Issue 37

P. Velev et alii, Frattura ed Integrità Strutturale, 37 (2016) 272-279; DOI: 10.3221/IGF-ESIS.37.36 274 Preparation of magnetic nanocomposites. The polymer composites are prepared manually by mixing of the diluted with water unsaturated resin and hydrosol of γFe 2 O 3 nanoparticles applying different concentrations. The sum of the added water and nanoparticles solution is equal and corresponds to degree of filling 0.5%. R ESULTS AND DISCUSSION t is well known that maleic, respectively fumaric bonds in the unsaturated polyester resins are not able to homopolymerize. In the presence of another unsaturated monomer, copolymerization takes place and the molecules of the unsaturated polyester resins have been cross-linked (bonded molecularly by the second monomer). Styrene and, more seldom other vinyl monomers are used most often for this purpose [21]. In this investigation, unsaturated polyester resin containing 44% styrene was used. Initially, the copolymerization of the unsaturated polyester resin containing 44% styrene was performed using different amount of initiator in order to determine the time for reaching the optimal copolymerization temperature during the process (Fig. 2). It was established that during the copolymerization reaction, the increased amount of initiator lead to higher reaction temperatures reached at shorter times. The same dependence was established for the change of adiabatic temperatures with the time (Fig. 3). On the base of these results, the initiator concentration of 2 wt.% (or 0,4 g for 20 g resin) was chosen as an optimal concentration for the copolymerization process. 0 20 40 60 80 100 120 140 160 180 1 2 3 4 5 6 7 8 9 10 11 12 13 t, min T, °C 0.3 g 0.4 g 0.5 g 0.6 g 0.7 g Figure 2: Dependence on the reaction temperature with the time for the copolymerization of unsaturated polyester resin with different amount of initiator. The examination on the extracted substances and swelling in resin solvent showed that regardless of the way in which it is heated and cooled, the reaction does not complete. The copolymerization processes proceeded slowly. Therefore after reaching of max exp T , the sample is transferred to the thermostat at temperature equal to the temperature max exp T . After heating for 1 hour, the sample is placed in the reactor and the rate with which the temperature decreased is measured (Fig. 3). It was established that after one hour of keeping the maximum temperature, the copolymerization process is completed. The extracted substances are decreased until the minimum values – under 4%, and the swelling in ethyl acetate decreased below 2.3%. To prepare magnetic nanocomposites on the basis of unsaturated polyester resin Fe 2 O 3 nanoparticeles are synthesized according to eq. 1: FeCl 2 (1mol) + FeCl 3 (2mol)→Fe 3 O 4 →oxidation γFe 2 O 3 The synthesized Fe 2 O 3 nanoparticles used as filler to prepare magnetic nanocomposites possess an average hydrodynamic diameter ( D h ) of 60±0.7 nm at particles size distribution (PDI) of 0.38 as measured by DLS (Fig. 4). I