Production and characterisation of biopolyol based semi rigid polyurethane foams

The need for using environment-friendly and natural chemicals has been increasing due to growing environmental concerns. The sustainable chemistry efforts within this scope aim at limiting the use of petroleum based products. Since polyurethanes are one of the most commercially used polymers, the research on the production of various materials with bio-sources are focused on polyurethanes. Polyols and isocyanates are the two major components used in polyurethane foam production. The aim of this thesis is to use biopolyols from renewable sources instead of synthetic polyols to produce semi-rigid polyurethane foams. For this purpose, biopolyols obtained from different natural sources such as soy oil, castor oil, tall oil and biosuccinic acid were used. One component foam (OCF) technology was utilized for the foam production. Each biopolyol was tested in different ratios and the technical properties of the foams obtained were compared with the reference foam sample produced with only synthetic polyols. OCF technology is based on a prepolymer reaction in a vessel pressurized with blowing/propellant gases. The characterization of the prepolymer synthesized in pressurized vessel provides information about the performance of the foam during application. Therefore, in order to investigate the effect of different biomasses on semi-rigid foams, the prepolymers contained in the aerosol foams were also synthesized in atmospheric conditions and compared with the reference prepolymer. The structural and thermal properties of the prepolymers were determined by FTIR-ATR, TGA and DSC analyzes. For foam characterization, FTIR-ATR, TGA, mechanical (compressive strength, dimensional stability, tack free time and density determination) and morphological (Scanning Electron Microscopy (SEM)) tests were performed. The peaks of urethane bonds in FTIR spectra revealed that the polyurethane prepolymer synthesis, and then after the semi-rigid foam production have been successfully achieved in all of the samples with the selected method and raw materials. Biopolyol based polyurethane prepolymers and foams were thermally analyzed together with the synthetic reference samples. Thermogravimetric analysis results indicated that the use of biopolyols retards the thermal degradation. Comparison of the glass transition temperature (Tg) of the prepolymer synthesized using 100 % biopolymer with the syntethic prepolymer's (-33,4°C) showed that while soy oil and castor oil based polyol usage makes the structure flexible, biosuccinic acid based polyester polyol hardens it due to the ester bonds. The compressive strength results of the semi-rigid foams exhibited that the strength of the reference foam against compression applied to compress 80% of its volume was measured to be approximately 0.26 MPa, whereas the biosuccinic acid based polyester polyol foam has reached its maximum value of 0.84 MPa. The densities of all foams, including the reference, were measured to be in the range of 19 and 25 kg/m3. The dimensional stability was achieved with the maximum value of %5 and tack free time required for a good foam was measured between 6-10 mins in all samples. SEM images of the cell morphology of foams which were produced with the %25 biopolyol and reference sample showed that the use of biosuccinic acid-based polyester polyol adjusts the cell morphology by reducing the cell size. The results indicate that the semi-rigid foam production can be successfully performed using the biopolyols studied in this thesis. The closest values to the synthetic reference foam properties were obtained for the foams produced with the ratio of %25 biopolyol. Thus, as a result of our study, it can be concluded that including 25 % biopolyols in the production of OCF semi rigid foams can be a natural and sustainable approach without any performance concerns.