Modification Of Carbon Black And Its Effect On The Structure And Properties Of Styrene Butadiene Rubber Composites

To date, rubber is the only material with high elasticity, which has been regarded as an important strategic material. Rubber products, such as tires, hoses, seals, conveyor belts and so on, are widely used in transportations, irrigation works, defense industry, aerospace and other fields. However, most synthetic rubber is unable to meet the requirements of practical application after vulcanization except for natural and chloroprene rubber with strain induced crystallization. So the addition of reinforcing filler into the matrix is becoming an essential step towards large-scale production and industrial application. The reinforcing fillers, such as carbon black(CB), silica, can not only improve the mechanical properties of rubber products, also endow the composites with good abrasion resistance, heat resistance, oil resistance and other performances. Moreover, the inclusion of fillers can effectively prolong the service life of rubber product and greatly lower the production cost. However, there is a big challenge that a weak interface interaction, derived from the great difference of surface characteristic between the filler and rubber, leads to a great damage for the static and dynamic performance of the composite. Meanwhile, the influence of the filler dispersion, interface structure and network structure of the composites on the overall properties of rubber composites lacks of systematic and in-depth theoretic analysis and study.In our work, CB, as the most commonly used reinforcing filler in rubber are studied. Based on the structure design route, we have attempted to design the interfacial interaction between the CB and modifier, and modified CB and rubber. The effect of surface characteristic of CB, dispersion state, interface structure and rubber network on static and dynamic performances of styrene butadiene rubber(SBR) composite are investigated. This work provide the important guidance of the theory and practice to prepare high performance rubber composites filled with CB.A simple and effective solid-phase method was employed to prepare the modified CB, in which a Diels-Alder reaction may occur between N-cyclohexylmaleimide(CM) and conjugated double bond on the CB surface. After modification, the CB, covered with cyclohexyl groups, exhibits a lower surface energy, improving the affinity with the SBR matrix. The rubber processing analysis(RPA) analysis revealed that the modification process can effectively reduce the filler network in the rubber compound, accompanied with the improved dispersion of filler. The differential scanning calorimetry(DSC) measurement proved that the inclusion of modifier CM can greatly improve the immobilized rubber layer content, markedly enhancing the interfacial adhesion in the composites. The mechanical performance analysis indicated that the reinforcement effect of modified CB is optimal when the dosage of modifier CM is 8% of the CB loading. Compared with un-modified system, the tensile strength, modulus at 100%, modulus at 300% and tear strength of SBR/8%CMCB were increased by 12.1%, 4.0%, 2.3% and 10.1%, respectively. Also, wear-resisting performance and the dynamic fatigue thermal performance of composites are also greatly improved. The dynamic performance analysis can be seen that the rolling resistance of SBR/8%CMCB is reduced by 6.7%, as compared with un-modified system. Also, the scanning electron microscope(SEM) and transmission electron microscope(TEM) observation suggested that the modified CB can be well dispersed into the matrix, without apparent aggregations.The imidazole derivatives such as 2-undecylimidazole(UI) and 2-mercapto-1-methylimidazole(MMI) were utilized as novel modifier for preparing modified SBR/CB composites. The imidazole groups on UI and MMI can interact with CB in form of hydrogen-bond interaction, which further suppress the aggregation of CB particles. Also, the undecyl or thiol groups can be reacted with the SBR chains via physical entanglement or thiol-ene chemistry, finally enhancing the rubber-filler interfacial interaction. The swelling tests and DSC analysis indicated that the inclusion of UI and MMI can greatly improve the interfacial adhesion. With adding 1.0 phr UI or MMI into the matrix, the immobilized rubber content increase up to 10.7% and 11.4%. The SEM and TEM observations revealed that CB particles can be well dispersed into the matrix after modified by UI and MMI. The mechanical performance analysis declared that the SBR/CB composites modified by MMI exhibit superior properties than the blank SBR and conventional SBR/CB composites. For example, compared with blank SBR composite, the tensile strength, modulus at 100% elongation, modulus at 300% elongation, and tear strength of SBR/CB modified with 1 phr MMI are greatly improved by 20.1%, 7.5%, 10.3% and 12.0%, respectively. The rolling resistance of SBR/MMI-1.0 is reduced by 10.4%, and the wet grip property is increased by 3.8%.Sol-gel method and thermal treatment are performed to prepare a novel CB-nSiO2 hybrid filler, in which silica sol(nSiO2) were decorated onto the surface of CB. The chemical binding between CB and nSiO2 is proved by X-rayphotoelectron spectroscopy(XPS) and Fourier transform infrared spectroscopy(FTIR). The nSiO2 nanoparticles are attached onto the CB particles according to the TEM images. Subsequently, the obtained CB-nSiO2 hybrid filler was further employed as reinforced filler to fabricate SBR composites. With the inclusion of Triethoxy(3–octanoylthio–1–propyl)(NXT) as a modifier, the Payne effect of SBR/CB-nSiO2 is greatly reduced, which is lower than that in the SBR/CB/SiO2 composites. That is to say, the filler network is effectively reduced. By analyzing, the coupling agent NXT can interact with silicon hydroxyl groups of hybrid filler, also, the carboxyl groups can participate in rubber vulcanization, grafting into the rubber molecular chains. The mechanical performance analysis indicated that the tensile strength, modulus at 100 %, modulus at 300 %, tear strength of R/C-36-nS-4 composite are increased by 22.0 %, 7.7 %, 13.9 % and 14.6 % as compared with those of R/C-40, respectively. Moreover, the rolling resistance of R/C-36-nS-4 is reduced by 18.3% and the wet grip property is simultaneously increased by 13.1%, respectively. And the DSC analysis suggested that the introduction of NXT can effectively enhance the interfacial interaction between the hybrids filler and rubber. For example, the immobilized rubber chains layer around the filler particles was improved to 15.2%, greatly higher than that of mixed filler system. Such superior performance makes hybrids filler very competitive for application in the green tire production.