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 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.

Replacing styrene with biobased monomers to produce fully biobased unsaturated polyester resins (UPRs) turned out to be quite a challenging task. Styrene has been recognized as a hazardous and a potentially carcinogenic substance for human health. Using dimethyl itaconate as an alternative reactive diluent to styrene, which can be obtained from renewable resources, enables low viscosity for easy manipulation of mentioned UPRs. Fully biobased UPRs in question were based on itaconic acid, succinic acid, and propylene glycol, which were then diluted with dimethyl itaconate. Having in mind that UPRs can be used as a matrix for composite materials, this paper examines the effect of different weight ratios of spent coffee grounds as a filler. To determine the application of thus obtained composite materials, characterization consisted of examining mechanical properties based on viscosity measurements, uniaxial stretching experiments, FTIR spectroscopy and gel content analysis.

In this paper, biocomposite materials were developed by reinforcing a bio-based unsaturated polyester resin with cellulose nanofibers, addressing the growing demand for sustainable and high-performance materials. The inherent hydrophilicity and abundant surface functionalities of nanocellulose, while advantageous in some applications, pose challenges for integration with hydrophobic polymer matrices such as unsaturated polyester resins. To overcome these limitations and enhance interfacial compatibility, a novel and eco-friendly surface modification approach was developed, using dimethyl itaconate as an esterification agent. This resulted in significant improvements in the mechanical and thermal properties of the biocomposites, as evidenced by a 23% increase in tensile strength when compared to neat resin, and an elevation in the glass transition temperature of all samples containing modified cellulose nanofibers. These findings emphasise the potential of the developed modification strategy to enhance not only the performance but also the sustainability profile of polymer composites.