Carbon black has been widely used as a stabilizer, antistatic agent, colorant, filler, and reinforcing agent in the rubber industry. Precipitation method white carbon black has reinforcing properties similar to carbon black [1]. The surface of carbon black contains some oxygen-containing groups such as phenolic, lactone, and carbonyl groups, while the surface of white carbon black has a uniform layer of silanol groups [2]. With the development of the tire industry and the demonstration of the advantages of white carbon black in reducing tire rolling resistance, the application of white carbon black in the rubber industry continues to expand. However, in applications, white carbon black must undergo surface modification to compensate for its performance shortcomings [3]. The commonly used surface modified silane coupling agent is bis - [3- (triethoxysilicon) propyl] tetrasulfide compound (hereinafter referred to as Si69). Currently, there are many literature reports on the application of Si69 in the rubber industry [4,5], but there are few reports on the interaction between carbon black and white carbon black and Si69. This work investigated the interaction between carbon black and silica with Si69 through extraction experiments, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM).
1 Experimental method
1.1 Raw material carbon black: High wear-resistant furnace black, grade N330, produced by Shanghai Tianma Carbon Black Factory; Precipitation method white carbon black: brand SR190, produced by the white carbon black plant of Taining Synthetic Ammonia Plant in Jiangsu Province; Si69: Produced by Guangzhou Nonferrous Metals Research Institute; All other additives are commonly used in the rubber industry.
1.2 Sample Preparation Modified Carbon Black (or White Carbon Black): Add carbon black (or white carbon black) to a three necked flask, stir while adding Si69 dropwise (with a mass ratio of 100/16), raise the temperature to 143 ℃, keep it warm, and continue stirring for 30 minutes. Lower the temperature and discharge the material, seal it for use. Treat the carbon black (or white carbon black) without Si69 in the same way as above, then extract the sample with acetone under the same conditions for 24 hours, dry it in a 70 ℃ oven to a constant weight, weigh and calculate its loss rate Vulcanized rubber formula (mass fraction, same below): NR70, BR20, NBR10, 2.5 stearic acid, 4 zinc oxide, 4010NA2 anti-aging agent, DTDM0.5 accelerator, NOBS0.4 accelerator, carbon black (or white carbon black) 50, paraffin 1.2, aromatic oil 10, sulfur 1.5, Si69 (0,4,6,8). Place the mixed rubber overnight and prepare a vulcanized rubber sample at 143 ℃ x positive vulcanization time.
1.3 Performance testing XPS analysis: The sample was treated under high vacuum conditions for 4 hours and scanned and analyzed using the EscalabMK II XPS instrument from VG in the UK. The vacuum degree of the analysis room is 2.3 × 10-6Pa, and the energy flow is 20eV. C1s (284.6eV) is used for energy calibration, and the X-ray source is MgK α. TEM analysis was performed using the LKB2088 ultra-thin slicer from LKB, Sweden. The samples were cut at low temperatures (-150~-130 ℃) and observed and photographed under the JEM-100C VII transmission electron microscope produced by Japanese electronics company.
2 Results and Discussion
2.1 Extraction analysis: Si69 with a mass fraction of 13.8% was added, and the weight gain of the reaction products between carbon black or white carbon black and Si69 was 4.3% and 5.3%, respectively. The results indicate that carbon black or white carbon black undergoes a chemical reaction with Si69. The oxygen-containing groups on the surface of carbon black form a certain chemical connection with Si69. At the same time, some Si69 may physically diffuse into the pore active points on the surface of carbon black, forming physical adsorption, which makes the modified carbon black more easily dispersed in rubber and improves the interfacial effect between rubber and carbon black. There are a large number of silanol groups on the surface of silica, which are prone to chemical reactions with Si69. After modification, covalent bonds are introduced between silica and polymers, which can improve the interaction between polymers and silica. The experiment also shows that the interaction between white carbon black and Si69 is stronger than that between carbon black and Si69.