Bio-Polyurethane Foams Modified with a Mixture of Bio-Polyols of Different Chemical Structures

We report on rigid polyurethane (PUR) foams prepared using different contents of a mixture of two bio-polyols (20-40 php). The bio-polyols were obtained through epoxidation and a ring opening reaction. Different chemical structures of the bio-polyols resulted from the use of 1-hexanol and 1,6-hexanediol as opening agents. The bio-polyols were characterized by hydroxyl values of 104 and 250 mgKOH/g and viscosities of 643 and 5128 mPa·s, respectively. Next, the influence of the bio-polyols on the foaming process of PUR systems as well as the foam properties was evaluated. The bio-foams modified with different contents of the bio-polyols were next compared with a reference foam obtained using a polyether petrochemical polyol. The effect of the apparent density reduction as a result of replacing the petrochemical polyol was minimized by decreasing the water content in the formulation. It was found that the modification of the recipe by changing the content of water, acting as a chemical foaming agent, did not affect the foaming process. However, the introduction of the bio-polyols mixture limited the reactivity of the systems by reducing the maximum temperature of the foaming process. The bio-materials with comparable apparent densities to that of the reference material were characterized by similar values of the thermal conductivity coefficient and a decrease in their mechanical strengths. A deterioration of mechanical properties was caused by the plasticization of the polyurethane matrices with the bio-polyols containing dangling chains. However, all materials were dimensionally stable at room temperature.