No description available.

No description available.

No description available.

No description available.

The study described in this thesis examines how modification with different thermoplastics affects the structure and properties of a tetrafunctional epoxy re5ín_ Polyetherimide (PEI) is found to give the best improvement in fracture properties without loss in Youngs Modulus and the PEI/epoxy system is used as the basis for further study. The influences of PEI concentration, initial cure temperature, test temperature and the presence of a second thermoplastic additive, are investigated. The information provided gives insight into the likely mechanisms of toughening in tetrafunctional epoxy/thermoplastic blends. Flory-Huggins Lattice Theory is used to describe miscibility behaviour for a number of curing thermoplastic/epoxy blends and the predictions compared with the actual morphologies observed. Further, the sensitivity of the expected miscibility behaviour to fluctuations in Flory Huggins interaction parameter X12 and number-average molecular weight Mn of the thermoplastic, is considered. Dynamic mechanical analysis is used to monitor the changing viscoelastic properties of curing thermoplastic/epoxy blends, allowing investigation of the way different thermoplastics influence the state transformation profile of a curing epoxy resin.

This thesis is concerned primarily with the curing of epoxy resin and the effect of gamma-irradiation on the electrical properties of epoxy resin systems. The particular systems examined were a diglycidyl ether of bisphenol A (DGEBA, Ciba Geigy MY750) epoxy resin cured using one of two hardeners. These were a hydroxyalkylated polyamine (Ciba Geigy HY956) and a dodecenyl-succinicanhydride (DDSA) with an accelerator of benzyldimethylamine. Different methods of examining the curing of the epoxy resin system have been carried out including differential scanning calorimetry (DSC), infrared spectroscopy (I.R.), dielectric measurements, volume resistivity measurements and thermally stimulated discharge current. The results of dielectric relaxation measurements obtained during the curing of the epoxy resin system were interpreted on the basis of a model considering the growing polymer molecules to be in solution, the solvent being the unreacted monomer and hardener. The investigation of the effect of gammairradiation on the electrical properties (conduction mechanism and dielectric behaviour) of the epoxy resin system was achieved by examining the electrical properties of the fully cured epoxy resin system before and after irradiation and the results compared. To establish the electrical properties of the fully cured epoxy resin system before and after irradiation, a series of experiments which provide information about the conduction mechanism, the dielectric properties, the infrared spectra (I.R.) and the glass transition temperature (Tg) obtained from (DSC) measurements were carried out. For the epoxy resin system MY750/HYS56, it was found that the D.C. conductivity, dissipation factor and capacitance values increase, whereas the glass transition temperature (Tg) and the activation energy, E, obtained from D.C. measurements decreased for the irradiated samples. Furthermore, a modification in the I.R. spectrum in the 1600 to 1800 cm⁻¹ range due to the formation of carbonyl groups (C = O) in the irradiated sample has been observed. However in the case of epoxy resin system MY750/DDSA, it was found that the dissipation factor and capacitance values decrease, whilst the glass transition temperature (Tg) and the activation energy obtained from dielectric measurements increased for the irradiated samples.

No description available.

No description available.

No description available.

Advanced composite materials possessing high specific stiffness and strength have been successfully employed as structural materials in the aerospace, military and automotive industries. Despite the advantages that composites have over other materials, further development has been restricted by their brittleness. The aim of this research project was to improve the energy absorbing capabilities of unidirectional glass fibre epoxy resin composites by coating the fibres with an interlayer. UHMWPE was used as the interlayer because of its outstanding toughness while EPDM of low modulus was used to assess the difference between energy absorption through plastic deformations (UHMWPE) and highly elastic deformations (EPDM).