Thermoplastic Toughening

Fig. 6. Scanning electron micrographs of various morphologies produced with tailor-made thermoplastics toughened epoxy resins (A) homogeneous, (B) particulate, (C) phase inverted, (D) and (E) cocontinu-ous. (From Flamerton, L, Ed. Chemistry and Technology of Cyanate Ester Resins, Blackie Academic and Professional Glasgow, 1994.)...

Gop Gopala, A., Wu, H., Harris, F., Heiden, P. Investigation of readily processable thermoplastic-toughened thermosets. I. BMIs toughened via a reactive solvent approach. J. Appl. Polym. Sci. 69 (1998) 469 77. 

Asi Asif, A., Rao, V. L., Saseendran, V., Ninan, K. N. Thermoplastic toughened layered silicate epoxy ternary nanocomposites - Preparation, morphology, and thermomechanical properties. Polym. Eng. Sci. 49 (2009) 756-767. 

Ale Alessi, S., Conduruta, D., Pitarresi, G., Dispenza, C., Spadaro, G. Accelerated ageing due to moisture absorption of thermally cured epoxy resin/polyethersulphone blends Thermal, mechanical and morphological behaviour. Polym. Degradation Stability 96 (2011) 642-648. llAsi Asif, A., Rao, V. L., Ninan, K. N. Preparation, characterization, thermo-mechanical, and barrier properties of exfoliated thermoplastic toughened epoxy clay ternary nanocomposites. Polym. Adv. Technol. 22 (2011) 437 47. 

Current Modifications of Epoxies. Particulate Toughening of Thermosets. . Rubber Toughening of Thermosets. . . Thermoplastic toughening of thermosets Epoxy Fibre Composites. ... 

Particulate thermoplastics toughen by crack bridging, crack pinning and by stress concentration which produces shear banding. Amine curing agents are most often used to cure thermoplastic modified epoxies. 

Toughening oftetrafiinctional epoxies has proven especially difflcult. However, by use of specially formulated polysulfones and polyetherimide thermoplastics, toughening and improvement in hot/wet properties have been achieved for two tetrafunctional epoxies cured with an aromatic amine curing agent. 

Thermoplastic toughened epoxies have been found to have a variety of morphologies. These include discrete particles, a solid solution of the thermoplastic and the epoxy, a CO- continuous stmcture, as well as a phase inverted structure. Many investigators have found the co-continuous structure most effective for toughening. 

Unlike rubber-toughened epoxy polymers, the relationship between the microstructure and toughness of thermoplastic-toughened epoxy polymers is not fully understood. Several studies have been initiated the focusing on fracture properties and fractrography of thermoplastic-toughened epoxy systems to establish the definitive relationships between microstructure and fracture properties. However, as discussed in detail next, the complex nature of materials precludes straightforward interpretations. 

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