Physical and rheological properties of crumb rubber/styrene–butadiene–styrene compound modified asphalts

In order to improve the storage stability and tenacity of crumb rubber modified (CRM) asphalt, CRM compound modified asphalt was prepared by the addition of styrene–butadiene–styrene (SBS) and sulfur. The addition of SBS improved the tenacity of CRM asphalt, due to the formation of a dense polymer network. The storage stability of crumb rubber (CR)/SBS‐modified (CRSM) asphalt was improved by the addition of sulfur. The rheological tests confirmed the effect of SBS and sulfur on the physical properties of CRM asphalt to some extent and showed the susceptibility of CR/SBS/sulfur‐modified (CRSSM) asphalt to dynamic shearing. The morphology observation showed the compatibility of CRSM asphalt was improved greatly by vulcanization. POLYM. COMPOS., 38:1918–1927, 2017. © 2015 Society of Plastics Engineers     

Improved properties of SBS‐modified asphalt with dynamic vulcanization

Storage‐stable styrene‐butadiene‐styrene triblock copolymer (SBS)‐modified asphalt was prepared by dynamic vulcanization. The vulcanization characteristics of the asphalt/SBS/sulfur blend were studied using a strain‐controlled rheometer. The vulcanization of SBS in the asphalt resulted in a marked increase in the torque of the blend. In addition, the vulcanization of a butadiene rubber (BR)/sulfur blend was significantly influenced by the addition of asphalt through a curemeter. The existence of asphalt can accelerate the vulcanization of BR/sulfur blend and reduce its reversion. The preparation process of storage‐stable SBS‐modified asphalt by dynamic vulcanization was identified by a plot of the electric current versus time. The addition of sulfur to the SBS‐modified asphalts resulted in the formation of chemically vulcanized network structures in the modified binders. The physical properties of the SBS‐modified asphalt containing sulfur were compared to those of the modified binders without sulfur. The storage stability of the SBS‐modified asphalt was effectively improved by the addition of sulfur. The rheological properties of the SBS‐modified asphalts before and after adding sulfur were characterized by using dynamic shear rheometry and a rotational viscometer. As indicated by the monitored morphology, the compatibility and high‐temperature storage stability of SBS‐modified asphalts were improved by the addition of sulfur.     

Fundamental characterization of SBS‐modified asphalt mixed with sulfur

The purpose of this study was to characterize the mechanical behavior of asphalt modified by styrene–butadiene–styrene (SBS) and sulfur. Viscosity, microscopy, and rheological tests were conducted to understand the engineering properties of the polymer‐modified asphalt (PMA). Without the addition of sulfur, the polymer‐modified asphalt was microheterogeneous and was made up of two distinct finely interlocked phases, especially at high SBS concentrations. After the addition of sulfur, the PMA was observed to have smaller asphalt domains and a fairly homogeneous dispersion of the asphalt in the SBS matrix. The compatibility between polymer and asphalt produced an elastic network into the asphalt. The addition of sulfur resulted in an excellent elastic system and substantially increased the rheological properties of the PMA. Because of the colloidal nature of asphalt cements, their engineering properties were greatly improved because of the reinforcement of the SBS polymer and the physical‐chemical interaction between SBS and asphalt. The difference in the softening point between the top and bottom layers decreased significantly, and elastic recovery increased when was sulfur was present. A viscoelastic model was examined and shown to be appropriate for predicting the rheological properties ofthe asphalt–SBS blend mixed with sulfur. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2817–2825, 2007     

Morphology and rheological behavior of maltene–polymer blends. I. Effect of partial hydrogenation of poly(styrene‐block‐butadiene‐block‐styrene‐block)‐type copolymers

Because of the importance of the maltene–polymer interaction for the better performance of polymer‐modified asphalts, this article reports the effects of the molecular characteristics of two commercial poly(styrene‐block‐butadiene‐block‐styrene‐block) (SBS) polymers and their partially hydrogenated derivatives [poly{styrene‐block[(butadiene)_1?x–(ethylene‐co‐butylene)_x]‐block‐styrene‐block} (SBEBS)] on the morphology and rheological behavior of maltene–polymer blends (MPBs) with polymer concentrations of 3 and 10% (w/w). Each SBEBS and its parent SBS had the same molecular weight and polystyrene block size, but they differed from each other in the composition of the elastomeric block, which exhibited the semicrystalline characteristics of SBEBS. Maltenes were obtained from Ac‐20 asphalt (Pemex, Salamanca, Mexico), and the blends were prepared by a hot‐mixing procedure. Fluorescence microscopy images indicated that all the blends were heterogeneous, with polymer‐rich and maltene‐rich phases. The rheological behavior of the blends was determined from oscillatory shear flow data. An analysis of the storage modulus, loss modulus, complex modulus, and phase angle as a function of the oscillatory frequency at various temperatures allowed us to conclude that the maltenes behaved as pseudohomogeneous viscoelastic materials that could dissipate stress without presenting structural changes; moreover, all the MPBs were more viscoelastic than the neat maltenes, and this depended on both the characteristics and amount of the polymer. The MPBs prepared with SBEBS were more viscoelastic and possessed higher elasticity than those prepared with SBS. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

The research for high‐elastic modified asphalt

High‐elastic modified (HEM) asphalt was prepared by the addition of styrene‐butadiene‐styrene (SBS), plasticizer, and crosslinker to base asphalt. The effect and proportion of each modifier in asphalt were studied using physical and rheological tests. It was found that SBS determined the high‐temperature performance of HEM asphalt mainly. Plasticizer (dioctyl phthalate) is very helpful in improving the low‐temperature flexibility and elastic recovery. Crosslinker (sulfur) is necessary in maintaining high‐temperature stability. In this study, Fourier transform infrared, hydrogen nuclear magnetic resonance analysis, and microscopy observation were used to investigate the structural characteristics of modified asphalts further before and after ageing. The research showed the structural characteristics of modified asphalt were influenced evidently by ageing. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42132.     

Use of rheological compatibility criteria to study SBS modified asphalts

Polymer‐modified asphalts (PMAs) were prepared using Bachaquero asphalt and styrene–butadiene–styrene (SBS) type copolymers. Their rheological behavior was compared to that of unmodified asphalt and of a compatible commercial PMA. Materials were submitted to frequency sweeps between 10^?1 and 10² rad/s from 0 to 50°C. Storage stability tests were performed for 72 h at 160°C. Ring and ball softening points from the top and the bottom of the blends were compared and were used along with fluorescence microscopy to evaluate stability. Samples prepared with styrene–ethylene–butylene–styrene (SEBS) showed improved compatibility and stability as compared with SBS‐modified asphalts, probably because of a higher stability to thermal degradation from the absence of double bonds. An additional improvement in stability and compatibility was observed for SEBS functionalized with maleic anhydride (SEBS‐g‐MAH)–modified blends. Better compatibility, however, did not improve rheological behavior at low temperatures. The systems studied are so complex from a chemical point of view that the rheological criteria normally used to predict compatibility of polyblends did not give enough information regarding the compatibility of the modified asphalts. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1772–1782, 2003     

Preparation and properties of high viscosity modified asphalt

High viscosity modified (HVM) asphalt was prepared by the addition of styrene–butadiene–styrene (SBS), plasticizer, crosslinker. The effect and proportion of each modifier in the preparation of HVM asphalt were studied. SBS was the major modifier and determined the basic properties of HVM asphalt. Plasticizer (furfural exact oil) and crosslinker (sulfur) as additional modifiers were necessary in improving the workability, stability, and aging resistance of modifier. The effect of aging and additional modifiers on the structure and rheological behavior of SBS modified (SM) asphalt was displayed by adopting various rheological tests. Plasticizer declined the rutting resistance of SM asphalt and increased the viscous behavior of SM asphalt after aging. The use of crosslinker led to the formation of polymer network and improved the aging resistance of SM asphalt. The morphology observation shows crosslinker led to the formation of polymer network and improved the compatibility between SBS and asphalt. Plasticizer prompted the swelling and dispersion of SBS in asphalt and improved the effect of crosslinker further. Aging destroyed the polymer phase seriously and there was still residual polymer phase in asphalt. POLYM. COMPOS., 38:936–946, 2017. © 2015 Society of Plastics Engineers     

Influence of ageing on rheology of SBR/sulfur‐modified asphalts

The effect of short‐term and long‐term oxidative ageing on the rheological, physical properties, the morphology, and thermodynamic behavior of the styrene‐butadiene rubber (SBR)‐ and SBR/sulfur‐modified asphalts is studied respectively. The dynamic rheological tests show the two major effects of ageing on the rheological behavior of the asphalt binders. Ageing prompts the degradation of polymer and increases the viscous behavior of the binders, on the other, ageing improves the elastic behavior of the binders due to the changed asphalt components, the final rheological behavior of the aged binders depends on the combined effect. The SBR/sulfur‐modified asphalt is more susceptible to ageing and dynamic shear due to the structural instability and show a viscous behavior with increasing the sulfur level after ageing. Under the influence of repeated shear force, the high‐temperature property of the SBR/sulfur‐modified asphalts declines. The morphology observation shows the compatibility between polymer and asphalt is improved with further ageing especially for the SBR/sulfur‐modified asphalt. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Characterization of end‐functionalized styrene–butadiene–styrene copolymers and their application in modified asphalt

End amino, carboxylic acid, and hydroxyl functionalized styrene–butadiene–styrene (SBS) triblock copolymers were prepared with 1,5‐diazabicyclo[3.1.0]hexane, carbon dioxide, and epoxy ethane as capping agents, respectively. The effects of the end polar groups on the morphology and dynamic mechanical properties were investigated. Transmission electron microscopy images suggested that the group at the end of the polystyrene (PS) segment made the morphology of the PS domains disordered and incompact. Dynamic mechanical results showed that the storage and loss modulus increased after SBS was end‐functionalized. End amino and carboxylic acid groups improved the compatibility and storage stability of SBS‐modified asphalt. However, the effect of the end‐hydroxyl group on the improvement of the storage stability of SBS‐modified asphalt was not obvious. The differential scanning calorimetry analysis of SBS‐modified asphalt further showed that the compatibility and storage stability of SBS‐modified asphalt were improved by the attachment of amino or carboxylic acid groups through the anionic polymerization method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 8–16, 2007     

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     

The effect of the architecture and concentration of styrene–butadiene compatibilizers on the morphology of polystyrene/low‐density polyethylene blends

The effect of styrene–butadiene block copolymers (SB) with varying number of blocks and length of styrene blocks on the morphology, rheology, and impact strength of 4/1 polystyrene/low‐density polyethylene (PS/LDPE) blends was studied. The scanning and transmission electron microscopy and X‐ray scattering were used for determination of the size of LDPE particles and the localization and structure of SB copolymers in blends. It is shown that the dependence of the LDPE particle size on the amount of added SB and localization of SB copolymers in blends is predominantly controlled by the length of their styrene blocks. It follows from thermodynamic considerations that the reason is the difference in composition asymmetry between SB with short and long styrene blocks. Coalescence of particles of SB having short styrene blocks at the surface of LDPE droplets and movement of SB with long styrene blocks to the PS–LDPE interface were observed during annealing of PS/LDPE/SB blends. Pronounced migration of SB copolymer during annealing shows that their localizations in blends in steady state on long steady mixing and at thermodynamic equilibrium are different. The values of tensile impact strength of PS/LDPE/SB blends correlate well with the size of LDPE particles and the amount of SB at the interface. Viscosity of PS/LDPE/SB depends on molecular structure of SB copolymers by a manner different from that of tensile impact strength. The results of this study and literature data lead to the conclusion that the compatibilization efficiency of SB copolymers for a certain polystyrene‐polyolefin pair is a function of not only molecular parameters of SB but also of the polystyrene/polyolefin ratio, the amount of SB in a blend, and mixing and processing conditions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2803–2816, 2006     

Effect of the molecular structure of ethene–propene and styrene–butadiene copolymers on their compatibilization efficiency in low‐density polyethylene/polystyrene blends

The effect of the molecular structure of styrene–butadiene (SB) block copolymers and ethene–propene (EPM) random copolymers on the morphology and tensile impact strength of low‐density polyethylene (LDPE)/polystyrene (PS) (75/25) blends has been studied. The molecular characteristics of SB block copolymers markedly influence their distribution in LDPE/PS blends. In all cases, an SB copolymer is present not only at the interface but also in the bulk phases; this depends on its molecular structure. In blends compatibilized with diblock copolymers, compartmentalized PS particles can also be observed. The highest toughness values have been achieved for blends compatibilized with triblock SB copolymers. A study of the compatibilization efficiency of SB copolymers with the same number of blocks has shown that copolymers with shorter PS blocks are more efficient. A comparison of the obtained results with previous results indicates that the compatibilization efficiency of a copolymer strongly depends both on the blend composition and on the properties of the components. The compatibilization efficiency of an EPM/SB mixture is markedly affected by the rheological properties of the copolymers. The addition of an EPM/SB mixture containing EPM with a higher viscosity leads to a higher improvement or at least the same improvement in the tensile impact strength of a compatibilized blend as the same amount of neat SB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Blends of SBS triblock copolymer with poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polystyrene mixture

Blends of styrene–butadiene–styrene (SBS) or styrene–ethylene/1‐butene–styrene (SEBS) triblock copolymers with a commercial mixture of polystyrene (PS) and poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) were prepared in the melt at different temperatures according to the chemical kind of the copolymer. Although solution‐cast SBS/PPO and SBS/PS blends were already known in the literature, a general and systematic study of the miscibility of the PS/PPO blend with a styrene‐based triblock copolymer in the melt was still missing. The thermal and mechanical behavior of SBS/(PPO/PS) blends was investigated by means of DSC and dynamic thermomechanical analysis (DMTA). The results were then compared to analogous SEBS/(PPO/PS) blends, for which the presence of a saturated olefinic block allowed processing at higher temperatures (220°C instead of 180°C). All the blends were further characterized by SEM and TGA to tentatively relate the observed properties with the blends' morphology and degradation temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2698–2705, 2003     

Effect of molecular structure of styrene–butadiene block copolymers on morphology,rheological properties,and impact strength of polystyrene/polyethylene blends

The effect of molecular structure of six model styrene–butadiene (SB) block copolymers with various number of blocks and two lengths of styrene blocks on morphology, rheological properties, and impact strength of polystyrene (PS)/high‐density polyethylene (PE) blends was studied. It was found that location of SB copolymers in the blends is determined by the length of styrene blocks. The length of styrene blocks has similar effects on impact strength and linear viscoelastic properties of the blends. On the other hand, the correlation was not found between the effects of a number of blocks on impact strength and linear viscoelastic properties of the blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2303–2309, 2003     

Blends of poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 toughened by maleated polystyrene‐based copolymers: Mechanical properties,morphology, and rheology

Poly(2,6‐dimethyl‐1,4‐phenylene oxide)/polyamide 6 (PPO/PA6 30/70) blends were impact modified by addition of three kinds of maleated polystyrene‐based copolymers, i.e., maleated styrene‐ethylene‐butylene‐styrene copolymer (SEBS‐g‐MA), maleated methyl methacrylate‐butadiene‐styrene copolymer (MBS‐g‐MA), and maleated acrylonitrile‐butadiene‐styrene copolymer (ABS‐g‐MA). The mechanical properties, morphology and rheological behavior of the impact modified PPO/PA6 blends were investigated. The selective location of the maleated copolymers in one phase or at interface accounted for the different toughening effects of the maleated copolymer, which is closely related to their molecular structure and composition. SEBS‐g‐MA was uniformly dispersed in PPO phase and greatly toughened PPO/PA6 blends even at low temperature. MBS‐g‐MA particles were mainly dispersed in the PA6 phase and around the PPO phase, resulting in a significant enhancement of the notched Izod impact strength of PPO/PA6 blends from 45 J/m to 281 J/m at the MBS‐g‐MA content of 20 phr. In comparison, the ABS‐g‐MA was mainly dispersed in PA6 phase without much influencing the original mechanical properties of the PPO/PA6 blend. The different molecule structure and selective location of the maleated copolymers in the blends were reflected by the change of rheological behavior as well. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The viscoelastic properties of polymer‐modified asphalts

The linear viscoelastic properties of one family of base asphalts, unmodified or modified by the simple addition of an elastomer or by further in‐situ crosslinking, have been investigated. The time‐temperature superposition principle was shown to be valid for the base as well as for the modified asphalts. The addition of the elastomer styrene‐butadiene (SB) copolymer increased drastically the storage modulus and the elastic character of the asphalts. The thermal susceptibility of the polymer modified asphalts was considerably reduced and this combined with an increased resistance to deformation (larger complex modulus) suggests much better performances for road applications. The chemically modified asphalt containing 3% SB showed similar viscoelastic properties as the physical blend containing 6% SB.     

The influence of styrene–butadiene diblock copolymer on styrene–butadiene–styrene triblock copolymer viscoelastic properties and product performance

The effects of the styrene–butadiene (SB) diblock copolymer on the viscoelastic properties of styrene–butadiene–styrene (SBS) triblock copolymers were examined in both in the the neat state and within specific product applications. The addition of the SB diblock copolymer into a pure SBS triblock copolymer resulted in a significant decrease in the plateau storage modulus and a quantitative linear rise in tan delta. In a pure triblock, in which all endblocks are anchored in polystyrene domains, all entanglements are physically trapped. The SB diblock embodies untrapped polybutadiene endblocks that are able to relax stress by chain reptation through the rubbery polybutadiene matrix. The SB diblock copolymer quantitatively lowered the microphase separation temperature (MST) of the SBS triblock copolymer. These changes in linear viscoelastic behavior manifest themselves into a reduction in the efficiency and performance of the SBS triblock copolymer in asphalt pavement binders and hot-melt adhesive blends. Specifically, the SB diblock diminished the complex shear modulus and elasticity of a polymer-modified asphalt, which translated into lower predicted rutting specification values. The increase in diblock content altered the viscoelastic response of the hot-melt adhesive blend, translating into a reduction in the shear holding power and shear adhesion failure temperature. The lack of network participation, coupled with the relaxation of the polybutadiene endblocks, accounts for the lower strength and greater temperature susceptibility of the diblock-containing systems. © 1995 John Wiley & Sons, Inc.     

Effects of the molecular structure of impact modifier and compatibilizer on the toughening of PBT/SBS/PS‐GMA blends

This work aims at studying the toughening process of poly(butylene terephthalate) (PBT) through its blends with styrene‐butadiene‐styrene block copolymers (SBS), in the presence of poly(styrene‐ran‐glicydil methacrylate) (PS‐GMA) as reactive compatibilizer. High values of impact strength were attained for PBT/SBS blends without the compatibilizer; however, this improvement is achieved for blends with SBS having similar viscosity compared to PBT, at high SBS content (40 wt %) and for blends prepared under specific processing conditions. The efficiency of the in situ compatibilization of PBT/SBS blends by PS‐GMA was found to be strongly dependent on the SBS and PS‐GMA molecular characteristics. Better compatibilizing results were observed through fine phase morphologies and lower ductile to brittle transition temperatures (DBTT) as the interfacial interaction and stability of the in situ formed compatibilizer are maximized, that is, when the miscibility between SBS and PS‐GMA and reaction degree between PBT and PS‐GMA are maximized. For the PBT/SBS/PS‐GMA blends under study, this was found when it is used the SBS with higher polystyrene content (38 wt %) and with longer PS blocks (M_w = 20,000 g mol^?1) and also the PS‐GMA with moderate GMA contents (4 wt %) and with molecular weight similar to the critical one for PS entanglements (M_c = 35,000 g mol^?1). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5795–5807, 2006     

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