Natural oils from watermelon, cherry, black currant, grape and pomegranate fruit seeds were applied in the synthesis of biopolyols using the transesterification reaction. In this manuscript, the preparation possibility of open-cell foams from a polyurethane system in which petrochemical polyol was fully replaced with biopolyols is analyzed. Firstly, polyurethane foam systems were developed on a laboratory scale, and they were next tested under industrial conditions. It was shown that the foaming method has a significant impact on the foaming process and the cell structure of obtained foams as well as their thermal insulation properties. Based on the conducted research, it was found that the method of processing the polyurethane system has a significant impact on the properties of open-cell spray foams. Foams produced under industrial conditions have a much higher cell density, which has a positive effect on their selected physical–mechanical properties compared to foams produced on a laboratory scale. The open-cell biofoams obtained using a high-pressure machine had apparent densities 12–17 kg/m³, thermal conductivity coefficients 35–37 mW/m·K, closed-cell contents < 10% and were dimensionally stable at low and high temperatures.

This paper presents the effect of the isocyanate index of polyurethane foams on the properties of repolyols and rebiopolyols obtained through glycolysis and on the foaming process of the new polyurethane systems. An FTIR spectral analysis confirmed that as the isocyanate index decreased, the intensity of the bands’ characteristic of urethane and urea bonds also decreased, indicating a lower proportion of carbonyl groups and hard segments in the polymer structure. Simultaneously, an increase in the hydroxyl number of the repolyols and the rebiopolyols was observed, along with a decrease in their viscosity and average molar masses. Both effects are consequences of a lower degree of cross-linking in the parent foams. An analysis of the foaming process using a Foamat apparatus revealed that the viscosity and the molar mass of the repolyols and the rebiopolyols significantly affected the system’s reactivity, maximum reaction temperature, and the time required to reach it. Differences in foaming dynamics resulted in different cellular structures of the foams, their apparent density, and mechanical properties. The foams obtained from the repolyols derived from foams with a lower isocyanate index exhibited a lower degree of cross-linking and a lower strength, while the foams with the rebiopolyols tended to shrink. The intensity of the shrinkage was limited by a higher degree of cell openness. These results confirm the crucial role of the properties of repolyol and rebiopolyol in shaping the reactivity, morphology, and properties of final polyurethane foams, providing a basis for designing new, sustainable polyurethane systems.

Five types of fruit seed oils have been described from the perspective of their potential use in the synthesis of biopolyols. The overall goal is to increase the participation of biopolyurethanes in polymer production, aligning with the European Green Deal. Blackcurrant, cherry, grape, pomegranate, and watermelon seed oils were characterized by iodine value, acid value, density, average molecular weight, viscosity, and fatty acid profile. The thermal properties of the oils were also determined using thermogravimetry (TGA) and differential scanning calorimetry (DSC). In order to obtain reactive compounds for the synthesis of biopolyols, the vegetable oils were modified using the transesterification reaction with triethanolamine. The resulting biopolyols were characterized by their hydroxyl number, acid number, density, average molar mass, and viscosity. The biopolyols were then used to produce thermal-insulating polyurethane foams by completely replacing petrochemical polyols with counterparts derived from fruit seeds. The obtained foams were described by their closed cell content, apparent density, thermal conductivity coefficient, dimensional stability, maximum stress at 10% deformation, thermal stability, oxygen index, and water absorption. In addition, an analysis of the foaming process revealed that the properties of fruit seed oil after chemical modification had an impact on the properties of the open-cell polyurethane foams and the foaming process itself.

Biopolyols derived from solid fats of both vegetable origin (coconut oil (P/CO) and palm oil (P/PA)) and animal origin (pork fat (P/PO) and duck fat (P/DU)) were used to produce thermal insulation polyurethane foams. The biopolyols were characterized by hydroxyl numbers in the range of 341–396 mgKOH/g, a viscosity of 60–88 mPa·s, and a functionality of 2.3–3.4. Open-cell polyurethane foams were obtained by replacing from 50 to 100 wt.% of a petrochemical polyol with the biopolyols from solid fats. The most advantageous properties were found for the materials modified with the biopolyol based on pork fat, which was attributed to its high degree of cell openness. At a low apparent density, the foam materials were characterized by good dimensional stability. The use of solid fats offers new possibilities for modifying thermal insulation polyurethane foams.