Cationic benzoxazine polymerization in bulk and on carbon fiber surface

Carbon reinforcements, such as carbon blacks, carbon fibers and whiskers are the most used in the plastics industry. The first part of this work reviews the surface properties of carbon reinforcements and several of the chemical and physical surface modifications made in the effort to improve composite performance.; The influence of the acidic surface groups of carbon fiber in the curing of 6,6{dollar}spprime{dollar}-bis(2,3-dihidro-3-phenyl-4H-1,3-benzoxazinyl) ketone benzoxazine monomer is investigated by means of attenuated total reflection Fourier transform infrared spectroscopy using a 40 nm-thick coating of monomer. The reaction of the monomer with the fiber surface is also investigated using a series of anthracenes as model compounds. Anthrarobin is used to model the surface hydroxyls, while 9 anthracenecarboxylic acid is used to model the carboxylic acid surface groups and anthraquinone is used to model the quinone surface groups. The influence of each model compound on the benzoxazine ring opening is reported and a reaction mechanism proposed.; The purified monofunctional benzoxazine monomers used in this study have very low reactivity, and some do not undergo thermally initiated polymerization after exposure to elevated temperatures for up to 30 h. In this work a boron trifluoride-water complex is used to initiate the polymerization of the monofunctional benzoxazine monomers that do not polymerize when heated. The reactions are studied by means of Fourier transform infrared spectroscopy, investigating the influence of boron trifluoride, moisture and heat. The influence of the amine basicity on reactivity is also investigated, as well as the behavior of a bifunctional monomer.; Finally, a new polymerization mechanism for benzoxazines is proposed, based on the experimental findings.