Preparation and thermomechanical properties of epoxy resins modified by octafunctional cubic silsesquioxane epoxides

Abstract

The thermomechanical properties of octafunctional cubic silsesquioxane‐modified epoxy resins associated with dicycloaliphatic hardener (4,4′‐dimethyldiaminodicyclo hexyl methane) were studied using thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis. The structures of epoxy resin containing cubic silsesquioxane epoxides were characterized by Fourier transform infrared spectroscopy and wide‐angle X‐ray scattering techniques. In this work, octa(dimethylsiloxybutylepoxide) octasilsesquioxane (OB), and octa(glycidyldimethyl‐siloxyepoxide) octasilsesquioxane (OG), were synthesized and used as additives to improve the properties of a commercial epoxy resin by exploring the effects of varying the ratio of OB or OG. The commercial Ciba epoxy resin (Araldite LY5210/HY2954) was used as a standard. It was found, by thermogravimetric analysis and dynamic mechanical analysis, that the highest thermal stability was observed at N = 0.5 (N = number of amine groups/number of epoxy rings). No glass transition temperature was observed by adding 20 mol % OB to the Ciba epoxy resin, indicating the reduction of chain motion in the presence of octafunctional cubic silsesquioxane epoxide. The storage modulus of the OB‐modified epoxy resin also increased, especially at higher temperatures, compared with the Ciba epoxy resin under identical curing conditions. Fourier transform infrared data elucidated the preservation of cubic silsesquioxane structure after curing at high temperature. In contrast, the OG/Araldite LY5210/HY2954 systems gave poorer thermomechanical properties. The low viscosity of OB at room temperature (∼ 350 cPs) makes it suitable for composite processing and, when used in conjunction with the Ciba epoxy, lowers the viscosity of this system as well. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3490–3503, 2004

Viscoelastic properties and residual stresses in polyhedral oligomeric silsesquioxane‐reinforced epoxy matrices

“…It has been found that the glass transition temperature of POSSreinforced epoxy nanocomposites either increases, 24,28,29,35,38 decreases, 27,31,[38][39][40] stays unchanged, 30,32,37,39 , or even disappears 37 with the addition of POSS depending on the chemical structure of the functional group (R group) on the POSS and the POSS loading. In general, the glass transition temperature of the nanocomposites decreases when the R group on the POSS is long and flexible and a ''soft'' interface can be formed between the nanoparticle and matrix; 27,32,40,45 on the other hand, T g increases if the interface is rigid and the polymer chain motions are hindered by their covalent bonding to POSS clusters.…”

“…20 mol %), the glass transition of epoxy/octa(dimethylsiloxy butyl) epoxide nanocomposites disappears as measured by dynamic mechanical analysis (DMA) or differential scanning calorimetry (DSC) due to restricted segmental motion caused by the rigid POSS cage and a very high crosslink density. 37 The moduli of the POSS-filled nanocomposites similarly depend on the POSS structures. The glassy modulus of the nanocomposites is found to either increase due to the nanoreinforcement of the nanoparticles 27,31,39 or decrease; 37 furthermore, the rubbery modulus also either increases presumably due to the increased crosslink density or the reinforcement of the nanoparticles 28,30,43 or decreases due to the decreased crosslink density associated with the flexible structure of the POSS.…”

“…37 The moduli of the POSS-filled nanocomposites similarly depend on the POSS structures. The glassy modulus of the nanocomposites is found to either increase due to the nanoreinforcement of the nanoparticles 27,31,39 or decrease; 37 furthermore, the rubbery modulus also either increases presumably due to the increased crosslink density or the reinforcement of the nanoparticles 28,30,43 or decreases due to the decreased crosslink density associated with the flexible structure of the POSS. 27 One study also showed that the instantaneous modulus of the nanocomposites is not affected by the incorporation of POSS, although the physical aging process of the composites in the glassy state was found to be retarded.…”

Preparation and properties of epoxy resin/polyhedral oligomeric silsesquioxane hybrid materials

“…However, EP thermosets, like most polymers, lack thermal resistance and flame retardancy, particularly in certain applications where flame retardancy is a most required feature. The modification of EP via POSS could endow the materials improved thermal and oxidative resistance, flame retardancy, and dielectric properties [9][10][11][12][13][14][15]. Several studies on POSS modified epoxy resins were reported in the last decades.…”

Free-volume properties of epoxy composites and its relation to macrostructure properties

“…They are the most commonly used engineering thermosets because of their good to excellent engineering properties [3][4][5], and as organic matrix it has excellent heat, moisture, and chemical resistant and good adhesion to many substrates [6,7].…”