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Title: Toughening epoxy polymers and carbon fibre composites with core-shell particles, block copolymers and silica nanoparticles
Author: Chen, Jing
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Epoxies are a class of high-performance thermosetting polymers which have been widely used in many industrial applications. However, unmodified epoxies are susceptible to brittle fracture due to their highly crosslinked structure. As a result, epoxies are normally toughened to ensure the feasibility of these materials for practical applications. Recently, a new generation of toughening agents such as polysiloxane based core-shell rubber (CSR) particles, amphiphilic block copolymers and silica nanoparticles have been developed to toughen epoxies. These new toughening agents will be studied in this thesis to pursue ultra-tough and stiff epoxies without compromising other desirable properties. Polysiloxane based CSR particles were able to toughen an anhydride cured epoxy over a wide range of temperatures from -109 °C to 20 °C. At -109 °C, the fracture energy of the epoxy could still be increased from 174 to 481 J/m2 with the addition of 20 wt% of the CSR particles. The toughening mechanisms of these CSR particle modified epoxies were identified as shear band yielding and plastic void growth. A series of commercial poly(methyl methacrylate)-b-poly(butylacrylate)-b-poly( methyl methacrylate) (MAM) triblock copolymers were studied as toughening agents in two epoxy systems. The fracture toughness was generally increased by these block copolymers, although their toughening performance was dependent on the crosslink density of the epoxies and the morphologies of the modified epoxies. The MAM modified epoxies were also studied as the matrix materials in fibre-reinforced composites to investigate the transfer of toughness from the matrix materials to the composites. Full (1 to 1) and nearly full toughness transfer was obtained for the composites. Hybrid toughening using a combination of the MAM block copolymer and silica nanoparticles has also been investigated in the same epoxy systems. The addition of the silica nanoparticles further increased the toughness of the MAM modified epoxies if micron-sized MAM particles present.
Supervisor: Taylor, Ambrose Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available