Effects of particle size and structure of carbon blacks on the abrasion of filled elastomer compounds

The effects of the particle size and structure of various carbon blacks on friction and abrasion behavior of filled natural rubber (NR), styrene–butadiene rubber (SBR) and polybutadiene (BR) compounds were investigated using a modified blade abrader. The effect of particle size and structure on abrasion resistance should be considered for the optimum design of desired wear properties. Characteristic parameters were introduced from the particle size and the structure of carbon blacks, with a linear relationship between the Young’s modulus and these characteristic parameters. The frictional coefficient depended not only on the particle size, but also on the structure of carbon black. The rates of abrasion were decreased with increasing surface area and developing structure of carbon blacks. Abrasion rates of the compounds were found to be proportional to a power n of the applied frictional work input. It was also observed that BR compounds caused much slower wear than NR and SBR compounds. The worn surfaces of the rubber compounds filled with carbon black having smaller particle size and a more developed structure showed narrower spaced ridges and better abrasion resistance. It means that smaller particle size and better structure development of carbon black resulted in improved abrasion resistance.     

Effect of expanded graphite and modified graphite flakes on the physical and thermo-mechanical properties of styrene butadiene rubber/polybutadiene rubber (SBR/BR) blends

The aim of the present research work is to develop expanded graphite (EG) and isocyanate modified graphite nanoplatelets (i-MG) filled SBR/BR blends, which can substitute natural rubber (NR) in some application areas. The present study investigated the effect of i-MG on the physical, mechanical and thermo-mechanical properties of polybutadiene rubber (BR), styrene butadiene rubber (SBR) and SBR/BR blends in the presence of carbon black (CB). Graphite sheets were modified to enhance its dispersion in the rubber matrices, which resulting in an improvement in the overall physical and mechanical properties of the rubber vulcanizates. Compounds based on 50:50 of BR and SBR with ∼3 wt% nanofillers with CB were fabricated by melt mixing. The morphology of the filled rubber blends was investigated by wide angle X-ray diffraction (WAXD) and high resolution transmission electron microscopic (HR-TEM) analyses. The intercalated and delaminated structures of the nanofiller loaded rubber blends were observed. Scanning electron microscopic (SEM) analysis of the cryo-fractured surfaces of the rubber compounds showed more rough and tortuous pathway of the fractured surfaces compared to the fractured surfaces of the only CB loaded rubber composites. Filled rubber compounds exhibit increase in the ΔS (torque difference) value, reduced scorch and cure time compared to their respective controls. Dynamic mechanical thermal analysis (DMTA) of the filled rubber compounds shows an increase in the storage modulus compared to the controls. Isocyanate modified graphite nanoplatelets (i-MG) containing rubber compounds in the presence of CB showed an increase in the mechanical, dynamic mechanical, hardness, abrasion resistance and thermal properties compared to the alone CB filled rubber vulcanizates.     

Microscopic studies on the mechanisms of wear of NR,SBR and HNBR vulcanizates under different conditions

Microscopic investigations, undertaken to understand the mechanism of wear of natural rubber (NR), styrene-butadiene rubber (SBR) and hydrogenated nitrile rubber (HNBR) vulcanizates abraded against hard rock, a knurled aluminium disc and a silicone carbide abrader under different conditions, are reported. The wear of NR and SBR vulcanizates against hard rock at low normal load (6 kPa) takes place by a fatigue wear mechanism and it switches over to frictional wear at high normal load (above 18 kPa). In HNBR vulcanizates the wear takes place by an abrasive wear mechanism. Ridges are observed on worn surface of swollen N R and SBR vulcanizates at low normal load, but at higher normal load the wear takes place by catastrophic fracture and extensive plough marks along the direction of abrasion are observed. The wear of NR and SBR vulcanizates proceeds by frictional wear, even at elevated temperatures. In HNBR vulcanizates, the mechanism changes from abrasive wear at 25C to frictional wear above 50C. Above 50C, ridges are observed and the spacing between adjacent ridges increases with rise of temperature.     

Scanning electron microscopy studies on tensile rupture of rubber

Tensile rupture of natural rubber (NR) and styrene-butadiene rubber (SBR), vulcanized by sulphur and peroxide systems, both with and without fillers, has been studied by scanning electron microscopy (SEM). NR gum fracture surfaces show evidence of straininduced crystallization, which is absent in SBR. The fracture surfaces of filler-reinforced NR and SBR vulcanizates are characterized by their roughness and by the presence of short and curved tear lines. Increase of cross-link density changes the fracture mode. Peroxide-cured SBR undergoes brittle fracture, whereas sulphur-cured SBR shows a smooth surface with a few straight tear lines.     

Interphase transfer of tackifier between poly(butadiene) and poly(styrene-co-butadiene)

The interphase transfer behavior of poly(styrene-co-α-methyl styrene), which is known as a tackifier in rubber industry, is investigated using poly(butadiene) rubber (BR) and poly(styrene-co-butadiene) rubber (SBR). The films of pure rubbers and the blends with the tackifier were prepared by a solution-cast method using toluene as a solvent. Two sheets composed of different rubbers, in which the tackifier was mixed at least in one rubber sheet, were piled together and annealed beyond the glass transition temperature T _g of the tackifier. The transfer phenomenon of the tackifier between the sheets was evaluated by the peak shift in the tensile loss modulus E″ curve, ascribed to T _g of the rubbers, which was measured by the dynamic mechanical analysis. Moreover, crystallization temperature of BR was also employed as a measure of the transfer, because the tackifier retards the crystallization of BR. It is found that the tackifier moves from one rubber to another during annealing procedure to reduce severe localization. When the content is the same in each rubber, the tackifier immigrates from BR to SBR, suggesting a better miscibility with SBR. This behavior is attributed to the small difference in the solubility parameter between SBR and the tackifier as compared to that between BR and the tackifier.     

混炼工艺对SBR/BR/CB共混硫化胶性能的影响

为了研究混炼工艺对最终硫化胶性能的影响,利用HAAKE转矩流变仪对不同配比的丁苯橡胶/顺丁橡胶/炭黑进行混炼,混炼采用两种不同的混炼顺序——一种是炭黑首先与丁苯橡胶(SBR)混炼,然后加入顺丁橡胶(BR)混炼;另一种是BR与炭黑混炼之后再加入SBR进行混炼。对制得共混物进行结合胶含量、拉伸以及动态力学性能测试。结果显示,在相同配比下,炭黑首先跟份数多的富相橡胶混炼可以得到较多的结合胶,有利于体系的补强;动态力学测试结果表明硫化胶的粘弹特性受第一段混炼所用橡胶的影响较大,炭黑与柔顺性较好的BR先混炼,共混体系工艺相容性较好。     

Scanning electron microscopy studies on tensile,tear and abrasion failure of thermoplastic elastomers

The tensile strength, tear resistance and abrasion resistance of four different types of commercial thermoplastic elastomers have been studied and their fracture surfaces examined by scanning electron microscopy. Thermoplastic polyurethane (TPU) showed elastic deformation under tensile fracture, whereas in 1,2 polybutadiene (1,2 PB) the fracture was initiated by craze formation and propagated by tear failure. Styrene-isoprene-styrene block copolymer (K1107) showed ductile type failure whereas in styrene-butadiene-styrene block copolymer containing a higher proportion of styrene and silica filler (K5152), the fracture occurred by shearing action. The tear failure surfaces of the thermoplastic elastomers showed different fracture patterns which could be correlated with the tear strength of the materials. The tear fracture surface of 1,2 PB showed stick-slip tear lines and that of TPU had a broad tear path with vertical striations. The fracture surfaces of K5152 and K1107 had the characteristics of laminar tearing and uninterrupted continuous tearing processes, respectively. The abrasion resistance of the samples was in the order TPU>1,2 PB>K5152, which was manifested through the type of ridge patterns formed on the abraded surfaces. Abraded surfaces of TPU, 1,2 PB and K5152 showed closely spaced stable ridges, widely spaced ridges bridged by elongated fibrils and highly deformed ridges, respectively.     

用红外光谱法研究橡胶/炭黑的界面相互作用

用红外光谱法(FI-IR)研究了橡胶微观结构、炭黑表面基团对橡胶/炭黑的界面相互作用的影响。研究表明,炭黑加入后各分子基团的振动均发生红移。炭黑与富电子的分子链相互作用大,即天然橡胶(NR)>丁基橡胶(BR)>丁苯橡胶(SBR)>丁腈橡胶(NBR);对侧基的影响小于对主链的影响。极性基团丙烯腈含量(ACN)增加,除ν(C≡N)外碳链上的其它基团均发生蓝移,且支链上双键基团所受影响最大。炭黑加入后,减弱了ACN含量增加对链段间作用力的影响,随ACN含量增加各基团蓝移较纯胶的小。门尼黏度仅影响δCH2的振动峰位。     

填充剂表面改性对硫化胶磨耗性能及形态的影响

研究了13种表面改性剂对白炭黑填充天然橡胶／顺丁橡胶（NR／BR）硫化胶磨耗性能及其形态的影响，结果表明，改性剂改变了白炭黑和橡胶的结合形式，进而影响硫化胶的耐磨性，其耐磨性的优劣顺序为：硅烷类偶联剂＞表面活性剂＞钛酸酯类偶联剂，SEM照片对硫化胶磨面的形态分析起到了宏观力学性能和微观的结构分析所达不到的作用，硫化胶的耐磨性越差，其磨纹表面的凸棱越粗。     

通用橡胶/硫磺/DM体系硫化中的交联网络演变

通过对不同硫化时间的顺丁橡胶(BR)、丁苯橡胶(SBR)、天然橡胶(NR)胶料的转矩硫化仪转矩值、交联密度、凝胶含量变化规律及胶料溶解情况的分析,研究了三种通用聚二烯烃橡胶硫化过程中交联网络形成过程.结果表明,硫磺/二硫代二苯并噻唑(DM)硫化体系的三种胶料在硫化初期(硫化诱导期)产生了类似于支化的初级交联;在硫化起步...     

橡胶分子链在玻璃纤维表面的接枝

采用分子结构中含不饱和双键的偶联剂对玻璃纤维进行表面处理,然后在玻璃纤维表面涂覆过氧化物引发剂（ＢＰＯ）及橡胶溶液、使橡胶分子链在引发剂的作用下与玻璃纤维表面的偶联剂进行接枝反应,在玻璃纤维表面接枝了一层橡胶分子链,初步分子橡胶分子链在玻纤表面的反应机遇,对几种橡胶（ＥＰＤＭ、顺丁橡胶、丁苯橡胶、丁腈橡胶、氨丁橡胶）在玻璃纤维表面的接枝能力及反应条件对橡胶分子链在玻璃纤维表面接枝率的影响进行了研究。     

改性累托石粉体的制备及其填充橡胶复合材料的结构与性能

利用喷雾干燥法制备了硅烷偶联剂KH550改性的累托石粉体, 考察了喷嘴进口温度对制备的累托石粉体表面性质、结构及形貌的影响。将累托石粉体分别加入到丁苯橡胶(SBR)、天然橡胶(NR)和丁腈橡胶(NBR)中, 通过熔融共混法制备了改性累托石/橡胶复合材料, 研究了累托石在橡胶基体中的分散状态及其对基体的增强效果。结果表明: 随着进气温度的提高, 与累托石复合的KH550的量也随之增加; KH550分子插层进入累托石层间, 阻碍了片层的再聚集, 片层堆砌更加无序蓬松; 改性累托石在SBR中出现了局部团聚现象, 在NBR中分散较均匀, 而在NR中分散状态最好; 与相应的纯橡胶相比, 改性累托石填充的SBR和NBR基复合材料的各项力学性能均有所提高, 而其填充的NR基复合材料的定伸应力提高, 拉伸强度和撕裂强度基本不变, 断裂伸长率有所下降。     

多壁碳纳米管填充丁苯橡胶复合材料的研究

采用浓硝酸(HNO3)氧化处理后的多壁碳纳米管(MWNTs)与丁苯橡胶(SBR)及其他配合剂在开炼机上进行混炼加工制备MWNTs／橡胶复合材料，并与炭黑补强橡胶体系进行对比，进而研究了MWNTs／橡胶复合材料的物理性能，并初步探讨了该材料微观结构与性能之间的关系。结果表明：随着MWNTs质量百分含量的增加，橡胶复合材料的力学性能也随之增高；MWNTs／橡胶复合材料的抗撕裂强度(25．9kN／m)、硬度(58)、磨耗(0．22mL/1．61km)性能较炭黑／橡胶体系要好。由MWNTs补强的橡胶对开发具有低滚动滞后性和抗疲劳损失的轮胎胎面胶将有很大的实用潜力。     

Morphology and mechanical behavior of 1,2 polybutadiene — natural rubber blends

The effect of a thermoplastic rubber, 1,2 polybutadiene, on the mechanical behavior of natural rubber (NR) at different compositions has been studied. The morphology of the blends was studied by dynamic mechanical analysis and by solvent extraction of NR. The mechanical properties such as tensile strength, tear strength and hardness are found to increase with increasing 1,2 polybutadiene content in the blend. 50/50 blend has been found to exhibit the highest elongation. The abrasion resistance decreases with increasing NR content but the decrease is faster beyond 50% by weight of NR. The tear and abrasion fracture surfaces as revealed by scanning electron microscopy complement the quantitative results obtained by standard testing methods. The blends are found to exhibit higher hysteresis loss than either of the components at low strain level. The mechanical properties have also been correlated to the morphology of the blends.     

Effect of corn powder as filler in radial passenger tyre tread compound

The present context of technological scenario, requirement of developing low rolling resistance passenger radial tyres with naturally occurring environmental friendly materials is inevitable. Several studies have been reported by using silica filler in place of carbon black for improving the rolling resistance property. In the present study, an attempt has been made to investigate the effect of biodegradable Indian corn powder in tyre tread compound as filler. The effect of corn powder in gum and filled compound of both natural rubber (NR) and styrene butadiene rubber (SBR) based compound has been studied. It was found that corn powder of 200-mesh size increased thermal stability of NR compound and acted as a non-reinforcing filler. It also affected the fatigue properties and abrasion loss when the carbon black was partially replaced with corn powder. However, an improvement in the temperature build up (TBU) and tan δ at 60 °C (a representative of rolling resistance property of tyre) was observed.     

轮胎胶高剪切应力诱导脱硫反应的影响因素

采用在轮胎胶粉与三元乙丙橡胶(EPDM)混合物的熔融挤出过程中提高双螺杆挤出机螺杆转速的高剪切应力诱导方法,研究了轮胎胶粉品种和烷基酚多硫化物促进剂对轮胎胶脱硫共混物的凝胶含量、溶胶分子链结构及脱硫共混物共混丁苯橡胶再硫化材料力学性能的影响。试验结果表明,胶粉品种对所得脱硫共混物溶胶中的双键含量及再硫化材料的拉伸强度具有重要影响;烷基酚多硫化物促进剂420和450具有明显促进脱硫反应和抑制交联副反应的作用,有效减小再硫化材料凝胶粒子尺寸,聚合型促进剂450兼具有抗氧化降解和抑制加成副反应的功能。     

环保型水切割胶粉对天然橡胶力学性能和动态性能的影响

采用环保型水切割胶粉及力化学改性胶粉（MRP）与天然橡胶（NR）复合制备胶粉-NR复合胶,并探讨了胶粉用量对复合胶力学性能和动态性能的影响。通过红外和热失重分析确定了胶粉的主要成分为NR和丁苯橡胶（SBR）,且改性后胶粉大分子链结构未发生明显变化。通过橡胶加工分析仪研究了胶粉用量及改性对复合胶加工性能的影响。采用炭黑分散仪研究并观察了胶粉在NR中的分散情况。结果表明,胶粉改性后与NR的相容性提高,二者界面结合力增大,MRP-NR复合胶加工性能改善。炭黑分散结果表明,胶粉用量越多,其分散性越差,改性后胶粉的分散性提高,MRP-NR复合胶的力学性能最优,拉伸强度为27.9 MPa。     

Effect of grafting cellulose acetate and methylmethacrylate as compatibilizer onto NBR/SBR blends

Compatibilizer is used for improving of processability, interfacial interaction and mechanical properties of polymer blends. In this study acrylonitrile butadiene rubber (NBR) and styrene-butadiene rubber (SBR) blends were compatibilized by a graft copolymer of acrylonitrile butadiene rubber (NBR) grafted with cellulose acetate (CA) i.e. (NBR-g-CA) and acrylonitrile butadiene rubber (NBR) grafted with methylmethacrylate i.e. (NBR-g-MMA). Compatibilizers were prepared by gamma radiation induced grafting of NBR with cellulose acetate (CA) and methylmethacrylate (MMA) were added with different ratios to NBR/SBR (50/50) blend. The compatibilized blends were evaluated by rheometric characteristics, physico-mechanical properties, swelling behavior, scanning electron microscope (SEM) and thermal analysis. The results showed that, the blends with graft copolymer effect greatly on the rheological characteristics [optimum cure time (Tc₉₀), scorch time (Ts₂), and the cure rate index (CRI)]. The physico-mechanical properties of the investigated blends were enhanced by the incorporation of these graft copolymers, while the resistance to swelling in toluene became higher. SEM photographs confirm that, these compatibilizers improve the interfacial adhesion between NBR/SBR (50/50) blend which induce compatibilization in the immiscible blends. The efficiency of the compatibilizer was also evaluated by studying the thermogravimetric analysis.     

Quantitative mapping of surface elastic moduli in silica-reinforced rubbers and rubber blends across the length scales by AFM

The surface elastic moduli of silica-reinforced rubbers and rubber blends were investigated by atomic force microscopy (AFM)-based HarmoniX material mapping. Styrene–butadiene rubbers (SBR) and ethylene–propylene–diene rubbers (EPDM) and SBR/EPDM rubber blends with varying concentrations of silica nanoparticles (0, 5, 10, 20, 50 parts per hundred rubber, phr) were prepared to investigate the effect of different composition on the resulting morphology, filler distribution and elastic moduli of a specific rubber or rubber blend sample. For SBR, the elastic modulus values varied from 0.5 MPa for unfilled SBR to 5 MPa for 50 phr reinforced SBR with the increase in the concentration of filler. For EPDM, the corresponding values increased from 1.4 MPa for unfilled EPDM to 4.5 MPa for 50 phr reinforced EPDM. Local stiff and soft domains in silica-reinforced SBR and EPDM rubbers and rubber blends were identified by HarmoniX AFM imaging. While the stiff silica particles show modulus values as high as 2 GPa, the rubber matrix reveals modulus values in the range of ca. 30 MPa for the rubber blends to ca. 300 MPa for the unfilled rubbers. The lower value of elastic modulus of the EPDM phase in the blend, compared to the blank EPDM compound can be attributed to the presence of Sunpar oil in the compound which has a very good affinity with EPDM and decreases the rubber modulus. The elastic moduli maps revealed an increase of the areal fraction of silica particles showing an intrinsic surface modulus value with rising silica content in the compound preparation mixture. HarmoniX AFM measurements revealed the formation of larger silica aggregates in EPDM in contrast to SBR where isolated silica particles were observed. For silica-reinforced rubber blends a phase separation into a soft (ca. 40 MPa) and a significantly harder phase could be observed (ca. 500 MPa–1.5 GPa) indicating the incorporation of silica particles in the SBR phase. Using HarmoniX AFM imaging significantly higher surface elastic moduli were observed compared to those obtained by bulk tensile testing. Possible reasons for the observed differences between bulk modulus values and those measured by AFM are discussed in detail, including the aspect of different averaging procedures like inherent to surface probing by AFM versus bulk tensile testing, different filler distributions in SBR and EPDM and the AFM modulus calibration procedures.     

Mechanical and fractographic behavior of natural rubber-cellulose II composites

Composites of natural rubber (NR) and cellulose II (Cel II) were prepared by co-coagulation of natural latex and cellulose xanthate mixtures. The influence of increasing amounts of Cel II, varying from 0 to 30 phr, on the mechanical properties was investigated. The topography of the fracture surfaces of tensile, tear and abrasion specimens after testing was observed by scanning electron microscopy (SEM). The fracture surface morphology was correlated with the mechanical properties. As the cellulose II content increases, the materials showed a gradual change in the mechanical properties and in the fracture mechanisms. The composite with 15 phr of Cel II was found to give the best tensile and tear performances. The failure surfaces and the fracture mechanisms of unfilled and filled natural rubber composites depended on the nature of the test-tensile, tear or abrasion. The SEM evaluation of the tensile fracture surfaces was the best observation method to show the effect of cellulose II on the elastomeric matrix.