This paper reports on the use of an epoxidized hyperbranched polymer (HBP) as an additive to an epoxy anhydride resin system. The hyperbranched polymer used was an aliphatic polyester with a molecular weight of around 10 500 g mol −1 . The epoxy resin mixture used was a combination of a difunctional diglycidyl ether of bisphenol A (DGEBA) epoxy and an epoxy novolac, and was cured with a catalysed anhydride curing agent. It has been shown that, at a concentration range of 0 to 20 wt% addition, the HBP is able to almost double the fracture toughness, with little evidence of any deleterious effects upon processing and the durability of the cured resin system. The flexural modulus and stress, however, were found to both decrease by about 30% as a result of HBP addition while the T g was found to decrease by about 10%. The processability of the uncured resin systems has been investigated by using rheological and calorimetric techniques and it was found that the processability window, as determined by the gel time and viscosity changes, was relatively unaffected by HBP addition. The fracture surfaces were evaluated by using scanning electron microscopy which showed that the unique structure of the HBP facilitates an enhanced interaction with the polymer matrix to achieve excellent toughness enhancement of the polymer matrix. The durability of the epoxy network has been investigated via thermogravimetric analysis (TGA) and solvent uptake, and the HBP has been shown to have little systematic deleterious effect upon the degradation temperatures and the total amount of solvent absorbed.

Samples of an aerospace structural epoxy composite (8552/IM7) were subject to long-term (% 1 year) thermal aging at temperatures of 708, 1208, 1708, and 2008C (in air). The changes to the chemical and physicochemical structure of the composite were analyzed by a range of different techniques, including gravimetric analysis, Fourier transform infrared (FTIR), and dynamic mechanical analysis (DMA) to compare the effects of different severities of degradation treatment. The results highlighted the large differences in chemical effects between the surface and the interior of the composite with very minor changes in the latter even at quite high aging temperatures and long aging times. The oxidative changes at the surface, however, varied from highly selective molecular changes for particular chemical groups at the lower aging temperatures (708 and 1208C), to quite general and extensive oxidative degradation at the higher aging temperatures (1708 and 2008C). The results indicated that the mechanical changes in an aged composite of this type will vary greatly with the material thickness and surface protection as well as the aging temperature the composite is exposed to.

In this study, we have electrospun poly(vinyl alcohol)(PVA) nanofibers and PVA composite nanofibers containing multiwall carbon nanotubes (MWNTs) (4.5wt%), and examined the effect of the carbon nanotubes and the PVA morphology change induced by post-spinning treatments on the tensile properties, surface hydrophilicity and thermal stability of the nanofibers. Through differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) characterisations, we have observed that the presence of the carbon nanotubes nucleated crystallization of PVA in the MWNTs/PVA composite nanofibers, and hence considerably improved the fiber tensile strength. Also, the presence of carbon nanotubes in PVA reduced the fiber diameter and the surface hydrophilicity of the nanofiber mat. The MWNTs/PVA composite nanofibers and the neat PVA nanofibers responded differently to post-spinning treatments, such as soaking in methanol and crosslinking with Glutaric Dialdehyde, with the purpose of increasing PVA crystallinity and establishing crosslinked

Samples of an aerospace-grade epoxy composite (M20/IM7) are subject to long-term ($ 1 year) thermal aging at temperatures of 708C, 1208C, 1708C, and 2008C (in air) and the changes to the chemical and physicochemical structure of the composite are analyzed by a range of different techniques, including gravimetric analysis, FTIR, DSC, and DMA to compare the effects of different severities of degradation treatment. The results show that at the lower temperatures, the oxidative degradation changes are very selective for chemical defect groups, particularly near the sample surfaces. However, at the higher temperatures, combinations of further cure reactions and generalized oxidative degradation changes (again from the surface inwards) make for a highly complex ageing pattern for this particular composite material.

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