Evaluation of rheological and image properties of styrene‐butadiene‐styrene and ethylene‐vinyl acetate polymer modified bitumens

This article presents a laboratory evaluation of conventional, fundamental, rheological, and morphological characteristics of styrene‐butadiene‐styrene (SBS) and ethylene vinyl acetate (EVA) polymer modified bitumens. Polymer modified bitumen (PMB) samples have been produced by mixing a 50/70 penetration grade unmodified (base) bitumen with SBS and EVA copolymer at different polymer contents. The fundamental viscoelastic properties of the PMBs were determined using dynamic (oscillatory) mechanical analysis and presented in the form of temperature and frequency‐dependent rheological parameters. The morphology of the samples as well as the percent area distribution of polymers throughout the base bitumen have been characterized and determined by means of fluorescent light optic microscopy and Qwin Plus image analysis software, respectively. The results indicated that polymer modification improved the conventional and rheological properties of the base bitumen. It was also concluded that the temperature and frequency had a significant effect on complex modulus of PMBs. The behavior of EVA and SBS PMBs had exhibited quite difference at 50°C. Moreover, it was found out that at low polymer contents, the samples revealed the existence of dispersed polymer particles in a continuous bitumen phase, whereas at high polymer contents a continuous polymer phase has been observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological properties of styrene butadiene styrene polymer modified road bitumens

The use of polymers for the modification of bitumen in road paving applications has been growing rapidly over the last decade as government authorities and paving contractors seek to improve road life in the face of increased traffic. Currently, the most commonly used polymer for bitumen modification is the elastomer styrene butadiene styrene (SBS) followed by other polymers such as styrene butadiene rubber, ethylene vinyl acetate and polyethylene. This paper describes the polymer modification of two penetration grade bitumens with SBS. Six polymer modified bitumens (PMBs) were produced by mixing the bitumens from two crude oil sources with a linear SBS copolymer at three polymer contents. The rheological characteristics of the SBS PMBs were analysed by means of conventional as well as dynamic mechanical analysis using a dynamic shear rheometer (DSR). The results of the investigation indicate that the degree of SBS modification is a function of bitumen source, bitumen-polymer compatibility and polymer concentration, with the higher polymer concentrations in a high aromatic content bitumen producing a highly elastic network which increases the viscosity, complex modulus and elastic response of the PMB, particularly at high service temperatures. However, ageing of the SBS PMBs tends to result in a reduction of the molecular size of the SBS copolymer with a decrease in the elastic response of the modified road bitumen.     

Evaluation of physical,rheological, and structural properties of vulcanized EVA/SBS modified bitumen

In this study, the performance and modification mechanism of EVA (ethylene‐vinyl‐acetate) modified (EM), EVA/SBS (Styrene‐Butadiene‐Styrene) modified (ESM), and EVA/SBS/sulfur modified (ESSM) bitumens were evaluated. The physical, rheological, morphological, and structural properties were determined before and after aging, and compared with those of base bitumen. These properties were evaluation using conventional physical methods, Fourier transform infrared spectrometer, optical microscopy, dynamic shear rheometer, and bending beam rheometer, respectively. The results showed that sulfur was useful in bitumen, EVA, and SBS modification by forming a vulcanized crosslinking polymer network. The vulcanization improved most of the physical properties of ESM bitumen, especially high‐ and low‐temperature performance, and toughness and tenacity (previously not evaluated in the literature). Meanwhile, vulcanization improved the compatibility between polymers and bitumen and increased the aging resistance of ESM bitumen. Vulcanization reactions took place without new functional groups being presented in the infrared spectrum. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44850.     

Influence of styrene-butadiene-styrene polymer modification on bitumen viscosity

Effects of polymer content/structure and bitumen type on viscosity characteristics of styrene-butadiene-styrene (SBS) polymer modified bitumens were investigated. The study indicated that SBS polymers were not inert additives and increases in kinematic and dynamic viscosities of the modified bitumens were not directly proportional to polymer content; a marked viscosity increase was observed when the polymer content increased from 3 to 6% by weight of the blend. Modification with a sufficiently high polymer content also increased the degree of non-Newtonian behaviour of the bitumens. The base bitumens and modified bitumens containing 3% SBS were observed to be essentially shear rate independent, while those containing 6 or 9% SBS displayed shear-thinning behaviour. Compared to the modified bitumens with linear SBS, the modified bitumens with branched SBS demonstrated a higher degree of shear-thinning behaviour. These effects were dependent on ranges of shear rate and temperature. The increased degree of non-Newtonian behaviour was observed to influence the correlations between kinematic and dynamic viscosities.     

Effect of montmorillonite on properties of styrene–butadiene–styrene copolymer modified bitumen

Clay/styrene–butadiene–styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of sodium montmorillonite (Na‐MMT) and organophilic montmorillonite (OMMT). The structures of clay/SBS modified bitumen composites were characterized by XRD. The XRD results showed that Na‐MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. Effects of MMT on physical properties, dynamic rheological behaviors, and aging properties of SBS modified bitumen were investigated. The addition of Na‐MMT and OMMT increases both the softening point and viscosity of SBS modified bitumens and the clay/SBS modified bitumens exhibited higher complex modulus, lower phase angle. The high‐temperature storage stability can also be improved by clay with a proper amount added. Furthermore, clay/SBS modified bitumen composites showed better resistance to aging than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen, and the degradation of SBS. POLYM. ENG. SCI., 47:1289–1295, 2007. © 2007 Society of Plastics Engineers     

Artificial aging of polymer modified bitumens

This paper presents an investigation of artificial aging of polymer modified binders, prepared from three base bitumens and six polymers. Aging of the binders was performed using the Thin Film Oven Test (TFOT), the Rolling Thin Film Oven Test (RTFOT), and modified RTFOT (MRTFOT). The binders were characterized by means of infrared spectroscopy, different types of chromatography, and dynamic mechanical analysis. It was found that the effect of aging on the chemistry and rheology of the modified binders was influenced by the nature of the base bitumens and was strongly dependent on the characteristics of the polymers. For styrene–butadiene–styrene (SBS) and styrene–ethylene–butylene–styrene (SEBS) modified binders, aging decreased the complex modulus and increased the phase angle. Aging also increased the temperature susceptibility of these modified binders. The rheological changes of SBS modified bitumens were attributed to polymer degradation and bitumen oxidation. However, for SEBS modified bitumens, the mechanisms of aging are unclear. In the case of ethylene vinyl acetate (EVA) and ethylene butyl acrylate (EBA) modified binders, the process of aging increased the complex modulus and elastic response (decreased phase angle), and reduced temperature susceptibility. These changes were mainly due to the oxidative hardening of the base bitumens. The study also showed statistically significant correlation between TFOT, RTFOT, and MRTFOT. However, no definite conclusions could be drawn regarding the difference in severity of aging between these methods. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1811–1824, 2000     

Evaluation of the properties and microstructure of plastomeric polymer modified bitumens

This paper presents a laboratory study of modified bitumen containing plastomeric polymers; Evatane® 2805, Elvaloy® 3427, and Elvaloy® 4170. A 50/70 penetration grade base bitumen has been mixed with plastomeric polymers at different proportions by means of a high shear laboratory type mixer. The properties and microstructure of the samples have been determined and characterized using conventional and empirical test methods and fluorescence microscopy respectively. Qwin Plus image analysis has also been investigated in order to determine the % area distribution of plastomeric polymers throughout the base bitumen. The results indicated that polymer modification improved the conventional properties of the base bitumen such as; penetration, softening point, temperature susceptibility, etc. The microstructure and properties of the polymer modified bitumens are dependent on the type of polymer, the solubility of polymer in bitumens and polymer content. At low polymer contents, the samples revealed the existence of dispersed polymer particles in a continuous bitumen phase, whereas at high polymer contents a continuous polymer phase has been observed for the Evatane® 2805 and Elvaloy® 3427 polymers. Among the plastomeric polymers no significant polymer phase has been observed for the reactive terpolymer Elvaloy® 4170 although its conventional properties have been improved. It is also found out that a relationship exists between the polymer content and percent area distribution of polymers except for reactive terpolymer.     

Rheological properties of bitumen modified with ethylene butylacrylate glycidylmethacrylate

This article presents experimental results related to rheological viscoelastic properties of polymer modified bitumens, PmBs. Experiments were performed by a dynamical shear rheometer before and after thermo‐oxidative aging. Two types of bitumens with different asphaltene contents were modified by the addition of two types of reactive ethylene terpolymers, Elvaloy AM, and Elvaloy 4170, with a different percentage of reactive functional group, glycidylmethacrylate, GMA. Results of the investigation indicate that the degree of reactive polymer modification is a function of bitumen type, bitumen‐polymer compatibility, and polymer concentration. Polymer modification improves the following physical properties of the base bitumen: penetration, softening point, temperature susceptibility, and elastic recovery. Reactive polymers are effective binder modifiers that improve the susceptibility to high temperature of asphalt mixes, and also their rutting resistance, contribute to their good storage stability and make them less sensitive to aging. This is a result of the formation of a chemical bond between the polymer and molecules of asphaltenes. POLYM. ENG. SCI., 54:1056–1065, 2014. © 2013 Society of Plastics Engineers     

Effect of processing variables on the linear viscoelastic properties of SBS‐oil blends

Block copolymers, especially styrene‐butadiene‐styrene three‐block copolymers (SBS), are recognized as especially effective asphalt modifiers because of their thermoplastic elastomeric properties. The concentration of copolymer, its ability to swell by the maltenic oils, and the processing variables are essential in the development of a three‐dimensional network in the polymer‐rich phase that enhances the vis‐coelastic properties of these modified binders. This swollen polymer phase may influence the mechanical properties of the modified bitumens and synthetic binders. This paper deals with the influences that processing variables exert on the linear viscoelastic properties of oil/SBS mixtures in a wide range of temperatures. From the experimental results obtained we may conclude that most of the oil/SBS blends studied are highly structured thermoplastic gels above a critical SBS concentration that depends upon temperature, time of processing and surrounding atmosphere.     

Rheological examination of temperature dependence of conventional and polymer‐modified road bitumens

Rheological characterization of two types of road bitumens, conventional and polymer‐modified, has been examined in the temperature range between 20°C and 140°C. Tests were carried out before and after ageing following a thin‐film oven test. Polymer‐modified bitumens exhibit non‐Newtonian behaviour up to the 120°C due to a complex secondary structure formed by added polymers. For conventional bitumens, Newtonian behaviour was observed above 60°C. Special attention was paid to measurements and to analysis of the dynamic data of oscillatory shear. The mechanical spectra in a wide frequency range have been obtained using the WLF time‐temperature superposition principle. The analysis of viscoelastic data clearly showed the differences between the two types of bitumen. Conventional bitumens were more sensitive to temperature and to the ageing effects. For polymer modified bitumens, the elastic contribution to viscoelastic response was more pronounced, and independent of temperature and ageing.     

Synthesis and thermal stability of bitumen–polymer ionomers

Road bitumens, when combined with polymers such as styrene-butadiene-styrene (SBS) block copolymers, show improved mechanical properties. The corresponding blends, however, are thermodynamically unstable, and phase separation quickly occurs at higher temperatures. A solution is proposed for improving the thermal stability of these blends: It is based on the formation of reversible, ionic interactions between the bitumen and the SBS, thereby leading to a mixed, ionomeric network. Both compounds are first chemically modified by the grafting of carboxylic acid groups, then mixed, and, finally, the available acid groups are partially or totally neutralized by adding zinc acetate dihydrate to the blends. Comparison of the thermal stability of the resulting ionomeric blends with that of the untreated blends is discussed. The use of ion-ion interactions to enhance miscibility, which, for the first time, has been extended to bitumen–polymer systems, is shown to be a means of obtaining stable blends.     

Preparation and properties of bitumen modified with the maleic anhydride grafted styrene‐butadiene‐styrene triblock copolymer

A procedure to improve the properties of styrene‐butadiene‐styrene (SBS) copolymer modified bitumen by grafting of maleic anhydride (MAH) onto SBS in the presence of benzoyl peroxide (BPO) as initiator was proposed. The effects of the grafting degree (GD) on the properties of modified bitumen were investigated. FTIR spectroscopy was employed to verify the grafting of MAH onto SBS. The GD of MAH onto SBS was determined by a back titration procedure. To assess the effects of the GD of grafted SBS on properties of modified bitumen, the softening point, penetration, ductility, elastic recovery, penetration index, viscosity, storage stability, and dynamic shear properties were tested. Experimental results indicated that the SBS grafted with maleic anhydride (SBS‐g‐MAH) copolymer was successfully synthesized by solvothermal method, and different GD of the SBS‐g‐MAH was obtained by control the MAH concentration. The GD of the MAH onto SBS has great effect on the rheological properties of the modified bitumen, and the high temperature performance and storage stability of modified bitumen were improved with the GD of the MAH onto SBS increasing. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

沥青改性用SBS市场分析及生产开发建议

通过对国内外苯乙烯类热塑性弹性体SBS产品在制鞋、沥青改性、聚合物改性和粘合剂等方面的市场及消费需求分析,预测了SBS产品在改性沥青行业的需求情况和发展趋势。随着国内高等级高速公路的快速发展,我国对改性沥青用SBS的需求量将会有较大的增长。针对我国目前的生产实际情况,提出了下一步改性沥青用SBS的生产开发建议。     

High temperature stability of different polymer‐modified bitumens: A rheological evaluation

Polymer‐modified binders are increasingly used by the pavement industry. In practice, the bituminous binders are stored at high temperatures previous to its application on the road. The instability problems of the bitumen due to the polymer‐rich phase separation may affect the final properties of the pavement. Most polymers tend to be insoluble, to some degree, in the bitumen matrix, and phase separation may result. Chemical compatibility between the polymer additive and the bitumen, and processing conditions, are crucial to obtain suitable properties of the polymer‐modified bitumens. In this work, different polymer‐modified binders were manufactured by using a high‐shear mixing device. Once a good mechanical dispersion of the polymer in the bitumen matrix was achieved, the binders were stored in tubes at high temperatures. During the storage, the unstable polymer‐rich phase segregates and starts to ascend up to the surface. The progression of the polymer phase separation was followed through the evolution of the linear viscoelastic and the viscous properties of the samples collected, after different storage periods, from the top part of the storage tube. From the experimental results obtained, we may conclude that the use of a reactive polymer as additive is a promising alternative to obtain more stable binders. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 103: 1166–1174, 2007     

Blends of bitumen with polymers having a styrene component

The properties of a 100 penetration grade bitumen are modified considerably, and in a number of ways by the addition of 10 to 40 parts per hundred (pph) of a homopolystyrene and graft, block and random copolymers of styrene with butadiene and acrylonitrile. At low temperatures some blends have a similar stiffness to or even lower stiffness than the bitumen, but generally the blends are more than one order of magnitude stiffer, even when a rubber is added. The contrasting behavior is displayed by a polystyrene and a high impact polystyrene, ～3% to 4% of grafted rubber on the latter being sufficient to cause the enhancement, even at the 10 pph level, by two different random styrene‐butadiene copolymers, and also by blends consisting of different amounts of SBS block copolymer. Some polymers apparently trigger a Hartley inversion of the micellar structure of the asphaltene micelles. High low temperature stiffness correlates roughly with a lower Tg' as measured by the peak maximum in the E″ plots of the dynamic mechanical thermal analysis (DMTA) and by the steps in the differential scanning calorimetry (DSC) curves at temperatures below O°C. Tan δ maxima and DSC traces detected the glass transition in the continuous phase and in the dispersed phases, but none of these amorphous polymers formed a crystalline phase, though the DSC traces of the polystyrene and the SBS blends suggested that the polymer‐rich phases underwent an aging/ordering process on cooling. Our SBS blends differ in phase inversion behavior and the pattern of loss processes from others that had a smaller asphaltene component.     

Effect of polymer additives and process temperature on the physical properties of bitumen‐based composites

Polymer modified bitumen (PMB) is a binder obtained by the incorporation of polymer into the bitumen by mechanical mixing or chemical reaction. This study deals with the modification of bitumen with three types of polymers (LDPE, EVA, and SBS) in the presence of filler (CaCO₃). The morphological, mechanical, rheological properties, and thermal conductivity of the PMBs have been analyzed by scanning electron microscopy, tensile testing, melt flow index (MFI) measurements and hot wire method, respectively. The results indicate that the above‐mentioned properties of PMBs are influenced by polymer and bitumen nature and its composition. The mechanical properties of composites prepared at different temperatures exhibit small differences. In general, the inclusion of polymer increases tensile strength and Young's modulus and reduces percentage strain and MFI values, also, polymer inclusion reduces the thermal conductivity values of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polyethylene dispersions in bitumen: The effects of the polymer structural parameters

Polymer‐modified bitumens are very important to the transportation sector. Polyethylene is one of the most used polymers in bitumen modification. The effects of the structural parameters of polyethylene on its dispersion in bitumen and the performance of the resulting polymer‐modified bitumens were studied. With the addition of different polyethylenes to bitumen, the performance of bitumen at high temperatures increased as the polymer melt‐flow index (MFI) decreased. At low temperatures, the performance of bitumen decreased as the polyethylene MFI decreased. Furthermore, a decrease in the polyethylene MFI intensified its dispersion instability. At very low MFIs, the dispersions were unstable, even under the very high shear forces applied by a double mixer. Moreover, changes in the polyethylene MFI did not improve the dispersion stability at an elevated temperature (165°C). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3183–3190, 2003     

Rapid FTIR method for quantification of styrene‐butadiene type copolymers in bitumen

The mid‐IR molar absorptivity for polystyrene (PS) and polybutadiene (PB) blocks were obtained for five styrene‐butadiene‐styrene (SBS) and SB copolymers, including linear, branched, and star copolymers, and their blends with bitumen. The average absorptivity for PS and PB blocks was 277 and 69 L mol⁻¹ cm⁻¹ and it was little affected by the S/B ratio or the copolymer architecture. In the presence of bitumen, Beer's law was obeyed but the respective PS and PB absorptivity was 242 and 68 L mol⁻¹ cm⁻¹, possibly because of weak interactions between the copolymer and bitumen. The absorptivity values were used to calculate the concentration of SB‐type copolymers in blends with bitumen with an accuracy of 10% or better. The method can be used to probe the stability of bitumen–copolymer blends in storage at 165°C, to determine the copolymer concentration in commercial polymer modified bitumen (PMB), and to assess the resistance of PMB to weathering. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1034–1041, 2001     

Surface modification of natural substrates by atom transfer radical polymerization

Surface modification of various solid polysaccharide substrates was conducted by grafting methyl acrylate (MA) and styrene via atom transfer radical polymerization (ATRP) to produce well‐defined polymer grafts. The hydroxyl groups on the surfaces of the substrates were reacted with 2‐bromoisobutyryl bromide followed by graft copolymerization under ATRP conditions. The studied substrates were filter paper, microcrystalline cellulose, Lyocell fibers, dialysis tubing, and chitosan films. The modified substrates were analyzed by FT‐IR, water contact angle measurements, TGA, and SEM. FT‐IR characterization of the grafted substrates showed significant differences between the different substrates in the amount of grafted polymer. Higher amounts of polymer seem to be possible to graft from native cellulose substrates than from regenerated cellulose substrates. To investigate whether the grafted polymers were “living” after a longer time period, a second layer of polystyrene was grafted from a filter paper modified with PMA one year ago. FT‐IR characterization of the filter paper showed a peak corresponding to styrene, indicating that a block copolymer had been formed on the surface. Graft copolymerization can be used to change and tailor the surface properties of the polysaccharide substrates. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4155–4162, 2006     

Ageing by UV radiation of an elastomer modified bitumen

Laboratory methods to simulate the short- and long-term ageing occuring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of UV radiations. If the impact of thermal ageing on the degradation of SBS elastomers in bitumens has been extensively studied, there is not study dealing with the photo-oxidation of these copolymers in a bituminous matrix. So, the aim of our study was to investigate, by FTIR spectrometry and SEC chromatography, whether the architecture of elastomers (linear or radial) might have any influence on their ageing by UV radiation in a bituminous matrix. The results show that the elastomers oxidation kinetic, unlike the disappearance kinetic of trans-butadiene double bond, does not depend on their architecture. But, when putted into the same base bitumen, the two copolymers show exactly the same oxidation kinetic and the same decreasing kinetic of trans-butadiene double bond. So, this study has revealed that inside the bituminous matrix, on the one hand, the elastomers architecture does not influence on its degradation when submitted to UV radiation and, on the other hand, there is a “protection” of the elastomers by the studied bitumen towards UV radiation.