Leonel Matías Chiacchiarelli

The combined influence of chemical structure and cellular morphology on the performance of high-density polyurethane foams has received limited attention. In this work, three foams based on a commercial petrochemical polyol (SD441) were compared with three foams produced from a mixture of epoxidized soybean-oil polyol and glycerol at densities ranging from approximately 100 to 300 kg/m³. The biobased foams exhibited substantially lower compressive strength than the petrochemical materials, with longitudinal strength ranging from 0.60 to 4.07 MPa compared with 1.03 to 8.92 MPa for the petrochemical foams. Electron microscopy revealed larger cells, greater anisotropy, and pronounced morphological heterogeneity in the biobased materials, particularly at higher densities. Despite their lower initial storage modulus, the biobased foams exhibited greater resistance to thermally induced softening: at 170 °C, they retained approximately 32–39% of their initial storage modulus, compared with only 6–8% for the petrochemical foams. A second DMA heating run, together with FTIR and DSC results, indicated irreversible structural changes during the first heating cycle. The reduction in residual isocyanate content and changes in the carbonyl and amide II regions were consistent with further network development during heating, suggesting additional post-curing in the biobased foams. DSC identified two exothermic events in the biobased materials: a broad event between 60 and 245 °C, consistent with additional reactions, and a second event between approximately 255 and 300 °C that overlapped with the onset of thermal degradation observed by TGA. In contrast, the type of blowing agent strongly influenced the degradation temperature but had no significant effect on mechanical performance within the investigated density range. Overall, the results demonstrate a distinct trade-off between mechanical and thermomechanical performance in high-density biobased polyurethane foams, highlighting the influence of polyol molecular architecture, network development, and cellular morphology on their behaviour.

The growing demand for low-impact materials and the need to valorize agricultural residues have increased interest in mycelium-based biocomposites as sustainable alternatives for construction applications. This study developed and validated a production protocol for mycelium-based biocomposites derived from vineyard pruning residues (VPR). Viticultural waste was inoculated with Ganoderma spp. to obtain a cohesive and mechanically resistant material. After characterizing the VPR fibers, the growth rate and colonization capacity of three Ganoderma strains were compared by image analysis, and Ganoderma sessile was selected as the most suitable strain. Specimens were then fabricated to evaluate the effects of packing density, geometry, and drying conditions on shrinkage and deformation. The results showed that post-molding dehydration at 80 °C effectively minimized dimensional deformations and moisture content. Furthermore, packing density significantly influenced compressive and flexural performance, as well as dimensional stability. Densely packed composites exhibited superior mechanical behavior compared with loosely packed specimens, reaching a compressive strength of 0.23 MPa, an elastic modulus of 2.48 MPa, and a flexural strength of 0.39 MPa, thereby outperforming reported values for MBCs utilizing other natural fibers. Overall, the proposed protocol enables the fabrication of functional molded biocomposites from locally available vineyard residues, supporting the valorization of agricultural waste within cleaner production framework.

The transition toward sustainable thermoplastic polyurethanes (TPUs) is a key challenge for reducing the carbon footprint for a wide range of applications, from industrial to transportation, including advanced applications such as 3D‐printed sensors and soft actuators. In this study, a series of aromatic TPUs incorporating soy‐based crosslinkers with comparable hydroxyl functionality but different molecular weights were synthesized to elucidate the relationships among crosslinker structure, concentration, and isocyanate index. The use of a low‐molecular‐weight triol (92 g/mol) led to remarkable enhancements in mechanical performance, increasing the elastic modulus by 190% (up to 400 MPa) and tensile strength by 61% (up to 23.6 MPa) at only 2.5 wt%. Conversely, a high‐molecular‐weight triol (1000 g/mol) exhibited a soft plasticizing effect, reducing the modulus by 38% at 17.9 wt%. Despite these contrasting effects, Dynamical Mechanical Analysis (DMA) indicated that the addition of the biobased crosslinkers did not compromise reprocessability, while the isocyanate index was the dominant factor. These findings demonstrate the dual role of bio‐based crosslinkers, capable of either reinforcing or softening TPU matrices, offering a versatile design strategy to tailor thermomechanical performance while maintaining a biobased content exceeding 50 wt%.

Enhancing the flame retardancy of bio‐based rigid polyurethane foams (RPUFs) is a crucial step toward improving the sustainability of the polyurethane industry. In this work, we systematically analyzed the effect of increasing the isocyanate index (NCO _index ) and the flame retardant (FR) content using a polyol with high renewable content (> 97 wt.%). We found outstanding results regarding the CO _(g) /CO _2(g) index, the most important safety parameter in terms of human safety, whereas a significant reduction of 78% and 69.6% was observed as a function of increasing the NCO _index and FR content, respectively. In addition, the FR did not cause an increase in the total smoke production (TSP); on the contrary, it decreased up to 31.4% after increasing the FR concentration. The MAHRE parameter was also substantially improved, up to 40.6%, indicating the formation of a thicker char layer that protected the foam during burning. This was achieved simultaneously with outstanding improvements in the specific compressive strength of up to +155%. The studies were substantiated by a comprehensive physicochemical characterization using TGA analysis, water absorption, initial thermal conductivity, FTIR analysis, and cell geometry using SEM. These results are of paramount importance to promote the use of bio‐based RPUFs with enhanced fire retardancy.

Enhancing the flame retardancy of biobased rigid polyurethane foams is a crucial step towards improving the sustainability of the polyurethane industry. In this work, we systematically analyzed the effect of increasing the isocyanate index (NCOindex) and the flame retardant content using a polyol with high renewable content (>97 wt.%). We found outstanding results regarding the CO(g)/CO2(g) index, the most important safety parameter in terms of human safety, whereas a significant reduction of 78% and 69.6 % was observed as a function of increasing the NCOindex and flame retardant (FR) content, respectively. In addition, the FR did not cause an increase of the total smoke produced (TSP), on the contrary, it decreased up to 31.4% after increasing the FR concentration. The MAHRE parameter was also substantially improved, up to 40.6%, indicating the formation of a thicker char layer which protected the foam during burning. This was achieved simultaneously with outstanding improvements of the specific compressive strength of up to +155%. The studies were substantiated by a comprehensive physico-chemical characterization using TGA analysis, water absorption, initial thermal conductivity, FTIR analysis and cell geometry using SEM. These results are of paramount importance to promote the use of biobased rigid polyurethane foams with enhanced fire retardancy.

A systematic study of the post‐cure cycle of soy‐based polyurethane thermosets was conducted as a function of crosslinker content, post‐cure temperature and time. An improvement of 207% of the flexural strength, up to 175 MPa, was measured by increasing the crosslinking content to 60 wt% and by using a post‐cure cycle temperature of 110°C. Similarly, the flexural modulus also increased by 199%, up to 3.2 GPa, while maintaining a flexural strain to failure of 6.60%. In situ studies of the post‐cure cycle using dynamical mechanical analysis revealed the interplay between the two interpenetrating polymer networks as a function of crosslinker content. At a crosslinker content below 40 wt%, two rubbery to glass transition temperatures (T_g) were found at 60 and 200°C, respectively. At 60 wt%, only one T_g at temperatures close to the degradation temperature was identified (250°C). Scanning electron microscope micrographs of the fracture surface revealed the formation of stress induced cracks which were mitigated through the use of a temperature stepped post‐cure cycle. The formation of soft segments with high degradation temperatures (485°C) were revealed by thermogravimetric analysis, which can be attributed to the presence of additional covalent bonds such as allophanate and carbodiimide that were also identified through Fourier transform infrared analysis. The results revealed in this work are key for the development of biobased polyurethanes applied for the polymer composite industry. In this regard, this study represented the first analysis of the post‐cure cycle of a soy‐based polyurethane thermoset.

Thermosetting polyurethanes were obtained using an aromatic isocyanate and a hydrophobic polyol formulation obtained from epoxidized soybean oil (ESO) crosslinked with glycerin. A systematic DSC analysis of the effect of catalyst type, crosslinker concentration, isocyanate index and ESO crystallization on cure kinetics was conducted. The combination of a stannic catalyst at 0.2 wt% and glycerin at 20 wt% produced a cure kinetics governed by an autocatalytic heat flow where vitrification played a key role in the formation of chemical bonds. The evolution of T_g as a function of conversion, which followed Di‐Benedetto's predictions, supported the hypothesis that vitrification was a preponderant phenomenon during cure. Dynamic Mechanical Analysis (DMA) of a post‐cured sample revealed a Tg centered at 220°C, whereas quasi‐static flexural mechanical tests shown a flexural modulus of 2.14 GPa and a flexural strength of 99.4 MPa. Rheological experiments at isothermal conditions supported the hypothesis that vitrification played a key role in the evolution of apparent viscosity. A master model using Kim‐Macosko equations was obtained for the proposed formulation. The results presented in this work will serve to further extend the use of biobased polymers applied in the polymer composite industry.

The incorporation of nanofillers and the use of biobased polyols might have a deleterious effect on the aging performance of rigid polyurethane foams (RPUFs) applied in the insulation and marine industries. To study this, RPUFs obtained from petroleum based (RPUF) and castor oil (RPUF_RIC) polyols were nanostructured with bacterial nanocellulose (BNC) up to 0.3 wt%. Water immersion experiments revealed that the normalized water absorption (NWA) at the steady state was not affected by lower BNC contents (0.2 wt%) caused a decrease of up to 13.69%. The previous results reinforce the hypothesis that the incorporation of BNC in both conventional and biobased polyurethane systems do not cause significant changes on the aging performance of the resulting foams, provided that low BNC concentrations are employed.