Linear Styrene Research Articles

Integrating Mechanistic-Empirical Pavement Analysis in the Life Cycle Assessment Use Phase and Monetization of Environmental Impacts to Promote Low Carbon Transportation Materials

This study attempted to integrate the Mechanistic-Empirical Pavement Design Guide (MEPDG) analysis into the life cycle assessment (LCA) framework to explore the potential of terminal blend rubberized bitumen (TBRB) technology as a sustainable alternative to traditional paving materials in the United Arab Emirates (UAE). In addition, the concept of environmental impact monetization is introduced for quantifying shadow prices to be used in cost–benefit analyses and encourage the adoption of sustainable technologies in pavement construction. The findings demonstrate that hot mixed asphalt (HMA) with TBRB outperforms asphalt mixtures with neat bitumen (NB) and polymer-modified bitumen (PMB) containing 7% linear styrene–butadiene–styrene, with respect to durability and environmental impacts. The cradle-to-grave analysis, which includes maintenance and rehabilitation cycles based on the MEPDG results, alters the hierarchy among scenarios compared to conventional cradle-to-gate analyses, highlighting the importance of the use phase in LCA. Overall, the asphalt mixture with TBRB exhibits 83% and 63% less global warming potential than mixtures with NB and PMB, respectively. The monetization process through the distance-to-target approach returned the shadow price of US$157 per metric ton of CO2eq in the UAE. Based on this value, the HMA with TBRB, if selected over those with NB and PMB, offers environmental savings of US$47,186/km-lane and US$15,852/km-lane for the case study investigated.

Multiple linear regression and artificial neural networks for highly selective cationic β‐diimine‐methallyl nickel (II) catalyst for styrene dimerization reaction to 1,3‐diphenyl‐1‐butene

The objective of the present study is to develop predictive models to input and output parameters for linear styrene dimerization reactions. These reactions involve the conversion of two styrene molecules into 1,3‐diphenyl‐1‐butene, which is a commonly used intermediate in the production of various industrial chemicals. Multiple linear regression (MLR) and artificial neural network based on multilayer perceptron (MLP) and radial basis function were used to model 1,3‐diphenyl‐1‐butne dimerization process in order to evaluate its performance. The neural network has been trained and tested by experimental data. The effect of various parameters (such as complex concentration) on styrene conversion (Conv%) and turnover of frequency (TOF) has been investigated in the proposed work. The results found by the proposed predictive models were analyzed and compared with the experimental results. Based on the comparison of the results, the radial basis function neural network (RBFNN) model outperformed the other models (MLR and MLP) with a correlation coefficient of (0.987 for Conv% and 0.947 for TOF) and lower root mean square errors for the output parameters. This result demonstrates that the RBFNN is an efficient technique to predict the styrene conversion and turnover frequency of the dimerization reaction. It was exposed that the control strategies learned are robust and can be transferred to similar dimerization reaction configurations.

Fabrication of MoS2-based environment friendly modifier via tannic acid assisted diethylenetriamine co-deposition for the preparation of composite SBS modified asphalt

MoS2 produced by naturally existing molybdenite has excellent potential as nano-fillers for improving matrix properties of cementitious materials. In this study, following the co-deposition of diethylenetriamine-tannin (DETA-TA) coating on the surface of MoS2, an environment friendly modifier i.e. DETA-TA-MoS2 was prepared, which was in turn applied to prepare DETA-TA-MoS2 incorporated linear styrene–butadienestyrene (SBS) polymer modified asphalt (LSPMA). Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction and scanning electron microscopy confirmed that DETA-TA rough coating was successfully deposited on the surface of MoS2. Its multi-tentacle structure and synergistic bionic design awarded the modifier with rougher surface and increased number of potential reaction sites, thus forming a stronger mechanical interlocking with LSPMA. Fluorescence microscopy results indicated that a good spatial network structure of DETA-TA-MoS2/LSPMA was developed as compared with that of LSPMA. Conventional performance tests, dynamic shear rheological and multi-stress creep recovery tests revealed that the viscoelasticity and rutting resistance of LSPMA were significantly improved after the addition of DETA-TA-MoS2 modifier. Compared with LSPMA, the storage modulus (G′) of 0.07%DETA-TA-MoS2/LSPMA increased by 26.4%, while average creep compliance of 0.07%DETA-TA-MoS2/LSPMA decreased by 61.7% (0.1 kPa) and 39.6% (3.2 kPa). This study provides important guidelines for the fabrication of DETA-TA-MoS2/LSPMA modified asphalt as an efficient alternative to conventional SBS modified asphalt for practical applications in highway and construction industries.

Evaluation of the adhesion and healing properties of modified asphalt binders

The adhesion between asphalt binder and aggregate plays a fundamental role in the mixture’s resistance to moisture damage and fatigue cracking. And self-healing is another inherent property of asphalt binder which is related to the mixture’s durability. Many efforts have been taken to understand those individual properties, while few research focuses on evaluating the adhesive property of binder-aggregate system incorporating the effects from binder’s self-healing, especially for the modified binders that is expected to improve the mixture’s durability. In this study, a modified binder bond strength (BBS) test procedure including a sample healing setting was employed to evaluate the compound effects of adhesion and self-healing property of five representative modified asphalt binders with varies modifiers at several dosages. The results show that the linear styrene–butadienestyrene (SBS), high-density polyethylene (HDPE), crumb rubber, and terminal blend (TB) crumb rubber modified binders have negative effect on bonding strength of binder-aggregate system without considering their self-healing properties. However, the recovery of pull-off tensile strength (POTS) of the HDPE and crumb rubber-modified binders after several failure-healing cycles exhibit significant higher ratios than those of base binder and SBS/TB crumb rubber-modified binders which are similar at their optimum dosages. Furthermore, the measured bonding-strength recovery capability of tested binders has a very well correlation with their mixtures’ fatigue performance determined by the four-point beam (4PB) fatigue tests. This indicates that the proposed method can provide a better understanding of pavement performance of modified binders In addition, the Fourier transform infrared spectroscopy (FTIR) test was conducted to study the mechanism of modifiers on improving long-term adhesive behavior of the binders in terms of chemical response. It is found that the methylene plus methyl hydrogen to carbon (MMHC) index of FTIR spectrum of modified binders has a control on their self-healing and the aggregate selective adsorption of their long-chain molecules, and it shows a good agreement with the bonding-strength recovery ratios.

Investigation of the rutting performance of various modified asphalt mixtures using the Hamburg Wheel-Tracking Device test and Multiple Stress Creep Recovery test

Asphalt modification technology is diversifying and developing complexity to overcome early permanent deformation and ensure satisfactory performance for asphalt concrete pavements. The Hamburg Wheel Tracking Device (HWTD) test has been reported to be successful in assessing asphalt mixtures’ rutting performance. This study includes a comprehensive investigation of the effects of different additives at various contents upon the HWTD testing results of asphalt mixtures. According to the degree of their improvement of the rutting performance in the HWTD test, additives were classified into three categories: (1) the first grade including linear styrene–butadiene–styrene (SBS), branched SBS and Gilsonite; (2) the second grade including high-density polyethylene, and polyphosphoric acid; and (3) the third grade including crumb rubber. Additionally, it was found that higher dosages of modifiers do not necessarily result in the improvement of Hamburg performance, and an optimal content exists for most additives. After the extensive mix testing, the dynamic shear rheometer (DSR) testing results were correlated to the HWTD test results in two categories: polymer modified asphalt and non-polymer modified asphalt. It was found that the compliance value Jnr3.2 from the Multiple Stress Creep Recovery (MSCR) test did not underestimate the rutting resistance of polymer modified asphalt compared to non-polymer modified asphalt as the current rutting factor G*/sin δ did. Jnr3.2 was more reliable than G*/sin δ in characterizing the anti-rutting performance of asphalt mixtures no matter they were polymer modified or non-polymer modified. However, different criteria for Jnr3.2 should be adopted for the polymer modified asphalt and non-polymer modified asphalt respectively.

Comparison and relationship between indices for the characterization of the moisture resistance of asphalt–aggregate systems

The complex and diversified asphalt modification makes it harder for the assessment of testing methods capable of characterizing the performance of different modified asphalt in the presence of water. In this study, three representative test methods addressing the moisture performance of asphalt were evaluated and compared: surface free energy (SFE) test, binder bond strength (BBS) test and Hamburg wheel tracking device (HWTD) test. Results indicate that the HWTD test can be a benchmark test while the BBS test is a screening test in characterizing the moisture performance of various modified asphalt. In addition, the surface energy component obtained from the receding procedure in the Wilhelmy Plate Method correlated better with the adhesion property of asphalt than those based on the advancing procedure did. The various indices obtained from the three tests were classified as suitable or unsuitable indices on the basis of the analysis of specific additives. Furthermore, based on the degree of their improvement in the moisture performance, additives were classified into three grades: (1) the first grade including linear styrene–butadiene–styrene (SBS), branched SBS and gilsonite; (2) the second grade including high-density polyethylene, and polyphosphoric acid; (3) the third grade including asphalt rubber and terminal blend asphalt. Finally, it was found that base binders with shorter-chain structures and lower aromatics contents showed better moisture resistance in the HWTD test. High mobility of base asphalt binder negatively influenced the corresponding mixture’s moisture sensitivity.

Correlating Molecular Structure to the Behavior of Linear Styrene–Butadiene Viscosity Modifiers

The effect of linear styrene–butadiene polymer structure on the temperature–viscosity behavior of model polymer-base oil solutions is investigated using molecular dynamics simulations. Simulations of alternating, random, and block styrene–butadiene polymers in a dodecane solvent are used to calculate viscosity at 40 and 100 °C, reference temperatures for characterizing their function as viscosity modifiers. Mechanisms underlying this function are explored by quantifying the radius of gyration and intramolecular interactions of the polymers at the same reference temperatures. The block styrene–butadiene configuration exhibits the least change in viscosity with temperature, characteristic of a good viscosity modifier or viscosity index improver, and the behavior is correlated to the ability of this structure to form smaller coils with more intramolecular interactions at lower temperatures and then expand as temperature is increased. The results indicate that there is a correlation between styrene–butadiene polymer structure, additive function, and the mechanisms underlying that function.

Synthesis, glycosylation and NMR characterization of linear peracetylated d-galactose glycopolymers

Linear styrene glycopolymers containing peracetylated d-galactose units were prepared. Their glycosylation to introduce residues mimicking a substrate for copper amine oxidases was studied with the help of model molecules and NMR investigation.

Relationship between fractal, viscoelastic, and aging properties of linear and radial styrene–butadiene–styrene polymer-modified bitumen

The present study is aimed at evaluating the morphological and interfacial properties of the polymer and bitumen (BIT) in linear styrene–butadiene–styrene (SBS-L) block copolymer and radial SBS (SBS-R) block copolymer-modified BIT (PmB) by fractal analysis. Fluorescence microscopy technique coupled with image analysis was used to measure the particle size distribution and fractal dimension of PmB morphology formed in mixtures. Fractal analysis approach was proposed as quantitative description method to evaluate nonuniformity of phase-separated SBS polymer particles/fibrils in PmB. Fractal-like structures in fluorescence micrographs of PmB morphology with the polymer phase-separated particles/fibrils were quantified using interface D[BW], BIT-rich phase D[B+BW], and SBS-rich phase D[W+BW] box-counting fractal dimensions. The overall morphological structure became more compact or more fibril organized as the polymer content attained overcritical values. The relatively high values for the BIT-rich phase D[B+BW] fractal dimension suggests that the PmB mixtures have a structure with extremely high space-filling capacity. Polymer-BIT mixture properties by the conventional laboratory performance tests and by the rheological measurements before and after the Rolling Thin Film Oven Test have been correlated with the PmB mixtures fractal dimensions.

Shear strength of sandwich core materials subjected to loading rates relevant to water slamming

Sandwich composite materials are widely used within the marine industry, particularly as hull panels. Water impact loads, known as slamming, can be very significant for these structures, particularly for high-speed craft. The transient nature of slamming loads means that the loads are applied very quickly, which can cause stress and strain rates that are high enough to affect the resulting strength of the core material, particularly for polymeric foams. The aim of this paper is to characterise the shear strength of cores at slamming relevant loading rates. Two testing approaches are used: a custom servo-hydraulic beam testing system and a drop-weight impact testing machine. Core materials studied included aramid honeycomb, cross-linked and linear polyvinyl chloride, polyethylene terephthalate and styrene acrylonitrile foams, representing a range of different levels of ductility and maximum elongation. For the moderate and high elongation core materials, there were significant increases in shear strength for dynamic loads; however, the strength of most of the materials does not appear to be sensitive to the exact loading rate.

Preparation and properties of conventional asphalt modified by physical mixtures of linear SBS and montmorillonite clay

The effect of additions of organically modified clay and a sulfur-based compound on the technological, as well as rheological properties of a conventional asphalt that was modified by a linear styrene–butadiene–styrene block copolymer, was studied via three factors and five levels of statistical experiment. Blends were prepared with conventional physical mixing. The linear viscoelastic properties of asphalt binders were studied in small-amplitude sinusoidal oscillations by a dynamic shear rheometer, and the low-temperature properties of the tested polymer modified asphalts were determined from their creep characteristics measured in a bending beam rheometer. In particular, it was shown that the organoclay had a positive influence on rheological properties of the studied systems, specifically on service temperatures.

Evidence for Complex Molecular Architectures for Solvent-Extracted Lignins.

Lignin, an abundant, naturally occurring biopolymer, is often considered "waste" and used as a simple fuel source in the paper-making process. However, lignin has emerged as a promising renewable resource for engineering materials, such as carbon fibers. Unfortunately, the molecular architecture of lignin (in vivo and extracted) is still elusive, with numerous conflicting reports in the literature, and knowledge of this structure is extremely important, not only for materials technologies, but also for production of biofuels such as cellulosic ethanol due to biomass recalcitrance. As such, the molecular structures of solvent-extracted (sulfur-free) lignins, which have been modified using various acyl chlorides, have been probed using small-angle X-ray (SAXS) and neutron (SANS) scattering in tetrahydrofuran (THF) solution along with hydrodynamic characterization using dilute solution viscometry and gel permeation chromatography (GPC) in THF. Mass spectrometry shows an absolute molecular weight ≈18-30 kDa (≈80-140 monomers), while GPC shows a relative molecular weight ∼3 kDa. A linear styrene oligomer (2.5 kDa) was also analyzed in THF using SANS. Results clearly show that lignin molecular architectures are somewhat rigid and complex, ranging from nanogels to hyperbranched macromolecules, not linear oligomers or physical assemblies of oligomers, which is consistent with previously proposed delignification (extraction) mechanisms. Future characterization using the methods discussed here can be used to guide extraction processes as well as genetic engineering technologies to convert lignin into value added materials with the potential for high positive impact on global sustainability.

Viscoelastic relaxation of styrene–butadiene–styrene block copolymers with different topological structures

AbstractThe viscoelastic relaxation of linear styrene–butadiene–styrene triblock copolymer (l‐SBS) and star styrene–butadiene–styrene triblock copolymer (s‐SBS) with four arms were investigated with differential scanning calorimetry and dynamic rheological measurements. Three characteristic viscoelastic responses of l‐SBS and s‐SBS in the plot of the loss tangent (tan δ) and temperature at different frequencies (ω's), which corresponded to the relaxation of the polybutadiene (PB) block (peak I), the glass transition of the polystyrene (PS) phase (peak II), and the mutual diffusion between the PB blocks and PS blocks (peak III), respectively, were observed in the experimental range. Although ω was 0.1 rad/s, a noticeable peak III was gained for both l‐SBS and s‐SBS. The dynamic storage modulus (G′) of l‐SBS showed two distinct types of behavior, depending on the temperature. At temperature (T) < T2 (where T2 is the temperature corresponding to peak II), G′ of l‐SBS displayed a very weak ω dependency. In contrast, at T > T2, G′ decayed much more rapidly. However, G′ of s‐SBS displayed a very weak ω dependency at both T < T2 and T > T2. Only near T2 did s‐SBS decay with ω a little sharply. These indicated, in contrast to l‐SBS, that s‐SBS still exhibited more elasticity even at T > T2 because of its crosslinking point between the PB blocks (the star structure). In the lower ω range, l‐SBS exhibited a stronger peak III than s‐SBS despite the same styrene content for l‐SBS and s‐SBS. The high tan δ value of peak III for l‐SBS was considered to be related to the internal friction among the PB blocks or the whole l‐SBS chain, not the PS blocks. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The effect of polymer modification on hot mix asphalt fracture at tensile loading conditions

A laboratory investigation was conducted to evaluate the effect of both cross-linked and linear styrene–butadiene–styrene (SBS) modifiers on the cracking resistance of hot mix asphalt (HMA) mixtures. Five types of asphalt mixtures composed by the same aggregate gradation but different asphalt binders were produced in the laboratory. The cracking performances of the mixtures were evaluated using a viscoelastic fracture mechanics-based model entitled ‘HMA Fracture Mechanics’. Crack localisation and crack growth were investigated performing the indirect tensile test and the semi-circular bending test. A digital image correlation system capable of providing full-field strain maps was applied. The results show the benefit of SBS modifiers to the mixture's cracking resistance in terms of reduced rate of damage accumulation and increased tensile limits to failure. Finally, significant damage and first fracture have shown to be strongly more localised in modified specimens than in the unmodified one.

Transport and Magnetic Properties of CrO<sub>2</sub>-Polymer Magnetic Composites

We report the transport and magnetic properties of sintered CrO2-polymer composites. In order to improve the elastic properties of the CrO2-based composites, we investigated two types of styrene-based copolymers: poly(methyl methacrylate)-styrene (9/1 and 5/5) and linear polysiloxaneg- styrene as well as poly(methyl methacrylate)–butadiene 9/1. The electric transport and magnetoresistance are consistent with the spin tunneling model at low temperatures but the contribution of spin independent channels becomes important at high temperature and high fields. All composites display ferromagnetism at room temperature with saturation at low fields and a slightly temperature-dependent coercive field for the samples grafted either with butadiene or with styrene except for CrO2-polysiloxane-g-styrene composite where it exponentially decreases with increasing temperature.

Thermomechanical and Rheological Asphalt Modification Using Styrene−Butadiene Triblock Copolymers with Different Microstructure

This paper shows the state of the art of Mexican asphalt, AC-20 grade, modified by linear styrene−butadiene triblock copolymers (SBS), which include variations in their chemical structures, specifically, total styrene and 1,2-butadiene vinyl contents. The main objective of this work was studying the influence of variation in the 1,2-butadiene vinyl content between 9 to 41% (wt/wt), and also variation in the styrene content between 10 and 45% (wt/wt). Both variables were changed in the structure for the SBS copolymer in order to see the effect on thermal and rheological properties when they are used as asphalt modifiers. The research includes composition characterization and thermal properties of raw and modified asphalt. Analytical characterization of SBS polymers was carried out too by means of differential scanning calorimetry, fluorescence microscopy, and a parallel plate rheometer. Results obtained showed that SBSs with a molecular weight of 200 000 ± 10 000 Daltons get the maximum performance in the softening point and maximum rheological failure temperature when the styrene content is around 30% and vinyl groups move from 20 to 30% into the polymer microstructure with an appropriate viscosity level at 135 °C according to Strategic Highway Research Program standards.

Mechanism and kinetics of ordering in diblock copolymer thin films on chemically nanopatterned substrates

AbstractLamellae forming diblock copolymer domains can be directed to assemble without defects and in registration with chemically nanopatterned substrates. Initially, thin films of the lamellar poly(styrene‐b‐methyl methacrylate) block copolymer form hexagonally close‐packed styrene domains when annealed on chemical nanopatterned striped surfaces. These styrene domains then coalesce to form linear styrene domains that are not fully registered with the underlying chemical surface pattern. Defects coarsen, until defect‐free directed assembly is obtained, by breaking linear styrene domains and reforming new structures until registered lamellae have been formed. At all stages in the process, two factors play an important role in the observed degree of registration of the block copolymer domains as a function of annealing time: the interfacial energy between the blocks of the copolymer and the chemically nanopatterned substrate and the commensurability of the bulk repeat period of the block copolymer and the substrate pattern period. Insight into the time‐dependent three‐dimensional behavior of the block copolymer structures is gained from single chain in mean field simulations. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3444–3459, 2005

A correlation of the limiting viscosity number, molecular mass and composition of statistical linear styrene–methyl methacrylate copolymers

Statistical copolymers of styrene and methyl methacrylate of different compositions were synthesized by the radical solution copolymerization in a batch isothermal reactor. Copolymers were characterized by the size exclusion chromatography (SEC), elemental analysis and dilute solution viscometry. Experimental limiting viscosity numbers were described by the Mark–Houwink–Kuhn–Sakurada correlation as the function of the molar mass and by the Mendelson correlation as the function of both the molar mass and copolymer composition. A new correlation of the intrinsic viscosity number, molar mass and composition was developed, based on semiempirical considerations. The correlation takes into consideration all the effects which affect the dimensions of random linear copolymer coils in solvents. The new equation was found to be superior to the Mendelson’s one in correlating the experimentally obtained intrinsic viscosities.

NMR Investigation of Segmental Dynamics in Disordered Styrene−Isoprene Tetrablock Copolymers

13C and 2H NMR relaxation time measurements were performed on four linear styrene−isoprene tetrablock copolymers (SISI) of overall molecular weight about 12 000 g/mol in order to characterize the segmental dynamics of both components. The two isoprene blocks are equal in length as are the two styrene blocks. A wide range of temperatures (from 285 to 530 K) and several compositions (volume fraction of styrene: 23%, 42%, 60%, and 80%) were investigated. Previous small-angle neutron scattering (SANS) results by Lodge et al. showed that these materials are homogeneous on length scales much larger than the radius of gyration. The segmental correlation times for both components in SISI were extracted by fitting the experimental data to the modified Kohlrausch−Williams−Watts (mKWW) orientation autocorrelation function and Vogel−Tammann−Fulcher (VTF) temperature dependence. While previous measurements found that the global dynamics in this system are quite homogeneous, these NMR measurements show that the segmental relaxation times of styrene and isoprene segments differ by orders of magnitude. At high temperatures, the dynamics of styrene segments are about 10 times slower than that of isoprene segments; this can be attributed to the difference in the intrinsic mobility of the two types of segments. The segmental dynamics of 5% polyisoprene (PI) tracers in one tetrablock matrix are very similar to that of the matrix isoprene segments.

Influence of interfacial structure on morphology and deformation behavior of SBS block copolymers

Linear styrene- block-butadiene- block-styrene (SBS) triblock copolymers having different interfacial structures were investigated. In spite of the nearly equivalent chemical composition (about 70 vol% of styrene), these copolymers show significantly different morphologies. It was shown that the origin of the modified morphology in asymmetric block copolymers is the intermixing of short polystyrene (PS) chains or chain segments into the polybutadiene (PB) phase. It has a consequence of an increase in the glass transition temperature of the soft phase (PB phase here) and a significant decrease of the whole relaxation time of the materials. The larger the interfacial volume, the more PS molecules can mix into the PB phase. Moreover, it seems that the extent of the stress transfer in heterogeneous polymeric systems is crucially influenced by the interface. The tapered interface in an SBS block copolymer, for example, permits a more effective stress transfer compared to the sharp interface resulting in a higher degree of orientation in the individual phases of the materials.