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The microwave synthesis of Ag nanoparticles on zinc stearate (ZnSt/Ag) was performed to obtain an antimicrobial additive for a polypropylene matrix. Thermoplastically prepared polymer composites contained (1, 3, 5 and 10) % of mass fractions of ZnSt/Ag. The effect of the presence of additives on the morphology and mechanical properties of composites was studied by scanning electron microscopy and stress-strain analysis. The antimicrobial activity of the composites was studied according to the ISO 22196 standard. The results showed that sufficient antimicrobial activity of the composites against both Gram-positive and Gram-negative bacterial strains was observed in the case of the composites with the highest filling studied. Keywords: antibacterial, polypropylene composite, zinc stearate, Ag nanoparticles Izvedena je bila sinteza nanodelcev Ag na cinkovem stearatu (ZnSt/Ag) z mikrovalovi, da bi dobili protimikrobni dodatek polipropilenski osnovi. Termoplasti~no pripravljeni kompozit polimera je vseboval (1, 3, 5 in 10) % masnega dele`a ZnSt/Ag. Vpliv prisotnosti dodatkov na morfologijo in mehanske lastnosti kompozitov je bil prou~evan z vrsti~no elektronsko mikroskopijo in analizo napetost-raztezek. Protimikrobna aktivnost kompozita je bila prou~evana skladno s standardom ISO 22196. Rezultati so pokazali, da je primerna protimikrobna aktivnost pri sevih, gram pozitivnih in gram negativnih bakterij, dose`ena v primeru kompozita z najve~jim prou~evanim dodatkom.

Abstract This work is dedicated to polyester urethane (PEU)-based biocomposites, with special focus placed on techniques for compatibilisation to heighten interfacial adhesion between the PEU matrix and flax fibres. Tests were conducted on the effects of modification so as to increase interfacial adhesion between the flax fibres and the polyester matrix. These tests involved a commercial silane-based compatibilising additive, two experimentally synthesised agents, oleic acid (OA) and di-tert-butyl peroxide (DTBP). Furthermore, the flax fibres underwent acid or alkali treatment. The biocomposites were characterised by gel permeation chromatography, infrared spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Mechanical properties were investigated through tensile testing. Biocomposites with a commercial silane-based additive and synthesised agent, based on maleic-anhydride, were assessed as the best solution. Nevertheless, all modifications, excluding alkali treatment of fibres, significantly increased the performance of the material.