Asphalt modified by SBS triblock copolymer: Structures and properties

Abstract

Microstructural transformation of a poly(styrene‐b‐butadiene‐b‐styrene), SBS, triblock copolymer blended with asphalt was studied as the asphalt composition was varied from 0 wt% to 96 wt%. Transmission electron microscopy (TEM), dynamic mechanical spectrometry (DMS), and differential scanning calorimetry (DSC) were used. The blends were made in batch mixers at 200°C, or by solution casting from a nonselective solvent (trichloroethane) at ∼28°C. Asphalt partially solubilizes the polybutadene (PB) midblock of the SBS producing saturated PB microdomains along with macrodomains of asphalt. When the asphalt concentration was varied from 10 to 90 wt%, the asphalt phase separated into a variable number of large domains, while the SBS‐rich regions formed a continuous matrix. Networks of SBS‐rich regions were observed at low magnification; these are referred to as macro‐networks. At higher magnification, networks that are stabilized by polystyrene (PS) microdomains (denoted micro‐networks) are also formed. The presence of a macro‐network is also confirmed by stress relaxation tests. The macro‐network broke down into microgel‐like structures when the asphalt composition exceeded 90 wt%. Examination of the interior of the SBS‐rich regions showed that the shape of the PS microdomains transformed from short cylinders to lamellae, hexagonally perforated lamellae (HPL), back to lamellae, short cylinders, and finally to spheres. DMS and DSC indicate a systematic increase in the PB glass transition temperature (Tg) and negligible change in the Tg of PS as the asphalt content increases. Triblock copolymers that can form a macro‐network at low concentration will be more desirable for highway pavement modification.

Modelling and numerical simulation of phase separation in polymer modified bitumen by phase-field method

“…the separation of polymer-rich phase from bitumen-rich phase [11]. Many previous studies [1][2][3][4][5][12][13][14][15] have experimentally investigated the effects of bitumen and polymer properties and their compatibility on the PMB morphology and storage stability. However, these studies found it difficult to demonstrate the key parameters controlling the phase separation process.…”

“…As an important material for road construction and maintenance, polymer modified bitumen (PMB) and its storage stability have been studied for decades [1][2][3][4][5][6][7][8], but the problem of PMB storage instability has still not been resolved for all cases [9]. With an improper selection of raw materials or production process, the polymer may separate from the bitumen during the PMB storage and transport.…”

Processing of bitumens modified by a bio-oil-derived polyurethane

“…In that sense, mastic is the actual product used to hold coarser aggregates particles together in the asphalt mixtures [5]. Consequently, bitumen is the only deformable component and forms the continuous matrix of the mastic (and, therefore, of the asphalt mixtures) contributing significantly to road performance [6].…”

Asphalt Pavement Material Improvement: A Review

“…Dynamic mechanical spectroscopy, (DMS) and differential scanning calorimetry (DSC) analysis indicated a systematic increase in the PB glass transition temperature (T g ) and a negligible change in the (T g ) of the PS as the asphalt content increase. Apparently, tri-block copolymers that can form a macro-network at low concentration seem to be more desirable for highway pavement modifications [63]. Further findings of another study [64] have been carried out on the basis of stress controlled fatigue testing at 20 o C and 0 o C indicating that SBS exhibited a better fatigue property when compared to unmodified AC-5 Asphalt (ordinary asphalt/base asphalt).…”

“…In an earlier study, A. Adedeji, et al, (1996) have blended SBS tri-block copolymer while they have varied the asphalt composition from 0.0% to 96.0% by weight using two types of methods. The first method is called solution casting, where stock solutions of asphalt and SBS in non-selective solubilizing tri-chloroethane were all mixed, and the second type is called the melt process where the samples were made in batch mixer at 200 o C. Result showed that asphalt has solubilized partially the poly-butadiene (PB) mid-block of the SBS to produce saturated (PB) micro-domains network along with the macro-domains network of asphalt.…”