Effects of ultraviolet irradiation on the static and dynamic properties of neoprene rubbers

Rubbers deteriorate when they are exposed to ultraviolet irradiation for long periods of time. By conducting a series of hardness measurements and simple tension tests, the static properties of neoprene rubbers before and after exposure to various durations of ultraviolet irradiation were first measured. It is found that the Shore A hardness and tensile modulus of neoprene rubbers after exposure to ultraviolet irradiation are increased but their elongation at break, tensile strength, and energy to break are significantly decreased. On the basis of a complex spring model of a vibration system, the dynamic shear properties of neoprene rubbers before and after exposure to different durations of ultraviolet irradiation were then determined from the experimental results of dynamic transmissibility tests. It is also found that the storage modulus, loss modulus, and loss factor of neoprene rubbers are drastically affected by the duration of ultraviolet irradiation they experienced. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal aging on mechanical properties and crosslinked network of natural rubber/zinc Dimethacrylate composites

This article dealt with the relationship between mechanical properties and crosslinked networks of natural rubber (NR) reinforced by zinc dimethacrylate (ZDMA) after thermal aging. After thermal aging at the present experimental conditions, the covalent crosslink density showed a decrease all the time, whereas the ionic crosslink density was stable at 80°C but decreased at a higher temperature. The decrease in the total crosslink density after aging indicates the degradation of the crosslinked network. However, an experimental phenomenon observed was that the tensile strength and tear strength increased in a certain degree after aging at 80°C or at a 100°C for a short time. In addition, the thermal stability of the NR/ZDMA composite was evaluated by thermal gravimetric analysis. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

ACM/FKM并用胶的性能研究

研究了不同并用比的氟橡胶（FKM）和丙烯酸酯橡胶（ACM）并用胶的硫变特性、物理机械性能、耐老化性、热稳定性和压缩永久变形性能。实验结果表明：ACM与FKM可以很好地混合并且各自交联,从而制备综合性能优异的并用胶;并用比为30/70的ACM/FKM并用胶综合性能较佳,二段硫化后其物理机械性能和压缩永久变形性能明显改善,且耐热空气老化性能优异;热重分析结果表明,并用胶有很好的热稳定性。     

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     

特种氯丁橡胶热氧老化研究

通过对特种氯丁橡胶在热空气中进行加速老化,比较了其老化前后性能的变化,得出了该橡胶的性能变化与老化时间的函数关系,并建立了100％定伸应力、拉伸强度、断裂伸长率、强韧度、撕裂强度与邵尔A硬度之间的关联关系。结果表明：在整个老化期间,100％定伸应力、硬度逐渐增加;拉伸强度、断裂伸长率、强韧度、撕裂强度逐渐降低;机械性能与硬度呈线性关系。     

舰船用高性能密封橡胶研究(Ⅲ)氟橡胶硫化胶热老化性能研究

研究了热氯老化时间、温度对舰船用氟橡胶硫化胶物理性能的影响。结果表明，氟橡胶硫化胶随着老化温度的升高和老化时间的延长，硬度和拉伸强度呈现先升高后降低的趋势，而伸长率一直降低，恒定压缩永久变形一直上升。耐热添加剂Fe2O3、SnO2i可显著提高氟橡胶的耐热空气老化性能。     

Crack initiation and propagation in circular rubber bearings subjected to cyclic compression

The fatigue failure mechanism of rubber bearings under cyclic compression is important in evaluating their fatigue lives and thus is analyzed theoretically and numerically here. At first, the stress distributions in a bonded rubber cylinder derived from three different existing models were utilized to calculate the cracking energy densities within it. Next, the location of fatigue crack initiation and the direction of subsequent crack propagation in circular rubber bearings were consecutively determined. Furthermore, finite element numerical results were compared to those obtained theoretically from the three models to check their validity in predicting the fatigue crack initiation and propagation in circular rubber bearings. Based on the quasi‐statically theoretical and numerical results, it is found that the fatigue cracks initiate first at the outermost boundary between rubber and steel plates and propagate later inwards to the center of circular rubber bearings. The corresponding fatigue failure mechanism obtained theoretically and numerically is consistent with experimental findings reported previously. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

氯丁橡胶的老化和寿命预测研究

通过对氯丁橡胶在55℃、70℃、85℃、100℃下热空气加速老化的实验,研究了氯丁橡胶的老化机理并进行了寿命预测。红外分析结果说明氯丁橡胶的老化机理为：热氧老化在C=C上进行;85℃、]00℃侧基C1脱离主链。以扯断伸长率为指标进行寿命预测,可知氯丁橡胶在本实验条件下的贮存寿命约为20a。     

Effect of different nanoparticles on thermal,mechanical and dynamic mechanical properties of hydrogenated nitrile butadiene rubber nanocomposites

Organically modified and unmodified montmorillonite clays (Cloisite NA, Cloisite 30B and Cloisite 15A), sepiolite (Pangel B20) and nanosilica (Aerosil 300) were incorporated into hydrogenated nitrile rubber (HNBR) matrix by solution process in order to study the effect of these nanofillers on thermal, mechanical and dynamic mechanical properties of HNBR. It was found that on addition of only 4 phr of nanofiller to neat HNBR, the temperature at which maximum degradation took place (T_max) increased by 4 to 16°C, while the modulus at 100% elongation and the tensile strength were enhanced by almost 40–60% and 100–300% respectively, depending upon nature of the nanofiller. It was further observed that T_max was the highest in the case of nanosilica‐based nanocomposite with 4 phr of filler loading. The increment of storage modulus was highest for sepiolite‐HNBR and Cloisite 30B‐HNBR nanocomposites at 25°C, while the modulus at 100% elongation was found maximum for sepiolite‐HNBR nanocomposite at the same loading. A similar trend was observed in the case of another grade of HNBR having similar ACN content, but different diene level. The results were explained by x‐ray diffraction, transmission electron microscopy, and atomic force microscopy studies. The above results were further explained with the help of thermodynamics. Effect of different filler loadings (2, 4, 6, 8, and 16 phr) on the properties of HNBR nanocomposites was further investigated. Both thermal as well as mechanical properties were found to be highest at 8 phr of filler loading. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

配方因素对均聚型/共聚型氯醚橡胶共混物耐热老化性能的影响

采用机械共混方法制备了均聚型/共聚型氯醚橡胶(CO/ECO)共混物,考察了配方因素对共混物耐热老化性能的影响。结果表明,CO和ECO二者的共混比对共混物耐热老化性能影响不大。增强剂的种类对耐热老化性能影响较为显著,以填充沉淀法白炭黑和气相法白炭黑共混物的耐热老化性能较好;以炭黑为增强剂时,其用量以40~50份为佳。以三聚硫氰酸为硫化体系硫化的共混物,其热稳定性优于以1,2-亚乙基硫脲为硫化体系硫化的共混物。添加各种软化剂,均会导致共混物耐热老化性能下降;而各种防老剂中,以防老剂NBC、4010 NA和RD对共混物的防老化效果为最好。     

Electrical insulation properties of silicone rubber under accelerated corona and thermal aging

A contactless method based on energy shift of high-energy cut-off of the x-ray bremsstrahlung, the so-called Duane Hunt Limit and a conventional low voltage electrical technique (three-probes technique) is applied on thermal and corona aged silicone rubber (SiR) to measure, respectively, the surface potential, V_s, and the surface resistivity, ρ_s. The effect of aging on these quantities, representing the dielectric properties, is studied. The results are highly reproducible and highlight a good correlation between V_s and ρ_s. It was observed that thermal aging combined with electrical aging deteriorates more the electrical properties of the polymer than thermal aging alone. Explanations for electrical characteristics (V_s, ρ_s) change with aging are supported by attenuated total reflection Fourier transform infrared spectroscopy spectra analysis and a chemical mechanism of aging in three steps (i.e., oxidation-polycondensation, degradation, and thermal cracking). The surface degradation of the polymer is revealed by images of surface morphology obtained by using scanning electron microscopy (SEM). Roughness is greater for combined thermal and corona aging mode compared to thermal aging alone. In addition, the surface degradation of SiR polymer is confirmed by the loss of its hydrophobicity.     

Mechanical properties,oil resistance,and thermal aging properties in chlorinated polyethylene/natural rubber blends

The use of natural rubber (NR) for partly substituting elastomeric chlorinated polyethylene (CPE) was determined. Mechanical and thermal aging properties as well as oil resistance of the blends were also investigated. The amount of NR in blends significantly affected the properties of the blends. The blends with NR content up to 50 wt % possessed similar tensile strength to that of pure CPE even after oil immersion or thermal aging. Modulus and hardness of the blends appeared to decrease progressively with increasing NR content. These properties also decreased in blends after thermal aging. After oil immersion, hardness decreased significantly for the blends with high NR content, whereas no change in modulus was observed. The dynamic mechanical properties were determined by dynamic mechanical thermal analysis. NR and CPE showed damping peaks at about ?40 and 4 °c, respectively; these values correlate with the glass‐transition temperatures (T_g) of NR and CPE, respectively. The shift in the T_g values was observed after blending, suggesting an interfacial interaction between the two phases probably caused by the co‐vulcanization in CPE/NR blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 22–28, 2002; DOI 10.1002/app.10171     

热空气老化粘弹性丁基橡胶阻尼材料的性能及其老化机理研究

采用热空气加速老化试验方法对粘弹性丁基橡胶阻尼材料的老化性能及其老化机理进行了研究,获得了老化前后丁基橡胶阻尼材料力学性能、阻尼性能及其变化规律。研究结果表明：在所选定的热空气老化65℃×310天试验条件下,阻尼材料的拉伸强度提高了1MPa,阻尼性能曲线整体向高温区域平移了10℃,而有效阻尼温域基本保持不变,与模拟计算结果一致,可以满足等效25℃×10年储存条件下的使用要求。同时,采用FTIR和SEM技术分析了阻尼材料在热氧老化条件下分子链结构和微观结构的变化,得到了粘弹性丁基橡胶阻尼材料的热空气老化机理。     

Influence of silica loading on the mechanical properties and resistance to oil and thermal aging of CR/NR blends

Blends of 75/25 chloroprene rubber(CR)/natural rubber (NR) filled with various loadings of precipitated silica were prepared and their processability and mechanical properties as well as their resistance to thermal aging and oil were determined. The blend morphology was also studied using the atomic force microscopy technique. The results reveal that the mixing energy and the Mooney viscosity of the compound are increased continuously with increasing silica loading. It is also found that both scorch and optimum curing times are shortened while the total crosslink density is increased with increasing silica loading. The positive effect on cure could be explained by the chemical reaction between the allylic chlorine atom of CR and the silanol group on silica surface. The tensile strength, modulus, and hardness of the blend vulcanizate are noticeably improved while the compression set at elevated temperature is impaired with increasing silica loading. The results also reveal that both thermal aging resistance and oil resistance of the blend vulcanizates, as represented by the relative properties, are enhanced with the addition of silica. The resistance enhancement is believed to arise from the combination of the dilution effect, the increased crosslink density and also the reduction of NR dispersed phase size. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of thermal aging on fatigue of carbon black–reinforced EPDM rubber

Deterioration of the parameters measuring the fatigue of rubber compounds as a result of thermal aging was investigated. The energy to break, tear strength, fatigue life, and fatigue crack propagation rate of EPDM rubber compounds reinforced with three different types of carbon black before and after different periods of thermal aging were measured and compared through a series of static and cyclic loading tests. The experimental results indicated that the fatigue resistance of EPDM rubber compounds with different types of carbon black was consistently reduced because of changes in the molecular structure and crosslink density as a result of thermal aging. Meanwhile, the intrinsic flaws of carbon black–reinforced EPDM rubber compounds after 6 months of thermal aging were smaller, regardless of the type of carbon black. Therefore, the effects of thermal aging on the fatigue of rubber compounds are significant and should be taken into account in designing rubber components. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1244–1251, 2007     

Effects of elevated temperature and crude oil on the properties of a hydrogenated nitrile butadiene rubber elastomer

The stability and durability of hydrogenated nitrile butadiene rubber (HNBR) material in crude oil environments are of great importance for petroleum equipment to resist leakage and to ensure reliability. In this paper, an HNBR material was fabricated, and the degradation of the HNBR material was investigated in simulated crude oil environments. One crude oil and three temperatures (50 °C, 75 °C, and 100 °C, based on actual crude oil operations, were used in this study. Weight changes for the HNBR specimens were monitored after exposure to the environments over time. Optical microscopy was used to show the topographical changes on the specimen surfaces. Attenuated total reflection Fourier transform infrared (ATR‐FTIR) spectroscopy was employed to study the surface chemistry of the HNBR material before and after exposure to the simulated crude oil environments at selected times. Mechanical property tests (tensile and compressive stress–strain tests, tear strength test, and compression set test) were conducted to assess the changes in mechanical properties of the HNBR specimens before and after exposure to the environments. The test results show that the physical–mechanical properties of the HNBR material changed significantly. The temperature and the crude oil had a direct effect on the degradation of the mechanical properties. The ATR‐FTIR test results indicate that the surface chemistry changed via chain crosslinking in the material after exposure to the environments over time. The degradation mechanisms of the HNBR material after exposure to the crude oil could be due to the presence of chain crosslinking, chain mobility, and backbone scission. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44012.     

端羟基聚丁二烯液体橡胶老化性能研究

研究了不同防老剂种类及用量,不同环境温度条件下,端羟基聚丁二烯（ＨＴＰＢ）液体橡胶粘度变化规律。结果表明,加入防老剂,尤其是２２４６可以显著改善ＨＴＰＢ的老化性能,且防老剂２２４６最佳用量为０．２％￣０．５％,室温下,ＨＴＰＢ不加防老剂的贮存期长达１年。     

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     

宽温域下氟醚橡胶的加速老化行为和机理研究

基于氟醚橡胶使用环境的特殊性,从物理和化学角度,在宽温域（-40～225℃）条件下对某国产氟醚橡胶在4050航空润滑油中老化后的质量、力学性能、化学结构、元素组成及热稳定性等有关参数进行了研究,分析了老化温度和老化时间对氟醚橡胶性能的影响规律。结果表明：在相对较宽温域-25～200℃内氟醚橡胶的耐介质老化性能优异,其物化性能在长期老化过程中保持稳定;当老化温度达200℃以上时,溶胀和氧化反应增强,随着老化时间的增加,材料逐渐由软而韧变为硬而脆;特别是在高温225℃下,脱氟化氢反应导致大量C—F键断裂,F元素含量显著减少,同时氧化反应增强并生成CO键,导致O元素含量增多;低温老化过程中氟醚橡胶的质量、化学结构及元素含量基本不变,但-40℃时的玻璃化转变行为会导致力学性能的下降。     

Thermal stability of butyl/EPDM/neoprene based rubber compounds

Tyre curing bladders are usually prepared by using butyl/neoprene based compounds. To demonstrate the heat resistance and to extend the service life of a bladder, the mechanical properties of butyl/neoprene/ethylene–propylene–diene rubber (EPDM) based compounds in different compositions were analyzed and compared. In this study, the effects of partial replacements of IIR with different types of EPDM in different proportions were studied. Rheological and mechanical properties of vulcanizates were measured before and after the thermal ageing. Curing characteristics of unvulcanized compounds and mechanical properties, permanent set, fatigue index, and IRHD hardness of vulcanized compounds were measured. The better results were obtained by using the recipes containing Keltan 27 type EPDM of 10–20 phr. Mechanical properties of recipes decreased due to high EPDM ratio in the recipes studied. The service life of tyre curing bladders can be increased by the replacement of EPDM with butyl rubber in appropriate type and quantity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 557–563, 2007