The benefit of being acquainted with thermal properties, especially the thermal stability of polyurethanes (PU), and simplified methods for their improvement is manifold. Considering this, the effect of embedding different amounts of unmodified and surface-modified TiO₂ nanoparticles (NPs) within PU, based on polycaprolactone (PCL) and Boltorn^® aliphatic hyperbranched polyester, on PU properties was investigated. Results obtained via scanning electron microscopy, swelling measurements, mechanical tests and thermogravimetric analysis revealed that TiO₂ NPs can be primarily applied to improve the thermal performance of PU. Through surface modification of TiO₂ NPs with an amphiphilic gallic acid ester containing a C12 long alkyl chain (lauryl gallate), the impact on thermal stability of PU was greater due to the better dispersion of modified TiO₂ NPs in the PU matrix compared to the unmodified ones. Also, the distinct shape of DTG peaks of the composite prepared using modified TiO₂ NPs indicates that applied nano-filler is mostly embedded in soft segments of PU, leading to the delay in thermal degradation of PCL, simultaneously improving the overall thermal stability of PU. In order to further explore the thermal degradation process of the prepared composites and prove the dominant role of incorporated TiO₂ NPs in the course of thermal stability of PU, various iso-conversional model-free methods were applied. The evaluated apparent activation energy of the thermal degradation reaction at different conversions clearly confirmed the positive impact of TiO₂ NPs on the thermal stability and aging resistance of PU.

The scope of the present study was to prepare fully bio-based unsaturated polyester resins (UPRs) with comparable properties to the commercial formulations. The focus was set on the determination of the optimal prepolymer formulation using the same set of diacids (itaconic and succinic acid) and different diols (propylene glycol, isosorbide and neopentyl glycol) or its equimolar mixtures, keeping the fixed molar ratio of 1:1:2.1 in all feed compositions. Instead of commonly used styrene, bio-based dimethyl itaconate was used as a reactive diluent (RD). The rheology of the obtained resins was studied in detail. The effect of the used diol on structural (FTIR), thermal (DSC), thermomechanical (DMA), and mechanical (tensile) properties was explained. The properties of UPRs were found to be highly dependent on the diol used in the prepolymer formulation. The UPR with an equimolar ratio of propylene glycol and neopentyl glycol was shown to be the most promising candidate to compete with the commercial petroleum-based resins.

TiO2 nanoparticles, obtained by acid catalyzed hydrolysis of titanium isopropoxide, were surface modified by three gallic acid esters with different hydrophobic part length: octyl, decyl and lauryl gallate, and then used to prepare TiO2/epoxy nanocomposites. The characterization of the surface modified TiO2 nanoparticles was performed by FTIR and UV-Vis spectroscopy. The influence of different gallic acid esters and content of modified TiO2 nanoparticles on the glass transition temperature (Tg), rheological, barrier and mechanical properties of the nanocomposites was investigated by DSC, DMA, water vapor permeability test and König pendulum. The presence of the surface modified TiO2 nanoparticles in epoxy resin caused the increase of Tg and decrease of the water vapor permeability. However, the length of the nonpolar gallate part showed no effect on Tg of the synthesized nanocomposites, while the increase of the nanofiller content resulted in the increase of Tg. With increasing the hydrophobic part chain length of gallate ligand, the water vapor transmission rate decreased, while the hardness of the nanocomposites did not change.