Toughened epoxy polymers via rearrangement of network topology

摘要: The highly crosslinked molecular architecture of thermosets makes this class material strong but brittle. It is advantageous to enhance the ductility without sacrificing strength, glass transition temperature (Tg), and modulus. hypothesis was tested that altering chemical structure, network topology a dense thermoset can be engineered dissipate more energy before rupturing covalent bonds, producing tougher ultimate tensile density, or temperature. A processing technique termed “Reactive Encapsulation Solvent/Drying” (RESD) used in which epoxy curing conducted presence varying amounts inert small-molecule solvent, followed by drying/annealing process solvent removed. Density measurements freeze-fracture surface analysis revealed resulting RESD materials are not porous their relaxed state after annealing. Comparing dynamic mechanical response modified unmodified (conventional) structures no significant differences glassy modulus Tg. However, quasi-static testing showed upon stretching, have volumetric capacity up 2.5 times ones. SEM micrographs fracture surfaces specimens indicated nano-sized cavities on thermosets, were present breaking. Therefore, distinct topological features likely origin large improvement ductility. Topology-based toughening potentially an important step toward developing better high performance polymers composites.