Issue 37

P. Velev et alii, Frattura ed Integrità Strutturale, 37 (2016) 272-279; DOI: 10.3221/IGF-ESIS.37.36 277 0.24 0.33 0.25 0.23 0.00 0.10 0.20 0.30 0.40 0.0 0.1 0.3 0.5 Magnetic nanoparticles , % Flexural strength, MPa Figure 7. Flexural strength of magnetic composites in dependence on the filler content in %. Magnetic nanoparticles content % ρ v , [ Ω.m] ρ s , [ Ω] 0 1.0.10 12 4.5.10 14 0.1 0.82. 10 11 2.0.10 13 0.3 0.42.10 11 1.5.10 13 0.5 0.35.10 11 1.0.10 13 Table 2 : Variation of ρ v and ρ s in dependence on the magnetic nanoparticles content The obtained values for the density of the magnetic composites are presented in Tab. 3. Magnetic nanoparticle content, % Density, g/cm 3 0 1.21 0.1 1.14 0.3 0.82 0.5 0.98 Table 3: Density of magnetic composite in dependence on the amount of the filler As seen the density of the polymer composites decreases with increasing the amount of the magnetic nanoparticles content. The decreased density showed that probably there are some gas formations in the resins. The observed lower values of the some physicomechanical properties in the magnetic composites in comparison to the pure resin is probably due to the detected decreased density in the composites with increasing the amount of magnetic nanoparticles content. The higher mechanical strength possesses the pure resin and the composite containing 0.1% magnetic nanoparticles. The pH nanoparticles solution is 3.5. Since the hydrolysis of UPER has to be conducted at pH 8, the amount of NH 4 OH which has to be added to the mixture has to be increased in order to reach the desired alkalinity of the solution with the increasing concentration of magnetic nanoparticles. The neutralization process probably provokes the gas formations in the composites. This state is confirmed from the results for the degree of weight (Fig. 8) and volume (Fig. 9) swelling of the polymer composites.