Introduction This paper studies thermally initiated radical co- polymerization of mixtures of dimethacrylate mono- mers containing triethylene glycol dimethacrylate (TEGDMA) and 2,2-bis[4-(2-hydroxy-3-metha- cryloxypropoxy)phenyl]propane (bis-GMA) in a 25/75 (bis-GMA/TEGDMA) mass ratio. These systems may reasonably be considered to be simplified models of the resins used at present in commercial filling com- posites [1, 2]. Theoretically, the reactivity of the C=C double bonds of the methacrylate groups in different dimethacrylate monomers is similar. This means that the curing mechanism should not change when we change the mixture of dimethacrylates or during cur- ing. In reality, however, different factors may have sig- nificant effects on the curing kinetics. These factors in- clude the high rigidity and viscosity of the resins (which can reduce the mobility of the monomers), the concentration of radical species, autocatalysis, the for- mation and the connection of microgels, etc. This leads us to expect that the systems will exhibit relatively complex curing and that the kinetic parameters may change slightly during the reactive process. In most of the research carried out to date, the curing kinetics of these systems has been considered kinetically, from a mechanistic point of view (both in photo-initiated and in thermally initiated processes) [3–5]. Although in certain cases these studies allow us to determine the ki- netic constants of initiation, propagation and termination, the working method is complex and if the reactivity is high it is not always possible to determine the constants correctly. Furthermore, they necessarily presuppose that the reaction rate is directly propor- tional to the monomer concentration (mechanism of or- der n with n=1). This paper analyses the kinetic meth- ods usually used in the study of heterogeneous solid-state reactions and attempts to adapt them to non-isothermal curing of these systems, and thereby determine the complete kinetic triplet. A paper to be published at a later date compares the results obtained with those obtained in isothermal curing, both ther- mally initiated and initiated by UV radiation. The ki- netics of the latter systems is of great interest in the de- velopment of materials for carrying out dental repairs. A second objective of the present paper is to compare the different methodologies used to deter- mine kinetic parameters. In general, linear integral methods were used and compared to their differential equivalents, and also to several non-linear methods. The kinetic study may begin with the use of an isoconversional method; in this case we need to know the relationship between the degree of conversion and the temperature, a–T for different heating rates. This method allows us to establish whether the activation energy depends on the conversion. If E does not vary with a, the study is straightforward and one single ki- netic triplet describes the curing. If E changes with a, 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2007 Akadémiai Kiadó, Budapest Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 89 (2007) 1, 233–244 COMPARATIVE KINETIC STUDY OF THE NON-ISOTHERMAL THERMAL CURING OF bis-GMA/TEGDMA SYSTEMS A. Cadenato, J. M. Morancho, X. Fernández-Francos, J. M. Salla and X. Ramis * Laboratori de Termodin´mica, Departament de M´quines i Motors TÀrmics, ETSEIB, Universitat Polit Àcnica de Catalunya Diagonal 647, 08028 Barcelona, Spain The thermal polymerization kinetics of dimethacrylate monomers was studied by differential calorimetry using non-isothermal ex- periments. The kinetic analysis compared the following procedures: isoconversional method (model-free method), reduced master curves, the isokinetic relationship (IKR), the invariant kinetic parameters (IKP) method, the Coats–Redfern method and composite integral method I. Although the study focused on the integral methods, we compared them to differential methods. We saw that even relatively complex processes (in which the variations in the kinetic parameters were only slight) can be described reasonably well using a single kinetic model, so long as the mean value of the activation energy is known (E). It is also shown the usefulness of isoconversional kinetic methods, which provide with reliable kinetic information suitable for adequately choosing the kinetic model which best describes the curing process. For the system studied, we obtained the following kinetic triplet: f(a)=a 0.6 (1–a) 2.4 , E=120.9 kJ mol –1 and lnA=38.28 min –1 . Keywords: dimethacrylate monomers, non-isothermal kinetics * Author for correspondence: ramis@mmt.upc.edu