Curing of epoxy/novolac system modified with reactive liquid rubber and carbon filler Urszula Szeluga 1 ( ), Lidia Kurzeja 2 , Henryk Galina 3 1 Centre of Polymer & Carbon Materials, Polish Academy of Sciences, 41-819 Zabrze, Poland 2 Institute for Plastic Processing “Metalchem” Toruń, the Branch House for Paints and Plastics in Gliwice, 44-100 Gliwice, Poland 3 Faculty of Chemistry, University of Technology, 35-959 Rzeszów, Poland E-mail: ula@karboch.gliwice.pl; Fax: + 48(0-32) 271-29-69 Received: 17 April 2007 / Accepted: 23 December 2007 Published online: 12 January 2008 – © Springer-Verlag 2008 Summary The curing behaviour of epoxy resins modified with reactive liquid rubber, using a novolac resin as a hardner was studied by means of differential scanning calorimetry in isothermal (100, 130 and 150°C) and non-isothermal conditions (2, 5, 10 and 15°C min -1 ). The influence of carboxyl- (CTBN) and epoxy- (ETBN) terminated butadiene-acrylonitrile copolymers on the kinetic parameters and glass transition temperature (T g ) of cured epoxy systems was determined. The effect of grinded bituminous coal as an organic filler into epoxy network was also investigated. The carboxyl-end groups strongly enhanced the curing rate, in contrast to the epoxy- terminated rubber (ETBN) that had only a minor effect on the curing reactions. The presence of coal accelerated curing in its early stage. The T g of completely cured epoxy was practically unaffected by the presence of carbon filler and reactive rubbers and was equal about 132°C. The apparent curing activation energies were determined. A smaller activation energy was observed only for CTBN/epoxy/novolac system. The effect of reactive rubber and coal on the Charpy impact resistance of cured epoxy systems was also discussed. Introduction Epoxy-phenolic resins are very important thermosetting polymers used as a matrix component for high performance fibre or powder containing composites [1-5]. This material combines the properties of phenolic resin (low cost, high impact resistance and hardness) and properties of epoxy resin (flexibility and low shrinkage) [6]. The epoxy compounds containing new or modified additives and/or fillers offer possibilities as materials with special properties or new combination of properties. The disadventageous decrease in the impact strength of filled epoxies can be minimized by introducing elastomeric materials [7,8]. Numerous works have been carried out on the toughening of epoxy materials by introduction of soft or rigid particles [8-15], but most often the flexible copolymers like liquid rubbers based on the carboxyl- terminated (CTBN) and epoxy-terminated butadiene-acrylonitrile (ETBN) were used for modification of epoxy resins [8-11]. Polymer Bulletin 60, 555–567 (2008) DOI 10.1007/s00289-008-0889-7