Thermoset modified with polyethersulfone: Characterization and control of the morphology

Abstract

Thermoset (TS) epoxy resins can be toughened with a thermoplastic (TP) for high-performance applications. The final structure morphology has to be controlled to achieve high mechanical properties and high impact resistance. Four polyethersulfone-modified epoxy resins are considered. They consist of different epoxy monomer structure (TGAP, triglycidyl-p-aminophenol and TGDDM, tetraglycidyl diaminodiphenylmethane) and a fixed amount of thermoplastic, and they are cured with two different amounts of curing agent. A reactioninduced phase separation occurs for all formulations generating morphologies, different in shapes and scales. The aim is to control the final morphology and in particular its dominant length scale. This morphology depends on the phase separation process, from the initiation to its final stage. The initiation relies on the relative miscibility of the components and on the stoichiometry between epoxy and curing agent. The kinetics depends on the viscosity of the systems. The different morphologies are characterized by electron microscopy or neutron scattering. Dynamic mechanical analysis allows confirming the presence of a phase separation even when it is not observable by electron microscopy.Vermicular morphologies with few hundreds nanometer width are obtained for the systems containing the TGAP as epoxy monomer. Systems formulated with TGDDM presents morphologies on much smaller scale of order a few tens of nanometers. We interpret the different sizes of the morphologies as a consequence of a larger viscosity for the TGDDM systems as compared to the TGAP ones rather than by a latter initiation of phase separation. K E Y W O R D S epoxy resins, morphology, polymer blends, toughening

Engineering Benzoxazine/Epoxy/Imidazole Blends with Controllable Microphase Structures for Toughness Improvement

“…4 The apparent activation energy of MZ-catalyzed polymerization of ER or BZ was determined through the differential scanning calorimetry (DSC, TA Instruments Q20) method. The heating ramp with different rates (5,10,15, and 20 °C min −1 ) was set for DSC scanning over the range of 25 to 350 °C. Thermodynamic properties of BZ/ER/MZ blends were investigated by the Dynamic Mechanical Analysis (DMA, TA Instruments Q800) in 3-point bending mode, with the maximum strain amplitude of 20 μm and an oscillating frequency of 1 Hz, The temperature was set between 40 and 300 °C at a heating rate of 5 °C/min.…”

“…Therefore, strategies for toughness improvement without sacrificing their thermal-mechanical properties are needed to exploit the potential of BZ/ER blends in manufacturing structural parts. 3,4 The reported improvement methods include the development of new structural TS resins 5,6 or polymer catalysts, 7 copolymerization with other TS resins, 8 blending with rubbers or thermoplastic (TP) resins to form multiphase morphologies, 9,10 or hybridization with nanomaterials. 11,12 Among these strategies, the introduction of multiphase structures into TS blends, which could prohibit crack propagation or absorb more energy through plastic deformation when blends were subjected to external impact force, 13−19 is the most promising method to significantly improve their toughness.…”

“…As one of the most promising thermoset / thermoset (TS/TS) blends, benzoxazine (BZ) / epoxy (ER) blending systems have attracted great interest in the development of high-performance engineering materials, owing to their good processability, thermal resistance, and mechanical strength. , When used as structural materials, however, BZ/ER resins usually show unsatisfactory toughness and fracture strain. Therefore, strategies for toughness improvement without sacrificing their thermal-mechanical properties are needed to exploit the potential of BZ/ER blends in manufacturing structural parts. , The reported improvement methods include the development of new structural TS resins , or polymer catalysts, copolymerization with other TS resins, blending with rubbers or thermoplastic (TP) resins to form multiphase morphologies, , or hybridization with nanomaterials. , Among these strategies, the introduction of multiphase structures into TS blends, which could prohibit crack propagation or absorb more energy through plastic deformation when blends were subjected to external impact force, − is the most promising method to significantly improve their toughness. Reaction-induced phase separation (RIPS), a process that a uniform mixture of the resin precursor undergoes a phase separation from the homogeneous structure to a multiphase structure during the in situ curing reactions of the TS resin, has been widely used to fabricate multiphase structures in TP-modified TS resin systems. , This method could significantly improve the toughness of the TS resin and maintain its high modulus, glass transition temperature ( T g ), and excellent thermal stability. , …”

Mechanical and Thermal Properties of Epoxy/Poly(Styrene‐co‐Acrylonitrile) (SAN)/Organoclay Nanocomposites

“…Epoxy resins belong to the class of thermosets, which is extensively used in varying engineering applications ranging from electronics to automobile. [1][2][3][4] As the cure reaction progresses, the crosslink density of the epoxy resin increased, which lead to the brittleness of the material and hinders the end use applications. This resulted in the concern over the ultimate properties of the cross-linked epoxy.…”

Physico-Mechanical and Thermal Properties of Thermoplastic Poly(Vinyl Alcohol) Modified Thermosetting Urea Formaldehyde Resin

“…Better internal bond strengths of particleboards above the requirements of the standard EN 312 were obtained by the incorporation of 10% of hydroxymethylated thick spent sulfite liquor (TSSLH) with UF resin [23]. Highly branched polyurea (HBPU) was synthesized to modify traditional low molar ratio UF resin and with the addition of HBPU, the formaldehyde emission level of the plywood panels was decreased by more than 30% [24].Thermoset epoxy resins were modified with thermoplastic polyethersulfone for highperformance applications [25]. Incorporation of plasticizers, like thermoplastic or rubbers to increase the toughness of thermosets is the most promising strategy [26].Thermoplastic PVA is a water soluble hydrophilic synthetic polymer [27].…”