The influence of vegetable-oil based polyols on physico-mechanical and thermal properties of polyurethane foams.

Polyurethanes (PU) during the last 50 years have become one of the most developing polymers and it is almost impossible to find an industry field, where they are not used. This term concerns a wide range of materials, both expanded and non-expanded products. PUs are widely used in many applications as foams (flexible, semiflexible and rigid foams), elastomers, adhesives, fibers and obtained by the exothermic reaction of an oligomeric polyol (the substance which contains at least two hydroxyl groups) and polyfunctional isocyanates. PU foams are considered to be one of the most efficient materials for insulation with many desirable properties (very low conductivity, low density and water absorption, dimensional stability and high ecoeficiency index to save energy). Nowadays, rigid polyurethane foams are synthesized using vegetable-oil based polyols, which is connected to their abundance and economy. What is more, materials synthesized from renewable resources can almost fully replace their petrochemical analogs. Several types of vegetable oils have been already used, such as soy bean oil, palm oil, linseed oil and sunflower oil. Such oils are characterized by low amount of functional groups, however present in the structure unsaturated bonds can be successfully converted into hydroxyl groups. The great possibility is using waste cooking oil to synthesize polyol, but the biggest problem is low number of hydroxyl value and contaminations from food. This short communicate presents a discussion about the influence of various polyol systems on physical, mechanical and thermal insulation properties, as well as on the cellular structure of PU foams.