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Thermosetting systems based on DGEBA epoxy resin and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer were prepared and investigated. Different mixtures were obtained by using different contents of EPE block copolymer in order to study the influence of the modifier on the properties of the final materials. All thermosetting systems were prepared without using any solvent...
Trial-and-error approaches for experimentally designing and optimizing the polymer matrix for advanced composites are time-consuming and expensive. The simulation for curing behavior and structure–property relationships of epoxy resins can provide a guideline for designing resin matrix which will possess desirable properties. So far there are few reports in which the accuracy of the molecular simulation...
An allyl terminated hyperbranched polyester (HBP) was added to an epoxy formulation containing a trithiol compound to perform a thiol-ene click reaction. By this procedure a flexible thioether network was formed. The photoirradiation of the reactive mixture, which contained a cationic photoinitiator, converted the thioether network in a multifunctional thermal macroinitiator, capable to initiate the...
Epoxy resins are inherently brittle. Thus they are toughened with reactive liquid rubbers or core–shell elastomers. Surface-modified silica nanoparticles, 20 nm in diameter and with a very narrow particle size distribution, are available as concentrates in epoxy resins in industrial quantities since 10 years. Some of the drawbacks of toughening, like lower modulus or a loss in strength can be overcompensated...
Yield in amorphous glassy polymers has been studied in shear and uniaxial tension/compression, where the volume change is relatively small and the deviatoric components of the strain/stress tensor are dominate. In order to study volumetrically driven yield in a different geometry, a specially designed experimental set-up was developed to create a longitudinal deformation that is dilatationally dominated...
Epoxy resins containing polyhedral oligomeric silsesquioxane (POSS) N-phenylaminopropyl nanocomposites were prepared. Modulated differential scanning calorimetry (MDSC) was performed to evaluate the thermodynamic glass transition (T g ) of these materials. The transmission electron microscopy (TEM) images reveal that the dispersion of the POSS in the resin was effective when concentrations...
Epoxy formulations containing mixtures of two different size distributions of silica-based particles (micron-size and nanometer-size) were explored for possible synergistic toughening effects. The influence of bimodal particle size distribution and silica particle content on the glass transition temperature (T g ), coefficient of thermal expansion (CTE), Young's modulus (E), tensile yield...
The synthesis and characterization of a new type of hyperbranched polyester with a flexible ethoxylated Bisphenol-A structure and terminal hydroxyl groups is reported. The influence of the hyperbranched polyester on the curing and thermomechanical properties of both unfilled and silica filled epoxy-novolac systems was studied. The curing behavior was investigated by differential scanning calorimetry...
The microstructure of a mesogen-containing epoxy resin that exhibits high thermal conductivity (0.33 W/m K) was investigated by observations of the scanning electron microscope (SEM) and the polarized optical microscope (POM). It was found that there are many spherulite structures formed in the resin. We supposed that the reason for the high heat-conductivity obtained in the resin is ascribed to the...
Epoxy-functionalized HBP was synthesized and used as toughening additive in epoxy based UV-curable formulations. The addition of the HBP-epox induced an increase of epoxy group conversion, probably through both an activated monomer mechanism, involving the residual hydroxyl groups, and a copolymerization reaction, involving the epoxy functionalities present on the surface of the HBP. Phase separation...
The addition of silica nanoparticles (23 nm, 74 nm, and 170 nm) to a lightly crosslinked, model epoxy resin, was studied. The effect of silica nanoparticle content and particle size on glass transition temperature (T g ), coefficient of thermal expansion (CTE), Young's modulus (E), yield stress (σ), fracture energy (G IC ) and fracture toughness (K IC ), were investigated....
Suspensions of titania nanoparticles in benzyl alcohol were synthesised from TiCl 4 by means of non-hydrolytic sol–gel (NHSG) process. The stable suspensions were mixed with an aliphatic epoxy resin and subsequently photo-polymerised in the presence of a cationic photo-initiator to produce transparent composite films. The presence of titania didn’t influence significantly the polymerisation...
We have studied the preparation of a new class of epoxy thermosets from diglycidyl ether of bisphenol A (DGEBA) modified with an amphiphilic star polymer (SP), initiated either by 1-methyl imidazole or ytterbium triflate, anionic and cationic initiators, respectively. The curing process has been characterized by means of DSC, FTIR and rheology. The last technique allowed us to monitor the shrinkage...
Molybdenum-phenolic resin (Mo-PR) was grafted onto the surface of multi-walled carbon nanotubes (MWCNTs) to obtain modified MWCNTs (CNT-PR). Compared to epoxy resin, epoxy resin/CNT-PR nanocomposites showed the improvements in flame retardancy and mechanical properties. Structural characterization showed that the grafted Mo-PR improved the dispersion of MWCNTs in epoxy resin and enhanced the interfacial...
A well-defined multiarm star copolymer, hyperbranched poly(glycidol)-b-poly(ε-caprolactone), with an average of 100–110 arms per molecule and a molecular weight of arms of 1000 g/mol (s-PCL) and a linear PCL analog (l-PCL) were used as modifiers in the curing of diglycidylether of bisphenol A (DGEBA) using ytterbium triflate as cationic initiator. The effect of the polymer topology on the curing and...
A new hyperbranched polymer (HBP) was obtained via an iterative synthetic procedure that consists of esterification and thiol-ene click reaction. This polymer was used as a latent multifunctional macroinitiator for the dual curing of a commercially available cycloaliphatic epoxy resin and this process was studied by photo-DSC and FTIR. The presence of thioether groups in the HBP structure leads, by...
A low-melting organic-inorganic glass with a high molecular weight soluble in solvents was synthesized by hydrolytic polycondensation of phenyltriethoxysilane followed by a subsequent heat treatment. Softening point and thermostability were strongly increased after heat treatment. The composites of glass/epoxy and glass/clay/epoxy were studied with respect to their thermal properties, fire behavior...
This paper presents a novel two-stage chronological procedure developed for the synthesis of bicontinuous epoxy–silica hybrid polymers. The epoxy–silica polymers are produced by solvent-free hydrolysis of tetraethylorthosilicate into the liquid epoxy resin, followed by the crosslinking of epoxide groups with a diamine curing agent. The two types of bicontinuous epoxy–silica hybrid polymers prepared...
Core crosslinked star (CCS) polymers, which have crosslinked poly (divinyl benzene-co-styrene) [P(DVB-St)] core and multiple arms of polystyrene-b-poly(ethylene oxide) diblock copolymer (PEO-b-PS) [denoted as PEO-b-PS/P(DVB-St) CCS], were synthesized via atom transfer radical polymerization(ATRP). PEO-b-PS/P(DVB-St) CCS polymer was spherical with average diameters of scores of nanometers from transmission...
Novel thermally reworkable, phosphorus-containing, di- and tri-functional liquid cycloaliphatic epoxy resins were designed and synthesized. Their chemical structures were characterized by means of MS, FTIR, 1 H NMR and 31 P NMR methods. After curing, the products were transparent and stable up to 220 °C, while exhibited quick thermal decomposition at the temperature range of 255–280 °C...
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