Characterization Methods for Silica Dispersion in Rubber
Huang, Ruonan (2023)
Huang, Ruonan
2023
Master's Programme in Materials Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2023-11-28
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202311159679
https://urn.fi/URN:NBN:fi:tuni-202311159679
Tiivistelmä
The primary objective of this thesis is to comprehensively characterize the dispersion of silica particles in rubber composites. Through accessing the impact of silica dispersion on the rubber, the result from different experiments gives practical value. It provides recommenda-tions for optimizing silica dispersion techniques in rubber manufacturing processes to enhance the performance and sustainability of rubber products.
When silica is dispersed in rubber, it can effectively enhance rubber’s mechanical proper-ties such as strength, abrasion and tear resistance, and also slightly affect the other proper-ties. Therefore, good silica dispersion is needed to achieve the increase of the properties, so characterising the dispersion of silica in rubber after mixing allows understanding whether the mixing conditions need to be improved. For the manufacturers and researchers, understanding silica dispersion in rubber is essential for research and development of new rubber compounds with optimized properties, which can lead to the creation of innovative and high-performance rubber products.
The dispersion of silica in rubber is distinguished by the uniformity and consistency of fine scale of the diameter of silica particles within the rubber matrix, it is classified to micro disper-sion (less than 2 µm) and macro dispersion (2-100 µm). In order to understand the silica dis-persion in rubber, two types of characterisations are used, a direct approach to characterise silica dispersion directly and an indirect approach by characterising the physical properties that are affected by silica dispersion. The direct characterisation methods include disper-GRADER, scanning electron microscopy, optical microscopy and micro computed tomography, which allow direct observation of silica particles on the surface or inside the sample, and com-parison of the dispersion by comparing images of better dispersed samples with poorly dis-persed samples. In the indirect methods, e.g., tensile tests, rheometer measurements are used, and in general, better dispersed silica samples have better physical behaviour.
Two samples were provided by Nokian Tyres for this study, with sample 1 showing better silica dispersion than sample 2. Both were produced using the same recipe, but the mixing procedure was different. The disperGRADER, which is actually used in the industry, is the most direct, economical and fastest method and allows the number of agglomerates at a cer-tain scale to be calculated. Scanning electron microscopy and optical profilometer can also show the dispersion of silica agglomerates on a sample surface. These two methods allow di-rect visualisation of the silica dispersion, but since other substances (e.g., ZnO) are also pre-sent in the recipe, the presence of these substances can affect the analysis of the silica vol-ume fraction to a certain extent. Among the indirect methods, tensile test, hardness test and rheometer are commonly used in the industrial scale to characterise whether the silica is well dispersed or not. Although it is said that good silica dispersion will make the rubber harder and stronger, the properties of rubber are affected by many factors at the same time. So even though indirect characterisation can quantitatively analyse the dispersion of silica, the results obtained may not accurately express the dispersion of silica, and it is necessary to compare the two to judge the advantages and disadvantages of the dispersion of silica.
In general, the feasibility of each characterisation method is judged through a combination of "direct and indirect methods" and "qualitative and quantitative analyses", and the possible advantages and disadvantages of each method in practical applications are discussed after putting them into practice. In general, in addition to disperGRADER, SEM can also directly characterise silica dispersion, and for indirect methods such as tensile test, hardness test, mooney viscosity, DMA, etc., it is possible to indirectly understand silica dispersion by means of relevant physical data obtained from the test.
When silica is dispersed in rubber, it can effectively enhance rubber’s mechanical proper-ties such as strength, abrasion and tear resistance, and also slightly affect the other proper-ties. Therefore, good silica dispersion is needed to achieve the increase of the properties, so characterising the dispersion of silica in rubber after mixing allows understanding whether the mixing conditions need to be improved. For the manufacturers and researchers, understanding silica dispersion in rubber is essential for research and development of new rubber compounds with optimized properties, which can lead to the creation of innovative and high-performance rubber products.
The dispersion of silica in rubber is distinguished by the uniformity and consistency of fine scale of the diameter of silica particles within the rubber matrix, it is classified to micro disper-sion (less than 2 µm) and macro dispersion (2-100 µm). In order to understand the silica dis-persion in rubber, two types of characterisations are used, a direct approach to characterise silica dispersion directly and an indirect approach by characterising the physical properties that are affected by silica dispersion. The direct characterisation methods include disper-GRADER, scanning electron microscopy, optical microscopy and micro computed tomography, which allow direct observation of silica particles on the surface or inside the sample, and com-parison of the dispersion by comparing images of better dispersed samples with poorly dis-persed samples. In the indirect methods, e.g., tensile tests, rheometer measurements are used, and in general, better dispersed silica samples have better physical behaviour.
Two samples were provided by Nokian Tyres for this study, with sample 1 showing better silica dispersion than sample 2. Both were produced using the same recipe, but the mixing procedure was different. The disperGRADER, which is actually used in the industry, is the most direct, economical and fastest method and allows the number of agglomerates at a cer-tain scale to be calculated. Scanning electron microscopy and optical profilometer can also show the dispersion of silica agglomerates on a sample surface. These two methods allow di-rect visualisation of the silica dispersion, but since other substances (e.g., ZnO) are also pre-sent in the recipe, the presence of these substances can affect the analysis of the silica vol-ume fraction to a certain extent. Among the indirect methods, tensile test, hardness test and rheometer are commonly used in the industrial scale to characterise whether the silica is well dispersed or not. Although it is said that good silica dispersion will make the rubber harder and stronger, the properties of rubber are affected by many factors at the same time. So even though indirect characterisation can quantitatively analyse the dispersion of silica, the results obtained may not accurately express the dispersion of silica, and it is necessary to compare the two to judge the advantages and disadvantages of the dispersion of silica.
In general, the feasibility of each characterisation method is judged through a combination of "direct and indirect methods" and "qualitative and quantitative analyses", and the possible advantages and disadvantages of each method in practical applications are discussed after putting them into practice. In general, in addition to disperGRADER, SEM can also directly characterise silica dispersion, and for indirect methods such as tensile test, hardness test, mooney viscosity, DMA, etc., it is possible to indirectly understand silica dispersion by means of relevant physical data obtained from the test.