Implementation of Circular Economy Principles in the Synthesis of Polyurethane Foams

The main strategy of the European Commission in the field of the building industry assumes a reduction of greenhouse gas emissions by up to 20% by 2020 and by up to 80% by 2050. In order to meet these conditions, it is necessary to develop not only efficient thermal insulation materials, but also more environmentally friendly ones. This paper describes an experiment in which two types of bio-polyols were obtained using transesterification of used cooking oil with triethanolamine (UCO_TEA) and diethylene glycol (UCO_DEG). The bio-polyols were next used to prepare low-density rigid polyurethane (PUR) foams. It was found that the bio-polyols increased the reactivity of the PUR systems, regardless of their chemical structures. The reactivity of the system modified with 60% of the diethylene glycol-based bio-polyol was higher than in the case of the reference system. The bio-foams exhibited apparent densities of 41-45 kg/m³, homogeneous cellular structures and advantageous values of the coefficient of thermal conductivity. It was observed that the higher functionality of bio-polyol UCO_TEA compared with UCO_DEG had a beneficial effect on the mechanical and thermal properties of the bio-foams. The most promising results were obtained in the case of the foams modified in 60% with the bio-polyol based on triethanoloamine. In conclusion, this approach, utilizing used cooking oil in the synthesis of high-value thermal insulating materials, provides a sustainable municipal waste recycling solution.