Studies On Preparation Of Colloidal Antimony Pentoxide, Its Properties And Flame Retardation To Epoxy Resin

Antimony is a valuable nonferrous metal, and research and development of antimony products are of important significance. In developed countries such as the United States and Japan, about 60% to 70% of antimony consumption find their application in flame retardant. Colloidal antimony pentoxide is one of the best flame retardants. However, studies on antimony flame retardant in China are still laggard even though she has the richest antimony resources, so primary products dominate all other antimony consumptions, and only 5% of antimony are consumed in flame retardant application. Until now no reports on flame retardation of colloidal Sb₂O₅ to epoxy resin have been found. In this paper, colloidal Sb₂O₅ was prepared by oxidation with hydrogen peroxide, and major studies were concentrated on colloidal formation., various properties and flame retardation to epoxy resin. It is meaningful for the developments of antimony and flame retardant industries in China.In the preparation of colloidal Sb₂O₅ by oxidation, affecting factors on the colloidal formation could be variety of stabilizers and its addition amounts, quantity of H₂O₂ and its adding methods, reaction temperature and proportion between solid reactant and liquid. H₃PO₄, NH₄H₂PO₄, TEA and THAM are the best stabilizers. When molar ratio of H₃PO₄ to Sb is from 0.15 to 0.30, or when that of TEA to Sb is from 0.25 to 0.35, colloidal Sb₂O₅ is obtained, which has 45% Sb₂O₅ by weight. The spherical particles in it have an average diameter of 40⁵0nm, and the sol has a viscosity of 6⁷cp at 25℃. The aqueous sol prepared in this way can be stable at least for one year. When H3PO4 is used as stabilizer, proportion between solid reactant and liquid and reaction temperature have greater influences on colloidal formation. While if TEA is used as stabilizer, the effects of reaction temperature decrease, and addition amount of TEA becomes the most significant factor. The stable colloidal Sb₂O₅ is electronegative, absolute value of ζ potential is as high as 60mV, and the aqueous sol has an obvious UV absorption in the range of 190³00nm. The oxidation product is of cubic crystal structure of Sb₂O₅·4H₂O if there is only little amounts of stabilizers, and it is thermal stable under 500℃.For the first time, stabilization mechanism of stabilizers in the Sb₂O₅ sol was investigated by the electric conductivity method combining the analysis of XRD andIR. Results show that when H3PO4 is used as stabilizer, the colloid such as nAx"'yOH^MH2O'jH+]"(nx+y-j)H+ is stabilized by static electricity, and Ax' stands for PO43", H2PO4" or HPO42', while if TEA is used as stabilizer, it engages in the formation of colloidal nucleuses of S. When molar ratio of TEA to Sb is 0.25, the colloid is formed as LS'nOE^'xH2O'mTEAH+]'(?-/?) TEAH+. Additionally, effects of organic solvents on the stability of Sb20s sol were indicated by abnormal electric conductivity curve and ratio of molar electric conductivity AAo. The lower the dielectric constant of organic solvent is, the greater the effect of destabilization is, for example, the destabilization of each organic solvent has the following sequence: glycoK DMF < THF. When Ifko decreases from 1.0 to 0.20, Sb2O5 particles coagulate seriously, and they precipitate if XAo decreases to even less than 0.10.Therefore, surface treatment is necessary for the application of colloidal Sb20s to epoxy resin. Contact angle, index and IR of it were measured in this paper. It was found that the dispersibility of Sb20s sol in DMF solvent is greatly improved by being treated with a siliane coupling agent such as KH. And Sb2Os-DMF organic sol is obtained under the effects of n-propyl amine and lactic acid, which has 40% Sb20s by weight. The particles in it have an average diameter of (94±14)nm, and the organic sol has a viscosity of 8.2cp at 25 °C. KH, n-propyl amine and lactic acid take respectively 4%, 2.5% and 2.0% of Sb2O5 solid by weight.Flame retardation of modified Sb20s to BDMA/DICY/E-44 system was further studied by the Limited Oxygen Index method in this paper. Results show that curing conditions such as components, temperature, time and methods are the influencing factors on properties of cured epoxy resin. The curing properties were worsened by antimony oxides in the following sequence: 40%Sb2Os-DMF organic sol>4%KH-Sb20s dry powders > Sb20s coarse powders > Sb2C>3 powders > Sb2Os-(DMF+ formamide)>45%TEA-Sb2O5 sol. Among all antimony oxides, 4%KH-Sb2O5 dry powders and 40%Sb2Os-DMF organic sol have the best flame retardation to the epoxy resin and increase its LOI from 19.5 to 30 or above. In comparison with using them alone, the composites of 40%Sb2O5-DMF colloid and FR-10 have a synergistic effect. When proportion between Br and Sb is 4.5:1 and LOI requirement is 30, addition amounts of 40%Sb2O5-DMF colloid and FR-10 can be as low as 3% and 8% respectively. Therefore environment-unfriendly effects of bromine flame retardant are abated.Reaction mechanism of the preparation of colloidal Sb20s was also discussed inthis paper. Firstly, H2O2 diffuses to and is absorbed on the surface of Sb2Cb. In the acidic environment, the preceding reaction happens: Sb2O3(s)+2H+—2SbO++H2O. Then the oxidation takes place on solid surface with electron transfer: 2SbO++2H2O2—Sb2O5(s)+2H++H2O. Sb2O5(s) enter the dispersion in forms of single molecular or ions: Sb2Os(s)—Sb2Os(aq). When the concentration of Sb2Os(aq) exceeds its solubility, it crystallizes from the solution. At last, colloidal Sb2Os forms under the action of stabilizers. When reaction temperature is higher than 70°C, effects of colloidal formation on the whole rate decrease. The oxidation between Sb2O3 and H2O2 accords with the model of non-reactive shrinking center, which is determined by surface chemical reaction, and the apparent reaction energy is 72.9kJmol' .