engleski

MODIFICATION OF PROPERTIES OF PLA NANOCOMPOSITES

Polylactic acid (PLA) is a polymer that has had a huge impact on the evolution of the bioplastics industry during the last 30 years. It is linear thermoplastic polyester derived from renewable sources that displays properties such as bio-compatibility, bio-degradability as well as the ability to be molded into different shapes. The latest endeavours are moving toward durable bioplastics, which is desired for long-term multiuse application in automotive, electronics, and other industries. The main goal of this work was to show a simple method of preparation of polylactide nanocomposites using a synthesized hybrid filler nSiO2@Fe. Hybrid filler was used to possibly, in any way, affect electric properties of produced PLA nanocomposites. Hybrid filler was synthesized using a method of reducing an iron salt (FeCl3) to elemental iron, also known as zero-valent nano iron (nZVI, Fe0), with NaBH4 as a reducing agent of the chemical reaction.[1] Nanosilica was used as a carrier for the reduced nZVI particles. Nanocomposite material was produced using the melt-mixing method. PLA was used as a composite matrix, to which commercial silica nanoparticles (nSiO2) and new synthesized hybrid nanoparticles of silica and iron nanoparticles (nSiO2@Fe) were mixed as filler with different mass ratios (1 % nanosilica, 1 % nanosilica +0.05 % hybrid filler, 0.5 % nanosilica +0.5 % hybrid filler and 0.5 % hybrid filler). Synthesized hybrid nanoparticles were analysed using UV-VIS spectroscopy and scanning electron microscope (SEM). The size of particles was determined using the dynamic light scattering method (DLS). Results of SEM and DLS showed that synthesized nanoparticle filler nSiO2@Fe were still in range of nanometre-scale (178 ± 118, 85 nm), and with the UV-VIS spectra of the filler, we could confirm the existence of both nSiO2 and Fe0 in the hybrid particles. Structural and thermal properties of pressed nanocomposites were analysed ; SEM micrographics showed that mainly a homogeneous dispersion of both nanofillers was achieved. Only one of the samples showed a nonuniform dispersion and formation of large agglomerates of fillers in the matrix (0.5 % nanosilica + 0.5 % hybrid filler). Performed measurements of thermal conductivity and electric resistivity reveal that the thermal conductivity of the PLA nanocomposites was not affected by the addition of nanosilica or hybrid nanofillers. As expected, nSiO2@Fe hybrid filler had an impact on the electric properties of the nanocomposite. The properties improved because hybrid filler had lowered the values of measured electric resistance of the PLA nanocomposites. Electric properties of nanocomposites were highly conditioned by the dispersion of the nSiO2@Fe hybrid filler in the PLA matrix, which is consistent with the SEM results.

composites, melt blending, zero-valent nano iron, nanosilica

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