Syntheses of epoxy‐bridged polyorganosiloxanes and the effects of terminated alkoxysilanes on cured thermal properties

Abstract

A series of epoxy-bridged polyorganosiloxanes have been synthesized by reacting multifunctional aminoalkoxysilanes with diglycidyl ether of bisphenol A (DGEBA) epoxy resin. The reactions of trifunctional 3-aminopropyltriethoxysilane (APTES), difunctional 3-aminopropylmethyldiethoxysilane (APMDS), and monofunctional 3-aminopropyldimethylethoxysilane (APDES) with DGEBA epoxy have been monitored and characterized by FTIR, 1 H NMR, and 29 Si NMR spectra in this study. The synthesized epoxy-bridged polyorganosiloxanes precursors, with different terminated alkoxysilane groups, are thermally cured with or without the addition of curing catalysts. Organometallic dibutyltindilaurate, and alkaline tetrabutylammonium hydroxide have been used as curing catalysts to investigate the thermal curing behaviors and cured properties of epoxybridged polyorganosiloxanes precursors. The maximum exothermal curing temperatures of epoxy-bridged polyorganosiloxanes precursors are found to appear around the same region of 120°C 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 (T d50 s) of cured network of trifunctional epoxy-bridged polyorganosiloxane (epoxy/ APTES). High T d50 s 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 or without the addition of catalyst, no obvious T g transition can be 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 investigated. The organic-inorganic hybrid, from epoxybridged polyorganosiloxanes after the thermal curing process, shows better thermal stability than the cured resin network of pure epoxy-diaminopropane.

Preparation of hybrid composites based on epoxy, novolac, and epoxidized novolac resins and silica nanoparticles with high char residue by sol‐gel method

“…It should be pointed that similar to the results obtained for SEH and SNEH composites, thermal stability of SMNENH increases by the addition of SiO 2 content from 4 to 8 wt%. It is also notable that SMNENH composites show higher thermal stability compared with CNR as a result of its hybrid structure .…”

“…CENR shows DTG peak point of 397.98C and char yield of 44.8%. A comparison between thermograms of SMNENH and SNEH [30][31][32]. Figure 6 displays SEM and TEM images of SiO 2 .…”

Exploring the optical and dielectric properties of bifunctional and trifunctional epoxy polymers

“…Several studies were devoted to the comparison of optical, thermic, and mechanical properties of epoxy polymers. Some of them reported the use of the same hardener and different epoxy resins, while other ones have used the same epoxy resin and investigated several hardeners [16][17][18][19][20][21][22][23][24][25][26][27][28][29].…”

Thermal Stability and Flame Retardancy of a Cured Trifunctional Epoxy Resin with the Synergistic Effects of Silicon/Titanium

“…11,12 In spite of severe drawback and environment-friendly development, halogenated flame retardants are not applicable in many fields. In recent years, considering environmental problems, halogen-free flame retardants containing nitrogen, 13 silicon, 14 phosphorus, 9 boron, 7,15 titanium, 16 and zirconium 17,18 have gradually been applied in the preparation of flame-retardant materials. In fact, the inorganic elements doped to the polymer play an effective role in forming a thermally stable phase and improving the thermal stability.…”

“…However, many of them will lead to various issues toward environment and human health because of the toxic and corrosive smoke released during combustion or thermolysis. , In spite of severe drawback and environment-friendly development, halogenated flame retardants are not applicable in many fields. In recent years, considering environmental problems, halogen-free flame retardants containing nitrogen, silicon, phosphorus, boron, , titanium, and zirconium , have gradually been applied in the preparation of flame-retardant materials. In fact, the inorganic elements doped to the polymer play an effective role in forming a thermally stable phase and improving the thermal stability. , Among them, silicon-containing compounds are typical flame retardants that can significantly exert thermal stability and flame retardancy for modifying EP. , Polyhedral oligomeric silsesquioxane with three-dimensional and cage-shaped structure has the advantages of environmental innocuousness, good thermal and oxidative stability, and flame retardancy. , Another common silicon-containing compound that has been widely used to improve the thermal, mechanical, and insulating performances of modifying resins is γ-aminopropyltriethoxysilane, which contains the reactive group −NH 2 that can be used as a curing agent for EP. − However, a single inorganic flame-retardant element cannot meet the increasing requirements for advanced applications, so the synergistic flame-retardant systems, which comprised multiple flame-retardant elements, have attracted researchers’ attention.…”