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EFFECTS OF DIFFERENT MIXING PROCESSES ON THE DISPERSION AND DYNAMIC PROPERTIES OF FILLERS IN SBR / BR

Научный труд разместил:
Morlugrinn
16 сентября 2020
Автор: Wang Hong Chu Lingling

УДК 678.742

Дата направления в редакцию: 11-03-2020 Дата рецензирования: 12-03-2020 Дата публикации: 20-06-2020

Ван Хонг Чу Линлин

Qingdao Black Cat Carbon Black Technology Co., Ltd., Qingdao, Shandong, 266042

Wang Hong Chu Lingling

Qingdao Black Cat Carbon Black Technology Co., Ltd., Qingdao, Shandong, 266042

ВЛИЯНИЕ РАЗЛИЧНЫХ ПРОЦЕССОВ СМЕШИВАНИЯ НА ДИСПЕРСИОННЫЕ И ДИНАМИЧЕСКИЕ СВОЙСТВА НАПОЛНИТЕЛЕЙ В SBR / BR

EFFECTS OF DIFFERENT MIXING PROCESSES ON THE DISPERSION AND DYNAMIC PROPERTIES OF FILLERS IN SBR / BR

Аннотация (нарус). В данной статье изучается влияние наполнителей на механические и динамические свойства каучука SBR / BR при трех различных последовательностях подачи. После инфильтрации предварительно обработанной белой сажи и каучука и добавления сажи агломерация наполнителя уменьшается, дисперсия белой сажи в каучуке улучшается, и полученная смесь каучука имеет самое высокое содержание связанной резины и лучшие механические свойства и износостойкость Изменяя параметры процесса, такие как температура и скорость перемешивания, обнаруживается, что механические свойства, такие как прочность на разрыв, увеличиваются с увеличением температуры с той же скоростью; при той же температуре, с увеличением скорости, измеритель диспергируемости и сканирующее электронная микроскопия показывают, что дисперсионные свойства технического углерода лучше, механические свойства каучука повышаются, температура сжатия повышается и потери на истирание Акрона уменьшаются, и содержание связанной резины и модуль хранения увеличиваются с увеличением скорости обработки. Когда скорость составляет 90 об / мин, скорость образования связанной резины и модуль накопления уменьшаются.

Abstract (in Eng). In this paper, the effects of fillers on the mechanical and dynamic properties of SBR / BR rubber under three different feeding sequences are studied. After infiltrating the pretreated white carbon black and rubber and adding carbon black, the agglomeration offiller is reduced, the dispersion of white carbon black in rubber is improved, and the blended rubber obtained has the highest content of bound rubber, and better mechanical properties and wear properties. By changing the process parameters, such as mixing temperature and mixing speed, it is found that the mechanical properties such as tensile strength and tear strength increase with the increase of temperature at the same speed; at the same temperature, with the increase of the speed, the dispersibility meter and SEM scanning show that the dispersion properties of carbon black are better, the mechanical properties of the rubber are increased, the compression temperature rise and the Akron abrasion loss are reduced, and the content of bound rubber and the storage modulus are increased with the increase of processing speed. When the speed is 90r / min, the formation rate of bound rubber and the storage modulus are reduced.

Carbon black is the most widely used filler at present, and its reinforcing effect on the mechanical properties of rubber is very significant. With the increasing popularity of "green tires", white carbon black has shown good mechanical properties in modified rubber, and its high elasticity and low heat generation make it the second-most suitable application after carbon black. Although the research on the mechanism of rubber reinforcement has been for a long time, the mechanism is still not clear[1]. For the same preparation

method, the morphology and structure will also be different due to different specific process conditions, where the feeding sequence, process parameters, and solution mixing will have a greater impact. Different mixing processes have a great impact on the dispersion of the filler and the combination of filler and rubber, that is, the formation of bound rubber has a greater impact. The bound rubber is considered to be an important index affecting the mechanical strength of rubber.

In this paper, the effects of mixing process,

including feeding sequence, mixing temperature and mixing speed, on the content of bound rubber, the dispersibility of rubber filler and the dynamic properties of rubber are studied.

1 Experimental part
1.1 Main raw materials

Styrene butadiene rubber (SBR-1712), China Petrochemical, BR9000, Beijing Yanshan Petrochemical, carbon black N234 and white carbon black from Jiangxi Blackcat Carbon Black Inc., Ltd., sulfur, accelerator NS, zinc oxide (ZnO), stearic acid (SA), anti-aging agent 4020, anti-RD and other ingredients commonly used in the rubber industry;

1.2 Rubber formula

Basic formula: SBR 103, BR 25, N234 45, white carbon black 25, Si69 2.5, ZnO 2.6, SA 1, 4020 1.5, RD 1, NS 2.3 and S 1.8.

1.3 Experimental equipment and performance test

(1) Mooney viscometer, MV2000, ALPHA; tensionen tester, 2020-DC, ALPHA; rubber pro-cessibility analyzer, RPA2000, ALPHA, DGAV carbon black dispersion meter, ALPHA, compression heat generator GT-RH -2000N; SEM, JSM-6700;

(2) Dynamic property test

RPA2000 rubber processibility analyzer produced by Alpha is used for testing;

Strain scanning test conditions: temperature 60 °C, frequency 60 Hz, strain range 0.25% to 100%;

1.4 Bound rubber

Weigh about 0.5g of the sample, package it in a stainless steel mesh with known mass, put it in 100ml of toluene solution, soak it for 72h, change the solvent, soak for 48h, take out the stainless

steel mesh, dry and weigh it, and calculate the bound rubber content according to the formula:

R(%)= \\wft - w, x [Af, + (m, + Mr)|] + [iv, x [Hr + [M; + AO]]

R (%): represents the content of bound rubber;

Wfg: represents the weight of bound rubber and filler after soaking and drying;

Ws: represents the quality of the sample not soaked;

Mf: represents the weight of the filler in the sample not soaked;

Mr: represents the mass of rubber in the sample not soaked;

2. Results and discussion
2.1 Effect of feeding sequence

The two-stage mixing is carried out in the internal mixer in the rubber laboratory. The speed of the stage I rotor is 70r / min, the temperature is 90 °C, the speed of the stage II rotor is 60R / min, the temperature is 70 ° , and sulfur and accelerant are added in this stage. The feeding sequence scheme of stage I mixing is as follows:

Scheme 1: add rubber SBR / BR -- 1min, add part of carbon black N234 + white carbon black +SI69--2.5min, add the remaining filler --4.5min, and add small material -- 6min for rubber discharge.

Scheme 2: add rubber SBR / BR -- 1min, add small material -- 2 min, add part of carbon black + residual filler of white carbon black -- 3.5 min, and add the remaining filler -- 6 min for rubber discharge.

Scheme 3: add rubber SBR / BR -- 1min, add pretreated white carbon black (i.e. white carbon black and proper amount of Si69 are mixed evenly in advance) --2min, add part of carbon black + 3.5min, add the remaining filler -- 4.5min, and add small material -- 6min for rubber discharge.

Table 1 Vulcanization Property Analysis under Different Feeding Sequences

Project ML1+4 100°C ML / (dNm) MH / (dNm) MH-ML / (dNm) t10 /s t90 /s 1/(t90-t10)

Option 1 67.8 2.6 17.93 15.3 1.97 8.05 0.1645

Plan 2 66.5 2.5 17.23 14.7 2.10 7.98 0.1701

Option 3 69.1 2.4 16.50 14.1 2.14 7.49 0.1870

Different feeding sequences have different degrees of effect on the property of the mixed rubber. From Table 1, it can be seen that the maximum torque MH and the torque difference (MH-ML) of the mixed rubber in mixing process scheme 1 and 2 are equivalent, but the torque difference of 3 is small, which is due to the fact that the carbon black and white carbon are added to the SBR / BR rubber together. Due to the different wetting degrees of the two fillers with the rubber and the effect of mixing time,

it is easy to form filler aggregate. Therefore, the torque value of scheme 1 and 2 is higher, while that of 3 is the lowest. Meanwhile, the curing time of scheme 3 is shorter than that of scheme 1 and 2, and the curing rate is the fastest, which is due to the fact that the pretreated carbon black is infiltrated with the rubber before it is added, making the carbon black be evenly dispersed in the rubber so as to reduce the agglomeration of filler, and improve its dispersion in the rubber.

2.1.1 Mechanical property analysis

Option Plan 2 Option 3

Option Plan 2 Option 3

Option Plan 2 Option 3

Figure 1. (a), (b) and (c) show the mechanical properties of different mixing processes

From Figure 1, it can be seen that the comprehensive mechanical properties of scheme 3 are the best, with high tensile strength, 300% definite elongation stress and tear strength, and low Akron abrasion loss, indicating that with the feeding sequence of scheme 3, white carbon black and carbon black can be evenly dispersed in the rubber, improving the mechanical properties of the whole rubber. In scheme 1 and 2, the sequence of adding small materials is different, but the way of adding filler is the same. In rubber mechanical properties, filler plays a leading role. Therefore, the difference of infiltration degree of white carbon black and carbon black in rubber affects its mechanical properties in rubber.

2.1.2 Content of bound rubber

The filler interacts with the polymer through physical adsorption, chemisorption, and mechanical interaction to form a bound rubber. In addition, the bound rubber has been considered as an important index of carbon black reinforcement[2].

It can be seen from Figure 2 that the bound rubber content of scheme 3 is the largest, that of scheme 1 is the second, and that of scheme 2 is the lowest. Therefore, it can be concluded that the bound rubber

content of the mixed rubber with white carbon black fully dispersed is higher than that of the carbon black. This is because after the white carbon black is added first in the scheme 3, the white carbon black and the rubber are first coupled to form a bound rubber under the action of the silane coupling agent, and the carbon black added later has improved dispersibility under the action of shear force, resulting in increased bound rubber content.

11 Optio
2

nf Option 3

Figure 2. Bound Rubber Content under Different Mixing Processes

2.1.3 Dynamic property analysis

a) Relationship between the storage modulus G& (b) Relationship between the storage modulus G& of f the mixed rubber and the strain the vulcanized rubber and the strain

Figure 3 (a) and (b) show the relationship between storage modulus G& and strain under different mixing processes

From Figure 3 (a), it can be seen that the storage modulus of the carbon black rubber under the three schemes of the mixing process decreases with increasing strain, and has a higher storage modulus under smaller strain, that is, as the strain increases, the storage modulus decreases rapidly. This is because when carbon black is added to rubber, carbon black and rubber adsorb to form a filler network under a smaller strain. Some rubber is covered by carbon black and loses its elasticity, so the stress is greater. When the strain increases, the adsorption and desorption between carbon black and rubber co-exist, the coated rubber is gradually released, and the stress decreases. When the strain is large enough to fully release the coated rubber, the stress no longer decreases, which is the Payne effect[3]. The Payne effect of scheme 3 is the strongest, which indicates that in this mixing process scheme, the filler network formed by the adsorption of fillers and rubber has a strong degree of network structure. However, in the other two process schemes, because the fillers are added in the same way, the change tendency of storage modulus with strain is basically the same and consistent with the change tendency of the bound rubber content.

Figure 3 (b) shows the strain scanning comparison of vulcanized rubber under three mixing processes. G&in vulcanized rubber under strain amplitude is the result of the interaction of cross-linked network and filler network[4]. It can be seen from the figure that the initial storage modulus G& of scheme 3 is slightly higher than that of the other two schemes when

the vulcanization dosage is equal, indicating that the interaction between filler and filler as well as filler and rubber is greater than that of the other two mixing schemes in this process scheme.

2.2 Effect of process parameters on the property of mixed rubber

The mixing process of rubber is the repetition of crushing, mixing, dispersing and simple mixing changes at the same time under the action of the mechanical shear force generated by the rubber elastomer and various ingredients when the rotor rotates, and finally achieves the desired physicochemical process of dispersion effect[5]. In this experiment, under the condition that other process parameters are constant and the temperature and the speed of the rotor are controlled, the effect of these two factors on the property of SBR / BR mixed rubber is studied. Through the property comparison of the above feeding sequence, mixing sequence in scheme 3 is adopted in this round of experiment.

Table 2 Sample Sequencing Table Prepared for Parameters of Different Mixing Processes

Speed/ nmin-1 Tempe-rature/°C 50 70 90

50 Sample 1 Sample 2 Sample 3
70 Sample Sample Sample

no. 4 no. 5 no. 6

90 Sample 7 Sample 8 Sample 9
2.2.1 Vulcanization property analysis

Table 3 Rubber Vulcanization Characteristics of Each Sample under Different Mixing Process Parameters

Project ML / (dNm) MH / (dNm) MH-ML / (dNm) t10 /s t90 /s 1/(t90 ^

Sample 1 2.46 17.27 14.81 2.30 8.84 0.152

Sample 2 2.36 17.45 15.09 2.29 8.75 0.155

Sample 3 2.36 17.74 15.38 2.28 8.72 0.155

Sample no. 4 2.38 17.84 15.46 2.39 8.94 0.153

Sample no. 5 2.42 17.64 15.23 2.36 8.76 0.156

Sample no. 6 2.43 17.68 15.25 2.35 8.74 0.156

Sample 7 2.51 17.49 14.98 2.44 8.74 0.158

Sample 8 2.48 17.69 15.21 2.35 8.64 0.159

Sample 9 2.45 17.83 15.38 2.3 8.51 0.161

From the data in Table 3, it can be seen that at the same temperature, with the increase of speed, the MH of samples 3, 6 and 9 is higher, indicating that with the increase of speed, the mixing effect is improved, and that the filler is evenly distributed in the rubber. Samples 1 and 4 have a long optimum curing time (t90), indicating that at low mixing temperatures and low speeds, the filler and ingredient are not evenly dispersed in the rubber, which is prone to agglomeration so as

to reduce the activation promotion effect of the vulcanizing agent, making it difficult to vulcanize the mixed rubber evenly, prolong t90 and reduce the curing rate. With the increase of mixing temperature and speed, the optimum curing time of samples 5 to 9 is shortened significantly, and the curing rate is increased, which indicates that at a suitable roll temperature and speed, the wetting rate of filler and rubber can be improved and the dispersion efficiency of ingredient.

2.2.2 Effect of different process parameters on physical and mechanical properties of the mixed rubber

Table 4 Effect of Different Process Parameters on Physical and Mechanical Properties of the Mixed Rubber

Tensile strength/ MPa

Elongation at break/%

Sample Sample Sample Sample Sample Sample Sample Sample Sample

1 2 3 no. 4 no. 5 6 7 8 9
20.1 21.4 21.5 20.8 21.5 22.0 22.2 22.9 21.8
424.4 422.7 420.4 426.8 418.1 411.1 412.2 400.5 387.9
300% definite

elongation stress 14.0 14.8 15.0 14.2 15.0 15.8 15.1 15.7 15.9 / mpa

Hardness (Sho-reA) / degree

69 68 67 68 68 68 69 68

Rebound/%

Tearing property KN/m

37 38 38 37 38 39 37 38
69
38
44.6 45.8 46.5 46.2 48.8 49.8 47.8 48.0 46.8

Compression fatigue temperature 41.7 40.4 39.7 41.5 40.6 39.1 41.4 40.1 39.7 rise / °C

Akron abrasion

cm3 / 1.61km

0.0902 0.0890 0.0880 0.0889 0.0865 0.0831 0.0815 0.0803 0.0868

It can be seen from Table 4 that at the same speed, as the temperature of the mixed rubber increases, the tensile strength, 300% definite elongation stress, and tear strength increase, while the elongation at break decreases. At the same temperature, as the speed increases, the mechanical properties increase, the compression temperature rises and the Akron abrasion loss decreases. However, in sample 9, the mechanical properties such as tensile strength and tear strength decrease, but the Akron abrasion loss increases, which is due to the fact that as the temperature or speed increases, the SBR / BR softens and the shear force on the rubber increases so as to increase the number of active sites in contact between the rubber and the filler and increase the mass fraction of the bound rubber generated, so the reinforcement property becomes better. However, at higher temperatures and high speeds, the shear deformation of the rubber increases, which increases the amount of heat generated, breaks the physical bonds between the molecules of the primary rubber, shortens the active chain end, weakens the activity, and reduces the

X value 6.6 7.5

Dispersion (%)) 92.8 96.9

White area % 8.8 5.4

Dispersion value of carbon black in the rubber is as follows when the temperature is 50 °C and 70 °C and the speed is 50 r / min and 90 r / min respectively. After increasing the speed, the white area in the rubber decreases, but the X value and the dispersion increase, that is, the agglomeration of the small pieces decreases, and the carbon black is evenly dispersed. Increasing the mixing temperature at the same speed will increase the dispersion of carbon black in the rubber. This is because after increasing the mixing temperature, the fluidity of the rubber is improved, and the

bound rubber generated by the filler, resulting in reduced rubber properties. It indicates that selecting the proper mixing temperature and speed can improve the mixing uniformity of the rubber. In the experimental research range, the mechanical properties of the rubber are better when 70 °C x 90r / min or 90 °C x 70r / min is used, but with the comprehensive factors such as mechanical properties and wear resistance of the rubber considered, the process conditions of 90 ° C x 70r / min should be selected.

2.2.3 Carbon black dispersion of different mixing process parameters

The carbon black dispersion in rubber is an important index for measuring the quality of mixed rubber, and it is also an important criterion for measuring the property of the finished mixed rubber. A carbon black disperser is used to analyze the dispersion of carbon black in the mixed rubber. The X value represents the dispersion level. The higher the level, the better the dispersion. The white area represents the area occupied by the white particles, which are the undispersed carbon black agglomerates.

Sample 7 Sample 9

6.9 8.1 7.8 7.2
94.8 98.7 97.2 95.9
6.9 3.6 4.5 4.9

dispersion rate of the carbon black in the rubber is increased, so that the carbon black can be evenly dispersed. Dispersion value of carbon black in the rubber when the temperature is 90 °C and the speed is 50 n / min and 90 r / min respectively. It can be seen from the data that the dispersity grade of sample 9 is reduced, which is due to the fact that at high temperature, high speed will cause the increase of heat generation, which will reduce the apparent viscosity of the mixed rubber, resulting in the decrease of shear stress and dispersion effect.

Table 5 Carbon Black Dispersion of Different Mixing Process Parameters

Sample no. Sample no. o. Sample 1 Sample 3 r

2.2.4 SEM analysis

(a) |b) (c)

Figure 4 (a), (b) and (c) are SEM cross-section scanning of rubber filled by carbon black at 70 °C and 50 R / min, 70 R / min and 90 R / min respectively

It can be seen from the figure that when the speed is from 50r / min to 90r / min, the roughness of the rubber section gradually decreases, indicating that the increase of the speed will increase the degree of carbon black infiltration in rubber.

2.2.5 Content of bound rubber

Figure 5 Bound Rubber Content of Each Sample

It can be seen from Figure 5 that at the same temperature, the amount of bound rubber increases with the increase of the speed, which is due to the fact that the molecular chain of rubber generates more active chain ends when it breaks under the action of high shear force and react with carbon black, so that the bound rubber content increases. At the same time, at the same speed, the increase in temperature increases the fluidity of

the rubber, thereby increasing the rate of powder feeding of the colloid, and enhancing the binding ability between the filler and the molecular chain of the rubber. When the temperature and speed continue to increase, the formed bound rubber network is damaged to a certain degree under the action of high temperature or high shear force, and the generation rate of the bound rubber decreases.

2.2.6 RPA analysis

(a) Relationship between the storage modulus G& (b) Relationship between the storage modulus G& of of the mixed rubber and the strain the vulcanized rubber and the strain

Figure 6 (a) and (b) show the relationship between the storage modulus G& and the strain of mixed rubber and vulcanized rubber at different speeds at 90 °C

It can be seen from Figure 6 (a) and (b) that at the same temperature, the storage modulus of the mixed rubber and vulcanized rubber at different processing speeds has a different tendency. When the strain is less than 10%, the speed is changed from 50r / min to 70r / min and the storage modulus gradually increases, and when the speed is 90r / min, the storage modulus decreases. This is because under the action of high shear force, the force between the filler and rubber molecules increases, and the content of the bound rubber generated increases. The bound rubber adheres the filler to the rubber matrix, and plays a bridge role between the rubber and carbon black filler. The movement of the rubber&s molecular chain is limited, showing a higher storage modulus in the macro view. However, when the shear force is too large, the molecular chain of rubber will be broken, resulting in peeling of the bonded rubber generated from the rubber, in damaging the formed bonded rubber network and in decreasing storage modulus.

Conclusion

1. It can be seen from the study of feeding sequence that under different feeding sequence,

after infiltrating the pretreated white carbon black and rubber and adding carbon black, the agglomeration of filler is reduced, the dispersion of white carbon black in rubber is improved, and the blended rubber obtained has the highest content of bound rubber, and better mechanical properties and wear properties.

2. As the temperature of the mixed rubber increases at the same speed, the tensile strength, 300% definite elongation stress, and tear strength increase, but the elongation at break decreases. At the same temperature, as the speed increases, the mechanical property increase, but the compression temperature rise and Akron abrasion loss decrease. The bound rubber content and storage modulus increase with the increase of processing speed, that is, when the speed is 90r / min, the generation rate of bound rubber decreases and the storage modulus decreases.
3. Proper mixing temperature and speed can improve the mixing uniformity of the rubber. In the different data of the above samples, with the comprehensive factors such as mechanical properties and wear resistance of the rubber considered, the process conditions of 90 ° C x 70r / min should be selected.

References

[1] Kraus, G. Degree of cure in filler-reinforced vulcanizates by the swelling method. Rubber chemistry and technology ,30(3),928-951

[2] Zhang Xinhui, Liu Yadong. THE EFFECTS OF THE BOUND RUBBER ON THE PROPERTIES OF NATURAL RUBBER [J]. Chinese Journal of Applied Chemistry, 1985, (04): 47-52.

[3] Wang Menghuan. Effect of Polymer-Filler and Filler-Filler Interaction on Dynamic Mechanical Properties of Filled Vulcanized Rubber [J]. the Industry, 2001 (21): 38-44

[4] Drozdov A D, Dorfmann A.The Payne effect for particle-reinforced elastomers [J].Polymer Engineering and Science, 2002, 42(3):591-604.

[5] Yu Aisheng, Xie Xiongchun, Chen Jiahui, et al. Study on Speed-variable Mixing in Internal Mixer [J]. the Industry, 2002, 22 (1): 46-48

© Wcmg Hong Chu Lingling, 2020

Ссылка на статью: Wang Hong Chu Lingling - Effects of Different Mixing Processes on the Dispersion and Dynamic Properties of Fillers in SBR/BR // Вести научных достижений. Естественные и технические науки - 2020. - №1. - С. 10-19. DOI: 10.36616/2687-1335-2020-1-10-19 URL: https://www.vestind.ru/ journals/architecture/releases/2020-1/articles?Viewpage=10

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