Effect of organoclay reinforcement on the curing characteristics and technological properties of SBR sulphur vulcanizates

Styrene‐butadiene rubber (SBR) nanocomposites with different organoclay contents (up to 15 phr) were prepared by a melt compounding procedure, followed by a compression‐molding step in which the SBR matrix was sulfur crosslinked. The vulcanizates were characterized in respect to their curing, mechanical and viscoelastic properties, and thermal stability. The optimum cure time decreased with increasing organoclay content. This effect was attributed to the ammonium modifier present in the organoclay, which takes part in the curing reaction acting like an accelerator. The results of mechanical test on the vulcanizates showed that the nanocomposites presented better mechanical properties than unfilled SBR vulcanizate, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/organoclay nanocomposites. The addition of organoclay did not significantly change the glass transition temperature. However, the heights of tan δ value at the glass transition temperature for the nanocomposites are lower than that of the unfilled SBR. This suggests a strong interaction between the organoclay and the SBR matrix as the molecular relaxation of the latter is hampered. The temperature at which 50% degradation occurs (T₅₀) and the temperature when the degradation rate is maximum (DTG_max) showed an improvement in thermal stability, probably related to the uniform dispersion of organoclay. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical and morphological properties of cellular NR/SBR vulcanizates under thermal and weathering ageing

The effects of addition of two chemical blowing agents in cellular rubber blend of natural rubber (NR) and styrene‐butadiene rubber (SBR) at a fixed blend ratio of 1 : 1 on cure characteristics, and mechanical and morphological properties were invesigated. The chemical blowing agents used in this work were Oxybis (benzene sulfonyl) hydrazide (OBSH) and Azo dicarbonamide (ADC). Three different fillers, fly ash (FA) particles, precipitated silica, carbon black (CB) at their optimum concentrations of 40 phr were used, the FA and silica particles being chemically treated by bis‐(3‐triethoxysilylpropyl) tetrasulphide. The results suggested that the overall cure time decreased with OBSH and ADC contents. The OBSH was more effective in cure‐acceleration of the NR/SBR blend than the ADC. The NR/SBR vulcanized foams produced by OBSH and ADC agents had closed‐cell structures. The specific density and mechanical properties of the blend tended to decrease with increasing blowing agent content. The CB gave NR/SBR foams with smaller cell size, better cell dispersion, and higher mechanical properties than the precipitated silica and FA particles. The heat ageing and weathering resulted in an increase in tensile modulus and hardness, but lowered the tensile strength, ultimate elongation and tear strength. The elastic recovery for cellular NR/SBR vulcanizates with FA was superior to that with CB and silica, the elastic recovery of the blends decreasing with blowing agent content. Resilience property was improved by the presence of gas phases. The optimum concentration of OBSH and ADC to be used for NR/SBR vulcanizates was 4 phr. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of liquid isoprene rubber on dynamic mechanical properties of emulsionpolymerized styrene/butadiene rubber vulcanizates

The effect of liquid isoprene rubber (LIR) on the dynamic mechanical properties of emulsion‐polymerized styrene/butadiene rubber (ESBR) vulcanizates was investigated by temperature sweep using dynamic mechanical analysis. The introduction of LIR led to ESBR vulcanizates having higher loss factor (tan δ) in the temperature range ? 30 to 0 °C, and lower tan δ in the range 60 to 80 °C. A small amount of LIR‐403 (LIR with carboxyl groups) led to a significant change in tan δ: the addition of LIR‐403 (3 phr) led to a 7.5% increase in tan δ from ? 30 to 0 °C, and a 24.9% decrease in tan δ from 60 to 80 °C. It was found that the introduction of LIR increased the bound rubber content in the ESBR compound. Equilibrium swelling experiments showed that the crosslink density of the vulcanizates increased after the introduction of LIR‐403 or LIR‐50 (general purpose LIR). The change in tan δ from 60 to 80 °C was related to polymer–filler interactions. The characteristic constant of filler–ESBR matrix interaction (m) was calculated. At a given filler volume fraction, the increase in m in the presence of LIR could be well related to the decrease in tan δ from 60 to 80 °C. The influence of LIR on filler network in the ESBR compound was also investigated by strain and temperature sweeps using a rubber processing analyzer. Copyright © 2011 Society of Chemical Industry     

Reinforcement of peroxide‐cured styrene–butadiene rubber vulcanizates by mathacrylic acid and magnesium oxide

Through the neutralization of magnesium oxide (MgO) and methacrylic acid (MAA), magnesium methacrylate [Mg(MAA)₂] was in situ prepared in styrene–butadiene rubber (SBR) and used to reinforce the SBR vulcanizates cured by dicumyl peroxide (DCP). The experimental results show that the mechanical properties, dynamic mechanical properties, optical properties, and crosslink structure of the Mg(MAA)₂‐reinforced SBR vulcanizates depend on the DCP content, Mg(MAA)₂ content, and the mole ratio of MgO/MAA. The formulation containing DCP 0.6–0.9 phr, Mg(MAA)₂ 30–40 phr, and MgO/MAA mole ratio 0.50–0.75 is recommended for good mechanical properties of the SBR vulcanizates. The tensile strength of the SBR vulcanizates is up to 31.4 MPa when the DCP content is 0.6 phr and the Mg(MAA)₂ content is 30 phr. The SBR vulcanizate have good aging resistance and limited retention of tensile strength at 100°C. The SBR vulcanizates are semitransparent, and have a good combination of high hardness, high tensile strength, and elongation at break. The T_g values of the SBR vulcanizates depend largely on the DCP content, but depend less on the Mg(MAA)₂ content and the MgO/MAA mole ratio. The contents of DCP, Mg(MAA)₂, and the MgO/MAA mole ratio have also great effects on the E′ values of the vulcanizates. The salt crosslink density is greatly affected by the Mg(MAA)₂ content and MgO/MAA mole ratio, but less affected by the DCP content. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2667–2676, 2002     

Preparation and performances of ethylene–propylene–diene terpolymer/acrylic rubber reinforced with a dough‐modeling compound

A novel composite was prepared by the addition of a dough‐modeling compound (DMC) reinforcement and an ethylene–propylene–diene terpolymer (EPDM)/acrylic rubber (ACM) matrix. We studied the DMC/EPDM/ACM mass ratio and vulcanizing process by testing the tensile strength, Shore A hardness, elongation at break, and wear and thermal properties. The results show that the mechanical properties, thermal properties, and wear resistance of the composites were good when the DMC/EPDM/ACM mass ratio was 70/25/75 and the cure conditions were 180°C under 10 MPa for 25 min. The crosslinking structure of the composites was studied by IR, and this further proved the interaction between DMC, ACM, and EPDM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical properties of deproteinized natural rubber in comparison with synthetic cis‐1, 4 polyisoprene vulcanizates: Gum and black‐filled vulcanizates

Gum and black‐filled vulcanizates having various crosslink densities were prepared from 2 types of rubber, namely, deproteinized natural rubber (DPNR) and synthetic cis‐1, 4 polyisoprene vulcanizates (IR). Their mechanical properties, such as tensile strength, tear strength, abrasion loss, and heat buildup resistance, at various crosslink densities as well as at similar optimum crosslink density were compared. For both gum and black‐filled systems, IR possessed a higher crosslink density than that of DPNR at a fixed curative content. Tensile and tear strength of all vulcanizates passed through a maximum with increasing crosslink density. For gum vulcanizates, tensile and tear strengths of DPNR and IR below the maximum were not much different. However, IR had a narrower tear strength peak relative to DPNR. At a comparable optimum crosslink density, DPNR exhibited higher tensile strength and crack growth resistance than IR. For black‐filled vulcanizates, tensile and tear strengths, and heat buildup resistance of DPNR and IR at a given crosslink density were similar. The results revealed that the properties of gum samples were more dependent upon crosslink density than the black‐filled ones because the reinforcement by carbon black overshadowed the intrinsic properties of the rubbers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1139–1144, 2005     

Synthesis and aging properties of reactive antioxidant NAPM in natural rubber vulcanizates

The rubber antioxidant N‐(4‐anilinophenyl) methacrylamide (NAPM) was synthesized by a two‐step reaction using thionyl chloride (SOCl₂) with methacrylic acid (MAA) and consequently 4‐aminodiphenylamine (ADPA) as precursors. NAPM was characterized by IR, ¹H NMR and elemental analysis. Thermal stability, aging property of NAPM and mechanical properties of natural rubber (NR) vulcanizates containing NAPM were investigated and compared with two other commercial antioxidants N‐isopropyl‐N′‐phenyl‐p‐phenylene diamide (4010NA) and N‐(1, 3‐dimethyl butyl)—N′‐phenyl‐p‐phenylene diamide (4020). It was found that NAPM was an effective antioxidant with a better thermal stability and higher antiaging resistance than unreactive antioxidants 4010NA and 4020. And unsaturation level of NR vulcanizates containing NAPM was lower than that of 4010NA and 4020. Moreover, an antiaging resistant mechanism of a surface reaction between NAPM and cis‐1, 4‐polyisoprene in NR was proposed to explain the better properties of NAPM based on the IR and SEM analyses. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The effect of crosslinking type on the physical properties of carboxylated acrylonitrile butadiene elastomers

Vulcanization of carboxylated nitrile rubber (XNBR) with different vulcanizing agents (i.e., zinc peroxide, sulphur, and a zinc peroxide–sulphur mixed system) was studied. Properties of the vulcanized compounds depend on the type of crosslinking produced (i.e., ionic or covalent) rather than the crosslinking density. Ionic crosslinks gave rise to greater stress relaxation, relaxation rates, and a greater generation of heat. In the relaxation spectra, tan δ versus temperature, two transitions appeared. Those occurring at the lower temperature corresponded to the polymer T_g, while the transition occurring at the higher temperature was associated with ionic structures. The properties of the vulcanized compounds with ionic crosslinks decreased drastically after treatment with ammonia, which acts as a plasticizer of the ionic aggregates formed. The effect of ammonia disappeared on expansion in solvent, which resulted in the recovery of the original crosslinks, producing a value of v_r—volume fraction of swollen rubber in equilibrium—close to the original value and the reappearance of the ionic transition. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 927–933, 1999     

Rheological behavior and processability of polypropylene blends with rubber ethylene propylene diene terpolymer

A study of the dynamic complex and steady shear viscosity of isotactic polypropylene (iPP), ethylene–propylene diene terpolymer rubber (EPDM) and three different blends of both polymers are presented over a range of temperatures and frequencies. Moreover, the processability of these materials is studied through torque measurements during blend mixing. The results obtained show that the viscosity gradually increases with rubber content in the blend and decreases with both temperature and frequency. Plots of η″ versus η′ (Cole–Cole plots) show that the blend with the lower rubber content (25%), has a certain rheological compatibility with neat PP. Furthermore, torque curves measured during blend mixing confirm these results, demonstrating that the blend with 25% of elastomer has a similar behavior of iPP during processing. To analyze the morphological structure of the blends, a dynamic mechanical analysis of the solid state is also presented. It is observed that the blends have two distinct values of T_g close to the corresponding values of the pure polymers, confirming that this type of blends based on a semicrystalline polymer and an amorphous elastomer forms a two‐phase system with a limited degree of miscibility between both components. In addition, the polymer present with the higher concentration forms the continuous phase and controls the rheological properties of the blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1–10, 2001     

Ionic elastomers based on carboxylated nitrile rubber and magnesium oxide

The crosslinking of carboxylated nitrile rubber (XNBR) with magnesium oxide (MgO) leads to an ionic elastomer with thermoplastic nature and better physical properties than the ones obtained with other metallic oxides. The crosslinking reaction leads to the formation of a metallic salt as unique product, as it could be seen on the ATR analysis of the samples, prepared at different reaction times. The mechanical properties of the material increase with the amount of crosslinking agent and segregation of an ionic microphase takes place. The presence of this microphase is demonstrated by a relaxation at high temperatures. The apparent activation energy of this relaxation is smaller than the activation energy of the glass transition of the elastomer, the former being more dependent on the amount of metallic oxide than is the latter. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1894–1899, 2007     

Effect of different types of carbon black on the mechanical and acoustic properties of ethylene–propylene–diene rubber

The effects of the incorporation of different types of carbon black as fillers on some selected physical and mechanical properties of ethylene–propylene–diene rubber (EPDM) based compounds were studied with the results of density, ultrasonic wave velocity, and tensile measurements. Ultrasonic wave velocities (both longitudinal and shear) were measured at frequencies up to 4 MHz at room temperature. The density, ultrasonic attenuation coefficient, and tensile strength results showed that rubber mixes containing general‐purpose furnace (GPF) black at a concentration of 25 phr had the best physical and mechanical properties. These results were interpreted to be due to the better compatibility of GPF black, which, because of its particle size and structure, filled the interstitial spaces in EPDM and provided better reinforcement of the elastomer. The use of a nondestructive technique such as ultrasonic measurement presents a new possibility for testing rubber and plastic products more efficiently. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

原位生成甲基丙烯酸锌增强天然橡胶的结构和性能

用ZnO与甲基丙烯酸(MAA)在天然橡胶(NR)基体中原位生成甲基丙烯酸锌(ZDMA),并在硫化剂过氧化二异丙苯(DCP)作用下制备了NR／ZnO／MAA纳米复合材料。用傅里叶变换红外光谱法、X射线衍射法、能量色散X射线法和扫描电子显微镜法分析了NR在混炼和硫化过程中的结构和形态变化,并研究了硫化胶的力学性能。结果表明,在NR混炼过程中加入摩尔比为0．5的ZnO／MAA。可以原位生成ZDMA;在硫化过程中,ZDMA在DCP作用下发生复杂化学反应,形成界面紧密结合的纳米复合材料,导致硫化胶的力学性能显著提高。当ZnO／MAA为加份时,硫化胶的拉伸强度、撕裂强度、扯断伸长率分别为30．6MPa,54．7kN／m,410％,其增强效果优于直接添加ZDMA。     

Properties of EVM vulcanizates reinforced by in situ prepared sodium methacrylate

Ethylene–vinyl acetate copolymer (EVM) vulcanizates with good mechanical properties and high transparency were obtained using sodium methacrylate (NaMAA) as a reinforcing agent. Sodium methacrylate was in situ prepared through the neutralization of sodium hydroxide (NaOH) and methacrylic acid (MAA) in an EVM and used to reinforce the EVM cured by dicumyl peroxide (DCP). Different factors such as the DCP content, NaMAA content, and the mol ratio of NaOH/MAA were included to study their effects on the mechanical properties, optical properties, stress‐relaxation behavior, and crosslink structure of the EVM vulcanizates. The rheological behavior of the EVM compounds was also investigated and compared with that of the high abrasion furnace carbon black (HAF)/EVM compounds. The experimental results show that with an increase of the NaMAA content the curing rate index (C_R) of the EVM compounds is greatly speeded up, while the Mooney viscosities of the compounds remain nearly unchanged. The mechanical properties and optical properties of the NaMAA‐reinforced EVM vulcanizates depend on the NaMAA content and the mol ratio of NaOH/MAA. The formulation of DCP of 3 phr and a NaOH/MAA mol ratio of 1.0 is recommended for the EVM vulcanizate with high mechanical properties. At a given NaOH/MAA mol ratio of 1.0, all the EVM vulcanizates are transparent and the light transmission is over 76% in the NaMAA content range of 10–50 phr. The NaMAA/EVM vulcanizates show faster stress relaxation and more obvious stress‐softening effects than those of the HAF/EVM vulcanizates. Crosslink density analysis indicated that the EVM vulcanizates contain both covalent and ionic bonds. The ionic crosslink densities greatly increase with an increasing NaMAA content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2192–2200, 2003     

Mechanical properties of crosslinked polyurethane elastomers based on well‐defined prepolymers

This article presents research findings for selected mechanical properties of polyurethane elastomers. The studied elastomers were synthesized with the prepolymer‐based method with the use of controlled molecular weight distribution (MWD) urethane oligomers and with the classical single‐stage method. Prepolymers with defined MWDs were obtained with the use of a multistage method, that is, step‐by‐step polyaddition. To produce elastomers, isocyanate oligomers were then crosslinked with triethanolamine, whereas hydroxyl oligomers were crosslinked with 4,4′,4′′‐triphenylmethane triisocyanate (Desmodur RE). The tensile strength of the obtained elastomers ranged from 1.0 to 7.0 MPa, the ultimate elongation approached 1700%, the Shore A hardness varied from 40 to 93°, and the abrasion resistance index fell within 15–140. The effects of the types of raw materials used, the chemical structures, the production methods, and the supermolecular structures on the mechanical properties of the obtained polyurethane elastomers were examined. When the obtained findings were generalized, it was concluded that the structural changes in the polyurethanes, which were favorable for intermolecular interactions, improved the tensile strength, hardness, and abrasion resistance of the materials and impaired their ultimate elongation at the same time. More orderly supermolecular structures and, therefore, superior mechanical properties were found for polyurethane elastomers produced with the prepolymer method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of crosslink structures on dynamic mechanical properties of natural rubber vulcanizates under different aging conditions

The effects of crosslink structures on the dynamic mechanical properties (DMPs) of unfilled and carbon black N330‐filled natural rubber (NR) vulcanizates cured with conventional (CV), semiefficient (SEV), and efficient (EV) cure systems and having about the same total crosslink densities were investigated before and after aerobic and anaerobic aging at 100°C. The three unfilled NR vulcanizates cured with the CV, SEV, and EV systems had about the same mechanical loss factor (tan δ) values at about 0°C but showed some apparent differences in the tan δ values in the order EV > SEV > CV at relatively high temperatures of 40–80°C before aging. However, N330‐filled NR vulcanizates gave higher tan δ values than the unfilled vulcanizates and showed little effect of the crosslink types on the tan δ at different temperatures over the glass‐transition temperature (T_g) before aging. Aerobic heat aging increased the T_g and tan δ values of the vulcanizates over a wide range of temperatures from ?80 to 90°C that was mainly due to the changes in the total density and types of crosslinks. The unfilled vulcanizates cured with the CV system showed the greatest change in DMP because of their poor resistance to heat aging. Aerobic heat aging of NR vulcanizates caused a more significant change in the DMP than anaerobic heat aging because of the dominant effect of the oxidative degradation during aerobic heat aging on the main‐chain structure, crosslink structures, and DMPs of the vulcanizates. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 710–718, 2001     

高耐磨炭黑填充型粉末SBR研究Ⅱ.硫化胶的物理机械性能

研究了高耐磨炭黑(N330)填充型粉末丁苯橡胶[P(SBR／N330)]硫化胶的物理机械性能。结果发现。炭黑乳化剂的用量、炭黑改性剂和包覆剂的用量及玻璃化转变温度对P(SBR／N330)硫化胶的物理机械性能的影响比较明显。在适宜的粉末化条件下制备的P(SBR／N330)，其硫化胶的物理机械性能与块状SBR／N330通过机械混炼得到的硫化胶的物理机械性能处于相同水平。P(SBR／N330)硫化胶拉伸断面形貌的SEM分析表明，包覆剂在用量为5份时形成的粒子与SBR基体结合紧密，在用量为15份时形成的粒子较易剥离。     

Fly‐ash particles and precipitated silica as fillers in rubbers. II. Effects of silica content and Si69‐treatment in natural rubber/styrene–butadiene rubber vulcanizates

This article explored the possibility of using silica from fly‐ash particles as reinforcement in natural rubber/styrene–butadiene rubber (NR/SBR) vulcanizates. For a given silica content, the NR : SBR blend ratio of 1 : 1 (or 50 : 50 phr) exhibited the optimum mechanical properties for fly‐ash filled NR/SBR blend system. When using untreated silica from fly‐ash, the cure time and mechanical properties of the NR/SBR vulcanizates decreased with increasing silica content. The improvement of the mechanical properties was achieved by addition of Si69, the recommended dosage being 2.0 wt % of silica content. The optimum tensile strength of the silica filled NR/SBR vulcanizates was peaked at 10–20 phr silica contents. Most mechanical properties increased with thermal ageing. The addition of silica from fly‐ash in the NR/SBR vulcanizates was found to improve the elastic behavior, including compression set and resilience, as compared with that of commercial precipitated silica. Taking mechanical properties into account, the recommended dosage for the silica (FASi) content was 20 phr. For more effective reinforcement, the silica from fly‐ash particles had to be chemically treated with 2.0 wt % Si69. It was convincing that silica from fly‐ash particles could be used to replace commercial silica as reinforcement in NR/SBR vulcanizates for cost‐saving and environment benefits. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Physical,mechanical, and viscoelastic properties of natural rubber vulcanizates cured with new binary accelerator system

Natural rubber was vulcanized with a new binary accelerator system based on 1‐phenyl‐2,4‐dithiobiuret (DTB) and dicyclohexyl benzothiazyl sulfenamide. A significant reduction in cure time was observed with the addition of DTB. The cure kinetics was investigated and the activation energy was determined. The mechanical properties were improved by adding DTB, and the maximum values are shown at an optimum concentration. Estimates of the concentration of crosslinks and of the relative proportions of different types of crosslinks were made by the chemical characterization of the vulcanizates. The crosslink densities obtained from swelling measurements and stress–strain measurements were compared with those obtained from modulus measurements. All of them follow a similar trend and support the observed mechanical properties. A dynamic mechanical analysis of the mixes was carried out and the activation energy was determined from Arrhenius plots. The glass‐transition temperature was found to increase with the increase in crosslink density and frequency of measurements. The stress–strain curves were found to not deviate from the strain crystallizing nature of natural rubber. The mechanical properties, network characterization, and processing characteristics were used to optimize the DTB concentration. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2193–2203, 2003     

Effect of carbon blacks on relaxation phenomenon of chlorobutyl vulcanizates

The effect of the types of carbon black on the physicomechanical, dynamic mechanical, and dielectric relaxation spectra in chlorobutyl vulcanizates was studied. The primary relaxation (α transition, the glass transition) was studied by dynamic mechanical analysis as a function of temperature (?60 to +100°C) and by positron annihilation lifetime spectroscopy (?70 to +100°C). Irrespective of the type of carbon black that was used, all composites showed glass‐transition temperatures in the range of ?29 to ?33°C, which was explained on the basis of the relaxation dynamics of polyisobutylene chains in the vicinity of the fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–10⁶ Hz. The nonlinear strain dependent dynamical parameters (Payne effect) were also evaluated at dynamic strain amplitudes of 0.07–5%. The nonlinearity in the tan δ and storage modulus was explained by the concept of filler–polymer interactions and the interaggregate attraction (filler networking). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1809–1820, 2006