| The rice yield of China is the first in the world. Rice hull was the most by-product of rice milling industry and a reproducible resource contained abundant silicon. Preparation of silica from rice hull was one of effective utilization ways of rice hull. At present its utilization in industry was limited because its big size and poor dispersity in organic solvents. At first small size nano-silica was obtained in this study. Further an optimum modification method, an optimumγ-methacryloxypropyltrimethoxy silane (MOPTMS) solvent, and modification condition of nano-silica were obtained by using MOPTMS as the modifier and improving the dispersity in many organic solvents of nano-silica as objective. The finally modified nano-silica could increase the strength of butadiene styrene rubber extensively used greatly. The main contents and results were as follows.Using the concentration of sodium silicate solution and the adding speed of H2SO4 (10 wt. %) as affecting factors, preparation method of small size nano-silica was obtained through the orthogonal experiment: H2SO4 (10 wt. %) solution was dropwise added at 14.5 ml/min per 300 mL of sodium silicate solutions (11.8 wt. %). The average size of the product was 30nm. TEM image suggested that the product agglomerated seriously.Nano-silica was modified by six different modification methods. An optimum modification method was obtained: nano-silica was directly modified and MOPTMS anhydrous alcohol solvent was dropwise added. DBP absorption number of nano-silica increased from 2.0 to 3.2 cm3/g and its surface–OH number reduced from 15.2 to 2.4 number/nm2. FT-IR and 29Si CP MAS NMR analysis suggested that nano-silica was modified. The lipophilic value increased from 0°to 2.12°. The hydrophobic value increased from 0 to 20.5%. Not layering in water turned into layering after 1 h and not dissolving in cyclohexane turned into layering after 20 min. Not outflowing in 1 mL pipette turned into outflowing after 25 s. TEM image indicated that nano-silica was well dispersed in organic solvents. The dispersity of nano-silica in anhydrous alcohol, CH2Cl2, CCl4, cyclohexane, and liquid paraffin increased from 0, 0, 0, 0, and 0.1 g/100mL to 9.4, 9.6, 9.8, 9.8, and 10.0 g/100mL respectively.Different concentrations of MOPTMS water solution, anhydrous alcohol solvent, acetone solution, 1-butanol solution, 1-hexanol solution, dichloromethane solution, ether solution and carbon tetrachloride solution were used to modify nano-silica. The result suggested that 0.4 M MOPTMS water solution was optimum. DBP absorption number of nano-silica increased from 3.2 to 3.4 cm3/g and its surface–OH number reduced from 2.4 to 0.6 number/nm2. FT-IR and 29Si CP MAS NMR analysis suggested that nano-silica was further modified.The lipophilic value increased from 2.12°to 2.44°. The hydrophobic value increased from 20.5% to 25.3%. Layering after 1 h in water turned into layering after 45 min and layering after 20 min in cyclohexane turn into layering after 30 min in cyclohexane. Outflowing after 25 s in 1 mL pipette turned into outflowing after 20 s. TEM image indicated that nano-silica was better dispersed in organic solvents. The dispersity of nano-silica in anhydrous alcohol, CH2Cl2, CCl4, cyclohexane, and liquid paraffin increased from 9.4, 9.6, 9.8, 9.8, and 10.0 g/100mL to11.1, 11.2, 11.3, 11.3, and 11.5 g/100mL respectively.The effect of the proportion of water and nano-silica, the concentration and amount of MOPTMS water solution, and the reaction temperature and time on the modification of nano-silica was researched. An optimum modification condition was obtained: the proportion of water and nano-silica was 10, the reaction temperature was 80°C, the reaction time was 1.5 h, the concentration of MOPTMS water solution was 0.4 M, and its amount was 30 mL/10g nano-silica. DBP absorption number of nano-silica increased from 3.4 to 3.5 cm3/g and its surface–OH number reduced from 0.6 to 0.45 number/nm2. FT-IR and 29Si CP MAS NMR analysis suggested that the nano-silica was greatly modified. The lipophilic value increased from 2.44°to 3.38°. The hydrophobic value increased from 25.3% to 28.0%. Layering after 45 min in water turned into layering after 30 min and layering after 30 min in cyclohexane turned into not layering in cyclohexane. Outflowing after 20 s in 1 mL pipette turned into outflowing after 15 s. TEM image indicated that nano-silica was better dispersed in organic solvents. The dispersity of nano-silica in anhydrous alcohol, CH2Cl2, CCl4, cyclohexane, and liquid paraffin increased from 11.1, 11.2, 11.3, 11.3, and 11.5 g/100mL to12.0, 12.1, 12.4, 12.4, and 12.5 g/100mL respectively.Two rubber samples were obtained by using nano-silica and the finally modified nano-silica as reinforcing agent and compared with the contrasted experiment. Their tensile strength, elongation at break and stress at a given elongation were measured. Compared with the contrasted experiment, the tensile strength of nano-silica and the finally modified nano-silica increased from 1.82 MPa to 17.05 and 21.83 MPa respectively. The elongation at break increased from 472% to 728% and 770% respectively. The stress at a given elongation increased from 1.23 MPa (300%) to 6.4 and 7.21 MPa (500%) respectively. The physical and chemical characteristics of the finally modified nano-silica were fit in the professional standards...
|
PDF Full Text Request