Effect of fillers and vulcanizing systems on the physicomechanical and electrical properties of EPDM vulcanizates

The physicomechanical and dielectric properties were investigated for ethylene propylene diene terpolymer (EPDM) rubber loaded with different white fillers, namely, kaolin, quartz, polyvinylchloride PVC, and talc. The white fillers were added at a fixed level of 20 phr. Two vulcanizing systems were used, tetramethyl thiuram disulfide (TMTD) and sulfur/N-cyclohexyl-2-benzothiazyl sulfenamide (S/CBS). It was found that the curing systems affect the dielectric properties more than the filler type. The effect of the curing system and type of filler on the physicomechanical properties before and after thermal aging were also investigated, and the data obtained were interpreted.     

Effect of fillers on the relaxation behavior of chlorobutyl vulcanizates

The effect of addition of fillers (carbon black (CB), carbon silica dual phase filler (CSDPF), and nanoclays) on the relaxation behavior of chlorobutyl vulcanizates has been 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 positron annihilation life time spectroscopy (?70 to +110°C). Irrespective of the filler and its loading, all the composites showed the glass transition temperature in the range of –29 to –33°C, which was explained on the basis of relaxation chain dynamics of polyisobutylene in the vicinity of fillers. The secondary relaxation (α* or β relaxation) was studied using dielectric relaxation spectra in the frequency range of 100–10⁶ Hz. Nanoclays had a profound influence on the secondary relaxation, whereas CSDPF and CB had a marginal effect. The nonlinear strain dependent dynamical parameters were also evaluated at double strain amplitudes of 0.07–5%. The nonlinearity in tan δ and storage modulus has been explained on the concept of filler–polymer interactions and the interaggregate attraction (filler networking). The “percolation limit” of the fillers in the composites has been studied by DC conductivity measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3161–3173, 2006     

Effect of modified carbon black on the filler–elastomer interaction and dynamic mechanical properties of SBR vulcanizates

A new modified carbon black (GCB) was prepared by adding special RFL latex into N220. Dynamic properties were obtained over a wide range of temperatures and strains on vulcanizates filled with GCB and unmodified carbon black, respectively. The results show that the GCB can effectively decrease the tan δ value at 60 and 90°C of SBR vulcanizates compared with that of the common unmodified carbon blacks, which responds to the fact that GCB is beneficial to lower rolling resistance and heat generation of the vulcanizates in comparison to that of the unmodified carbon black. Among the factors responsible for this, filler networking and filler–elastomer interaction play a dominant role. The effects of filler loading on mechanical properties of vulcanizates were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3707–3712, 2006     

Comparison of dynamic shear properties of styrene–butadiene vulcanizates filled with carbon black or polymeric fillers

The dynamic shear behavior of SBR 1500 vulcanizates filled with polymeric fillers of 24.6, 40.2, and 74.7 nm diameter and various filler loading up to 100 phr (parts per 100 parts of rubber), and its dependence of strain amplitude up to 14%, have been investigated. The results are compared with carbon-black-filled vulcanizates. The reinforcement ability of polymeric fillers is comparable to that of carbon black, depending on filler particle diameter. As expected, the smaller particles have a higher reinforcement effect than larger particles. The Payne effect, that is, the decrease of storage shear modulus G′ with increasing strain amplitude and the appearance of a loss modulus G″ maximum at strains of a few percent, has also been observed in vulcanizates with polymeric fillers. The loss modulus maximum of vulcanizates filled with polymeric fillers is at higher strain amplitudes and is less pronounced than for carbon-black-filled vulcanizates. The results are discussed shortly in terms of recent models based on the idea of filler networking within the rubbery matrix. The experimental G′ data are adjusted with the deagglomeration–reagglomeration Kraus model (1984). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 495–503, 1999     

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     

Use of rice husk ash as filler in natural rubber vulcanizates: In comparison with other commercial fillers

Rice husk ash is mainly composed of silica and carbon black remaining from incomplete combustion. Both silica and carbon black have long been recognized as the main reinforcing fillers used in the rubber industry to enhance certain properties of rubber vulcanizates, such as modulus and tensile strength. In this study, two grades of rice husk ash (low‐ and high‐carbon contents) were used as filler in natural rubber. Comparison was made of the reinforcing effect between rice husk ashes and other commercial fillers such as talcum, china clay, calcium carbonate, silica, and carbon black. Fourier transform infrared spectroscopy (FTIR) analysis was employed to study the presence of functional groups on the ash surface. The effect of silane coupling agent, bis(3‐triethoxysilylpropyl)tetrasulfane (Si‐69), on the properties of ash‐filled vulcanizates was also investigated. It was found that both grades of rice husk ash provide inferior mechanical properties (tensile strength, modulus, hardness, abrasion resistance, and tear strength) in comparison with reinforcing fillers such as silica and carbon black. However, the mechanical properties of the vulcanizates filled with rice husk ash are comparable to those filled with inert fillers. The addition of silane‐coupling agent has little effect on the properties of the ash‐filled vulcanizates. This is simply due to the lack of silanol groups on the ash surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2485–2493, 2002     

Effect of natural coagula maturation on the processability,cure, and mechanical properties of unfilled vulcanizates of Hevea natural rubber

Fresh latex from different Hevea brasiliensis clones was naturally coagulated, subjected to different durations of maturation, processed into solid rubber, and compounded into pure gum stocks and vulcanized. Coagula maturation had clone‐specific effects on the processability of the raw rubber: reduced for some clones, while others was less sensitive. The cure and mechanical behaviors of the compounded stocks and vulcanizates, respectively, were not sensitive to the clonal origin of coagula and their duration of maturation. Although coagula maturation could be associated with leaching, deactivation of inherent antioxidants in Hevea latex, as well as crosslinking and/or oxidation of polyisoprene chains, these results show that compounding with a standard pure gum recipe compensates for the Hevea latex constituents affected by maturation. Hence, extended maturation of Hevea coagula, for economic or other reasons, would influence much more the bulk behavior of raw rubber and have insignificant effects on the compounded stocks and vulcanizates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2359–2363, 2007     

Effect of surface‐modified zinc oxide as cure activator on the properties of a rubber compound based on NR/SBR

Zinc oxide (ZnO) and nano‐zinc oxide (nZnO) were surface modified by polyethylene glycol (PEG) and poly propylene glycol (PPG). Modification of particles were controlled by transmission electron microscopy, Brunauer, Emmett, Teller specific surface area measurement, infrared (IR) spectroscopy, and differential scanning calorimetry. IR spectra were shown that the interactions between surface modifiers and particles are hydrogen bonding. Modified particles were applied as an activator in vulcanization of natural rubber/styrene butadiene rubber (NR/SBR) blend. Dispersion of modified particles in rubber matrix was investigated by scanning electron microscopy and shown good results. Blend properties were improved by using modified particles. These improvements were due to the better hydrophobicity of modified particles, which were more compatible with nonpolar rubber matrix and caused better participation in curing process. Modification by PEG and PPG were shown better compound properties for ZnO and nZnO, respectively. Application of ZnO‐modified particles were presented better compound properties in comparison with nZnO‐modified particles. It has confirmed more effective mixing of ZnO‐modified particles in rubber matrix by using ordinary mixers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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 chemically modified waste rubber powder as a filler in natural rubber vulcanizates

Waste rubber powder (RP) was subjected to chemical modification by using different concentrations of oxidizing agents such as nitric acid and 30% hydrogen peroxide solution. This treatment leads to introducing some functional groups onto the surface of RP. The chemically modified RP was incorporated in natural rubber mixes either alone or in combination with carbon black (HAF). The physicomechanical properties of NR vulcanizates obtained were studied and compared to NR vulcanizates filled with untreated RP. It was found that the chemically modified RP improves tensile strength and aging resistance of NR vulcanizates compared with untreated RP. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 30–36, 2004     

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     

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。     

Acrylic rubber‐fluorocarbon rubber miscible blends: Effect of curatives and fillers on cure,mechanical, aging,and swelling properties

The cure characteristics and mechanical properties of gum and filled acrylic rubber (ACM), fluorocarbon rubber (FKM), and their blends of varying compositions were studied both under unaged and aged conditions. The rheometric study showed that optimum cure properties were obtained using a mixed curing system of blocked diamine, hexamethylenediamine carbamate (Diak #1), and ammonium benzoate. From varying the curing agents, the optimum levels of Diak #1 and ammonium benzoate were found to be 1.5 and 2.5 phr, respectively. The addition of different fillers and their loading influenced the cure properties, with increased torque and reduced scorch safety. The gum and filled 50:50 (w/w) ACM‐FKM showed overall performance in strength properties. Postcuring improved the strength of all the systems, especially the systems with a higher proportion of FKM. None of the properties changed significantly during aging of the blends. FKM and the blends containing a higher proportion of FKM were affected least by aging. Swelling of the blends was reduced by the addition of fillers. Dynamic mechanical thermal analysis showed a single tan δ peak corresponding to a single phase transition for both cured and filled blends. The storage modulus of the blend increased from the gum blend to the filled blend, indicating the presence of polymer‐filler interaction. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1442–1452, 2003     

Rheology,cure characteristics,physical and mechanical properties of tire tread reclaimed rubber/natural rubber compounds

This work aimed to examine the effect of addition of tire‐tread reclaimed rubber on the properties of two natural rubber (NR) compounds with respect to the reclaimed rubber concentration and mastication time, the properties of interest including rheological and cure characteristics, physical and mechanical properties. The results under the test conditions suggested that Mooney Plasticity and shear viscosity increased with reclaimed rubber content, but decreased with mastication time. The greater the molar mass of the natural rubber the higher the sensitivity to the change in compound viscosity due to mastication and reclaimed rubber content. The die swell was more dependent on the reclaimed rubber than the molar mass of the rubbers. The cure rate and scorch time were found to increase and decrease with reclaimed rubber content, respectively, whereas the cure time was independent of the reclaimed rubber content. For vulcanized rubbers, it was also observed that 100% modulus of the rubber increased with reclaimed rubber content, but this was not the case for tensile stress and elongation at break. The hardness and heat buildup properties of the vulcanizates increased with reclaimed rubber content whereas the tear strength became independent of the reclaimed rubber. The findings in this work suggested that the variations in the rheological and cure characteristics for the unvulcanized rubber were very much dependent on the molar mass of the rubber whereas the mechanical properties for the vulcanized rubber were influenced by crosslink density. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1723–1731, 2003     

甲基丙烯酸对氢氧化铝填充丁苯橡胶性能的影响

将甲基丙烯酸（MAA）用作Al(OH）3填充丁苯橡胶（SBR）复合材料的添加剂，结果表明，在高填充Al(OH）3的SBR中加入MAA可以较大幅度地提高其过氧化物硫化胶的力学性能。当Al(OH）3用量为150份（质量份，下同）时，随着MAA用量增加，SBR硫化胶的邵尔A型硬度和定伸应力逐渐增大，拉伸强度和撕裂强度有较大幅度的提高，当MAA用量为20份时，随着Al(OH）3用量增加，SBR硫化胶的邵尔A型硬度、定伸应力和撕裂强度逐渐增大，拉伸强度在Al(OH）3填充量为25份时最大，大量填充Al(OH）3的SBR硫化胶的阻燃性能较好，氧指数受MAA用量的影响较小，该SBR硫化胶亦具有良好的热空气老化性能。     

热塑性硫化橡胶的制备与性能

综述了热塑性硫化橡胶（TPV）的制备技术，制备工艺及微观结构，分析了影响TPV性能的因素，简介了几种典型非极性橡胶／非极性树脂型TPV，极性橡胶／非极性树脂型TPV，非极性橡胶／极性树脂型TPV，极性橡胶／极性树脂型TPV的制备与性能。     

硫化体系对氯化丁基橡胶/尼龙12动态硫化胶性能的影响

研究了氧化锌、N,N’-间苯撑双马来酰亚胺(HVA-2)/氧化锌和1,3-双柠糠酰亚胺甲基苯(PK 900)/氧化锌3种硫化体系下氯化丁基橡胶(CIIR)/尼龙(PA)12混炼胶的硫化特性及CIIR/PA 12动态硫化胶(TPV)的物理机械性能和微观相结构,并考察了PK 900与氧化锌不同配比对CIIR/PA 12TPV物理机械性能、流变性能及微观相结构的影响。结果表明,PK 900/氧化锌的硫化速率介于氧化锌和HVA-2/氧化锌两者之间,由其制备的TPV橡胶相粒径为1～2μm,均匀分布在树脂相中,物理机械性能最优;固定PK 900用量为3份时,随着氧化锌用量的减少,CIIR/PA 12 TPV的拉伸强度、扯断伸长率和100%定伸应力均呈现先增大后减小的趋势;当PK 900/氧化锌(质量比)为3/5时,CIIR/PA 12TPV的物理机械性能最佳,且呈现低剪切速率高黏度、高剪切速率低黏度的特性。     

增容剂对硅橡胶/热塑性聚氨酯热塑性硫化胶性能的影响

采用动态硫化法制备了甲基乙烯基硅橡胶（MVQ）/热塑性聚氨酯（TPU）共混型热塑性硫化胶（TPV）,考察了增容剂的种类及用量对TPV力学性能及加工流变性能的影响。结果表明,随着增容剂用量的增加,TPV的力学性能呈先上升后下降的趋势。相比于乙烯丙烯酸共聚物和乙烯与乙酸乙烯嵌段共聚物,用聚烯烃弹性体接枝马来酸酐（POE-g-MAH）作为增容剂时TPV的力学性能更为优异。3种增容剂均能提高TPV中MVQ相与TPU相的相容性。当POE-g-MAH的用量为6份时,TPV中MVQ相与TPU相的玻璃化转变温度靠近程度最大,两相界面较为模糊,增容效果最佳。     

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