The Modification Of SiCNWs And Its Rubber Matrix Nanocomposites:Preparation, Mechanism And Properties

Silicon carbide nanowires(SiCNWs) with large specific surface area and high length to diameter ratio has excellent physical and chemical properties such as high strength, high melting point, high thermal conductivity and inertness, etc. It is widely used in polymer matrix composites, metal matrix composites and ceramic composites as an candidate material with excellent properties. Therefore, SiCNWs can be an excellent reinforcement candidate material for polymer. Fluororubber(FKM) and nitrile butadiene rubber(NBR) have excellent high temperature resistance, solvent resistance and weather resistance which are widely used seal materials such as O rings, seal gasket, etc. It is a good kind of effective measure by adding nanofiller to improve the properties of the two kinds of rubber. Therefore, this paper mainly focused on the modification of SiCNWs and studied the effects of SiCNWs and m-SiCNWs on the mechanical properties and thermal conductivity of SiCNWs/FKM, m-SiCNWs/FKM and SiCNWs/NBR nanocomposites. In addition, the mechanism on modification of SiCNWs and the reinforcement of FKM and NBR were also investigated. The detailed research work divided into three aspects are as follows:(1) The SiCNWs were modified by 3-(trimethoxysilyl)propyl(KH570) and fluoroalkysilane(AC-FAS), respectively. The morphology and modification effects of SiCNWs were characterized by Fourier transform infrared spectroscopy(FTIR), water contact angle test, X-ray diffractometer(XRD), Scanning electron miocroscope(SEM), Energy dispersive spectrometry(EDS), etc. and the modification mechanism were put forward. For KH570, the effects of solvent(water, ethanol, water and ethanol volume ratio of 1:1) and the dosage of KH570(volume fraction of 1%, 2%, 3% and 4%) on the modification of SiCNWs were studied. The test results showed that the modification effect of SiCNWs was better when the water was used as solvent. When the modification temperature and time are 80 oC and 3 h, respectively, the best volume fraction of KH570 in water is 2 % and the water contact Angle is 119.5 °. For AC-FAS, the effects of temperature, time and the dosage of AC-FAS on the modification of SiCNWs were studied. The test results showed that the best modification temperature, time and dosage of AC-FAS are: 40 oC, 2h and 2 vol%, respectively, and the water contact Angle is 122.5 °.(2) The effects of post curing temperature(200 oC, 230 oC, 260 oC and 290 oC) and post curing time(0 h, 8 h, 16 h, 24 h, 32 h and 40 h) on the tensile strength, elongation at break, tear strength, compression set and dynamic mechanical properties of FKM were systematically studied by using bisphenol AF/BPP vulcanization system. The results show that the FKM exhibits optimal properties when the post curing temperature and time were around 260 oC and 24 h. The SiCNWs/FKM and mSiCNWs/FKM nanocomposites were prepared under the certain post curing temperature and time, and the reinforcement mechanism of m-SiCNWs on FKM was put forward. The effects of SiCNWs and m-SiCNWs(dosage is 0 phr, 2 phr, 5 phr, 9 phr and 14 phr) on the tensile strength, tear strength, modulus, elongation at break, thermal conductivity, etc. of FKM were studied. The test results show that the tear strength, modulus(stress at 100% strain), hardness and thermal conductivity of the nanocomposites were enhanced significantly compared to pure FKM by increasing the amount of added mSiCNWs and SiCNWs. The modulus(stress at 100%) of the m-SiCNW/FKM and SiCNW/FKM nanocomposites are improved by 102.0% and 58.8%, respectively, and the tear strength are improved by 17.6% and 13.6%, respectively, and the thermal conductivity at 100 oC are improved by 56.9% and 24.8%, respectively. Dynamic mechanical analysis shows that the storage modulus(E?) of the m-SiCNWs/FKM nanocomposites was improved, and the Tg shifted to a higher temperature by increasing the m-SiCNWs content, indicating a greater reinforcing effect of m-SiCNWs. Payne effect, as an important characteristic of rubber materials, was also investigated. The dispersion of m-SiCNWs and SiCNWs were characterized by transmission electron microscopy(TEM), SEM and RPA. The results show that the hydrophobic modification of SiCNWs is beneficial to the dispersion in FKM.(3) The SiCNWs/NBR nanocomposites were prepared by dry and wet mixing process, respectively. The effects of the two kinds of mixing process on the tensile strength, tear strength and wear resistance of SiCNWs/NBR nanocomposites were investigated. The test results show that the reinforcement of SiCNWs on NBR is greater when the wet mixing process is adopted. When the adding amount of SiCNWs was 5 phr, for dry mixing and wet mixing of NBR nanocomposites, the tensile strength of the SiCNWs/NBR nanocomposites were increased by 21.62% and 32.43%, respectively, and tear strength were increased by 15.88% and 28.77%, respectively. The SiCNWs was dispersed uniformly in NBR for wet mixing. In addition, the wear resistance of SiCNWs/NBR nanocomposites was inhanced compared with pure NBR. The dispersion of SiCNWs in SiCNWs/NBR nanocomposites by two mixing process was characterized by SEM. The results showed that the wet mixing process improved the dispersion of SiCNWs in NBR.The preparation of m-SiCNWs/FKM and SiCNWs/NBR nanocomposites provide a favorable exploration for the application of one-dimensional(1D) nanofiller in polymer composites.