Synthesis And Properties Of Boron-containing Bisphenol-S Formaldehyde Resin,Modified By Nano Materials And Applied To Cure Epoxy Resin

Phenolic resin which has good mechanical properties, heat resistance and chemical resistance has been widely used in many social fields including military and aerospace. Boron containing phenolic resin was studied because of its better thermal property than conventional phenolic resin. In order to improve phenolic resin’s thermal properties and broaden the scope of its application, in this thesis, boron containing bisphenol-S formaldehyde resin(BBPSFR) was synthesized in consideration of the rigid sulfonyl in bisphenol-S has higher mechanical properties and the attaching of better mechanical properties, BBPSFR was modified by nano materials, and the effect of nano materials on its thermal properties were discussed. BBPSFR and BBPSFR/nano materials composites were also used to cure epoxy resin, the curing kinetics and the properties of the composites were studied. The research provided the basis for the nanocomposite with both higher thermal properties and higher mechanical properties.In the first part, boron containing bisphenol-S formaldehyde resin(BBPSFR) was synthesized by formalin method. The structure of BBPSFR was characterized by 1H nuclear magnetic resonance(1H NMR). The thermal properties of BBPSFR were investigated through dynamic mechanical analysis, thermogravimetric analysis(TG) and thermogravimetry and mass spectrum analysis(TG-MS). The effect of boron content on the thermal properties and the thermal degradation process of BBPSFR were studied. The results showed that the borate and the six-member ring containing boron oxygen coordinate structure were formed during the curing process of BBPSFR. The glass transition temperature(Tg) and the thermal degradation stability of BBPSFR were enhanced by the addition of boron. Contrast to the resin without boron, the Tg of 2.0B(the mole ratio of bisphenol-S and boric acid was 3:2) was 264.4oC, which increased 104.0oC, the initial decomposition temperature(Ti) was 375.2oC, which increased 43.0oC. The activation energy(Ea) calculated by Flynn-Wall-Ozawa method decreased with the conversion in the degradation process, and Ea at the early stage of the degradation increased markedly when boron was added. The TG-MS results showed that: below 330 oC, the mass loss was mainly caused by the volatilization of small molecules and shedding of the end-hydroxymethyl. In the range of 330~560 oC, the mass loss was mainly caused by the oxidation and the breakage of most ether linkages, methylene and S─C bond. Above 560 oC, B─O bond was broken, phenol and fragments were released.In the second part, BBPSFR was modified by nano Al2O3 and octa(aminophenyl) polyhedral oligomeric silsesquioxane(OAPS) respectively, and its thermal degradation process was investigated. The results showed that Ti of BBPSFR was increased by the addition of nano Al2O3, when nano Al2O3 content was 15 wt%, Ti increased 26.0oC. However, the thermal degradation stability of modified BBPSFR decreased immediately after the decomposition started, the decomposition was catalyzed by nano Al2O3. And the decomposition reaction order is one. TG-MS results showed that nano Al2O3 catalyzed the decomposition of BBPSFR, especially at the later stage. The addition of OAPS improved the thermal stability of BBPSFR,Ti increased with the content of OAPS, Ti was increased 25.3oC when the content of OAPS was 12 wt%. And the decomposition process was divided into three stages, the reaction order in each stage was one, Ea value increased with increasing of OAPS content in all the three stages. The results showed that OAPS inhibited the decomposition and enhanced its thermal degradation stability.In the third part, BBPSFR was used to cure the common bisphenol-A epoxy resin(E51), the optimal proportion of BBPSFR and epoxy was discussed. BBPSFR/E51 was modified by in situ formed nano Si O2. The curing kinetics, dynamic mechanical properties(DMA), mechanical properties and electrical properties of the composites were determined. The results showed that the optimal mass proportion of BBPSFR and E51 was 3:7. The glass transition temperature decreased with the addition of nano SiO2, however, the storage modulus and the thermal stability of the composites were increased, for example, when the content of nano SiO2 was 9 wt%, the storage modulus at 25 oC was the maximum, which was 11.8 GPa, that was increased 74.4%, Ti got the maximum at the nano SiO2 content was 3 wt%, it was 335.1oC, which was 18.3oC higher than that of the resin without nano SiO2. The DSC results showed that nano SiO2 accelerated the cure of BBPSFR/E51, and the curing process of the composites could be described by the two-parameter(m, n) ?esták-Berggren autocatalytic kinetic model. The composites containing a small amount of nano SiO2 had higher tensile strength and impact strength, and the nano SiO2 content had no much effect on electrical properties of the composites. CNTs were used to modify the common bisphenol-A epoxy resin(E44) which was cured by BBPSFR, and the properties of the modified composite were investigated. The optimal mass proportion of BBPSFR and E44 was 4:6, the addition of CNTs also accelerated the cure of BBPSFR/E44, and the nonisothermal curing kinetics of the composite could be described by the ?esták-Berggren autocatalytic kinetic model. The addition of CNTs increased the Tg of the composite obviously, when CNTs content was 1.0 wt%, Tg was 212.4oC, which was 22.8oC higher than that of BBPSFR/E44 without CNTs. 0.5 wt% content of CNTs was dispersed uniformly in the matrix, so the tensile strength and the impact strength of the composites were the highest, the tensile strength was 91.98 MPa, and the impact strength was 89.34 kJ·m-2, which was 21.45 MPa and 39.02 kJ·m-2 higher than that of BBPSFR/E44 without CNTs, respectively.The o-cresol formaldehyde epoxy resin(o-CFER) was synthesized, and was cured by BBPSFR. The effect of nano SiO2, CNTs and reduced graphene oxide(r-GO) on the properties and curing of the resin were discussed, respectively. The results showed that o-CFER could be cured by BBPSFR and the optimal mass proportion of BBPSFR and o-CFER was 3:7. The nonisothermal curing kinetics of the three composites all could be described by the ?esták-Berggren kinetic model. The effect of nano SiO2: the thermal stabilities of the resin were improved significantly by nano SiO2, when the nano SiO2 content was 12 wt%, the residual weight at 600 oC was 47.8%, which was 34.3% higher than that of the residual weight of BBPSFR/o-CFER without nano SiO2. With the increasing of the nano SiO2 content. The impact strength increased firstly, then decreased, and it got the maximum value at 6 wt%, which was 149 kJ·m-2, and 44 kJ·m-2 higher than that of BBPSFR/o-CFER. The content of nano SiO2 content had no much effect on electrical properties, the electrical properties parameters were higher while the content of nano SiO2 content was less. The effect of nano CNTs: the thermal property of BBPSFR/o-CFER was improved significantly by the addition of CNTs. Tg increased 43.9oC and Ti increased 28.9oC by the addition of 3.0 wt% CNTs. The tensile strength and impact strength increased 21.8% and 12.4%, respectively by the addition of 1.0 wt%, the volume resistance and surface resistance of the composites were also improved. The effect of r-GO: the addition of a small amount of r-GO improved the Tg, thermal stability, tensile strength and impact strength of the composites. Tg increased 11.3oC when r-GO content was 0.5 wt%, and Ti of the composite with 2.0 wt% r-GO was 239.3oC, which was 25.6oC higher than that of BBPSFR/o-CFER, the tensile strength was 180 MPa, and the impact strength was 143 kJ·m-2, which increased 15.4% and 36.2%, respectively. The value of dielectric loss increased with the content of r-GO.