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     

The effect of long-term oxidation on the rheological properties of polymer modified asphalts

The effect of long-term aging on rheological properties of polymer modified asphalt binders was studied. Modifiers included diblock poly(styrene-b-butadiene) rubber, triblock poly(styrene-b-butadiene-b-styrene), and tire rubber. Asphalt aging was carried out either at 60 °C in a controlled environmental room or at 100 °C in a pressure aging vessel [AASHTO Provisional Standards, 1993]. Both dynamic shear properties and extensional properties were investigated. Polymer modification resulted in increased asphalt complex modulus at high temperatures, decreased asphalt complex modulus at low temperatures, broadened relaxation spectra, and improved ductility. Oxidative aging decreased asphalt temperature susceptibility, damaged the polymer network in binders, further broadened the relaxation spectrum, and diminished polymer effectiveness in improving asphalt ductility.     

New toughening mechanisms in rubber modified polymers

Abstract

Rubber toughening usually involves the addition of rubber particles to a rigid polymer in order to promote energy absorption through the initiation of local yielding, which takes the form of multiple crazing and/or extensive shear yielding. In addition to these classic mechanisms, recent studies of deformation mechanisms in various rubber modified polymers, using a range of electron microscopy techniques, have revealed two new mechanisms of energy absorption. Direct observations of micromechanical processes in high impact polystyrene and copoly(styrene/acrylonitrile)–acrylate blends, carried out in situ on the stage of a transmission electron microscope have shown that the rigid, glassy subinclusions found in both ‘salami’ and hard–soft–hard ‘core–shell’ rubber particles respond to high tensile stresses by cold drawing. Fibrillation begins in the rubber phase and then draws fibrils of glassy polymer from the subinclusions, causing initially spherical inclusions to become flattened discs before finally disintegrating. In addition, when thin sections of rubber toughened polypropylene are stretched in situ on the stage of the transmission electron microscope, hard–soft core–shell particles consisting of a polyethylene core and an ethylene/propylene copolymer rubber shell are able to initiate crazing in the matrix at -100°C, well below the glass transition temperature of the ethylene/propylene copolymer rubber. Micrographs illustrating these mechanisms are presented and discussed.     

Influence of modification process parameters on the properties of crumb rubber/EVA modified asphalt

Crumb rubber (CR) and ethylene vinyl acetate copolymer (EVA) were adopted as asphalt modifiers. Routine tests, softening point, penetration, and ductility were used to evaluate the basic properties of crumb rubber and ethylene vinyl acetate copolymers (CR/EVA) modified asphalt. The segregation experiment measured the storage stability. Modern test methods such as fluorescence microscopic photography technology was used to study stability of polymer modified asphalt. Infrared spectrum experiment was used to analyze the composition differences of the upper part and lower part of CR/EVA modified asphalt. Matlab software was employed to fit out the formulae of ductility, penetration, and softening point difference of modified asphalt and shearing temperature, shearing time and shearing rate separately. Compared with base asphalt, the properties of CR/EVA modified asphalt have been greatly improved. The formulae which were fitted out by Matlab software showed that the shearing time was the foremost factor affecting the properties of CR/EVA modified asphalt, followed by shearing temperature, and the last was shearing rate. The conclusions which were fitted by orthogonal experiment were basically consistent with the results of formulae which were fitted out by Matlab software. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43598.     

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     

硫化胶粉与脱硫胶粉改性沥青性能研究

对比分析了硫化胶粉和脱硫胶粉微观结构及其改性沥青基本路用性能,研究了硫化胶粉和脱硫胶粉在改性沥青过程中表现出的共性与差异及其原因。结果表明,加入硫化胶粉与脱硫胶粉,均能提高沥青基本路用性能,相同目数下,脱硫胶粉较硫化胶粉交联密度低,表面粗糙,表面极性增加,脱硫胶粉与沥青具有更好的相容性和稳定性,一定掺量下,硫化胶粉能赋予沥青更好的高温稳定性,脱硫胶粉能显著提高沥青低温延度,界面作用及胶粉网络结构的形成对改性沥青路用性能有重大影响。     

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     

Investigation on thermo‐rheological properties and stability of SBR modified asphalts containing palygorskite clay

One problem of polymer‐modified asphalts (PMAs) is the poor compatibility between polymer and asphalts. In this article, the effects of palygorskite clay (PC) and organomodified palygorskite clay (OPC) on the rheological and morphological properties of styrene butadiene rubber (SBR) modified asphalts are investigated. The dynamic mechanical analysis (DMA) of PC and SBR/PC (OPC) modified asphalts before and after ageing has been characterized by dynamic shear rheometer (DSR). The results indicate that the degree of SBR modification is a function of asphalt‐polymer compatibility. When the polymer concentration is higher, it produces a highly elastic network which increases the viscosity, complex modulus, and elastic response of the mixture, particularly at high service temperatures. However, ageing of the SBR and SBR‐PC mixtures result in a decrease in the elastic response of the modified asphalts. It also have been confirmed that the morphology observed by optical microscopy and scanning electron microscope (SEM) revealed the better compatibility between SBR/PC and asphalt. The storage stability of binder is improved significantly. Compared with PC, OPC shows better effect in improving viscoelastic properties and rutting resistance of the mixture, which contributes to the better improvement of interfacial adhesion based on larger size between layers in OPC‐modified asphalts. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

SBS对沥青性能的影响

通过测试软化点、针入度和延度对SBS改性沥青的性能进行表征.结果表明:使用线型或星型SBS作为沥青改性剂可以显著提高沥青性能.当硫黄稳定剂质量分数为0.2％,SBS质量分数为4％时,改性沥青的软化点、针入度和延度趋于稳定.此外,相较于线型SBS改性,星型SBS改性沥青的软化点稍高,针入度和延度相对更小.     

Evaluation of polyphosphoric acid on the performance of polymer modified asphalt binders

The aim of this research is to evaluate the effect of polyphosphoric acid (PPA) on the mechanical performance of styrene–butadiene–styrene (SBS) and styrene–butadiene–rubber (SBR) modified asphalt. Conventional properties, multiple stress creep recovery (MSCR), bending beam rheometer (BBR), and linear amplitude sweep (LAS) tests were conducted to evaluate the performance characteristics of asphalt at different PPA inclusions. Gel-permeation chromatography (GPC), saturates, aromatics, resins, and asphaltenes (SARA), and Fourier transform infrared (FTIR) were carried to reveal the molecular weight, component and infrared spectra of asphalt. Results showed that PPA hardened the asphalt, improved the rutting and fatigue performances of polymer modified asphalt (PMA) binder, but weakened the anti-cracking performances. Besides, storage stability had a significant improvement as the addition of PPA. The addition of PPA brought more macromolecules into asphalt and led to more high-average molecular weight compounds. Furthermore, PPA changed four component ratios of asphalt. Both PMA with or without PPA have similar absorption peaks. This may be due to absorption peak of PMA covered the changes in PPA modification process as the low content of PPA. 0.8% dosage of PPA may be considered optimum for composite modified binder combining the above experimental results for this binder source.     

Mechanical,Rheological, and Electrical Properties of Multiwalled Carbon Nanotube Reinforced Nanocomposites of 50/50 Acrylonitrile–Styrene–Acrylate/Zn+2 poly(ethylene-co-methacrylic acid) Ionomer Blend

The effect of variable amount of multiwalled carbon nanotubes on mechanical, rheological, and electrical properties of acrylonitrile–styrene–acrylate/Zn⁺²-poly(ethylene-co-methacrylic acid) ionomer blend system has been evaluated. Optical micrographs as well as alternating current conductivity data shows the formation of nanotube percolation network at 1 wt% nanotube content. The polymer/nanotube interaction increased the rate of tensile modulus to 55 GPa at low nanotube content. The polymer chain relaxation time was increased upto 1 wt% of nanotube content, but higher nanotube loading reduced the time. The zero-shear viscosity was function of nanotube content whereas the infinite-shear viscosity was independent of nanotube content.     

Dielectric properties of nanotube reinforced butyl elastomer composites

Dielectric relaxation behavior of multiwalled carbon nanotube reinforced butyl rubber composites has been studied as a function of variation in filler in the frequency range of 20–2 × 106 Hz. The effect of variation in filler loadings on the complex and real parts of impedance was distinctly visible, which has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium and relaxation dynamics of polymer chains in the vicinity of fillers. The electric modulus formalism has been used to further investigate the conductivity and relaxation phenomenon. The frequency dependence of AC conductivity has been investigated by using Percolation theory. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by AC conductivity occurred in the vicinity of 6–8 phr of filler loading. Scanning electron microscope microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Dielectric properties of exfoliated graphite reinforced flouroelastomer composites

Dielectric relaxation behavior of nano graphite reinforced flouroelastomer composites has been studied as a function of variation in filler in the frequency range of 0.01–10⁵ Hz. The effect of variation in filler loadings on the complex and real parts of impedance was distinctly visible which has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium and relaxation dynamics of polymer chains in the vicinity of fillers. The electric modulus formalism has been utilized to further investigate the conductivity and relaxation phenomenon. The frequency dependence of AC conductivity has been investigated by using Percolation theory. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by DC conductivity occurred in the vicinity of 2.5–3.5 phr of filler loading. Scanning electron microscope microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Electrical and Mechanical Properties of Some Butadiene Rubber Composites in the Vicinity of the Percolation Threshold

The electrical and mechanical properties of NBR/SBR blends with different compositions were studied before the addition of carbon black. The increase in permittivity ε′ and dielectric loss ε″ noticed by increasing NBR content is due to the increase in C ≡ N dipoles. The mechanical properties which include tensile and elongation at yield and rupture are also found to be increased. This work also includes the compatibility study, which was carried out using different tools and techniques (Heat of mixing, dielectric and scanning electron microscope). This study led to a conclusion that both blends are incompatible.

The electrical as well as the mechanical properties were carried out on NBR, SBR and NBR/SBR blend (50/50) to be loaded with different concentrations of high abrasion furnace black (HAF) in order to find out the percolation thresholds in relation to the net work formation.

The electrical conductivity of carbon-black-filled composites is increased from pure polymer to that of pure carbon, through the change in the different composites. Up till certain concentration of HAF (30 phr for both NBR and SBR) and 20 phr for NBR/SBR blends the conductivities of the composites are approximately the same and closed to that of the pure, electrically insulating polymer matrix. These concentrations are called percolation thresholds. Above such concentrations, the conductivity increases many orders of magnitude with very little increase in the filler amount. With this increase the tendency of conductivity chain formation increases through the aggregation of the carbon black particles network. The change in conductivity beyond the percolation threshold is expressed according to the percolation theory with straight line when plotted graphically versus P-P_c; P_c is the volume fraction of carbon black at the percolation threshold.

In addition to the conductivity term, the data of permittivity ε′ and dielectric loss ε″ given at different frequencies from 100 Hz up to 100 kHz show an abrupt increase at 30 phr HAF for NBR & SBR and 20 phr HAF for NBR/SBR. More over, the relaxation times obtained from the analyses of these data using Fröhlich and Havriliak-Nagami functions, which ascribe the orientation of the large aggregates caused by the movement of the main chain also show an abrupt increase at the same concentration of HAF.

The mechanical properties, which investigated through the measurements of tensile and elongation at yield and rupture indicate an abrupt increase at the same concentration of HAF found in the case of electrical measurements. This result gives evidence to the good applicability between both mechanical and electrical investigations through the network formations.

Any how, the percolation threshold found in case of NBR/SBR blend is less than that for NBR itself. This result is attributed to the uneven distribution of the filler in the incompatible blend matrix.     

Identification of rubber polymers in rubber blends

Abstract

Solid phase extraction (SPE) was used to separate pyrolysates of rubber blends. Then each rubber polymer in rubber blends was identified, based on interpreting infrared spectrum of separated pyrolysates. By using this method, nature–ethylene–propylene, ethylene–propylene–silicone, butyl–styrene–butadiene and ethylene–propylene–butadiene–acrylonitrile rubber blends were analysed. The analytical results show that each characteristic pyrolysate of polymer in rubber blend pyrolysate can be separated by SPE. The method for identification of rubber polymers in rubber blends by infrared coupled with SPE is flexible, rapid and low cost, compared with the method by pyrolysis gas chromatography coupled with infrared spectroscopy or mass spectroscopy.     

Combined modification of asphalt by waste PE and rubber

Waste PE (WPE) and rubber were combined to modify the ordinary oil asphalt in order to improve the performance of asphalt. In this study, the recycled waste packing polymer replacing the ordinary polymer modifiers modified the road asphalt through mechanical mixing for the first time. Results showed that softening point and ductility of asphalt increased, while the penetration degree decreased after the modification. The overall performance of the asphalt/WPE/RU system was superior to that of the asphalt/WPE system. FT‐IR analysis indicated that the modification actually was a physical process. The microstructure of the modified asphalt indicated that the shear yield and crack‐branching caused by the waste rubber powder were the main reasons for the improvement of the performance of asphalt. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Temperature and time dependence of conductive network formation: Dynamic percolation and percolation time

Temperature and time dependence of conductive network formation in vapor-grown carbon fiber (VGCF) filled high-density polyethylene (HDPE)/poly(methyl methacrylate) (PMMA), VGCF and ketjenblack (KB) filled HDPE/isotactic polypropylene (iPP) blends have been investigated. It is found that the filled conductive polymer composites are thermodynamically non-equilibrium systems, in which the conductive network formation is temperature and time dependent, a concept named as dynamic percolation is proposed. When the composites are annealed at a temperature above the melt point of polymer matrix, the dynamic process of conductive network formation can be monitored in a real time way. Such an in situ characterization method provides more interesting information about the dispersion of conductive particles in the polymer matrix. Furthermore, a thermodynamic percolation model is modified to predict the percolation time for VGCF and KB filled HDPE/iPP multi-phase systems during the annealing treatment, and it expresses experimental results well.     

Comparative study of the effect of sulfur on the morphology and rheological properties of SB‐ and SBS‐modified asphalt

The modification of asphalt with styrene‐ butadiene block copolymers and sulfur was studied to elucidate the effect of the molecular characteristics of the polymer, polymer content, and sulfur/polymer ratio on the physical properties of modified asphalts. Two types of styrene‐butadiene copolymers were used (SB and SBS), which differed considerably in terms of their chain architecture, average molecular weights, and size and distribution of their polybutadiene and polystyrene blocks, as shown by gel permeation chromatography, infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry. Sulfur/polymer/asphalt blends were prepared by a hot mixing process and characterized by conventional tests, fluorescence microscopy, and rheology. The results revealed that the morphology of the blends is strongly dependent on polymer concentration and sulfur/polymer ratio. In‐depth rheological characterization showed that the thermomechanical properties changed considerably upon addition of small amounts of sulfur. Collectively, these results suggest that sulfur increases the compatibility between polymer and asphalt by crosslinking polymer chains. Interestingly, the rheological behavior of blends prepared with a combination of SB and sulfur was similar to that exhibited by blends prepared with SBS either in the presence or absence of sulfur. This is explained by assuming that the addition of small amounts of sulfur to SB‐modified asphalt facilitates the formation of an elastomeric network that resembles the one found in SBS‐modified asphalt, effectively contributing to asphalt reinforcement. Nonetheless, the exact dosage of sulfur must be carefully controlled to prevent gel formation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Coir pith as low cost filler in microcellular soles based on natural rubber–high styrene resin

Abstract

The utilisation of coir pith (modified and unmodified) as filler in microcellular soles based on natural rubber–high styrene resin blends is presented. The cure characteristics and technical properties of microcellular soles have been evaluated. Coir pith can be used as a filler in amounts up to 50 phr without much reduction in properties. Optical micrographs of razor cut samples of microcellular sheets are presented; the sheets with modified coir pith show a more uniform cell structure.     

Effect of carbon‐based nanoparticles on the cure characteristics and network structure of styrene–butadiene rubber vulcanizate

The network structure of styrene–butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi‐walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory–Rehner model as well as the tube model theory. It is found that the network structure of CB‐filled SBR follows a three‐phase composite model including rigid particles, semi‐rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and polymer–filler interaction. For MWCNT‐filled SBR, the bound rubber does not show a substantial contribution to the network structure and mechanical performance, and these properties are greatly dominated by the higher aspect ratio and polymer–filler interaction. Additionally it is deduced that the crosslinking density of matrix rubber increases on incorporation of the fillers compared to unfilled matrix rubber. Copyright © 2012 Society of Chemical Industry