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Preparation of an SBS Latex–ModifiedBitumen Emulsion and PerformanceAssessmentH. M. Cai a , T. Wang a , J. Y. Zhang b & Y. Z. Zhang aa State Key Lab of Heavy Oil, China University of Petroleum (EastChina) , Dongying Shandong, Chinab Research Institute of Qilu Branch Co., SINOPEC , Zibo Shandong,ChinaPublished online: 17 May 2010.

To cite this article: H. M. Cai , T. Wang , J. Y. Zhang & Y. Z. Zhang (2010) Preparation of an SBSLatex–Modified Bitumen Emulsion and Performance Assessment, Petroleum Science and Technology,28:10, 987-996, DOI: 10.1080/10916460902939436

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Petroleum Science and Technology, 28:987–996, 2010

Copyright © Taylor & Francis Group, LLC

ISSN: 1091-6466 print/1532-2459 online

DOI: 10.1080/10916460902939436

Preparation of an SBS Latex–Modified Bitumen

Emulsion and Performance Assessment

H. M. CAI,1 T. WANG,1 J. Y. ZHANG,2 AND Y. Z. ZHANG1

1State Key Lab of Heavy Oil, China University of Petroleum (East China),

Dongying Shandong, China2Research Institute of Qilu Branch Co., SINOPEC, Zibo Shandong, China

Abstract For resolving the contradiction of the stability between styrene-butadiene-

styrene (SBS)-modified bitumen emulsion and the concentration of SBS, a method ofpreparing SBS latex is provided in this article. Results showed that SBS latex had

good stability properties and performance. The effect of emulsifier concentration onthe storage stability showed that the maximum stability of SBS latex–modified bitumen

emulsion (SBS-LMBE) was obtained at emulsifier weight concentration 1.0% andaddition of SBS latex to bitumen emulsion enhanced the difficulty of emulsification.

The effects of SBS latex on bitumen properties showed the penetration decreased,

whereas the softening point and ductility at 5ıC increased, which means that SBS latexplays a role in improving the properties of bitumen. Compared to the base bitumen,

saturate and aromatic of evaporation residue of SBS-LMBE decreased. However, resinand asphaltene increased. Analysis of the relationship between the components and

properties of bitumen showed that the components change caused by SBS latex wasbeneficial to the properties of bitumen. The colloidal index (CI) showed that SBS latex

also made the colloidal system more stable.

Keywords chemical components, colloidal index, modified bitumen emulsion, SBSlatex

1. Introduction

Modified bitumen emulsion is a new kind of binder used in road surfaces, which has

the advantages for both modified bitumen and bitumen emulsion. Some properties will

be improved, such as the thermal stability, high- and low-temperature performance,

durability, as well as adhesive property with aggregates. It also has better crack resistance

than pure bitumen emulsion at low temperature. Using a modified bitumen emulsion

can save bitumen by 10–20%. There is a wide range in using it, especially in slurry

seal (International Slurry-Surfacing Association, 1991) and microsurfacing technologies

(International Slurry-Surfacing Association, 1996). Hence, the preparation of modified

bitumen emulsion with good properties is necessary and there is a large market for it.

Styrene-butadiene-styrene (SBS) block copolymers can increase the elasticity of

bitumen and they are probably the most appropriate polymers for bitumen modification

(Becker et al., 1999). When SBS is used as a modifier, modified bitumen emulsion

is prepared through the process of SBS mixing with bitumen by means of high shear

Address correspondence to H. M. Cai, State Key Lab of Heavy Oil, China University ofPetroleum (East China), Dongying Shandong, 257061, China. E-mail: caihm123@163.com

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988 H. M. Cai et al.

and emulsification of SBS-modified bitumen. It is well known that the difficulty of

emulsification of modified bitumen increases with the concentration of SBS in base

bitumen (Sitz and Maysville, 1991). When the weight concentration of SBS in base

bitumen is below 3%, the modified bitumen can be emulsified very well; when the

concentration is at 3–5%, the modified bitumen can be emulsified, but the product is

not perfect; in particular, the storage stability usually cannot meet specifications. When

decreasing the concentration of SBS in base bitumen for good stability, other properties

will not meet specifications. In order to resolve the contradiction of product stability

and concentration of SBS, this article provides a method for preparing SBS latex and

evaluates the effect of SBS latex on bitumen emulsion.

2. Experimental

2.1. Preparation of SBS Latex

SBS polymer YH-792 was supplied by the Yueyang Baling Petrochemical Company

(Jiangyin, China). YH-792 is a linear SBS polymer that consists of different combinations

made from blocks polystyrene (30%) and polybutadiene of a very precise molecular

weight. The emulsifier was a mixture of three kinds of surfactants, including cationic

emulsifier JQT, nonionic emulsifier OP-10, and anion emulsifier disproportionated rosin

potassium soap at the weight ratio of 3:1:1. All of the emulsifiers are easily available on

the market, and some experiments (Cai, 2007) have proved that this mixing emulsifier has

the best ability of emulsification. The stabilizer was polyacrylamide and the coagulant

was styrene. Distilled water was used in the process. The experimental procedure for

preparing SBS latex is shown in Figure 1. In order to dissolve SBS, toluene was used as

a solvent.

Figure 1. Procedure for preparing SBS latex.

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SBS Latex–Modified Bitumen Emulsion 989

Table 1

The optimized technology parametersa

Toluene:

SBS

Emulsifier:

SBS

Water:

SBS Temperature

Coagulant:

SBS

Stabilizer:

SBS

3.5:1 0.08:1 2:1 65ıC 0.04:1 0.004:1

aAll ratios are weight ratio.

Through orthogonal test and single-factor research (Cai and Zhang, 2006), the opti-

mized technology parameters were obtained, which are given in Table 1.

2.2. Preparation of SBS Latex–Modified Bitumen Emulsion

One bitumen of 80/100 penetration grade was used in this study, which was produced

by Shengli Petroleum Refinery (Zibo, China). Characteristics of the bitumen are given

in Table 2. In order to produce SBS latex–modified bitumen emulsion (LMBE), tap

water, cationic emulsifier (JQT), and SBS latex were mixed and then added to a stirred

(8,000 rpm) aqueous system preheated to 70ıC; the heated base bitumen at 140ıC was

added gradually, andthe system was continuously stirred for 3 min. The weight ratio

of bitumen to water was 50:50. The concentrations of SBS latex and emulsifier were

changed in the SBS-LMBE, as described below.

2.3. Method of Analysis

2.3.1. Latex Tests. The SBS latex was subjected to the following conventional latex

tests. In describing the microstructure interaction and stability of SBS particles, a XSZ-H

microsope manufactured by Chongqing Optical Instrument Factory (Chongqing, China)

and a LIBRA® scanning electron microscope (SEM) manufactured by (ZEISS, Germany)

were used. A light microscope obtained the dispersion message of SBS particles in whole

system. SEM can show the message of every molecule depending on the dyeing of double

bond and high magnification. They all indicated the thermodynamic stability of latex.

2.3.2. Bitumen Tests. Conventional bitumen tests such as penetration, softening point,

and ductility tests were performed on base bitumen and SBS-LMBE. For evaluating

the effect of emulsifier on SBS-LMBE, storage stability was performed. In addition,

base bitumen and SBS-LMBE were fractionated by saturates, aromatics, resins, and

asphaltenes (SARA) analysis.

Table 2

Properties of the base bitumen

Test Results Specification

Penetration (25ıC; 0.1 mm) 85 GB/T4509

Softening point (ıC) 44.5 GB/T4507

Ductility (25ıC; cm) >140 GB/T4508

Solubility (%) 99.6 GB/T11148

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3. Results and Discussion

3.1. Properties of SBS Latex

3.1.1. Stability of SBS Latex. SBS latex was prepared according to the aforementioned

procedure (Figure 1) and technology parameters (Table 1). Emulsions are thermodynam-

ically unstable systems that break down over time through a variety of physicochemical

instability mechanisms, such as gravitational separation, coalescence, flocculation, in-

version, and Ostwald ripening, among others (Romero, 2002). The equilibrium of latex

is maintained as a result of the existing attractive van der Waals forces, as well as

electrostatic, steric, or other repulsive forces (Weiss and McClements, 2000). A latex

with perfect stability should not have these negative phenomena mentioned above, which

are indicated by the homogenous system and equilibrium of particles.

In order to study the dispersion of SBS latex, SBS latex was examined at room

temperature under a microsope at magnification levels of 400� and SEM at a magnifica-

tion level of 4000�. Light miscroscope and SEM images are shown in Figures 2 and 3,

respectively. In Figure 2, white particles are SBS and the whole system is homogenous,

and there is no demulsification phenomenon. From Figure 3 we can see that SBS particles

do not coalesce among each other, which shows that latex has good equilibrium. The

property of SBS detemines that all the SBS particles cannot have the same size, and an

SEM date processing system can calculate the size distribution of SBS particles form the

images, which is shown in Figure 4. The size distribution of particles concentrate in 1,700

and 2,200 nm, and number average diameter is 1,966 nm. There is a small difference

between particle sizes. All the messages indicate that SBS particles are dispersed very

well in latex and latex has good equilibrium, which shows that SBS latex has good

stability.

3.1.2. Performance Analysis. The performance was analyzed according to the corre-

sponding standard analytical methods of China, as shown in Table 3.

Figure 2. Light microscope image of SBS latex.

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SBS Latex–Modified Bitumen Emulsion 991

Figure 3. SEM image of SBS particles.

The analysis of SBS latex properties shows that solid content is 40.68%, which

satisfies the specification of over 40%. Particles with a positive charge which let latex

can be mixed with all cationic emulsified bitumen. The average particle size is 1.97 �m,

which matches the size of emulsified bitumen particles (1–2 �m). The pH shows that latex

is acidic, which may enhance the adhesion between bitumen and aggregates. Viscosity

and mechanical stability satisfy the specifications. Usually, the mechanical stability is

characterized by the residue content after mechanical mixing. A latex with poor mechan-

ical stability will break when stirred by strong mechanical or hydraulic shear.

From the analysis above, it is shown that the SBS latex has good dispersity and

stability, and the properties indicate that it is a qualified latex.

Figure 4. Size distribution of SBS particles.

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992 H. M. Cai et al.

Table 3

Properties of SBS latex

Properties

SBS

latex Specification

Analytical

methoda

Solid content, wt% 40.68 >40 GB 2958-82

Electric charge of dispersed droplets C C SH/T 0099. 3-91

Average particle size, �m 1.97 — b

pH 5.8 — GB 2954-82

Viscosity, mPa � s 41 <150 GB 2956-82

Mechanical stability, wt% 0.38 <0.5 GB 2955-82

Density, 20ıC, g/cm3 0.9901 — GB 2959-82

aGB is the Chinese standard method; SH/T is the industrial standard method.bFrom SEM image of size distribution.

3.2. Effect of Emulsifier Concentration on Storage Stability

When preparing modified bitumen emulsion, the equilibrium between latex and bitumen

emulsion is broken by the shearing action, and a new equilibrium is formed. If this new

equilibrium is not maintained, the preparation, storage, and modified bitumen emulsion

usage will be influenced to a large degree. Hence, storage stability is an important issue

for the evaluation of modified bitumen emulsion.

For comparing the level of difficulty in bitumen emulsification under the SBS latex

existing or not, bitumen emulsion (BE) was prepared too. The procedure was similar

to that of SBS-LMBE only without added SBS latex. The emulsifier concentration was

increased form 0.4 to 1.2% by weight. In SBS-LMBE the SBS latex content was 6% by

weight.

The effect of emulsifier concentration on the storage stability (5 days, SINOPEC,

2005) of SBS-LMBE and BE at 25ıC is shown in Figure 5. Selected to know the

effective concentration, which pronounces the maximum stability for the SBS-LMBE

and BE. It can be concluded from Figure 5 that the optimum concentration that exhibited

the maximum stability of SBS-LMBE and BE was recorded 1.0 and 0.8% by weight. In

the case of bitumen-in-water emulsions stabilized by cationic surfactants, the charge that

inhibits drop coalescence of each drop is basically the result of surfactant adsorption.

However, it is clear that if the surfactant concentration is low and the interfacial area

generated during stirring is large, then a considerable number of drops will not have

enough surfactant to overcome coalescence. Hence, bitumen-in-water emulsion will not

have good stability. With the increase of surfactant concentration, the drops will adsorb

more surfactant to overcome coalescence and the stability of emulsion is improved.

When surfactant concentration reaches a certain level, surfactants will reach equilibrium

concentrations at the interface, and the interfacial area of drops will be saturated by

surfactant. At this moment the interfacial area cannot be adsorbed even with the increase

of surfactant concentration, so the best stability will be achieved.

It is shown in Figure 5 that the equilibrium concentrations of surfactant in BE and

SBS-LMBE are 0.8 and 1%, respectively. The storage stability of BE is superior to that

of SBS-LMBE under the same surfactant concentration, so the addition of SBS increases

the difficulty of the emulsification process.

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SBS Latex–Modified Bitumen Emulsion 993

Figure 5. Effect of emulsifier concentration on storage stability.

3.3. Influence of SBS Latex Concentration on Bitumen Performance

The effects of SBS polymer modification on the penetration, softening point, and ductility

of the modified bitumen emulsion are shown in Figures 6, 7, and 8, respectively. The

emulsifier concentration was 1% by weight, and SBS latex concentration was increased

from 0 to 7% by weight. When SBS latex concentration is zero the value is the result of

emulsified bitumen. Generally, the penetration values at 25ıC decreased with the increase

of SBS latex content, whereas the softening points and ductility at 5ıC increased. There

Figure 6. Penetration value corresponding to SBS latex concentration.

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Figure 7. Softening point corresponding to SBS latex concentration.

is a significant large decrease in the penetration values and considerable increase in the

softening point and ductility based SBS latex at 7%. The increase of softening point

is favorable because bitumen with a higher softening point may be less susceptible to

permanent deformation (rutting). The changes of penetration value and 5ıC ductility are

also favorable, which made bitumen have better rutting and crack resistance. So adding

SBS latex to bitumen emulsion improved the performance of bitumen.

SBS latex improves the properties of bitumen emulsion because SBS copolymers

transfer their strength and elasticity from physical and cross-linking of the molecules to

a three-dimensional network in the evaporation residue of SBS-LMBE. The polystyrene

end blocks impart the strength to the polymer and the polybutadiene rubbery matrix

blocks give the material its exceptional viscosity. When SBS is blended with bitumen,

Figure 8. 5ıC Ductility corresponding to SBS latex concentration.

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SBS Latex–Modified Bitumen Emulsion 995

the elastomeric phase of the SBS copolymer absorbs the oil fractions from the bitumen

and swells up to nine times as much as its initial volume (Isacsson and Lu, 1995). At

suitable SBS concentration, a continuous polymer phase is formed through the polymer-

modified bitumen and significantly modifies the bitumen properties (Cavaliere and Diani,

1996).

3.4. Effects of SBS Latex on the Chemical Components and

Colloidal System of Bitumen

The chemical components of base bitumen and the evaporation residue of SBS-LMBE

were investigated according to the SARA analysis method. The results are listed in

Table 4, which shows that the saturate and aromatic contents decrease, whereas the resin

and asphaltene contents increase in SBS-LMBE compared with base bitumen. However,

saturate had a large degree of decreasing and resin had a large degree of increasing.

Saturate is the softest fraction in bitumen, and its penetration is extreme large,

whereas its softening point and viscosity are very small. Hence, bitumen with good

properties should not have too much saturates. This means that the decrease of saturates

is beneficial to the properties of bitumen. The properties of aromatics are similar to that of

saturates, but more aromatics in bitumen is a prerequisite. This is because the aromatics

can improve the aromaticity of bitumen dispersion medium, which will guarantee a stable

colloid system. It is said that high-quality bitumen should have about 50% aromatics

(Liang, 2000). The increase of resin can improve the plastic property, adhesiveness, and

ductility of bitumen. The suitable increase of asphaltene can improve the softening point

and penetration, but the content of asphaltene cannot be too high, or it will cause the

bitumen colloidal system to become a gel state and decrease the ductility.

In view of the close relation between compositions and properties of bitumen, many

scholars tried to determine the relationship between the ratio of each component and

properties. Loeber et al. (1998) and Mushrush and Speight (1998) gave a parameter

called the colloidal index (CI). CI is the index of evaluating the stability of colloid

system, and it is defined by Eq. (1).

CI DAr C R

S C A(1)

In the Eq. (1), S, Ar, R, A, and are the mass percentage of saturates, aromatics, resins,

and asphaltenes. From Eq. (1) we can see that the larger the denominator, asphaltene is

more easily formed in a floc network structure; when the elements are larger, asphaltene is

more easily formed in a viscous body. In particular, the increase of resin makes asphaltene

peptizing very well and makes the colloid system more stable. From Table 3 it can be

seen that the CI becomes larger and the resin content increases to a large degree, so

Table 4

The components analysis and colloidal index of base bitumen and SBS-LMBE

Bitumen

Saturates,

%

Aromatics,

%

Resins,

%

Asphaltenes,

%

Colloidal

index

Base bitumen 12.80 50.45 28.09 8.66 3.66

SBS-LMBE 3.59 50.13 37.19 9.09 6.87

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the CI shows that SBS-LMBE has better stability of colloid system than that of base

bitumen. However, it is not the bigger of CI the more stable of system, four fractions

should have a suitable ratio in a bitumen, and each component is essential.

4. Conclusions

Conclusions can be drawn as follows:

1. The results of light microscopy and scanning electron microscopy showed that pre-

pared SBS latex has good dispersion and stability. The analysis of properties show

that it is a qualified latex.

2. The maximum stability of SBS-LMBE was obtained at emulsifier concentration 1.0%.

The addition of SBS latex increases the difficulty of bitumen emulsification.

3. SBS latex can make the penetration decrease and softening point and 5ıC ductility

increase, which means that SBS latex can play a role in improving the properties of

bitumen.

4. SBS latex causes the chemical component and colloidal index of bitumen to change.

Saturates and aromatics decrease, whereas resins and asphaltenes increase. Through

analysis of the relationship between the components and properties it is shown that

the component changes of SBS latex make it beneficial to the properties of bitumen.

References

Becker, Y., Mendez, M. P., and Rodriguez, Y. (1999). Polymer modified asphalt. Wisconsin Tech.

9:39–50.

Cai, H. M. (2007). The study on the preparation and performance of modified asphalt emulsion.

China University of Petroleum (in Chinese).

Cai, H., and Zhang, J. (2006). The synthesis research of emulsified SBS and effect of it to modified

emulsified asphalt. Petroleum Asphalt 22–24. (in Chinese)

Cavaliere, M. G., and Diani, E. (1996). Dynamic mechanical characterization of binder and asphalt

concrete. Proceedings of Euroasphalt and Eurobitume Congress, Stolkholm, June 16–18,

pp. 114–118.

International Slurry-Surfacing Association. (1991). Inspector’s Manual. Washington, DC: Interna-

tional Slurry-Surfacing Association.

International Slurry-Surfacing Association. (1996). Recommended Performance Guidelines for

Micro-surfacing. Washington, DC: International Slurry-Surfacing Association.

Isacsson, U., and Lu, X. (1995). Testing and appraisal of polymer modified road bitumens: State

of the art. Materials and Structures 28:139–159.

Liang, W. (2000). Heavy Oil Chemistry. Dongying: China Petroleum University Press. (in Chinese)

Loeber, L., Muller, G., and Morel, J. (1998). Bitumen in colloidal science: Chemical, structural

and rheological approach. Fuel 77:1443–1450.

Mushrush, G. W., and Speight, J. G. (1998). Instability and incompatability of petroleum products.

In: Petroleum Chemistry and Refining, Speight, J. G. (Ed.). Washington, DC: Taylor & Francis.

Romero, N. (2002). Viscoelastic properties and stability of highly concentrated bitumen in water

emulsions. Colloid. Surface. Physicochem. Eng. Aspect. 204:271–284.

SINOPEC Qilu Company Refinery (2005). China Industry Method on Storage Stability of Emulsi-

fied Bitumen. Dongying, China: China University of Petroleum. (in Chinese)

SINOPEC Qilu Company Refinery (1992). China Industry Method on Asphalt Composition. Dongy-

ing, China: China University of Petroleum. (in Chinese)

Sitz, G. E., and Maysville, R. (1991). Process for the Production of Polymer Modified Asphalts

and Asphalt Emulsions. M.S. Patent No. 5,109,610.

Weiss, J., and McClements, D. J. (2000). Mass transport phenomena in oil-in-water emulsions

containing surfactant micelles: Solubilization. Langmuir 16:2145.

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