Influence of rubber composition on migration behaviors of antiozonants in carbon black‐filled rubber vulcanizates composed of NR,SBR, and BR

Migration behaviors of antiozonants in carbon black‐filled rubber vulcanizates with different rubber compositions of natural rubber (NR), styrene–butadiene rubber (SBR), and butadiene rubber (BR) were studied at constant temperatures of 40–100°C and outdoors. Three single rubber‐based vulcanizates, three biblends, and three triblends were used. N‐Phenyl‐N′‐isopropyl‐p‐phenylenediamine (IPPD) and N‐phenyl‐N′‐(1,3‐dimethylbutyl)‐p‐phenylenediamine (HPPD) were employed as antiozonants. Migration rates of the antiozonants became faster with increasing the temperature. The order of the migration rates in the single rubber‐based vulcanizates was BR > NR > SBR. The migration rates in the vulcanizates containing SBR, on the whole, increased with decreasing the SBR content, while those in the vulcanizates containing BR decreased with decreasing the BR content. Difference in the migration behaviors of the antiozonants depending on the rubber composition was explained both by the intermolecular interactions of the antiozonants with the matrix and by interface formed between dissimilar rubbers in the blends. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 237–242, 2001     

Influence of internal strain on change of crosslink density of natural rubber vulcanizates by thermal ageing

Change of crosslink density of natural rubber (NR) vulcanizates by thermal ageing at 60 °C has been studied under swollen conditions in solvents to investigate the influence of internal strain applied to the vulcanizate on the crosslink density change. The internal strain was controlled by swelling with various solvents such as n‐hexane, toluene, tetrahydrofuran (THF), methanol and water. The order of degree of the swelling is toluene ≈ THF > n‐hexane > methanol > water. The influence of curing system has been investigated with the vulcanizates cured by the conventional and EV cure systems. After thermal ageing, the apparent crosslink densities of the swollen vulcanizates in n‐hexane, toluene and THF decrease irrespective of the cure systems, while that of the swollen vulcanizate in water increases. For the swollen vulcanizates in methanol, the apparent crosslink density of the vulcanizate with the conventional cure system after thermal ageing increases while that of the vulcanizate with the EV cure system decreases. The decrement of the apparent crosslink density of the vulcanizate after thermal ageing becomes larger and larger upon increasing the internal strain. © 2001 Society of Chemical Industry     

甲基丙烯酸固态原位接枝改性炭黑对天然橡胶和顺丁橡胶性能的影响

考察了固态原位接枝改性制备的甲基丙烯酸接枝改性炭黑对天然橡胶(NR)和顺丁橡胶。(BR)静态力学性能、动态力学性能的影响。结果表明。甲基丙烯酸改性炭黑比普通商品炭黑填充的NR硫化胶具有更好的静态力学性能;甲基丙烯酸改性炭黑曼有利于降低NR和BR硫化胶的滚动阻力。同时,有利于提高NR硫化胶的抗湿滑性。     

Quantitative characterization of interfaces in rubber–rubber blends by means of modulated‐temperature DSC

Rubber–rubber blends are used widely in industry, for example, in tire manufacture. It is often difficult to characterize interfaces in such rubber–rubber blends quantitatively because of the similarity in the chemical structure of the component rubbers. Here, a new method was suggested for the measurement of the weight fraction of the interface in rubber–rubber blends using modulated‐temperature differential scanning calorimetry (M‐TDSC). Quantitative analysis using the differential of the heat capacity, dCp/dT, versus the temperature signal from M‐TDSC allows the weight fraction of the interface to be calculated. As examples, polybutadiene rubber (BR)–natural rubber (NR), BR–styrene‐co‐butadiene rubber (SBR), SBR–NR, and nitrile rubber (NBR)–NR blend systems were analyzed. The interfacial content in these blends was obtained. SBR is partially miscible with BR. The cis‐structure content in BR has an obvious effect on the extent of mixing in the SBR–BR blends. With increasing styrene content in the SBR in the SBR–BR blends, the interface content decreases. NR is partially miscible with both BR and SBR. The NBR used in this research is essentially immiscible with NR. The maximum amount of interface was found to be at the 50:50 blend composition in BR–NR, SBR–BR, and SBR–NR systems. Quantitative analysis of interfaces in these blend systems is reported for the first time. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1791–1798, 2000     

Improvement of the homogeneity of SBR/NBR blends using polyglycidylmethacrylate‐g‐butadiene rubber

Polyglycidylmethacrylate grafted butadiene rubber (PGMA‐g‐BR) was synthesized by a graft solution copolymerization technique. The PGMA content was determined through titration against HBr. The PGMA‐g‐BR was blended with styrene butadiene rubber/butadiene acrylonitrile rubber (SBR/NBR) blends with different blend ratios. The SBR/NBR (50/50) blend was selected to examine the compatibility of such blends. Compatibility was examined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and viscosity measurements. The scanning electron micrographs illustrate the change of morphology of the SBR/NBR rubber blend as a result of the incorporation of PGMA‐g‐BR onto that blend. The T_gs of SBR and NBR in the blend get closer upon incorporation of PGMA‐g‐BR 10 phr, which indicates improvement in blend homogeneity. The intrinsic viscosity (η) versus blend ratio graph shows a straight‐line relationship, indicating some degree of compatibility. Thermal stability of the compatibilized and uncompatibilized rubber blend vulcanizates was investigated by determination of the physicomechanical properties before and after accelerated thermal aging. Of all the vulcanizates with different blend ratios under investigation, the SBR/NBR (25/75) compatibilized blend possessed the best thermal stability. However, the SBR/NBR (75/25) compatibilized blend possessed the best swelling performance in brake fluid. The effect of various combinations of inorganic fillers on the physicomechanical properties of that blend, before and after accelerated thermal aging, was studied in the presence and absence of PGMA‐g‐BR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1559–1567, 2006     

Properties of natural rubber vulcanizates containing mechanochemically devulcanized ground tire rubber

The devulcanization of ground tire rubber (GTR) was carried out with a self-designed pan-mill type mechanochemical reactor. Gel fraction and crosslink density measurements confirmed the occurrence of stress induced mechanochemical devulcanization of GTR. The partially devulcanized GTR (dGTR) was blended with virgin natural rubber (NR) at different ratios. The curing characteristics and mechanical properties of these composites were investigated and compared with those composites of raw ground tire rubber (rGTR) and NR. The results showed that the tensile properties of the dGTR/NR vulcanizates were much better than those of the rGTR/NR vulcanizates, which are comparable to or even better than the virgin vulcanizate, indicating the significant benefit of mechanochemical devulcanization. At the GTR content of 10%, the tensile strength of the dGTR/NR blends increased to 23.2 MPa from 13.7 MPa of the rGTR/NR blends, enhanced by 69% through partial devulcanization of GTR, and the elongation at break increased by 47%.     

Migration behaviors of wax to surface in rubber vulcanizates

The migration behaviors of wax to the surface in rubber vulcanizates were studied using natural (NR), styrene–butadiene (SBR), and butadiene rubber (BR) vulcanizates. The migration experiments were performed in a convection oven at 60 and 80°C for 14 days. There were less than 10% of the normal alkanes of n-C₂₂H₄₆ to n-C₃₈H₇₈ that migrated to the surface in the vulcanizates and evaporated at 60°C for 14 days. The amount of normal alkanes that migrated to the surface in the vulcanizates and evaporated at 80°C for 14 days was decreased by increasing the molecular weight of the normal alkanes. The migration of the normal alkanes in the NR vulcanizate was more sensitive to the variation of the molecular size of the normal alkanes than those in the BR and SBR vulcanizates. The migration behaviors of the normal alkanes in the vulcanizates were very similar to their evaporation behaviors. Major factors influencing the migration behaviors of the wax were discussed using the calculations of structures of the normal alkanes and evaporation experiments of wax. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2587–2593, 1999     

Preparation of lignin-based filling antioxidant and its application in styrene-butadiene rubber

A novel filling antioxidant (Lig-g-RT) to improve the mechanical properties and antiaging performance of styrene-butadiene rubber (SBR) composites was prepared by grafting antioxidant intermediate p-aminodiphenylamine (RT) on the surface of lignin via the linkage of silane coupling agent. Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA) measurements confirmed that RT was successfully grafted on the surface of lignin to produce the functionalized Lig-g-RT which shows a better thermal stability than lignin. Compared with SBR/lignin composite, the SBR/Lig-g-RT composite using latex co-precipitation method exhibits a much better filler dispersion, which contributes to the maintain of the physical mechanical properties of SBR vulcanizates. Moreover, the SBR/Lig-g-RT vulcanizate exhibits less chemical crosslink concentration and higher entanglement density than SBR/lignin vulcanizate according to the Mooney–Rivlin model analysis. In addition, the stabilizing effect of lignin/Lig-g-RT on the carbon-black filled SBR vulcanizates is comparable with that of commercial antioxidant N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine (4020), especially the SBR vulcanizate filled with 10 phr Lig-g-RT obtains the optimum thermo-oxidative aging properties. This functionalized Lig-g-RT not only provides an intramolecular synergistic antiaging effect for SBR vulcanizates and an improvement of filler dispersion, but greatly extends the comprehensive utilization of industrial lignin.     

Continuous ultrasonic devulcanization of NR/SBR blends

The ultrasonic devulcanization of sulfur‐cured natural rubber (NR)/styrene–butadiene rubber (SBR) blends was studied with the goal of understanding the devulcanization of rubber vulcanizates in which two networks of different natures were present. Also, similarities and differences in the devulcanization behaviors of NR, SBR, and their blends were found. During the devulcanization of cured NR/SBR blends, we observed that, as for NR, the ultrasonic power consumption for 75/25 and 50/50 (w/w) NR/SBR blends passed through a maximum at 7.5 μm. For SBR and 25/75 (w/w) NR/SBR blends, the power consumption increased with increasing ultrasonic amplitude. The higher power consumption led to a higher degree of devulcanization. The crosslink densities of the devulcanized 25/75, 50/50, and 75/25 (w/w) NR/SBR blends were lower than those of the devulcanized NR and SBR, possibly because of the reduced degree of unsaturation. The tensile properties of the revulcanized blends were lower than those of the virgin vulcanized blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 160–168, 2002     

Effects of the interaction of hardness,resilience, and fatigue properties on the abrasion properties of rubber blends

The establishment of prediction model for abrasion properties of vulcanizates, based on their simple physio‐mechanical properties, is a hot research field in tribology. The hardness (H), resilience (R), and dynamic fatigue fracture parameters (m) of rubber vulcanizates were combined together in this article, named as hardness–resilience product (H^mR), and its relationships with the abrasion loss for various vulcanizates [natural rubber (NR), styrene–butadiene rubber (SBR), butadiene rubber (BR), and their blends] was investigated by using Akron and DIN abrader. The results showed that, for NR/SBR blends with different SBR content, compared with log(H⁴R), the abrasion loss had much better linear relationship with log(H^mR) for both Akron and DIN abrasion. This good linear relationship, for both Akron and DIN abrasion, also appeared in the SBR/BR blends with different BR content. Furthermore, for both blending systems (NR/SBR and SBR/BR), when all the data above were put together, the abrasion loss also had good linear relationships with its log(H^mR) no matter for Akron or DIN abrasion, which indicated that this linear relationship had some universality. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1212‐1219, 2013     

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     

Compatibilization of SBR/NBR blends using chemically modified styrene‐co‐butadiene rubber Part 2. Effect of compatibilizer loading

The present work focuses on the compatibization of styrene‐co‐butadiene rubber (SBR)/acrylonitrile‐co‐butadiene rubber (NBR) blends with dichlorocarbene modified styrene‐co‐butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential scanning calorimetry and dynamic mechanical analysis reveal molecular level miscibility in the blends in the presence of compatibilizer. The formation of interfacial bonding is assessed by analysis of swelling behaviour, cure characteristics, stress–strain data and mechanical properties. These studies show that the compatibilizing action of DCSBR becomes more prominent as the proportion of NBR in the blend increases. The resistance of the vulcanizate towards thermal and oil ageing improved with compatibilization. The change in technological properties is correlated with the crosslink density of the blends assessed from swelling and stress–strain data. © 2001 Society of Chemical Industry     

Investigation on the mechanical properties and oil resistance of sulfur cured nitrile rubber/hydrogenated nitrile butadiene rubber blends

Nitrile rubber (NBR)/hydrogenated nitrile butadiene rubber (HNBR) blends with various ratios were compounded with internal mixer and two-roll open mill. Mechanical properties and low-temperature performance (TR10) of the NBR/HNBR blends after aging under different conditions were investigated. Furthermore, equilibrium swelling test and moving die rheometer (MDR) test were used to systematically investigate the effects of HNBR dosage on the crosslink densities and curing behaviors. Vulcanization torque and crosslink densities decreased with an increase in HNBR content. The crosslink density of pure HNBR is higher than that of pure NBR, which is related to the macromolecular structures of the rubber. Compression sets of the NBR/HNBR vulcanizates were correlated with HNBR dosage indicating a linear relationship. Low-temperature performance of the NBR/HNBR blends was improved after being aged in the synthetic hydrocarbon hydraulic oils (SH-1 and SH-2). This work shows that the low-temperature performance and oil resistance could be better balanced by blending NBR with HNBR, while the mechanical properties maintain relatively high level.     

Processability characteristics and physico‐mechanical properties of natural rubber modified with rubber seed oil and epoxidized rubber seed oil

The processability characteristics and physico‐mechanical properties of natural rubber (NR) modified with raw rubber seed oil and epoxidized rubber seed oil have been studied. The modified mixes showed higher scorch time and lower cure rate, crosslink density, and ultimate state of cure compared to an unmodified mix. The thermal stability of the vulcanizates was practically unaffected by the modification. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1413–1418, 2000     

热空气老化对二烯类橡胶磨耗性能的影响规律研究

以丁苯橡胶（SBR）、顺丁橡胶（BR）和天然橡胶（NR）为研究对象,并以它们的基础配方为依据,研究了热空气老化对不同种类橡胶阿克隆磨耗和DIN磨耗性能的影响规律。研究结果表明,热空气老化对这3种橡胶的阿克隆和DIN磨耗性能的影响规律不同。对阿克隆磨耗性能来说,随老化时间的延长,丁苯橡胶和顺丁橡胶的耐磨性能提高,而天然橡胶的耐磨性随老化时间的延长而明显下降。对DIN磨耗性能来说,无论是丁苯橡胶、顺丁橡胶还是天然橡胶,它们的耐DIN磨耗性能都随着老化时间的延长而逐渐降低。防老剂的加入可以提高橡胶的耐阿克隆磨耗性能,但对DIN磨耗性能的影响却很小。     

活性预处理三元乙丙橡胶/天然橡胶并用胶的性能

采用硫载体硫化剂4,4′-二硫化二吗啉(DTDM)对三元乙丙橡胶(EPDM)进行活性预处理,研究了活性预处理EPDM/天然橡胶(NR)并用胶的性能,并探讨了活性预处理EPDM对并用胶力学性能影响的机理。结果表明,预处理EPDM/NR并用胶的共硫化程度得到改善,并用硫化胶的力学性能提高;并用硫化胶的耐老化性能优于NR硫化胶,但比未处理EPDM/NR并用硫化胶差;并用胶只存在1个玻璃化温度的转变区,两相的相容性得到改善;在高温动态条件下,EPDM与DTDM发生活性反应,但未生成大量凝胶。     

三种微生物脱硫废乳胶及其填充天然橡胶的力学性能比较

利用三种微生物鞘氨醇单胞菌、脂环酸芽孢杆菌和酵母菌对废乳胶(WLR)进行了脱硫再生,考察了脱硫过程中微生物的生长情况以及脱硫前后WLR溶胀和交联密度的变化,并将WLR和脱硫WLR(DWLR)以不同份数填充到天然橡胶(NR)中,对比了DWLR/NR硫化胶和WLR/NR硫化胶的力学性能和交联密度。结果表明,利用鞘氨醇单胞菌脱硫的WLR溶胀值较高,交联密度较低。随着乳胶用量的增加,填充NR硫化胶的拉伸强度和交联密度逐渐降低,扯断生长率逐渐增加。DWLR/NR硫化胶的力学性能明显优于WLR/NR硫化胶,且鞘氨醇单胞菌脱硫的DWLR/NR的力学性能明显优于其它两种微生物脱硫的DWLR/NR硫化胶。     

反式-1，4-聚异戊二烯硫化胶及其共混硫化胶的研究

研究了反式－１，４－聚异戊二烯（ＴＰＩ）硫化胶及其与ＢＲ，ＳＢＲ，ＮＲ共混硫化胶的性能。结果表明，通过控制硫黄用量即交联密度，可使ＴＰＩ硫化胶具有优异的力学和动态力学性能；ＴＰＩ与ＢＲ，ＳＢＲ，ＮＲ共混，工艺性能良好，当ＴＰＩ／ＢＲ，ＴＰＩ／ＳＢＲ和ＴＰＩ／ＮＲ共混比小于５０／５０时，共混硫化胶的力学和动态力学性能优于ＢＲ，ＳＢＲ和ＮＲ硫化胶，特别是拉伸疲劳寿命大大延长，这正是高性能轮胎所需要的     

Network evolution based on general-purpose diene rubbers/sulfur/TBBS system during vulcanization (I)

In order to investigate the rule of network evolvement during vulcanization of diene rubber, generally used diene rubbers, including natural rubber (NR), polybutadiene rubber (BR), and styrene butadiene rubber (SBR), were cured with the same curing agents but at different time. The cured rubbers were then analyzed with Rubber Process Analyzer (RPA2000), dissolution/swell, and Magnetic Resonance Crosslink Density Spectrometer (MR-CDS 3500). Through data analysis on torques obtained from RPA2000, gel contents from dissolution/swell experiment and crosslink densities obtained from MR-CDS 3500, a new concept about the formation of rubber network during induction period of vulcanization was proposed. The experiments showed that even in scorch delay period, crosslink density, gel content and torque of the three rubbers increased as curing time went. The increase of these parameters indicated the formation of primary crosslink among several macromolecules which could be called local primary network-the first stage of network development. After this stage, both crosslink density and gel content of these three rubbers increased abruptly. The change percent of torque, crosslink density and gel content increased from 5% to 15%, 13%-33% and 2.5%-20% respectively which meant that almost one third of the vulcanization had been carried out during this period. Corresponding photographs of dissolution/swell experiments showed that whole gels which only swell but didn't solve in their solvents were formed. So the mutation point can be taken as the second stage of network development - a fundamental network had been formed. For NR, BR and SBR, the critical average change percent for crosslink density, gel content and torque were 33%, 20% and 15% respectively. BR, NR and SBR formed local primary network during induction period and a continuous fundamental network at the beginning of crosslinking period. This is different from traditional vulcanization theory.     

Effect of prevulcanization on the rheological behavior of natural rubber/styrene butadiene rubber latex blends

The effect of prevulcanization on the rheological behavior of natural rubber (NR), styrene butadiene rubber (SBR) latices, and their blends was studied with special reference to shear rate, blend ratio, vulcanizing systems, prevulcanization time, and accelerator systems. The NR latex showed a sharp increase in viscosity with increase in prevulcanization time due to high extent of crosslinking. However, SBR latex showed marginal effect on viscosity with prevulcanization time due to its low dry rubber content and low degree of unsaturation. Blends showed variations in viscosity according to the change in composition. The use of a single accelerator was found to have marked influence on the viscosity of the blends compared with a combination of accelerators. Swelling experiments were carried out in order to determine the crosslink density of the blends. The viscosity changes have been correlated with the crosslinking density of the latices and their blends. © 1996 John Wiley & Sons, Inc.