Abstract
This study was focused on the synthesis and characterization of a fully bio-based unsaturated polyester resin (UPR) with good thermal properties suitable for the commercial production of composite polymers. UPRs based on different ratios of bio-based furan dicarboxylic acid (FDCA), itaconic acid, and diols were synthesized. The unsaturated polymers prepared were evaluated by differential scanning calorimetry, gel permeation chromatography, FTIR and 1H-NMR spectroscopy. The results showed positive effects of FDCA on the glass transition temperature (Tg) of these fully bio-based polyesters, especially when FDCA was combined with 1,2-propanediol. Optimal values of Tg were obtained in the range of 30–32 °C for UPRs synthesized starting with a higher concentration of FDCA in the monomer feed. The possibility of substituting styrene, which usually acts as a reactive diluent, with a greener and safer alternative during the crosslinking of UPRs, was also explored. Two bio-based reactive diluents were considered: dimethyl itaconate (DMI) and butanediol dimethacrylate. After crosslinking, an average Tg of 75 °C and a good crosslinking efficiency indicated by a gel content of 90% were achieved for the fully bio-based polyester obtained under milder reaction conditions and dilution with DMI. Life cycle assessment was performed on selected UPRs, and comparison with a reference fossil-based resin in terms of the calculated category indicator results confirmed the lower environmental impact of the newly prepared bio-based polyesters.
Highlights
Unsaturated polyesters (UPEs) are among the most versatile synthetic resins used in the manufacture of composite polymers [1, 2]
A standard fossil-based resin, i.e., an isophthalic-acidbased unsaturated polyester resin crosslinked with styrene;
This paper describes the production and characterization of bio-based unsaturated polyester resins as a step towards more sustainable industrial production of glass-fiber-reinforced composites based on a thermosetting matrix for the construction sector
Summary
Unsaturated polyesters (UPEs) are among the most versatile synthetic resins used in the manufacture of composite polymers [1, 2]. Unsaturated polyester resins (UPRs) have a wide range of applications, for example, in the construction sector, as well as in the field of transportation, tissue engineering and electronics [3,4,5]. We are currently in a transition from a fossil-based economy to the more sustainable production of industrial chemicals and materials compliant with a circular economy. This has led to interest among researchers and scientists in the integration of renewable resources as sustainable raw materials in the manufacture of UPRs [16,17,18]. Only a small number of studies have been carried out on bio-based thermosetting UPRs and few commercial products are available, despite their attractive properties and wide range of applications [20]
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