Contribution of Carbon Black to Thermal Conductivity of Natural Rubber

Transcription

1 Key Engineering Materials Online: ISSN: , Vol. 561, pp doi: / Trans Tech Publications, Switzerland Contribution of Carbon Black to Thermal Conductivity of Natural Rubber SONG Jun-ping a and MA Lian-xiang b Qingdao University of Science and Technology, Qingdao , China a sjpwzj@163.com, b oldhorse@qust.edu.cn Keywords: carbon black; thermal conductivity; rubber Abstract: Eight kinds of carbon black filled natural rubber composites were prepared, and thermal conductivity was studied. Acetylene black contributes much to the thermal conductivity of rubber, and tiny loading results in considerable improvement. The conductive carbon black 40B2 is advantageous for the improvement in thermal conductivity of rubber when its loading reaches middle level, and at its middle level, also tiny loading results in much improvement. Most kinds of carbon black for rubber application filled rubber composites have good properties except for N134 and N660, especially the poor contribution of N660. Additionally, in the case of carbon black filled rubber composites, addition of filler may not necessarily benefit the thermal conductivity when filler loading is not much. Introduction Carbon black is the normal reinforcing filler in rubber industry. Filled with carbon black in rubber, not only the amount of raw rubber and cost are reduced, but also a better mechanical properties and wear resistance of rubber products can be achieved. Carbon black filled natural rubber composites are widely used in tire industry because of the better properties, such as hardness, wear resistance, strength, and etc. Over the years, much research work has been done on carbon black filled natural rubber materials. Guo [1] studied the mechanical properties and conductivity properties of T60, T80 and acetylene black filled natural rubber composites. It shows that conductive carbon black has some reinforcing effect on natural rubber. The tensile strength, elongation at break, and tear strength are almost equal or a little better than N330 filled natural rubber composite. In addition, the specific area, the structure, the content and the conductivity property are important factors for the conductivity properties of the composites. Lin [2] modified carbon black with four kinds of rare earth oxides, and then filled the modified carbon black in natural rubber latex. The mechanical properties of rubber were improved. Jia [3] studied influence of the content of coupling agent Si69 on vulcanization characteristics and mechanical properties of carbon black filled natural rubber materials. It shows that when the content of Si69 is 1/10 of that of carbon black, the tensile strength, 300% modulus and anti-aging properties are the best. Zhang [4] used maleic anhydride pretreating carbon black, and studied the dynamic mechanical properties of carbon black filled natural rubber composites. A conclusion can be drawn that modifying carbon black with maleic anhydride, the rolling resistance is reduced. Liu [5] prepared carbon black filled natural rubber latex by latex mixing method. It shows that the mechanical properties of the composites are improved much. Under dynamic strain, the vulcanizates show nonlinear viscoelastic behavior. At low temperature, the composite shows higher loss factor. While at high temperature, the composite shows lower loss factor. It means that the material has better wet skid resistance and lower rolling resistance. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-12/05/16,10:48:34)

2 Key Engineering Materials Vol Compared with the mechanical properties, dynamic mechanical properties, and conductivity properties, research work on thermal conductivity of carbon black filled rubber composites is relatively few. Nano-particles have a high surface activity which will benefit thermal conductivity of nano-particles filled composites [6]. In this paper, the influence of carbon black on thermal conductivity of natural rubber was studied. Sample Preparation and Characterization The main materials in this study were natural rubber SMR, carbon black N134, N234, N330, N375, N539, N660, conductive carbon black 40B2 and acetylene black. All materials were used as purchased. Most kinds of carbon black were mixed with rubber by S(X)160A two-roll open rubber mixing machine, made by Shanghai Shuangyi Rubber and Plastic machine Ltd. Except for acetylene black, which was filled in rubber matrix by Rheomix3000OS torque rheometer, made by HAAKE company, Germany. HS-100T-FTMO-2PT mold cure machine, made by Shenzhen Jiaxin Electronic Equipment Ltd, was used for vulcanization of rubber. Vulcanizating temperature was 160 centigrade. The content of carbon black varies from lower quantity (10phr, 20phr), middle quantity (40phr, 50phr), to higher quantity (70phr, 80phr). Nanoflash LFA447 Laser Thermal Conduction Equipment was used for measuring thermal conductivity of carbon black filled rubber composite, which was made by Netzsch company, Germany. Results and Discussion Thermal Conductivity of Carbon Black Filled Rubber System Fig.1 shows thermal conductivity of carbon black filled natural rubber composites. The content of the filler is 10phr, 20phr, 40phr, 50phr, 70phr and 80phr. As is shown that acetylene black is more conducive to improve thermal conductivity of rubber, and the thermal conductivity of the filled rubber is much better than the others. In the case of conductive carbon black 40B2, when the content of it reaches middle-fill level, the roll of improvement in thermal conductivity of rubber becomes more and more obvious. In addition to the conductive carbon black, carbon black N539, N330, N234, N375 filled rubber system show good property. The thermal conductivity of carbon black N134 filled rubber composites is not very good. Carbon black N660 contributes little to the thermal conductivity of rubber. Contribution of Carbon Black to Thermal Conductivity of Rubber Table1shows the increasing rate in thermal conductivity with respect to matrix with the addition of carbon black at different content of the filler. It can be seen that the addition of carbon black brings different result in thermal conductivity of the carbon black filled rubber composites. Addition of some kinds of carbon black at certain content makes the thermal conductivity of rubber matrix decreased instead. Some kinds of carbon black seems having no effect on the thermal conductivity of rubber matrix at certain content. Others have effect on the thermal conductivity of rubber matrix at different extent. Therefore, although the thermal conductivity of carbon black is higher than that of rubber matrix, the addition of carbon black in rubber matrix may not able to improve the thermal conductivity.

3 160 Advanced Polymer Processing III Table2 shows the change rate in thermal conductivity with addition of 10phr of carbon black at lower, middle, higher filler content. It shows that for different kinds of carbon black, the change rate is different. In addition, for the same kind of carbon black, the change rate changes at different filler content level, and different kinds of carbon black show different relationship between change rate in thermal conductivity and the addition of 10phr along with different filler content level. Fig.1 Thermal conductivity of carbon black filled natural rubber (Acb is acetylene black)

4 Key Engineering Materials Vol Table1 Increasing rate in thermal conductivity with respect to matrix phr λ/% Composite N134 N234 N330 N375 N539 N660 40B2 Acetylene black λ λ Note: λ = 0 100% ; λ0is thermal conductivity of the matrix without carbon black, and the λ value is W/(m*K). 0 Table 2 Influence of increasing in filler content on thermal conductivity of the composites λ/% Lower Middle Higher Composite N N N N N N B Acetylene black λ2 λ1 Note: λ = 100% ; λ1is thermal conductivity of the composites before addition of 10phr λ 1 Content of carbon black, λ 2 is thermal conductivity of the composites after addition of 10phr of carbon black.

5 162 Advanced Polymer Processing III As is shown in table1 and table2, acetylene black is the best in improving thermal conductivity of rubber. When the content is very low, the improvement in thermal conductivity is already obvious. When the content of it is 40phr, the thermal conductivity of the composite is 200% of that of rubber matrix. In addition, very small amount of filler can result in considerable change rate in thermal conductivity of rubber. For conductive carbon black 40B2, with higher filler content, thermal conductivity is excellent. When the content of it is 70phr, the thermal conductivity of the composite is more than 200% of that of rubber matrix. And when the filler content reaches middle level, very small amount of filler can result in considerable change rate in thermal conductivity of rubber. It also can be seen that when the filler content is lower, some kinds of carbon black can make thermal conductivity of rubber decrease, such as N660 and N134; some kinds of carbon black have no contribution to thermal conductivity of rubber, such as N330 and N375.In the case of N660, the improvement in thermal conductivity of rubber is very little, and when the content reaches 80phr, the thermal conductivity of rubber matrix is increased by 50%. When the content of it is higher, more of it results in not much improvement in properties, and carbon black N134 is the same situation. Conclusions (1) Thermal conductivity of acetylene black filled natural rubber composite is very high, and it is far higher than the other carbon black filled natural rubber composites. Tiny loading can result in considerable improvement in thermal conductivity of rubber. When the content of it is 40phr, the thermal conductivity of the composite is 200% of that of rubber matrix. If more amount of the carbon black can be filled in rubber by some special mixing method, a kind of rubber material with pretty good thermal conductivity can be expected; (2) Thermal conductivity of 40B2 filled natural rubber composite is not very good until the loading reaches 50phr. When the content of it is 70phr, the thermal conductivity of the composite is more than 200% of that of rubber matrix. When the filler loading is at middle level, tiny loading can result in much improvement in thermal conductivity of rubber. Therefore, in the case of conductive carbon black, it is very advantageous for the improvement of the thermal conductivity of the rubber composites when the filler loading reaches a certain amount; (3) Thermal conductivity of N539, N330, N234 and N375 filled natural rubber composites is good. Thermal conductivity of N134 filled natural rubber composites is not good. But when the filling level is lower, tiny loading can result in much improvement in thermal conductivity of rubber. While when the filling level is higher, the situation is not like that, and N660 is the same situation. And the thermal conductivity of N660 filled natural rubber composite is far less than the others; (4) When filler content is lower, some kinds of carbon black can make thermal conductivity of rubber decrease, and some kinds of carbon black have no contribution to thermal conductivity of rubber. Therefore, for carbon black filled rubber composites, the addition of filler may not be able to improve the thermal conductivity; (5) Except for carbon black N660, when the filler content reaches 50phr, the increasing rate in thermal conductivity is about 50%, and when the filler content reaches 80phr, the increasing rate in thermal conductivity is about 100%.

6 Key Engineering Materials Vol Acknowledgement The author is terribly grateful to Natural Science Foundation of Shandong Province (ZR2012EEQ017) for financial support. References [1] W.Guo, X.Wu, Z.Z.Zheng. Research on mechanical and conductive properties of natural rubber /conductive carbon black, Ins Mat. 44(2011) [2]Y.L.Lin, K.Q.Xiao, A.Q.Zhang. Preparation and properties of rare earth modified carbon black/natural rubber composites, Chin Rare Earth Soc. 23(2005) [3]H.B.Jia, H.B.Zhou, F.Q.Dong. Influence of Si69 on properties of carbon black filled NR, Rubb Ind. 45(1998) [4]X.L.Zhang, D.M.Jia, M.Y.Huang. Effect of MAH modified carbon black on dynamic mechanical properties of vulcanized natural rubber, Synth Rubb Ind. 24(2001) 105. [5]H.Liu. Carbon black reinforced natural rubber latex prepared nanocomposites. Shanghai:East China University of Science and Technology, [6] G.W.Lee, M.Park, J.Kim. Enhanced thermal conductivity of polymer composites filled with hybrid filler, Composites: Part A. 37(2006)

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