Studies On The Modification Of Cyanate Esters By CTBN

High performance resin matrix composites have shown potentials in aerospace structures, aircrafts and civil industry and gain more and more attentions in recent years. As one of the most important advanced matrix, cyanate esters are considered as the key resin matrix system in the high performance resin matrix composites. Owning to their special chemical structures, cyanate esters possess the high performances, such as excellent mechanical properties, dielectric properties and high temperature resistant properties. So cyanate esters show the potentials in the resin matrix composites, adhesive, electrical encapsulation materials and insulated functional materials. However, the drawback of brittleness as most thermosetting resins has limited their widely applications.In this thesis, carboxyl-terminated liquid butadiene-acrylonitrile (CTBN) was applied to toughen the dicyclopentadiene bisphenol diyanate ester (DCPDCE) and biphenyl A cyanate esters (BADCy). The reactions, performance of cured resin and fiber-reinforced composites of the two systems were studied. The main research projects and results can be described as follows:1) Investigation of reactivity of the two modified systems. The results clearly indicate that CTBN can act as a catalyst in the systems. And the addition of CTBN has great influence on the curing of CE and effectively improves its reactivity properties.2) Investigation of the properties cured modified resins. The results show that CTBN can effectively improve the toughness properties of DCPDCE. On the contrary, the thermal and hydrothermal properties of the cured resin will be weakened. Impact strength and flexural strength can be improved by 16.7% and 6.7% while 2wt% CTBN is introduced into the BADCy systems, although the dielectric properties will be damaged a little. On the other hand, when 15 wt% CTBN is blended into the DCPDCE systems, the multiple properties can be attain to their best. The toughening mechanism of the cured resin is in accordance with the classical cavity shear yield theory based on the SEM images of the failure specimens from impact strength tests.3) Investigation of properties of fibers reinforced composites. The results also show that CTBN can effectively improve the mechanical properties of CE resin based fibers reinforced composites' mechanical properties although their dielectric, thermal and moisture resistance properties will be weakened.