake, diffusion, sorption and permeation constants decreased with nanoclay content with the minimum value at 5 phr nanoclay. The mechanism of solvent diffusion through the nanocomposites was found to be Fickian. Thermodynamic constants such as enthalpy and activation energy were also evaluated. The dependence of various properties on nanoclay content was correlated to the morphology of the nanocomposites. supported by morphological analysis.     

Effect of Cu strike coating on adhesion between Cu–Sn coated steel and rubber

In order to improve the adhesion between steel and rubber, a novel coating deposition technique has been developed, where steel substrate with orchestrated surface roughness was coated with double-layer coatings consisting of a thin Cu strike layer followed by a Cu–Sn layer with varying Sn compositions by immersion route. Coating surface characteristics studied using scanning electron microscope coupled with energy dispersion spectroscopy analyzer, electron probe micro analyzer, and inductively coupled plasma optical emission spectroscopy showed improvement in surface coverage with coating after employing the strike layer coating attributed to the better coating penetration in the deep roughness troughs. Peel test of the coated samples vulcanized with styrene butadiene rubber (SBR) was carried out which showed improvement in adhesion strength of the double-layer-coated samples inferring more uniform Cu-sulfide layer formation at interface due to more uniform coating coverage in these samples. Highest peel strength with uniform cohesive fracture within rubber was observed for optimum 2–3?wt% Sn content in the coatings. This result was further supported by pull-out test conducted on coated wire samples vulcanized with SBR.