Preparation and cryogenic mechanical properties of epoxy resins modified by poly(ethersulfone)

Abstract

A thermoplastic, poly(ethersulfone) (PES) was used to modify a bisphenol‐F based epoxy resin cured with an aromatic diamine. The initial mixtures before curing, prepared by melt mixing, were homogeneous. Scanning electron microscopy (SEM) micrographs of solvent‐etched fracture surfaces of the cured blends indicated that phase separation occurred after curing. The cryogenic mechanical behaviors of the epoxy resins were studied in terms of tensile properties and Charpy impact strength at cryogenic temperature (77 K) and compared to their corresponding behaviors at room temperature (RT). The addition of PES generally improved the tensile strength, elongation at break, and impact strength at both RT and 77 K except the RT tensile strength at 25 phr PES content. It was interesting to observe that and the maximum values of the tensile strength, elongation at break, and impact strength occurred at 20 phr PES content where a co‐continuous phase formed. Young's modulus decreased slightly with the increase of the PES content. Moreover, the tensile strength and Young's modulus at 77 K were higher than those at RT at the same composition, whereas the elongation at break and impact strength showed the opposite results. Finally, the differential scanning calorimetry analysis showed that the glass transition temperature (Tg) was enhanced by the addition of PES. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 612–624, 2008

Simultaneously increasing cryogenic strength, ductility and impact resistance of epoxy resins modified by n-butyl glycidyl ether

“…The peak after the second scan became relatively narrow. It was thus convenient to define T g after the second scan [12].…”

“…The most common approach to toughen a brittle epoxy resin is introduction of a toughening agent into the networks of the brittle epoxy resin. Previous studies were mainly focused on investigation of fracture resistance or toughness at room temperature (RT), but only a few studies have been conducted on cryogenic fracture resistance or toughness of epoxy resins [9][10][11][12][13][14][15][16]. Furthermore, the mechanical behaviors of materials at RT are generally very different from those at cryogenic temperatures so that their mechanical properties obtained at RT cannot simply be transferred to the cryogenic case.…”

“…Later it was realized that it is important to increase the compatibility and interfacial adhesion between epoxy matrix phase and thermoplastic modifier in order to improve the fracture resistance or toughness. Consequently, poly(sulfone) [28], polysiloxane [29], polyetherimide [30,31], poly(ether sulfone) [12,32,33] and poly-(ether ether ketone) [34,35] etc., have been successfully used to blend with epoxy resins as dispersed phases to effectively toughen epoxy resins. For thermoplastic-toughened epoxy systems, one major problem with the poor processability in using such engineering thermoplastic modifiers with a high viscosity, which is mainly caused by poor compatibility with uncured epoxy resins, still remains unresolved.…”

Morphologies and mechanical and thermal properties of highly epoxidized polysiloxane toughened epoxy resin composites

“…31 Experimentally, it is clear that soft second phases with fine sizes are beneficial to enhancement of the tensile strength of epoxy resins. 32,33 Similarly, the uniformly distributed soft second HEPSO phase with a small droplet size can release internal stress caused during curing to enhance the tensile strength. The dependence of the tensile strength of modified epoxy resins on the HEPSO content as shown in Figure 7 is determined by the two competing effects of reduced internal stress and lowered strength by introduction of soft HEPSO phase.…”

Preparation, intermolecular motion, and thermal properties of thiodiphenyl epoxy

“…Various thermoplastic materials were modified, 7 for instance, the polysulfone was modified or blended with epoxy resins. [8][9][10][11] As the sulfone segments might decompose at low temperature and provide various thermal sulfate derivatives char, 12 which char could improve the thermal stability of the epoxy resins. However, the sulfone segments might cause phase separation, whereas the epoxy resins blended or cured with the sulfone components.…”