During the investigations, functionalization of graphene oxide synthesized using modified Hummers’ method and its reduced form was performed. Mixtures of graphene oxide and reduced graphene oxide with pimelic acid and calcium hydroxide were prepared for functionalization. During the reaction, the molecules of pimelic acid were attached to the surface of graphene sheets. By forming links between the carboxylic groups of pimelic acid and graphene oxide, the durable connection was achieved. The functionalized graphene oxide and the reduced graphene oxide were used as additives in isotactic polypropylene crystallization. The influence of additives on crystallisation in non-isothermal conditions was examined using polarized optical microscopy and differential scanning calorimetry. The effect of the additives on the polypropylene structure was analysed using wide-angle X-ray scattering. For both functionalized compounds, the nucleating ability towards β-form of polypropylene was detected. Both additives showed the increase in the nucleation rate and promotion of growth of the β-form crystals. Nucleation efficiency similar to other nucleating agents used in the crystallization of the β-form of polypropylene was revealed.

Graphene and its derivatives, such as graphene oxide (GO) or reduced graphene oxide (rGO), due to their properties, have been enjoying great interest for over two decades, particularly in the context of additive manufacturing (AM) applications in recent years. High-impact polystyrene (HIPS) is a polymer used in 3D printing technology due to its high dimensional stability, low cost, and ease of processing. However, the ongoing development of AM creates the need to produce modern feedstock materials with better properties and functionality. This can be achieved by introducing reduced graphene oxide into the polymer matrix. In this study, printable composite filaments were prepared and characterized in terms of morphology and thermal and mechanical properties. Among the obtained HIPS/rGO composites, the filament containing 0.5 wt% of reduced graphene oxide had the best mechanical properties. Its tensile strength increased from 19.84 to 22.45 MPa, for pure HIPS and HIPS-0.5, respectively. Furthermore, when using the HIPS-0.5 filament in the printing process, no clogging of the nozzle was observed, which may indicate good dispersion of the rGO in the polymer matrix.

The alternative method of reducing the flammability of polyethylene terephthalate (PET) fibers, analogous to dyeing of PET fibers with dispersed dyes in a high-temperature bath, was proposed. A commercial organophilic montmorillonite Cloisite^®15A (C15A) was applied as a flame retardant. The aim of the presented work was to evaluate the effectiveness of the introduced modifier and the improvement of the flame-retardant properties of PET fibers by limiting oxygen index (LOI) and thermogravimetric analysis (TGA) measurements. Evolved gas analysis (EGA) by spectrometric method (FTIR) during coupled thermogravimetric analysis (TGA) was applied in order to confirm no increase in the toxicity of volatile degradation products released from burning modified fibers. The nanocomposite nature of modified fibers was confirmed based on the structural parameters of the fibers determined using wide-angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) X-ray diffraction methods.

In this study, flame-retardant poly(ethylene terephthalate) (PET) fibres were produced using a high-temperature bath method similar to dyeing fibres with disperse dyes. A mixture of aqueous solutions of silicon and phosphorus compounds was used as the flame retardant. Samples of the modified fibres were examined by thermogravimetric analysis. The residue left after limited oxygen index test was analysed by scanning electron microscopy. Effect of the flame retardant on changing the supermolecular structure of PET fibres was evaluated using wide-angle X-ray diffraction. Mechanical properties of the modified PET fibres as compared with standard fibres were also examined.