Preparation Of Hyperbranched Polyester Modified Nano-SiO₂/Carbon Nanotube Hybrids And Its Application In SBR

Nano-SiO₂, with high surface activity, high temperature resistance, no toxicity and no pollution, is a new type of rubber reinforcing material in the rubber industry. It has a good effect on the rubber, especially for the processing performance, mechanical properties, wear resistance and dynamic mechanical properties. However, nano-SiO₂ is easy to be agglomerate, which will influence the properties of the composites. The purpose of this study is to prepare rubber nanocomposites with high performance, thermal conductivity and thermal conductivity by improving the design of rubber packing network, which is helpful to broaden the application of Nano-SiO₂ in the polymer field,, and has a theoretical and practical significance for the research and application of rubber nanocomposites.In this paper, was prepared in a nitrogen atmosphere. And HL-SiO₂ was in situ synthesized by grafting from with N, N- di-hydroxyethyl amine-3-propionic acid methyl ester and α-caprolactone. The structure and morphology were characterized by FTIR, XPS, NMR and TG analysis. The results show that the hyperbranched polyester is successfully grafted at the surface of nano-SiO₂. Compared with the nano-SiO₂, the SEM shows that the dispersion and compatibility of HL-SiO₂ in the ethanol and rubber matrix is better.Then HL-SiO₂/ SBR composites were prepared by using direct mixing method. Vulcanization performance tests show that the curing time（T90） of the composites are much shorter and the composites’ total crosslinking density is increased with respect to SiO₂ / SBR composites. When the composites with 30 phr HL-SiO₂, the T90 was reduced to 3:18 min. What is more, HL-SiO₂/ SBR composites have a great improvement of mechanical properties and wear resistance. It shows that tensile strength, elongation at break, tear strength and wear resistance of the composites are increasing with the increase of contents of HL-SiO₂. The tensile strength, elongation at break of the composites with 30 phr HL-SiO₂ were 14.8 MPa and 22.2 kN/m2, and its wear resistance decreased to 289.4 mm3. DSC and SEM showed that HL-SiO₂ dispersed in the matrix with smaller particles and more uniform, and the interface of HL-SiO₂ and SBR combination is stronger. This is the reason for the improvement of the properties of the composite materials. HL-SiO₂/p-SiO₂/SBR and HL-SiO₂/ Si69-p-SiO₂/SBR composites were prepared by using 5 phr HL-SiO₂ replacing precipitated SiO₂. These can also improve composite curing performance, dynamic and static mechanical properties, wear resistance. DMA proved that the partial substitution of silica filler can enhance the SBR molecular chain motion limited.M-HL-SiO₂/SBR and M-HL-SiO₂/p-SiO₂/SBR composites with conductive and thermal conductivity were prepared by the introduction of MWNT. The study found that the HL-SiO₂ /MWNT hybrid filler can promote the processing performance, mechanical properties and wear resistance of the rubber compound. As for SBR nanocomposites with 14 phr MWNT, mechanical properties and wear resistance of M-HL-SiO₂/SBR is best. Compared with the MWNT/ SiO₂/SBR, its tensile strength increased the 24% and wear volume dropped by 16%, and thermal diffusion coefficient improved 26% and the resistivity dropped by four orders of magnitude compared with that of the pure SBR. DSC and SEM showed that the dispersion of hybrid filler in the rubber material is more uniform, and the limited layer of rubber molecular chain is more, which improved the macro properties of M-HL-SiO₂/SBR. The tensile strength, tear strength of M-HL-SiO₂/p-SiO₂/SBR composite increased with the increase of MWNT, and the volume resistance had a sudden drop in three orders of magnitude at the 15 phr MWNT. When the composites with 12 phr MWNT, DMA showed that the filler has the strongest effect on the molecular chain of rubber, so its wear resistance is the best.