SBR masterbatches with high silica loading by latex compounding method

Accepted Manuscript Preparation and performance of silica/SBR masterbatches with high silica loading by latex compounding method Yan Gui, Junchi Zheng, Xin Ye, Dongli Han, Meimei Xi, Liqun Zhang PII:

S1359-8368(15)00401-1

DOI:

10.1016/j.compositesb.2015.07.001

Reference:

JCOMB 3661

To appear in:

Composites Part B

Received Date: 22 April 2015 Revised Date:

27 June 2015

Accepted Date: 1 July 2015

Please cite this article as: Gui Y, Zheng J, Ye X, Han D, Xi M, Zhang L, Preparation and performance of silica/SBR masterbatches with high silica loading by latex compounding method, Composites Part B (2015), doi: 10.1016/j.compositesb.2015.07.001. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Preparation and performance of silica/SBR masterbatches with high silica loading by latex compounding method Yan Guib, Junchi Zhengb, Xin Yeb, Dongli Hanb, Meimei Xib, Liqun Zhanga,b,* a

Beijing 100029, PR China

Engineering Research Center of Elastomer Materials on Energy Conservation and Resources, Ministry of

SC

b

RI PT

State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology,

Education, Beijing 100029, PR China

M AN U

* Corresponding author.

Tel.: +86-010-64423312; fax: +86-010-64443413; E-mail address: [email protected]. Address: P.O. Box 57, Beijing University of Chemical Technology, Beisanhuan East Road, Beijing 100029, China.

TE D

Abstract: With the help of a new coupling agent Si747, silica water slurry and styrene-butadiene rubber (SBR) latex were successfully co-coagulated by the latex compounding method, even silica/SBR

EP

masterbatches with silica loading as high as 200phr could be prepared by such method. Compared to the traditional dry blending method, the latex compounding method had lower energy consumption during

AC C

mixing and better silica dispersion in rubber matrix. Meanwhile, the effect of the amount of silica in the SBR latex on the properties of silica/SBR composites was investigated, and the results showed that the larger the amount of silica in the rubber matrix, the stronger the filler network. The performance of these composites was good and the dispersion of silica was relatively homogeneous. Furthermore, the masterbatches with high silica loading were mixed with emulsion polymerized styrene-butadiene rubber (ESBR) or solution polymerized styrene-butadiene rubber (SSBR). The silica dispersed better in ESBR

1

ACCEPTED MANUSCRIPT than in SSBR. Keywords: A.Polymer-matrix composites (PMCs); A.Particle-reinforcement; E.Surface

RI PT

treatments.

1. Introduction

SC

In the rubber industry, fillers are used for property improvement or cost reduction [1][2]. Carbon black and silica are the most commonly used reinforcing fillers in elastomeric formulations[2]-[5]. Especially,

M AN U

silica has been applied in tread rubber for many years to reduce the fuel consumption of vehicles[6]. However, the high polarity and numerous hydroxyl groups of the silica surface make silica agglomerate tendentiously, resulting in poor dispersion of silica in the rubber matrix and weak rubber-filler interaction[7]. Different kinds of coupling agents are widely used in reducing the hydroxyl groups on the

TE D

silica surface[8], but the traditional dry blending way[9]-[11] of adding coupling agents to silica while mixing silica with rubber at the same time may suffer from problems such as low efficiency and high

procedures[12].

EP

processing temperature, which can cause high energy consumption and complex compounding

AC C

The latex compounding method was developed to solve the problem of incompatibility between the rubber and fillers and to improve the dispersion of fillers in the rubber matrix. The method was used to prepare starch/SBR composites[13] and starch/NR composites[14]. Clay was added into SBR latex[15] or NR latex[16] by this method. There were other fillers such as carbon nanotubes[17] or graphene[18] filled in rubber matrix by this method to form high-performance nanocomposites. In this study, we prepared silica/SBR masterbatches by the latex compounding method, which could

2

ACCEPTED MANUSCRIPT prevent dust from floating in the air during processing. Moreover, the latex compounding method to prepare masterbatches was less abrasive and scratching to machines during mixing on the two-roll mill in contrast with the traditional dry blending way of directly mixing silica with rubber. However, we added a

RI PT

newly invented coupling agent Si747 into silica water slurry before mixing the slurry with SBR latex. The new coupling agent was easy to manipulate and could result in extremely high silica loading in

SC

masterbatches. Furthermore, the masterbatches with high silica loadings could be used as fillers for other rubbers to produce environmentally friendly composites.

M AN U

In the rubber industry, traditional dry blending could lead to severe friction between silica particles and abrasion to machines, and might result in high processing temperatures[12], so the production of silica/rubber composites always need multistage processes of mixing and cooling, while our latex compounding method could achieve continuous production. However, in this study, we separated the

TE D

mixing procedure into three stages, supplemented a heating process on the hot roller during the preparation of silica/SBR compounds so that we could emulate industrial conditions and get better

EP

dispersion of silica in the rubber matrix as well.

The structure and dosage of silane coupling agents has great influences on the modification and of

silica/SBR

AC C

properties

composites[19][22].

Since

bis-(3-triethoxysilylpropyl)-tetrasulfide

(Si69)[23]-[26], the most commonly used coupling agent in the rubber industry, is oil soluble and was invalid in our latex compounding method, we chose Superlink Si747 instead, which is slightly soluble in water. We studied the effect of Si747 on the preparation of silica/SBR masterbatches. Furthermore, we compared the performance of silica/SBR composites prepared by our latex compounding method with that of silica/SBR composites prepared by the traditional dry blending way. In addition, we investigated

3

ACCEPTED MANUSCRIPT the effect of silica content on performance of silica/SBR composite, prepared high-silica-loading masterbatches and measured the properties of mixtures of these masterbatches with ESBR or SSBR.

RI PT

2. Experimental 2.1 Materials

SC

Commercial SBR (styrene content: 23.60 wt%) latex was purchased from Jilin Chemical Industrial Co., Ltd. (China), ESBR 1502 (styrene content: 23.38 wt%) and SSBR T2003 (styrene content: 25.37 wt%)

M AN U

were bought from Tianjin Changli Rubber Trade Co., Ltd. (China), industrial silica (nanoparticle size: 20 nm~30 nm, BET specific surface: 191.06 m2/g) water slurry was produced by Shandong Linglong Tyre Co., Ltd. (China), and 3-mercaptopropyl ethyoxyl di(tridecyl-pentaethyoxyl)silane (Si747) was obtained

TE D

from Shanghai Cheeshine Chemicals Co., Ltd. (China). All other materials were commercially available.

2.2 Preparation of silica/SBR masterbatches

EP

The solid content of the industrial silica water slurry was measured, and water was added into the slurry to dilute it to the concentration of 10% (e.g., 70 g of silica nanoparticles in 630 g of water). The

AC C

silane coupling agent (Si747) was added into the slurry. The mass ratio of Si747 to silica was 1 to 10 (e.g., 7 g of Si747 for every 70 g of silica nanoparticles). The slurry was stirred for 0.5 h and then blended with SBR latex. The solid content of the SBR latex was confirmed in advance, and the mass ratio of silica to SBR was 70% (e.g., 70 g of silica nanoparticles for every 100 g of SBR). The mass ration of silica to SBR was changed to 40%, 100%, 150%, and 200% later on to prepare masterbatches with different silica loadings. Afterwards, the mixture of silica and SBR latex was stirred for another 0.5 h and flocculated

4

ACCEPTED MANUSCRIPT with 2% CaCl2 solution. Finally, the sediments were washed by water for several times and dehydrated in a drying oven at 60℃ for 36 h to obtain silica/SBR masterbatches.

RI PT

2.3 Preparation of silica/SBR composites

The formulation for silica/SBR compound is shown in Table 1. A silica/SBR compound was obtained

SC

in two mixing stages. First, the masterbatch was masticated on a 6-inch two-roll mill (Shanghai Rubber Machinery Works No.1, China) with condensate water flowing in the machine tubes to keep the temperature

down.

Then

zinc

oxide,

stearic

acid,

and

M AN U

processing

N-isopropyl-N’-phenyl-1,4-phenylenediamine were added to the masterbatch one by one. Second, the compound was plasticated for 5 min on a hot two-roll mixing mill (Shanghai Rubber Machinery Works, China) at 150℃and then naturally cooled down to room temperature. Finally, one after another,

TE D

N-cyclohexyl-2-beozothiazole sulfonamide, diphenyl guanidine, and sulfur were uniformly blended with the cooled compound on the former 6-inch mill. The scorch time (T10) and optimum cure time (T90) of the

EP

compound were obtained by a P3555B2 Disc Vulkameter (Beijing Huanfeng Chemical Machinery Trial Plant, China). The composite was prepared by a XLB-D350×350-type Automatic Operation Vulcanizing

AC C

Press (Huzhou Dongfang Machinery Co., Ltd., China). The compound was vulcanized at 150℃ in a standard mold of 2-millimeter thickness to produce the silica/SBR composite. In order to compare the latex compounding method with the traditional dry blending method, we took two videos to record the procedure of preparing silica/SBR compounds on the two-roll mill by the two different methods. In the traditional dry blending method, Si747 and silica powder (obtained from the industrial silica water slurry dried in the oven at 60℃ for 48 h) were directly blended with ESBR1502 on

5

ACCEPTED MANUSCRIPT the two-roll mill before being mixed with other materials as shown in Table 1. The formulation for blending masterbatches with ESBR or SSBR is shown in Table 2.

RI PT

2.4 Characterizations

The vulcanization characteristics of silica/SBR compounds were measured at 150℃ by a P3555B2

SC

Disc Vulkameter (Beijing Huanfeng Chemical Machinery Trial Plant, China).

The filler dispersion was observed under a Tecnai G2 20 TEM (FEI Co., USA) with an accelerating

M AN U

voltage of 200 kV. The thin sections for TEM observations were cut by a microtome at -100℃ and collected on copper grids.

The filler dispersion was also observed under a Multimode8 AFM (Bruker Co, Germany) in the

testing.

TE D

ScanAsyst Mode at room temperature. The thin sections for AFM observations were polished before

The dynamic rheological properties of the silica/SBR composites were analyzed by an RPA2000

frequency of 1 Hz.

EP

(Alpha Technologies Co., USA) at 60℃. The strain amplitude was varied from 0.1% to 450% at the test

AC C

The viscoelastic properties of the composites were measured on a VA3000 DMTA (01 Db-Metravib, France) in the tension mode. The temperature was varied from -60℃ to 80℃ at a heating rate of 3℃ /min. The test frequency was 10 Hz and the strain amplitude was 0.1%. The static mechanical properties of the composites were investigated according to ASTM D638 by a CMT4104 Electrical Tensile Tester (Shenzhen SANS Test Machine Co., China) at a crosshead speed of 500 mm/min.

6

ACCEPTED MANUSCRIPT The energy consumption in preparing silica/SBR composites was determined by a 0.5-L internal mixer (Shanghai Kechuang Rubber and Plastic Machinery Equipment Co., China). The rotor speed was set to 40

RI PT

r/m.

3. Results and discussion

SC

3.1 Effect of Si747 on preparation of masterbatches

The pure silica water slurry without coupling agent is stirred as shown in Fig.1 A1, and SBR latex is

M AN U

added into the slurry (Fig.1 A2). The mixture is flocculated with CaCl2 solution (Fig.1 A3) and let stand for a few minutes (top view and side view are shown in Fig.1 A4 and A5, respectively). The silica compounded poorly with SBR because the masterbatch is largely clustered and the water phase is white and turbid with lots of silica in it. The procedure of adding the coupling agent Si747 into the silica water

TE D

slurry and filling the SBR latex is shown in Fig.1 B1-B5. With the addition of Si747 (Fig.1 B1), the final suspension is stratified quickly. The masterbatch is flocculated and settled at the bottom of the beaker as

EP

granulated sediments, while the supernatant is clear water. Furthermore, some of the turbid liquid (from the figure in Fig.1 A4) is transferred to and let stand in

AC C

Bottle 1 and the mixture of masterbatch with Si747 is transferred to and let stand in Bottle 2 as shown in Fig.2. When the turbid liquid stands still for one minute, Bottle 1 (prepare masterbatch without Si747) is white with lots of silica in it. But the mixture in Bottle 2 (prepare masterbatch with Si747) presents a stratified state, with white granulated masterbatches settled at the bottom of the bottle. After one day, there are lots of white sediments at the bottom of Bottle 1, which are obviously silica that has not compounded with SBR and become losses in the white turbid liquid during flocculation, while nothing

7

ACCEPTED MANUSCRIPT changes in Bottle 2. The homogeneous dispersion of silica particles in the water phase after stirring is shown in Fig.3 A. SBR is nonpolar, but silica has a polarity because of the numerous hydroxyl groups on its surface. As a

RI PT

consequence, the compatibility between SBR and silica is poor. When SBR latex alone is added into the silica water slurry (Fig.3 B), the compounding effect of SBR particles and silica is poor. As shown in

SC

Fig.1 A, the silica aggregates while SBR flocculated with little silica in it. What we hoped is that silica particles can disperse homogeneously and compound with SBR to form a good filler-rubber network with

M AN U

strong interaction between the filler and rubber matrix, as shown in Fig.3 C. Fig.1 B above shows that Si747 can greatly improve the compatibility between silica and SBR and enhance the compounding effect of silica and SBR. Si747 is added in preparing the masterbatches in the experiments discussed below.

TE D

3.2 Comparison of latex compounding method and traditional dry blending method In the traditional dry blending method to produce silica/SBR compounds, silica powder and Si747 are

EP

directly mixed with SBR on the two-roll mill. This traditional method is more time consuming than our latex compounding method, as shown in the video given in the supplemental material. It takes more than

AC C

6 minutes to add silica and Si747 into SBR by the traditional method, but the masterbatches can be masticated on the two-roll mill directly without this step, thus saving time and energy. Meanwhile, blending silica with SBR can cause a dust problem, high processing temperature, and serious abrasion to the two-roll mill. In the following comparisons of silica/SBR composites obtained by the two different methods, “dry” refers to the composites prepared by the traditional dry blending method, and “wet” refers to the composites prepared by the latex compounding method. The formulation to prepare silica/SBR

8

ACCEPTED MANUSCRIPT compounds is shown in Table 1.

3.2.1 Micromorphology of silica/SBR composites by TEM

RI PT

The TEM images in Fig.4 show the filler dispersion in silica/SBR composites prepared by the traditional dry blending method (A) and our latex compounding method (B). In the TEM images, the dark

SC

phase represents the dispersed silica nanoparticles. The dispersion of silica in the rubber matrix is an important factor in determining the comprehensive properties of the silica/SBR composites. A uniform

M AN U

dispersion, especially at the nanoscale, leads to superior properties of the composites. On the contrary, the filler aggregates in the rubber matrix form stress concentration points, resulting in inferior macroscopic properties such as the static and dynamic mechanical properties[22]. In Fig.4 A, large silica aggregates are observed in the rubber matrix, an indication of poor rubber-filler interaction. Fig.4 B shows less silica

TE D

aggregates and more homogeneous dispersion than Fig.4 A because of the addition of Si747 to the silica water slurry, which reduces the aggregation of silica and improves the silica dispersion in the SBR latex

EP

in the preparation of masterbatches. The latex compounding method of producing masterbatches in advance leads to more uniform dispersion of silica in the rubber matrix than the traditional dry blending

AC C

method of producing silica/SBR composites.

3.2.2 Dynamic rheological property of silica/SBR compounds by RPA The variation in storage molulus (G’) with strain amplitude of the silica/SBR compounds, as shown in Fig.5, is used to analyze the filler-network structure. For both the wet and dry compounds, the storage modulus decreases with the increase of strain amplitude. Furthermore, the two curves obtained by RPA

9

ACCEPTED MANUSCRIPT are almost coincident, indicating nearly equivalent filler network structures in the rubber matrix.

3.2.3 Viscoelastic property of silica/SBR composites by DMTA

RI PT

The temperature dependence of dynamic mechanical viscoelasticity of the silica/SBR composites is shown in Fig.6. It can be seen that the wet composite has a higher tanδ at the glass transition temperature

SC

than the dry composite because the better dispersion of silica in the rubber matrix weakens the filler network structure[27] and reduces the amount of rubber molecular chains trapped in the filler

M AN U

network[28][29]. With more rubber chains participating in chain segment relaxation, tanδ becomes higher.

Meanwhile, it is well known that the hysteresis of tread composites, characterized by tanδ at 60℃, is a key parameter associated with the rolling resistance of tires[29]. In addition, the hysteresis at 0℃is related

TE D

to the high-frequency nature of the dynamic strain involved in the skid process[30]. Therefore, high performance of tread rubber should have the combination of a high value of tanδ at 0℃ and a low value

EP

of tanδ at 60℃[31]. As shown in Table 3, the wet composite has a slightly higher tanδ at 0℃ but a much higher tanδ at 60℃ than those of the dry composite, indicating that the wet skid resistance can be

AC C

improved by the latex compounding method, but the rolling resistance needs to be reduced by other means.

3.2.4 Static mechanical properties of silica/SBR composites The static mechanical properties of silica/SBR composites are measured and the results are shown in Fig.7 and Table 4. It can be observed that the tensile stress, elongation at break, and tension set of the wet

10

ACCEPTED MANUSCRIPT composite are slightly higher while the moduli at 100% and 300%, tear resistance, and Shore A hardness are lower than those of the dry composite.

RI PT

3.2.5 Energy consumption by internal mixer

We investigate the energy consumption in preparing silica/SBR compounds by an internal mixer, and

SC

the results are shown in Fig.8. In Fig.8, “wet” refers to the energy consumption in mixing the masterbatch prepared by our latex compounding method with other ingredients in the internal mixer, and “dry” refers

M AN U

to the energy consumption in preparing silica/SBR compounds by the traditional dry blending method, i.e., directly mixing SBR, silica, Si747, and other ingredients in the internal mixer. It can be seen that our latex compounding method takes less time and consumes less energy than those of the traditional dry blending method, consistent with what is observed in our video in the supplemental material.

TE D

Thus, the latex compounding method of producing silica/SBR composites makes a better dispersion of silica in rubber matrix, and keeps properties approximate to those of composite prepared by traditional

EP

dry blending method. Meanwhile, the latex compounding method achieves environmentally friendly,

AC C

lower energy consumption and continuously process by preparing masterbatches successfully.

3.3 Effect of silica content on performance of silica/SBR composites We prepare masterbatches by filling SBR latex with different amounts of silica (40 phr, 70 phr, 100 phr, 150 phr, and 200 phr) (see Fig.9) by using the latex compounding method. At moderate silica contents, the masterbatches exist in the form of small granules. However, excessive amounts of silica can cause poor compounding effect, and the masterbatch appears as large, hard chunks, as shown in Fig.9 E.

11

ACCEPTED MANUSCRIPT Since the masterbatches filled with 150 phr and 200 phr of silica are too hard and hot to handle during mixing on the two-roll mill, only the masterbatches filled with 40 phr, 70 phr, and 100 phr of silica are

3.3.1 Vulcanization characteristics of silica/SBR compounds

RI PT

used in the characterizations below.

SC

Fig.10 and Table 5 show the vulcanization characteristics of silica/SBR compounds. Fig.10 shows that the incipient torque increases with the increase of silica content, and the torque at 100 phr is much higher

M AN U

than those at the other two silica contents, probably because of the strong interaction between the excessive silica in the rubber matrix. T90 increases with increasing silica content, as shown in Table 5, because the vulcanizers were absorbed by the excess silica. As a consequence, the curing rate and curing

TE D

efficiency were lowered during the vulcanization.

3.3.2 Micromorphology of silica/SBR composites by AFM

EP

The AFM images in Fig.11 show the filler dispersion in the silica/SBR composites. In the AFM images, the light color represents the dispersed silica nanoparticles. As analyzed above, homogeneous dispersion

AC C

at the nanoscale could lead to superior properties of composites. In Fig.11, there are few large silica aggregates in the rubber matrix, an indication of strong rubber-filler interaction. In particular, the composite with silica loadings as high as 100 phr has a uniform dispersion of silica in the rubber matrix, indicating that the latex compounding method is a good way to improve the dispersion of silica, even at high silica contents.

12

ACCEPTED MANUSCRIPT 3.3.3 Dynamic rheological property of silica/SBR compounds by RPA The plots of storage molulus (G’) versus strain amplitude for the silica/SBR compounds obtained by the latex compounding method is shown in Fig.12. The decrease in storage modulus with the increase in

RI PT

strain amplitude for rubber compound is called the Payne effect[32]. In Fig.12, with the increase of silica content, the incipient storage modulus increases and the plateau region narrows. The implication is that

SC

with increasing silica content, the Payne effect increases, the filler network strengthens, and the filler

M AN U

distribution in the rubber matrix worsens.

3.3.4 Viscoelastic property of silica/SBR composites by DMTA

The temperature dependence of dynamic viscoelasticity of the silica/SBR composites obtained by the latex compounding method is shown in Fig.13. It can be seen that the value of tanδ at the glass transition

TE D

temperature decreases with the increase of silica content. The silica/SBR composites containing 100 phr silica has a relatively uniform dispersion, which reduced the destruction and reconstruction of the filler

EP

network, lowered energy consumption, so the composites containing 100 phr silica had a relatively lower value of tanδ at 60℃. Meanwhile, the value of tanδ at 0℃ increases with increasing silica content in the

AC C

silica/SBR composite, as shown in Table 6. That is, the composite with 100 phr of silica has the best wet skid resistance of the three composites.

3.3.5 Static mechanical properties of silica/SBR composites The static mechanical properties of the silica/SBR composites prepared by the latex compounding method are measured, and the results are shown in Fig.14 and Table 7. It can be observed that the tensile

13

ACCEPTED MANUSCRIPT stress, elongation at break, and tear resistance of the silica/SBR composites decrease, but the moduli at 100% and 300% and Shore A hardness increase with increasing silica content. According to molecular chain slipping theory, the more silica particles in rubber matrix, the smaller space between silica particles，

RI PT

so the slippage of rubber chains between silica particles was confined, resulting in poor properties of the silica/SBR composites

SC

Thus, the silica content affects the performance of silica/SBR composites seriously. The latex compounding method is a good way to improve the dispersion of silica, and with high silica content, the

M AN U

static mechanical properties of the composites are relatively poor. But the increasing of silica content can improve the wet skid resistance of the silica/SBR composites.

3.4 Masterbatches with high silica loadings to mix with different SBRs

TE D

Masterbatches with high silica contents are successfully prepared by the latex compounding method. Considering the problems during mixing process of preparing silica/SBR compounds by the traditional

EP

dry blending method, we could make high-silica-loading masterbatches first, which already have a uniform dispersion of silica, and then use them to fill other rubbers to form composites that meet our

AC C

needs. We prepare the masterbatch filled with 200 phr of silica by the latex compounding method, and then mix it with ESBR or SSBR on the two-roll mill. In the discussion below, ESBR and SSBR refer to ESBR and SSBR mixing with the masterbatch, respectively.

3.4.1 Vulcanization characteristics of silica/ESBR and silica/SSBR compounds Fig.15 and Table 8 show the vulcanization characteristics of silica/ESBR and silica/SSBR compounds.

14

ACCEPTED MANUSCRIPT It can be seen in Fig.15 that T10 and T90 are shorter and the torque higher for SSBR than for ESBR. Furthermore, the slightly higher torque difference value for SSBR than for ESBR reflects the higher crosslink density of SSBR, which is determined by the structure of SSBR and the interaction between

RI PT

silica and SSBR.

SC

3.4.2 Dynamic rheological property of silica/ESBR and silica/SSBR compounds by RPA

The strain amplitude dependence of the storage molulus (G’) of the silica/ESBR and silica/SSBR

M AN U

compounds, as shown in Fig.16, is used to analyze the filler network. G’ decreases with the increase of strain amplitude for both ESBR and SSBR. The higher incipient storage modulus of SSBR shows that SSBR exhibits a higher Payne effect, which further indicates a poorer filler dispersion and a stronger filler network in the rubber matrix, all because of the relatively poor compatibility between SSBR and the

TE D

masterbatch, which is made from SBR latex.

EP

3.4.3 Viscoelastic property of silica/ESBR and silica/SSBR composites by DMTA The temperature dependence of dynamic viscoelasticity of the silica/SBR vulcanizates is shown in

AC C

Fig.17. It can be seen that ESBR has a much higher value of tanδ at the glass transition temperature than SSBR, resulting in a better dispersion of silica, less rubber chains trapped in the filler network and more rubber chains participating in chain segment relaxation. Meanwhile, SSBR has higher values of tanδ at 0℃ and 60℃ than ESBR, as shown in Table 9, indicating that SSBR has a higher ability to improve the wet skid resistance without decreasing the rolling resistance. Heinrich [33] used the idea of polymer confinement effects to explain the advantage of silica in

15

ACCEPTED MANUSCRIPT combination with pure SSBR. Silica has pores in the nanometer regime, and the injection of the linear SSBR into the nanopores during mixing is easier than that of the branched ESBR. As a result, SSBR has a stronger interaction with silica and a lower hysteresis during dynamic deformation at low frequencies

RI PT

than ESBR. Therefore, SSBR has a higher rolling resistance, contrary to our results. The disagreement can be explained by the poor compatibility between SSBR and the masterbatch, as indicated by the RPA

SC

results above.

M AN U

3.4.4 Static mechanical properties of silica/ESBR and silica/SSBR composites

The static mechanical properties are measured, and the results are shown in Fig.18 and Table 10. It can be seen that ESBR and SSBR have similar static mechanical properties except tensile stress and tear resistance. In the process of tearing, we can observe that the avulsion began from the right angle to

TE D

another tortuous direction as a result of the agglomeration of silica and the poor compatibility between the silica, SSBR, and masterbatch. As a consequence, SSBR has an unusually high tear resistance, but a

EP

relatively low tensile stress.

However, the performance of ESBR and SSBR with 200 phr of silica is not too bad, although the

AC C

dispersion of silica in the blended matrix of SSBR and the masterbatch is inhomogeneous.

4. Conclusions

The latex compounding method is used to prepare SBR masterbatches with high loadings of silica with the help of Si747, a coupling agent. The coupling agent significantly improves the dispersion of silica in the water phase in the preparation of silica/SBR masterbatches. The method is environmentally friendly

16

ACCEPTED MANUSCRIPT and time saving, and has low energy consumption. TEM and DMTA show that the dispersion of silica in the rubber matrix and the wet skid resistance of the silica/SBR composite are better than those of the silica/SBR composites prepared by the traditional dry blending method.

RI PT

In addition, our latex compounding method can produce masterbatches filled with different amounts of silica. Even at an amount of silica double that of SBR, the dispersion of silica is relatively uniform. The

SC

wet skid resistance increases with increasing silica content. However, too much silica in the rubber can lead to high Payne effect.

M AN U

The masterbatches filled with 200 phr of silica are blended with ESBR and SSBR. The silica/SSBR compound has a short cure time, a distinct advantage in industrial production. But the dispersion of silica is better in ESBR than in SSBR. And the rolling resistance of silica/ESBR composite is much lower than that of the silica/SSBR composite. We hope that the masterbatches with high silica loading can be applied

TE D

to other rubbers to meet various needs and become green materials in the future, and the preparation of silica/SBR masterbatches by the latex compounding method can have a practical and profound

EP

application in the rubber industry.

AC C

5. Acknowledgements The

research

was

supported

by

the

National

Basic

Research

Program

of

China

2015CB654700(2015CB654704) and the Foundation for Innovative Research Groups of the NSF of China (51221002).

References [1] Liliane B. The Reinforcement of Elastomeric Networks by Fillers. Macromol Mater. Eng 2004; 289(7):607-21. 17

ACCEPTED MANUSCRIPT [2] Rattanasom N, Saowapark T, Deeprasertkul C. Reinforcement of natural rubber with silica/carbon black hybrid filler. Polym Test 2007; 26:369-77. [3] Hassan HH, Ateia E, Darwish NA, Halim SF, El-Aziz AKA. Effect of filler concentration on the physico-mechanical properties of super abrasion furnace black and silica loaded styrene butadiene rubber. Mater Des 2012; 34:533-40. [4] Noriman NZ, Ismail H. Properties of Styrene Butadiene Rubber (SBR)/Recycled Acrylonitrile Silane Coupling Agent, Si69. J Appl Polym Sci 2012; 124:19-27.

RI PT

Butadiene Rubber (NBRr) Blends: The Effects of Carbon Black/Silica (CB/Sil) Hybrid Filler and [5] Brinke JWt, Dehnath SC, Reuvekamp LAEM, Noordermeer JWM. Mechanisic aspects of the role of coupling agents in silica-rubber composites. Compos Sci Technol 2003; 63:1165-74.

[6] Hilonga A, Kim JK, Sarawade PB, Quang DV, Shao GN, Elineema G, Kim HT. Synthesis of mesoporous silica with superior properties suitable for green tire. J Ind Eng Chem 2012; 18:1841-4.

SC

[7] Park SJ, Cho KS. Filler-elastomer interactions: influence of silane coupling agent on crosslink density and thermal stability of silica/rubber composites. J Coll Interface Sci 2003; 267:86-91. [8] Bertora A, Castellano M, Marsano E, Alessi M, Conzatti L, Stagnaro P, Colucci G, Priola A,

M AN U

Turturro A. A new modifier for silica in reinforcing SBR elastomers for the tyre industry. Macromol Mater Eng 2011; 296:455-64.

[9] Sae-oui P, Sirisinha C, Thepsuwan U, Hatthapanit K. Roles of silane coupling agents on properties of silica-filled polychloroprene. Eur Polym J 2006; 42(3):479-86.

[10] Stefanska KS, Walkowiak J, Krysztafkiewicz A, Jesionowski T. Polymer adsorption on the surface of highly dispered silica. Appl Surf Sci 2008; 254:3591-600.

[11] Dohi H, Horiuchi S. Locating a silane coupling agent in silica-filled rubber composites by EFTEM.

TE D

Langmuir 2007; 23(24):12344-9.

[12] Li Y, Han BY, Liu L, Zhang FZ, Zhang LQ, Wen SP, Lu YL, Yang HB, Shen J. Surface modification of silica by two-step method and properties of solution styrene butadiene rubber (SSBR) nanocomposites filled with modified silica. Compos Sci Technol 2013; 88:69-75. [13] Wu YP, Qi Q, Liang GH, Zhang LQ. A strategy to prepare high performance starch/rubber 65:109-13.

EP

composites: In situ modification during latex compounding process. Carbohydr Polym 2006; [14] Izmar MH, Afiq MM, Azura AR. Effects of different additions of sago starch filler on physical and

AC C

biodegradation properties of pre-vulcanized NR latex composites. Compos Part B Eng 2012; 43:2746-50.

[15] Zhang LQ, Wang YZ, Wang YQ, Sui Y, Yu DS. Morphology and Mechanical Properties of Clay/Styrene-Butadiene Rubber Nanocomposites. J Appl Polym Sci 2000; 78:1873-8.

[16] Wang YQ, Zhang HF, Wu YP, Yang J, Zhang LQ. Structure and properties of strain-induced crystallization rubber-clay nanocomposites by co-coagulating the rubber latex and clay aqueous suspension. J Appl Polym Sci 2005; 96:318-23. [17] Alimardani M, Abbassi-Sourki F, Bakhshandeh GR. An investigation on the dispersibility of carbon nanotube in the latex nanocomposites using rheological properties. Compos Part B Eng 2014; 56:149-56. [18] Matos CF,

Galembeck F,

Zarbin AJG.

Multifunctional and

environmentally

friendly

nanocomposites between natural rubber and graphene or graphene oxide. Carbon 2014; 78:469-79. [19] Jesionowski T, Zurawska J, Krysztafkiewicz A, Pokora M, Waszak D, Tylus W. Physicochemical 18

ACCEPTED MANUSCRIPT and morphological properties of hydrated silicas precipitated following alkoxysilane surface modification. Appl Surf Sci 2003; 205:212-24. [20] Jesionowski T, Ciesielczyk F, Krysztafkiewicz A. Influence of selected alkoxysilanes on dispersive properties and surface chemistry of spherical silica precipitated in emulsion media. Mater Chem Phys 2010; 119:65-74. [21] Xie YJ, Hill CAS, Xiao ZF, Militz H, Mai C. Silane coupling agents used for natural fiber/polymer

RI PT

composites: A review. Compos Part A 2010; 41:806-19. [22] Li Y, Han BY, Wen SP, Lu YL, Yang HB, Zhang LQ, Liu L. Effect of the temperature on surface modification of silica and properties of modified silica filled rubber composites. Compos Part A 2014; 62:52-9.

[23] Suzuki N, Ito M, Yatsuyanagi F. Effects of rubber/filler interactions on deformation behavior of silica filled SBR systems. Polym 2005; 46:193-201.

SC

[24] Sae-oui P, Thepsuwan U, Hatthapanit K. Effect of curing system on reinforcing efficiency of silane coupling agent. Polym Test 2004; 23:397-403.

[25] Ansarifar A, Azhar A, Ibrahim N, Shiah SF, Lawton JMD. The use of a silanised silica filler to

M AN U

reinforce and crosslink natural rubber. Int J Adhes Adhes 2005; 25:77-86.

[26] Castellano M, Conzatti L, Costa G, Falqui L, Turturro A. Surface modification of silica:1. Thermodynamic aspects and effect on elastomer reinforcement. Polym 2005; 46:695-703. [27] Robertson CG, Lin CJ, Rackaitis M, Roland CM. Influence of particle size and polymer–filler coupling on viscoelastic glass transition of particle-reinforced polymers. Macromolecules 2008; 41(7):2727-31.

[28] Ma PC, Kim JK, Tang BZ. Functionalization of carbon nanotubes using a silane coupling agent.

TE D

Carbon 2006; 44(15):3232-8.

[29] Wang MJ, Mahmud K, Murphy LJ, Patterson WJ. Carbon-silica dual phase filler, a new generation reinforcing agent for rubber. Part I. Characterization. KGK 1998; 51(5):348-60. [30] Zeng ZQ, Yu HP, Wang QF, Lu G. Effects of coagulation processes on properties of epoxidized natural rubber. J Appl Polym Sci 2008;109(3):1944-9.

EP

[31] Takino H, Nakayama R, Yamada Y, Kohjiya S, Matsuo T. Viscoelastic properties of elastomers and tire wet skid resistance. Rubber Chem Technol 1997; 70(4):584-94. [32] Payne AR. The dynamic properties of carbon black-loaded natural rubber vulcanizates. Part I. J Appl

AC C

Polym Sci 1962; 6(19):57-63.

[33] Heinrich G, Vilgis TA. Why Silica Technology Needs S-SBR in High Performance Tires? : The Physics of Confined Polymers in Filled Rubbers. KGK 2008; 61(7/8):368, 370-6.

Figure Captions

Figure 1 Preparation of masterbatches (A) without Si747 and (B) with Si747 Figure 2 Turbid liquid standing still for (A) one minute and (B) one day Figure 3 (A) Homogeneous dispersion of silica in water; (B) dispersion of silica after addition of SBR latex into silica water slurry; (C) ideal dispersion (homogenous dispersion of silica in SBR matrix) Figure 4 TEM images of silica/SBR composites prepared by (A) traditional dry blending method and (B) latex compounding method Figure 5 Strain amplitude dependence of storage modulus (G’) of silica/SBR compounds 19

ACCEPTED MANUSCRIPT Figure 6 Temperature dependence of loss factor (tanδ) of silica/SBR composites Figure 7 Static mechanical properties of silica/SBR composites Figure 8 Energy consumption in preparing silica/SBR compounds by internal mixer Figure 9 Masterbatches with different silica contents Figure 10 Vulcanization characteristics of silica/SBR compounds Figure 11 AFM images of silica/SBR composites with (A) 40 phr of silica, (B) 70 phr of silica, and (C)

RI PT

100 phr of silica obtained by latex compounding method Figure 12 Strain amplitude dependence of storage modulus (G’) of silica/SBR compounds Figure 13 Temperature dependence of loss factor (tanδ) of silica/SBR composites Figure 14 Static mechanical properties of silica/SBR composites

Figure 15 Vulcanization characteristics of silica/ESBR and silica/SSBR compounds

Figure 16 Strain amplitude dependence of storage modulus (G’) of silica/ESBR and silica/SSBR

SC

compounds

Figure 17 Temperature dependence of loss factor (tanδ) of silica/ESBR and silica/SSBR composites

AC C

EP

TE D

M AN U

Figure 18 Static mechanical properties of silica/ESBR and silica/SSBR composites

20

ACCEPTED MANUSCRIPT Table 1 Formulation of silica/SBR compound

b

Amount/phra

Masterbatch Zinc oxide Stearic acid N-Isopropyl-N’-phenyl-1,4-phenylenediamine N-Cyclohexyl-2-beozothiazole sulfonamide Diphenyl guanidine Sulfur

177.0b 3.0 2.0 1.0 1.5 1.5 1.5

RI PT

a

Material

Parts per hundred of rubber 177 phr of masterbatch=100 phr of SBR+ 70 phr of silica+ 7 phr of Si747

Table 2 Formulation of silica/ESBR or silica/SSBR compound

Amount/phra

SC

Material

112.0b 65 3.0 2.0 2.0 1.5 1.8 0.3 2.3

TE

D

Parts per hundred of rubber 112 phr of masterbatch=35 phr of SBR+ 70 phr of silica+ 7 phr of Si747 Table 3 Loss factor (tanδ) results of silica/SBR composites wet dry

tanδ at 0℃

tanδ at 60℃

0.199 0.197

0.182 0.146

EP

b

Table 4 Static mechanical properties of silica/SBR composites

AC C

a

M AN U

Masterbatch ESBR 1502 or SSBR T2003 Zinc oxide Stearic acid N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenedianine Paraffin N-tert-butylbenzothiazole-2-sulphenamide Bis-(dimethylthiocarbamoyl)-disulfide Sulfur

wet dry

Modulus at 100% (MPa)

Modulus at 300% (MPa)

Tensile stress (MPa)

Elongation at break (%)

Tension set (%)

Tear resistance (kN/m)

Shore A hardness (°)

1.4 1.7

6.1 9.3

23.0 21.5

586 525

24 22

41.4 52.1

55 64

Table 5 Vulcanization characteristics of silica/SBR compounds

40 phr 70 phr 100 phr

T10 (min:s)

T90 (min:s)

Min S (dNm)

Max S (dNm)

Max S – Min S (dNm)

4:16 3:00

12:04 24:08

9.77 14.46

38.16 38.24

28.39 23.78

0:27

33:22

29.81

53.77

23.96

ACCEPTED MANUSCRIPT Table 6 Results of loss factor (tanδ) of silica/SBR composites 40 phr 70 phr 100 phr

tanδ at 0℃

tanδ at 60℃

0.195 0.199 0.230

0.132 0.182 0.156

Modulus at 300% (MPa)

Tensile stress (MPa)

Elongation at break (%)

1.1 1.4 2.4

5.0 6.1 15.9

23.3 23.0 19.9

613 586 335

40 phr 70 phr 100 phr

Tear resistance (kN/m)

Shore A hardness (°)

46.8 41.4 31.5

52 55 64

SC

Modulus at 100% (MPa)

RI PT

Table 7 Static mechanical properties of silica/SBR composites

Table 8 Vulcanization characteristics of silica/ESBR and silica/SSBR compounds T90 (min:s)

Min S (dNm)

Max S (dNm)

Max S – Min S (dNm)

ESBR

7:09

21:29

12.23

50.76

38.53

SSBR

4:48

14:37

15.35

55.80

40.45

M AN U

T10 (min:s)

Table 9 Results of loss factor (tanδ) of silica/ESBR and silica/SSBR composites tanδ at 60℃

0.166 0.175

0.109 0.146

TE

D

ESBR SSBR

tanδ at 0℃

Table 10 Static mechanical properties of silica/ESBR and silica/SSBR composites Tensile stress (MPa)

Elongation at break (%)

Tension set (%)

Tear resistance (kN/m)

Shore A hardness (°)

2.3 2.8

9.1 9.2

20.1 17.4

510 513

30 30

56.1 101.8

72 77

EP

Modulus at 300% (MPa)

AC C

ESBR SSBR

Modulus at 100% (MPa)

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

AC C

EP

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT