In a previous publicaitons from the authors.laboratotry a method was developed to predict the structure and properties of low density polyethylene (PE-LD) that could be obtained over a very wide range of polymerization conditions. The method was proved using experimental data from the literature. However, some shortcomings of the method were noticed. The aim of this work was to overcome the shortcomings and to enable the better manipulation of experimental data using a computer. A computer program has been developed to establish the mathematical relationships between ethylene entropy and the structural parameters and density of Pe-LD. All available experimental data (more than 300 experimental points) have elaborated and confirmed our mathematical models and our theoretical predictions.

In this work, the attention was paid at the investigation of montmorillonite dispersion in epoxy/amine systems due to improved final properties of the nanocomposites. The influence of different montmorillonite content on the kinetics of curing of epoxy/Jeffamine D-230 systems was followed by differential scanning calorimetry (DSC). The curing of epoxy nanocomposites was performed using dynamic regime at three different heating rates: 5, 10 and 20°C/min. Three isoconversional methods were applied: two integral (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose methods) and one differential (Friedman method). The presence of montmorillonite (MMT) causes the beginning of curing at lower temperatures. The shape of the DSC curves has been changed by the addition of MMT, supporting the hypothesis of a change in the reaction mechanism. For hybrids with 3 and 5 wt.% of MMT, the Eα dependence is very similar to those found for the reference system (epoxy/Jeffamine D-230) for the curing degree less than 60%. The hybrid with 10 wt.% of MMT has lower energy activation in regard to the referent system without montmorillonite. Greater differences are observed in the second part of the reaction, where it is known that the curing process is more controlled by diffusion (α>0.60). The Ea value increases at the end of the reaction (α→1), which was observed for all systems, and is more pronounced in the presence of montmorillonite. [Projekat Ministarstva nauke Republike Srbije, br. III45022

Classic theory of free radical polymerization is based on two assumptions. The first is that the concentration of initiator is slightly changed and could be taken as a constant value. The second assumption is that the rate of initiation is equal to the rate of termination. Equation for the polymerization rate based on these assumptions can not successfully describe the initial stage of free radical polymerization. In order to solve this problem, three mathematical models were developed and used to verify of the mentioned assumptions. The models were fitted to experimental data and qualities of their fits were compared. Experimental data of isothermal bulk polymerization of methyl methacrylate were obtained by differential scanning calorimetry at 60, 70, 80 and 90°C with initiator concentration (AIBN) of 0.5 wt%. The best fit was shown by the model that assumes constant concentration of initiator during initial stage but takes into account that the rate of initiation is not equal to the rate of termination at the beginning