Nowadays, unsaturated polyester resins (UPR) are mainly obtained from non-renewable resources. The ever-increasing regulations and the continuous demand for more sustainability have led to extensive research towards more environmentally suitable alternatives to petroleum-based materials. However, one of the main disadvantages of bio-based UPR is their relatively high viscosity compared to petrochemical ones. In order to overcome this drawback, in this work, we investigated the possibility to lower the resin viscosity utilizing a mixture of dimethyl itaconate (DMI) and methyl methacrylate (MMA) as a reactive diluent. The effect of the DMI and MMA ratio on resin rheological properties was investigated. The optimal curing parameters were determined and all UPRs had a high gel content, which was shown to be dependent on the DMI and MMA ratio in the formulation. Furthermore, thermomechanical and mechanical properties of the resulting network were also found to be affected by the used reactive diluent mixture. A small substitution of DMI by MMA proved to be advantageous since it offers lower resin viscosity and improved mechanical properties.

The aim of this work was to investigate the influence of specific anions on the cross-linking process of highly methoxylated pectin using the following copper salts CuSO₄; Cu(C₂H₃O₂)₂; CuCl₂; and Cu(NO₃)₂ wherein the initial salt concentrations were varied from 0.5 up to 10 g l⁻¹. It was found that the anions affected the sorption capacity wherein the Cu²⁺ sorption capacity from the sulphate solution was the highest, while it decreased in the presence of CH₃COO⁻, Cl⁻ and NO₃ ⁻ ions, respectively. This difference was mostly pronounced at the higher initial salt concentrations (c₀(Cu²⁺) > 2 g l⁻¹). The obtained beads were characterized by FTIR, AAS, SEM/EDS microanalysis and mechanical compression tests up to 80% of deformation. The sorption data were applied to the Langmuir and Freundlich isotherm models and various calculated parameters confirmed the sulphate anion supportive nature in metal ion binding. The value of the K_f parameter for the cross-linking process of pectin in the presence of acetate, chloride and nitrate was approximately the same (K_f ≈ 0.027 g g⁻¹), while it was higher in the presence of sulphate anions by more than 20% (K_f = 0.0352 g g⁻¹). The predicted 1/n values (1/n < 1, 1/n > 1, 1/n = 1 for the sulphate, nitrate and acetate, and chloride anions, respectively) were the quantitative confirmation of the specific interactions involved in the cross-linking mechanism caused by different anions. The established anion influence was in accordance with the typical ion-specific influence on macromolecules in aqueous systems proposed by Hofmeister.

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.