Reducing the dependency from petroleum-based monomers and crosslinkers is an increasingly important goal for the plastics industry. This is being enabled by the growing diversity and availability of alternative biobased products derived from renewable resources, some of which are compatible with the production of more sustainable resins for high-performance applications. This paper presents the development of unsaturated polyesters (UPs) and their crosslinked resins (UPRs) based on 2,5-furandicarboxylic acid (FDCA) and other biobased building blocks. The original features of these UPs are derived from (i) the use of FDCA as an aromatic monomer replacing phthalic anhydride, (ii) the introduction of a FDCA–isosorbide (ISO) block into the polyester backbone with the presence of unsaturations provided by biobased fumaric acid, (iii) the use of ISO and 1,3-propanediol instead of ethylene glycol and 1,2 propylene glycol, and (iv) the reduction of styrene content using 2-hydroxyethyl methacrylate. The developed UPRs have a similar thermal and mechanical behavior to the petrochemical ones, presenting glass transition temperatures up to 102 °C, tensile modulus and strength up to 3.9 GPa and 63.3 MPa, respectively, and viscosity between 800 and 1250 cP, making these resins greener alternatives to fully petroleum-derived UPRs for high-performance applications.

This paper presents an experimental study of the wet freeze–thaw (FT) durability of a fibre–polymer composite produced by vacuum infusion using an innovative bio-based unsaturated polyester resin (UPR) and basalt fibres. As the benchmark, an equivalent composite produced with a conventional (oil-based) UPR was also tested. The composites were preconditioned in water immersion for 30 days at 20 °C followed by exposure to wet FT for up to 300 cycles; each FT cycle consisted of 3 h in dry freezing condition (−20 °C) and 8 h in thawing condition (23 °C) submerged in water. The composites’ properties were assessed after preconditioning and after 100, 200, and 300 FT cycles, through mechanical (tensile, compressive, in-plane shear, interlaminar shear) and thermomechanical (dynamic mechanical analysis) tests. Gravimetric and scanning electron microscope analyses were also carried out. The results obtained show that the preconditioning stage, involving water immersion, caused most of the damage, with property reductions of 5% to 39% in the bio-composite, while in the oil-composite they ranged between 4% and 22%, being higher for matrix-dominated properties. On the other hand, FT alone had an insignificant effect on the degradation of material properties; after exposure to FT, property recovery was observed, specifically in matrix-dominated properties, such as interlaminar shear strength, which recovered by 12% in the bio-composite during exposure to FT. The overall performance of the bio-composite was inferior to the conventional one, especially during the preconditioning stage, and this was attributed to the hydrophilicity of some of the components of its bio-based resin.

The growing concern over climate change and sustainability is promoting the development of partially bio-based unsaturated polyester resins (UPRs). However, being developed from renewable sources does not necessarily guarantee a better environmental profile for these materials, which justifies a detailed investigation of their environmental impacts. This paper presents a cradle-to-gate life cycle assessment (LCA) of five recently developed bio-based UPR formulations comprising renewably sourced chemical compounds, namely fumaric acid, dimer fatty acid, 2,5-furandicarboxylic acid, 1,3-propanediol, and isosorbide, as well as partially replacing styrene (50%) with 2-hydroxyethyl methacrylate as reactive diluent, considering inventory data from literature and purpose-made processes. As a benchmark, a typical oil-based UPR composition was also considered. The bio-based UPRs show improved environmental performance in various categories (e.g., climate change total, ozone depletion), reducing environmental impacts up to 90%. On the other hand, worse environmental performance was found in acidification, eutrophication (freshwater, terrestrial), and renewable primary energy impact categories. The main contributors to the higher impacts of the bio-based UPRs were found to be 2,5-furandicarboxylic acid, 1,3-propanediol, and 2-hydroxyethyl methacrylate. Fumaric acid and 1,3-propanediol have significant contributions to CO₂ sequestration. The single scores for the bio-based UPRs also show a reduction in impact ranging between 18 and 39% compared to the oil-based UPR.

This article describes the numerical modeling to investigate the safety factor of the quarry and dredging mining methods in the Volagonj area of Sylhet district in northeast Bangladesh. Two kinds of numerical models (A and B) are presented here. Both models consist of a single zone that includes gravelly sand deposits with some fine silt and clay. The zone also bears homogeneous rock/soil physical characteristics. Model A assumes safety factor of dredging mining method with variable slope angles and water column height of 40 m. Model B assumes safety factor of the quarry mining method associated with variable slope angles, where water column of the riverbed has not been considered. The numerical modeling results reveal that the safety factor of the model A ranges from 1.56 to 1.04. The safety factor ranges from 1.32 to 0.81 for model B. The calculated safety factor of the Volagonj rock quarry implies that the slope angle should not be greater than 70o for the dredging mining method. Because the critical safety factor values are 1.07 and 1.04 associated with slope angles 75o and 80o, respectively. For the case of the quarry mining, the appropriate slope angle also should not be greater than 60o.

The pursuit for more sustainable fibre-polymer composites has motivated the development of renewably sourced bio-based resins. Although these can provide short-term performance similar to that of conventional composites, uncertainties about their long-term durability are still an important limitation. This study investigates the freeze-thaw (FT) durability of a partially bio-based unsaturated polyester resin (UPR) composite, incorporating fumaric acid, 1,3-propanediol, and isosorbide, and reinforced with glass fibres, comparing its performance to that of an oil-based counterpart with identical reinforcement. The composites were preconditioned by immersion in water at 20°C for 30 days, followed by exposure to 300 FT cycles. Each FT cycle consisted of 3 h of dry freezing at −20°C, 8 h of thawing submerged in water at 23°C, and 2.5 h for temperature transitions. Water uptake at 20°C was monitored for up to 180 days. The materials were assessed through mechanical (tensile, compression, in-plane shear, interlaminar shear) and thermomechanical (dynamic mechanical analysis) testing. Most degradation occurred during preconditioning, with property reductions of 20%– 40%, with higher incidence in the bio-based composite. FT ageing led to further but slower degradation in both composites. In-plane shear strength retention of the bio- and oil-based composite was 59% and 93%, respectively, after the preconditioning, which further reduced to 38% and 75% after 300 FT cycles. In comparison, the tensile modulus of both composites remained almost unaffected (∼4-8% reductions). The findings highlight the need for further optimisation of bio-based resin formulations to improve their environmental durability and enable wider structural application.