engleski

POLYLACTIDE MODIFIED WITH GRAPHITE BASED FILLERS

Polylactide (PLA) composites with two types of fillers based on graphite, amorphous graphite (AG) and graphite flakes (GF) have been prepared. Graphite based materials are widely studied fillers due to their thermal characteristics and low cost. Methods of preparation were melt-mixing in a Brabender plasticorder at 190 °C and solution mixing in chloroform. The concentration of added fillers was: 0.1, 0.5, 1 and 5 mass % in Brabender mixer and 0.1 and 1 mass % of filler in case of solution mixing [1]. The homogeneity of composites was examined by SEM. Thermal properties of PLA and prepared composites were investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The mechanical properties of PLA and prepared composites were tested with the universal testing machine. Homogeneous distribution of filler without any agglomerates was achieved for both kinds of graphite fillers. However, due to the different shape and size of amorphous graphite and graphite flakes the fractured surfaces of composites differentiate significantly as it is shown in Fig. 1. Thermal stability of measured composites was improved significantly, with the exception of one sample. Composites prepared by melt-mixing displayed higher thermal stability relative to those prepared from solution. The influence of concentration of filler varied for different kind of filler and preparation method. The highest shift of initial degradation temperature was 60 °C. Results of DSC analysis reveal that preparation method influences the glass transition temperature (Tg) of prepared materials as opposed to the added fillers, which did not introduce any significant alteration of Tg regardless of their concentration. The mechanical tests performed on samples prepared by melt-mixing shown that addition of both kinds of fillers increased ductility of PLA. The difference between two kinds of added fillers was notified in Young modulus (E). Thus, composites with AG as filler displayed chiefly lower E modulus while in the GF composites it had similar value apart from composite with 0.1 mass % of filler that displayed an increase relative to PLA matrix.

graphite flakes, melt-mixing, solution mixing, thermal properties, mechanical properties

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