Tetrafunctional Epoxy toughening

The study considered here employed materials obtained from McDonnell Aircraft Co., through Dexter Hysol, under the Air Force program Development of Ultra Lightweight Materials . They contained the Courtaulds Research Apollo 45-850, consisting of 5 pm diameter carbon fibers in Dexter Hysol s HC 9106-3 di-, tri- and tetrafunctional epoxy resin, toughened by addition of the thermoplastic polyether sulfone (PES). The thermoplastic PEIS toughening agent, present in this epoxy matrix, is presumed to phase separate out once it has cured. These panels were fabricated in an autoclave by Dexter Hysol. 

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. 

Diamant and Moulton [ 184] have also investigated the toughening of a tetrafunctional epoxy resin using various ductile thermoplastic polymers possessing a high glass transition temperature. They observed that a mixture of epoxy resin and PES did not possess a two-phase structure, and that the fracture toughness of the modified system was not markedly different from the values measured for the unmodified epoxy. 

Spherical nanoparticies have also been used to toughen epoxies. Ragosta et al. increased the fracture toughness, K, of tetrafunctional epoxy cured with 4,4-diaminodiphenyl sulfone (DDS) from 0.5 to 1.2 MPam using 10 wt% of sihca particles (Ragosta et al. 2005). 

BucknaU, C. B. and Gilbert, A. H., Toughening tetrafunctional epoxy resins using polyetheramide, Polymer, 30,213-217 (1989). 

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