Non-Aqueous Syntheses and Properties of Epoxy and Polyamideimide Silica Hybrid Nano Composites

• Main Authors: Tzong-Ming Lee, 李宗銘
• Other Authors: Chen-Chi M. Ma
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/09112214424628621895

博士 === 國立清華大學 === 化學工程學系 === 94 === The design of inorganic nano silica into polymer matrix to form a polymer-nanosilica hybrid has been proven to be an effective way to improve the thermal and mechanical properties of polymers. A non-aqueous synthetic method to prepare nanometer scale silica in both epoxy and polyamideimide resin has been established through direct thermal heating under catalyst in this study. In the first part of this study, a series of epoxy-bridged ethoxysilane precursors have been synthesized by reacting multifunctional aminoalkoxysilanes with diglycidyl ether of bisphenol-A (DGEBA) epoxy resin. The reactions between aminoethoxysilanes with DGEBA epoxy have been monitored and characterized by FTIR, 1H NMR, and 29Si NMR spectra in this study. Organometallic dibutyltindilaurate, and alkaline tetrabutylamonium hydroxide have been used as curing catalysts to investigate the thermal curing behaviors and cured properties of epoxy-bridged ethoxysilane precursors. The maximum exothermal curing temperatures of epoxy-bridged polyorganosiloxanes precursors are found to appear around the same region of 120℃ in DSC analysis. The addition of catalysts to the Epoxy/APTES precursor shows significant influence on the cured structure; however, the catalysts exhibit less influence on the cured structure of Epoxy-APMDS precursor and Epoxy/APDES precursor. Curing catalysts also show significant enhancement in increasing the thermal decomposition temperature (Td50s ) of cured network of trifunctional epoxy-bridged polyorganosiloxane (Epoxy/APTES). High Td50s of 518.8 and 613.6 in the cured hybrids of Epoxy/APTES and Epoxy/APMDS precursors are also observed, respectively. When trialkoxysilane terminated epoxy-bridged polyorganosiloxanes precursor are cured with catalyst, there is no obvious Tg transition found in the TMA analysis of cured network. The cured network of trialkoxysilane terminated epoxy-bridged polyorganosiloxanes also exhibits the lowest coefficient of thermal expansion (CTE) among the three kinds of alkoxysilane terminated epoxy-bridged polyorganosiloxanes. The organic-inorganic hybrid from epoxy-bridged polyorganosiloxanes after thermal curing process shows better thermal stability than the cured resin network of pure epoxy-diaminopropane. The effects of molecular structures and mobility on the thermal properties of epoxy-bridged polyorganosiloxanes have been investigated by solid-state 29Si and 13C solid state NMR in this study. The structures of epoxy-bridged polyorganosiloxanes with respect to the catalysts are quantitatively investigated. Acidic BF3.MEA shows the best catalytic effects on the formation of T3 and D2 structures in the epoxy-bridged polyorganosiloxanes from tri-functional Epoxy-APTES and di-functional Epoxy-APMDS precursors, but basic NBu4.OH has better enhancement on the formation of M1 structure in the epoxy-bridged polyorganosiloxanes from mono-functional Epoxy-APDES precursor. TEM spectra show that the epoxy-bridged polysilsesquioxanes of Epoxy-APTES precursors exhibit polysilsesquioxanes nano domain around 45-55 nm under the catalysis of dibutyltindilaurate (DBTDL), but show bigger polysilsesquioxanes nano domain around 50-150 nm under the catalysis of basic tetrabutylammonium hydroxide (NBu4.OH) in epoxy matrix after direct thermal curing process. In the second part of this study, epoxy-bridged polysilsesquixanes-silica hybrid has been prepared by thermally curing of epoxy-bridged ethoxysilane precursor with various amounts of tetraethoxysilane (TEOS) under the catalysis of boron trifluoridemonoethylamine (BF3MEA) in this study. The epoxy-bridged ethoxysilane precursor was synthesized by reacting one mole of DGEBA epoxy with two moles of 3-Aminopropyltriethoxysilane. BF3MEA shows the best accelerating effect on the formation of -O-Si-O-structure during thermal curing process at 150℃ based 0.1% to 0.2% of TEOS. The effects of boron trifluoride monoethylamine (BF3MEA) on the molecular structures and thermal dynamic properties of cured epoxy-bridged polysilsesquixanes silica hybrid have been investigated. Solid-state 29Si NMR have been used to compare the distribution of both silsesquixanes , T, structures and the silicate , Q, structures of the epoxy-bridged polysilsesquixanes silica hybrid structures cured with or without the catalyst of BF3MEA. Spherical nano silica has been found in the TEM spectra of the epoxy-bridged polysilsesquixanes silica hybrid cured under the catalyst of BF3MEA. Spherical nanosilica with 20 nm of diameter was obtained under 0.1% of BF3MEA catalyst in the cured epoxy-bridged polysilsesquixanes matrix. The lowest coefficient of thermal expansion of the cured epoxy-bridged polysilsesquixanes silica hybrid has been found when 0.1% weight percent of BF3MEA was used as thermal curing catalyst. The glass transition temperatures of the cured epoxy-bridged polysilsesquixanes silica hybrid are no obvious Tgs in TMA and DMA analysis. In the third part of this study, non-aqueous synthesis of nano silica in diglycidyl ether of bisphenol-A epoxy (DGEBA) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly in DGEBA epoxy matrix at 80℃four hours under the catalysis of boron trifluoride monoethylamine (BF3MEA). BF3MEA was proved to be an effective catalyst for the formation of nano silica in DGEBA epoxy under thermal heating process. FTIR and 29Si NMR spectra have been used to characterize the structures of nano silica from this direct thermal synthetic process. The morphology of the nano silica synthesized in epoxy matrix has been also analyzed by TEM and SEM spectra. The effects of both the concentration of BF3MEA catalyst and amount of TEOS on the diameters of nano silica in the DGEBA epoxy resin have been discussed in this study. The nano silica containing epoxy exhibited the same curing profile as pure epoxy resin during the curing reaction with 4,4�S-diaminodiphenysulfone(DDS) from DSC analysis. The thermal cured epoxy-nanosilica composites from 40% of TEOS exhibited high glass transition temperature of 221℃, which was almost 50℃higher than pure DEGBA-DDS-BF3MEA cured resin network. Almost 60℃ upgrading of thermal degradation temperature has been observed in the TGA analysis of the DDS cured epoxy-nanosilica composites containing 40% of TEOS. In the fourth part of this study, non-aqueous synthesis of nano silica in polyamideimide(PAI) resin has been successfully achieved in this study by reacting tetraethoxysilane (TEOS) directly in PAI resin solution under the catalysis of boron trifluoride monoethylamine (BF3MEA) at 80℃. FTIR and 29Si NMR spectra have been used to observe and to characterize the structures of nano silica in the polyamideimide resin matrix. Nano silicas with diameters from 30nm to 90nm have been obtained based on different concentrations of BF3MEA catalyst. The thermal drying condition of polyamideimide-silica hybrid solution exhibits obvious correspondence to the thermal stabilities of the polyamideimide-silica hybrid film. The polyamideimide-silica hybrid films dried in air atmosphere exhibit higher thermal degradation temperatures and char yields than those dried in nitrogen atmosphere condition. The Tg of the polyamideimide-silica hybrid film containing 6% of nanosilica appears around 304℃and disappears when the concentration of the silica in the polyamideimide-silica hybrid film reaches 12 wt% from thermal mechanical analysis (TMA). The CTE of the polyamideimide-silica hybrid film also decrease to 43ppm/℃ in polyamideimide-silica hybrid film with 12 wt% of nanosilica. Strong hydrogen bonding interaction between the silanol group of nano silica and the amide groups of PAI resin has been observed in the FTIR analysis. The polyamideimide-silica hybrid film containing 12wt% of nanosilica exhibits tensile strength greater than 250Mpa, which is almost 3 times greater than pure polyamideimide film. The tensile modulus of the polyamideimide-silica hybrid film with 12 wt% naosilica is also found to reach 8.5Gpa. The mechanical strength of the polyamideimide-silica hybrid film increases with the content of naonsilica in the hybrid matrix.