Highly efficient in situ toughening of epoxy thermosets with reactive hyperbranched polyurethane

Abstract

Hyperbranched polyurethane (HBPU), with low‐molecular‐weight polyethylene glycol space segments between the branching points, was synthesized by a pseudo one‐pot procedure. HBPU was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and gel permeation chromatography. The HBPU was used as a modifier of diglycidyl ether of bisphenol A (DGEBA)/anhydride system. The rheological properties of HBPU‐G3/DGEBA blends were investigated by rotational rheometer. A slight decrease in viscosity of modified blends was observed by adding low content of HBPU and there was chemical reaction between HBPU and epoxy resin even without a hardener. The mechanical and thermal properties of the HBPU‐G3/DGEBA thermosets were characterized and compared with that of the neat epoxy thermosets. Their impact fracture surfaces were investigated by scanning electron microscopy, and the results indicated that no phase separation occurred in the DGEBA/anhydride system after the introduction of HBPU, which was confirmed by dynamic mechanical analysis and thermogravimetric analysis. After addition of 10 wt % HBPU, the toughness of the modified thermosets was found to be significantly improved without sacrificing their processability and thermal and mechanical properties to a large extent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40614.

An investigation of the relationship between the performance of polybenzoxazine and backbone structure of hyperbranched epoxy modifiers

“…The fibrils are also found on the fracture surfaces of samples containing 5% HBPEE‐1 and 5% HBPEE‐2. The improvement in toughness can be ascribed to an in situ homogeneous toughening mechanism . In a previous study, molecular simulation and positron annihilation lifetime spectroscopy demonstrated that the addition of hyperbranched modifiers could introduce nano‐sized cavities into cured hybrid systems.…”

Simultaneously reinforcing and toughening epoxy network with a novel hyperbranched polysiloxane modifier

“…The full width at half‐maximum (fwhm) values for the glass transitions of samples with various HBPSi contents are displayed in Table . In most cases, when fillers or modifiers were blended or reacted into an epoxy matrix, the fwhm tended to be broadened; this indicated an increased heterogeneity . However, as the content of was HBPSi increased to 5 wt %, fwhm decreases.…”

Dielectric Properties of Epoxy/POSS and PE/POSS Systems

“…These are solvents or chemicals that can become part of the ER network during the curing process, and therefore have the potential to directly affect physical properties of the ER system. These can contain an epoxy themselves, or be nonepoxy-based, like phenols, lactone compounds, divinyl ethers, polyols, lauric acid or polyurethanes [33][34][35][36]. Epoxy based reactive diluents are chemicals with one or more epoxide groups as part of their molecular structure, with most POSS used falling in the category of polyepoxies [37], compared to monoepoxies like glycidyl hexadecyl ether, which would have only a single epoxy group [38].…”