Multiphase polymer processing: Controlled-ingredient-distribution mixing and its effect on some properties of styrene-butadiene (SBR)/butadiene-acrylonitrile copolymer rubber blend compounds

The flex-crack-growth resistance and oil-swelling resistance of a styrene-butadiene (SBR)/butadiene-acrylonitrile co-polymer (NBR) rubber blend are studied as a function of the distribution of ingredients in the individual rubber phases. The blends consist of 70:30 weight ratio of SBR:NBR with incorporation of 82.5 phr carbon black and other ingredients via the controlled-ingredient-distribution mixing procedure. The results show that flex crack growth is affected by the distribution of carbon black. Better flex crack growth resistance could be achieved by adding 10 percent of carbon black to the NBR rubber phase and 90 percent to the SBR phase. The swelling of these rubber blends in ASTM #2 oil is also affected by the location of carbon black and by the mixing history. The blends with more black initially preloaded in the SBR phase have lower swelling, as have blends with shorter cross-mixing time or the mill. A simple equation based on the permeation/moduli of composite materials is proposed to describe the swelling of this rubber blend in terms of the swelling of the constituent rubber phases, the distribution of ingredient in the individual rubber phases, and the blend morphology. One of the key assumptions is to consider the individual black preloaded rubber as a continuum. The quantitative correlation with the observed swelling data is reasonably good.     

橡胶反应共混改性沥青的机理

以混入沥青前后的共混物硫化胶模拟反应共混改性沥青,对橡胶／硫化剂／沥青、橡胶／硫化剂2种共混物硫化胶进行了以甲苯为溶剂的抽提,并对抽提物进行了元素分析和红外光谱分析。结果表明,橡胶／硫化剂／沥青共混物硫化胶的抽提物仍呈黑色,其质量保留率小于橡胶／硫化剂共混物硫化胶。SBR／硫化剂／沥青共混物硫化胶的抽提物H／C值小于SBR／硫化剂共混物硫化胶,并且小于纯沥青;且含有沥青组分所特有的N原子。l376cm^-1的甲基对称弯曲振动特征吸收峰可作为共混物硫化胶的抽提物是否存在沥青的依据。含沥青共混物硫化胶中,沥青特别是沥青质与树脂组分参与了橡胶的交联反应。     

Natural rubber–styrene butadiene rubber latex blends: Time-dependent rheological behavior and film formation

This article focuses mainly on the effect of maturation time on the rheological behavior of unvulcanized natural rubber (NR)–styrene butadiene rubber (SBR) latex blends. Viscosity shows a composition-dependent behavior with maturation time. It was found that there is a marginal decrease in viscosity for all the systems with maturation time except for the 70/30 NR–SBR blend. In this blend, there is a sharp decrease in viscosity with maturation time. This is associated with the exchange of stabilizers with one another until an equilibrium is reached; that is, all the particles of the blend are stabilized with random mixture of stabilizers. The structural build up observed in 70/30 NR–SBR blend was found to be diminished as the maturation time increases. At equilibrium, there is no further exchange of stabilizers. The behavior of this blend has been explained with the help of a schematic model. The effects of blend ratio and surface active agents on the viscosity were also studied. In addition, the time-dependent flow behavior of prevulcanized latex blends was evaluated as a function of vulcanizing systems and prevulcanization time. There is a regular increase in viscosity with prevulcanization time. However, after 3 h, the viscosity of almost all blends levels off, indicating that the curing reaction is complete within this time. Finally, the morphological changes occurred during film formation of the blends were studied using scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1473–1483, 1998     

Morphology evolution of immiscible LDPE/PVC blends in the presence of compatibilizer and phase dispersant

Phase dispersion and coalescence in low‐density polyethylene (LDPE)/polyvinyl chloride (PVC) (70/30) blends influenced by compatibilizer and phase dispersant was studied. It was found that the morphology evolution of blends is sensitive to not only processing conditions (shear strength and mixing time) but also the added compatibilizer or phase dispersant. In our conditions, the stable phase morphology of each blend is obtained after mixing 15–25 min. In addition, the dispersed PVC phase in blends is easy to aggregate when the mixing rotor speed changed from high to low for the binary blends. As a compatibilizer, chlorided polyethylene (CPE) or nitrile rubber (NBR) can stabilize the morphology and hinder the coalescence of the dispersed PVC phase when added to the blends. However, the phase dispersant butadiene rubber (BR) or styrene butadiene rubber (SBR) could not stabilize the phase structure, although it could accelerate phase dispersion. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 763–772, 2004     

Mechanical and aging properties of cross‐linked ethylene propylene diene rubber / styrene butadiene rubber blends

The mechanical properties and aging characteristics of blends of ethylene propylene diene monomer (EPDM) rubber and styrene butadiene rubber (SBR) were investigated with special reference to the effect of blend ratio and cross‐linking systems. Among the blends, the one with 80/20 EPDM/SBR has been found to exhibit the highest tensile, tear, and abrasion properties at ambient temperature. The observed changes in the mechanical properties of the blends have been correlated with the phase morphology, as attested by scanning electron micrographs (SEMs). The effects of three different cure systems, namely, sulfur (S), dicumyl peroxide (DCP), and a mixed system consisting of sulfur and peroxide (mixed) on the blend properties also were studied. The stress‐strain behavior, tensile strength, elongation at break, and tear strength of the blends were found to be better for the mixed system. The influence of fillers such as high‐abrasion furnace (HAF) black, general‐purpose furnace (GPF) black, silica, and clay on the mechanical properties of 90/10 EPDM/SBR blend was examined. The ozone and water aging studies also were conducted on the sulfur cured blends, to supplement the results from the mechanical properties investigation. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2606–2621, 2004     

Development of novel elastomeric blends containing natural rubber and ultra-low-density polyethylene

This study sought to develop novel elastomeric compounds using natural rubber (NR) and ultra-low-density polyethylene (ULDPE). Blends were prepared by means of a two-roll mill for three ratios (70/30, 60/40, and 50/50 NR/ULDPE). Conventional vulcanization was performed in a compression mold. The physical and mechanical properties of the blend were determined according to ASTM standards. The results were compared with those obtained from NR blended with styrene-butadiene rubber (SBR). The morphological examinations with scanning electron microscopy indicated that ULDPE was compatible with NR; thus, the addition of a compatibilizer was not necessary. The cocontinuous phase was dominant in the NR/ULDPE blend containing 50 and 60 wt % NR. The tensile properties, tear resistance, and aging resistance of the NR/ULDPE blends were found to be superior to those of NR/SBR blends. On the other hand, the abrasion and flex cracking resistances of the NR/ULDPE blend were inferior to those exhibited by SBR blends but the Mooney viscosity and resilience of both blends fell in the same range. However, the addition of dicumyl peroxide appeared to have caused crosslinking of the ULDPE phase in the blend, which in turn increased the tensile properties and abrasion and aging resistance. The properties of the tertiary NR/SBR/ULDPE blend were investigated as well. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 650–660, 2001     

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     

橡胶改性PP共混体系的研究

本文研究了SBR／PP共混比、硫化体系、不同橡胶以及增容剂对橡胶／PP共混物力学性能的影响。试验得出：橡塑比（SBR／PP）在30／70,采用半有效硫化体系（CZ／S）时,所制得共混物力学性能较好,共混体系PP／POE的综合性能比PP／EPDM、PP／SBR、PP／NBR共混体系要好,加入增容剂PP－g－MAH可以显著提高共混物的力学性能。     

Carbon black distribution driven by its concentration and its effect on physico-mechanical properties of styrene butadiene rubber and butadiene rubber miscible rubber blends

This paper discusses the influence of partitioning of carbon black (CB) with its increasing concentration (i.e., 10, 20, 30, 40, and 50 phr) on physical and static mechanical properties of Styrene Butadiene Rubber (SBR)/Butadiene Rubber (BR) rubber–rubber blends (RRB's) in 70SBR:30BR blend ratio. Partitioning of CB towards BR in CB-filled SBR/BR RRB's is quantitatively determined via dynamic mechanical analysis (DMA). DMA confirmed increased partitioning of CB towards BR phase with increasing CB. DMA data on the partitioning of CB towards BR were in good agreement with nuclear magnetic spectra obtained by solid-state nuclear magnetic resonance spectroscopy (SS-NMR spectroscopy). Curing properties, relative density, hardness, tensile test, tear test, and transmission electron microscopy (TEM) on CB filled SBR/BR RRB's were carried out to determine the effect of increasing concentration of CB on physical, mechanical, and dispersion characteristics in comparison to neat SBR/BR RRB's.     

A study about the structure of vulcanized natural rubber/styrene butadiene rubber blends and the glass transition behavior

A study of the thermal behavior of cured elastomeric blends of natural rubber (NR) and styrene butadiene rubber (SBR) prepared by solution blending in toluene is presented. Binary blends with different compositions of NR/SBR were produced using a conventional cure system based on sulfur and TBBS (n-t-butyl-2-benzothiazole sulfonamide as accelerator. The compounds were vulcanized at 433 K up to an optimum time of cure determined by rheometric tests. From swelling tests, the crosslink densities of the compounds were obtained and compared with those obtained in similar blends prepared by mechanical mixing. The results were analyzed in terms of the disentangling of the chain structures of the SBR and NR phases and the achieved cure state of the blend. Using differential scanning calorimetry, the glass transition temperature T_g of each blend was measured. In most compounds, the value of T_g corresponding to each phase of the blend was determined, but in some blends a single value of T_g was obtained. The variation of T_g with the composition and cure level in each phase was analyzed. On the other hand, a physical mixture of two equal parts of NR and SBR vulcanized was measured and the results were compared to those of the NR50/SBR50 cured blend. Besides, to analyze the influence of the network structure, pure NR and SBR unvulcanized samples were measured. On the basis of all the obtained results, the influence of the interphase formed in the blend between SBR and NR phases is discussed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Improvement of Homogeneity of SBR/CR Rubber Blends with SBR-g-AA Grafted Rubber

The graft copolymerization of acrylic acid (AA) onto styrene butadiene rubber (SBR) was carried out in toluene at 80°C using benzoyl peroxide (BPO) as initiator. The synthesized styrene butadiene rubber-g-acrylic acid (SBR-g-AA) was characterized with Raman IR spectroscopy. A study was conducted on the use of SBR-g-AA for improving the homogeneity of styrene butadiene rubber/chloroprene rubber (SBR/CR) blend. The SBR-g-AA was incorporated into SBR/CR blend with different blend ratios. The homogeneity of such blends was examined with scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and determination of the dielectric properties. The scanning electron micrographs illustrate improvement of the morphology of SBR/CR rubber blend as a result of the incorporation of SBR-g-AA onto that blend. Also, the dielectric constant (permittivity) and the dielectric loss plots versus the SBR/CR blend ratio show straight lines upon incorporation SBR-g-AA, indicating and confirming the homogeneity of that blend. Physico-mechanical properties of the blend vulcanizates, in presence and absence of SBR-g-AA, were determined, and their thermal stability was evaluated after accelerated thermal aging. The results reveal that SBR/CR (25/75) blend possesses the best thermal stability. Swelling behavior in toluene, in motor oil, and in brake fluid of the blend vulcanizates was also assessed.     

Dynamic mechanical analysis of ethylene–propylene–diene monomer rubber and styrene–butadiene rubber blends

The effects of blend ratio, crosslinking systems, and fillers on the viscoelastic response of ethylene–propylene–diene monomer (EPDM)/styrene–butadiene rubber (SBR) blends were studied as functions of frequency, temperature, and cure systems. The storage modulus decreased with increasing SBR content. The loss modulus and loss tangent results showed that the EPDM/SBR blend vulcanizate containing 80 wt % EPDM had the highest compatibility. Among the different cure systems studied, the dicumyl peroxide cured blends exhibited the highest storage modulus. The reinforcing fillers were found to reduce the loss tangent peak height. The blend containing 40 wt % EPDM showed partial miscibility. The dispersed EPDM phase suppressed the glass‐transition temperature of the matrix phase. The dynamic mechanical response of rubbery region was dominated by SBR in the EPDM–SBR blend. The morphology of the blend was studied by means of scanning electron microscopy. The blend containing 80 wt % EPDM had small domains of SBR particles dispersed uniformly throughout the EPDM matrix, which helped to toughen the matrix and prevent crack propagation; this led to enhanced blend compatibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

氟橡胶/EPDM动态硫化共混物的研究

研究了动态硫化工艺条件和共混比对氟橡胶（ＦＫＭ）／ＥＰＤＭ共混物拉伸性能拉、热油老化性能和应力松弛性能的影响。结果表明：与直接静态硫化相比,动态硫化可避免两种硫化体系的相互影响;静态硫化共混物拉伸强度只有２ＭＰａ,而动态硫化共混物可达１０ＭＰａ以上;工艺条件对动态硫化共混物性能的影响不大;随共混物中ＥＰＤＭ用量的增大,共混物的热空气老化和热油老化性能均有所下降     

Thermoplastic natural rubber based on polyamide‐12: Influence of blending technique and type of rubber on temperature scanning stress relaxation and other related properties

Thermoplastic natural rubber based on polyamide‐12 (PA‐12) blend was prepared by melt blending technique. Influence of blending techniques (i.e., simple blend and dynamic vulcanization) and types of natural rubber (i.e., unmodified natural rubber (NR) and epoxidized natural rubber (ENR)) on properties of the blends were investigated. It was found that the simple blends with the proportion of rubber ～ 60 wt % exhibited cocontinuous phase structure while the dynamically cured blends showed dispersed morphology. Furthermore, the blend of ENR exhibited superior mechanical properties, stress relaxation behavior, and fine grain morphology than those of the blend of the unmodified NR. This is attributed to chemical interaction between oxirane groups in ENR molecules and polar functional groups in PA‐12 molecules which caused higher interfacial adhesion. It was also found that the dynamic vulcanization caused enhancement of strength and hardness properties. Temperature scanning stress relaxation measurement revealed improvement of stress relaxation properties and thermal resistance of the dynamically cured ENR/PA‐12 blend. This is attributed to synergistic effects of dynamic vulcanization of ENR and chemical reaction of the ENR and PA‐12 molecules. Furthermore, the dynamically cured ENR/PA‐12 blend exhibited smaller rubber particles dispersed in the PA‐12 matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Study of FTIR,Thermal Properties and Natural Weathering Test on NBRVirgin/Recycled with SBR Blends

The effects of styrene butadiene rubber/virgin acrylonitrile butadiene rubber (SBR/NBRv) blends and styrene butadiene rubber/recycled acrylonitrile butadiene rubber (SBR/NBRr) blends on properties such Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were carried out. Results indicated that, based on intensity of amine peak from FTIR at 85/15 blend ratio (R15) revealed optimum formation of crosslink between SBR and NBR either using virgin or NBRr. TG thermograms of SBR/NBRv blends of all ratios showed better onset thermal stability than SBR/NBRr blends. The change in the horizontal baseline from high to low energy level occurred in virgin NBR blends because the amount of reactive sites available in virgin NBR is higher compared to NBRr. Meanwhile NBRr blends showed T_c because the amount of crosslink occurred in these blends were slightly lower than NBRv blends. Up to 25 phr of NBRr, the tensile strength and elongation at break (E_b) retention of SBR/NBRv blends was better than SBR/NBRr blends after 6 months' weathering test except for M100. The scanning electron microscopy on the surface of both blends after 6 months exposure indicated that the severity of the crack was minimal for SBR/NBRr blends compared to SBR/NBRv particularly at 50/50 blend ratio designated the SBR/NBRr blends that contained more NBRr particles could reduce the degradation towards natural weathering.     

Studies on polymer blends: Blending methods for natural rubber and styrene-butadiene rubber

The relations between the properties and the blend ratios of natural rubber (NR) and styrene-butadiene rubber (SBR) blends were studied in comparison with four blending methods. The relations between the properties of unvulcanized and vulcanized blends and the blend ratios of blends prepared by means of solution blending, latex blending, roll blending, and Banbury mixer blending were studied. In practice, such rubber blending methods as roll blending are more effective for obtaining uniform blends than Banbury mixer blending the latter. In roll blending, it is more effective to blend NR and SBR by way of a master-batch in which the ingredients are compounded beforehand than to blend raw rubber. In solution and latex blending, very uniform blends are easily obtained. It was found, however, that the properties of NR/SBR blends prepared carefully showed a direct relation to their blend ratios, regardless of blending method used.     

Morphology of plastic/rubber blends

Blends of polypropylene (PP) and ethylene-propylene rubber (EPR) and blends of polystyrene (PS) and styrene-butadiene rubber (SBR) were prepared in a laboratory-scale internal mixer at various blend compositions and rotor rates. Blend morphology was studied by means of electron microscopy. For each blend pair under the given processing conditions, the phase inversion process occurred progressively with respect to the variation in blend composition; it is within this composition range of phase inversion that dual-phase continuity was observed. In addition, Characteristic torque values of blends were found to deviate negatively from a linear additivity rule; the composition range of maximum deviation from linear additivity corresponded approximately to the composition range where dual-phase continuity was observed. Sperling's predictive scheme was found to yield acceptable (although not completely satisfactory) estimates for compositions of dual-phase continuity in the present systems. It was also observed that partial cross-linking of SBR during the mechanical blending process, as suggested by the appearance of a cure peak in the torque curve and supported by infrared spectroscopic evidence, resulted in morphological features drastically different from those of the uncured blends.     

Mechanical properties of PVC/SBR blends compatibilized by acrylonitrile-butadiene rubber and covulcanization

The mechanical properties of poly(vinyl chloride) (PVC)/styrene-butadiene rubber (SBR) blends compatibilized by acrylonitrile-butadiene rubber (NBR) were studied. A sulfur curing system was employed to crosslink the rubber of the blends. In the case of the blends without any curing agents, an increase in NBR content did not improve the tensile strength and elongation-at-break. However, a significant improvement in the mechanical properties was observed when NBR was added as a compatibilizer and the blend was vulcanized. In the PVC/NBR/SBR (50/10/40) blends, the tensile strength and elongation-at-break increased with an increase in sulfur concentration. This improvement was attributed to covulcanization between NBR and SBR. The fracture toughness of PVC/NBR/SBR (50/10/40) blends was characterized by the critical strain energy release rate, G_c. In the case of the PVC/NBR-29/SBR (50/10/40) blends, an increase in sulfur concentration resulted in a dramatic increase in G_c. However, the G_c value of PVC/NBR-40/SBR (50/10/40) blends decreased with an increase in sulfur concentration owing to the brittle behavior of one of the blend components—the PVC/NBR-40 (50/10) phase.