Determination of chemical structure, mechanical properties and combustion resistance of polyurethane doped with boric acid

Abstract

The low fire resistance property of pristine polyurethane (PU) restricts its areas of usage in domestic applications and especially in the furniture industry. Therefore, PU based materials should be non-flammable besides having favorable mechanical and chemical properties. In this study, boric acid (BA) was added to the polyurethane foam as fire retardant. The effect of amount of BA (5%, 10%, and 15% (w/w)) on fire retardancy was examined. The thermal properties and the surface morphology of the structures were investigated. The amount of BA affected surface morphology. It was observed that BA affects the density and compressive strength in three directions with the physical change it causes in the cell structure. In the X-ray diffraction analysis of the unmodified hard polyurethane and the hard polyurethanes containing BA at different amounts (5%, 10%, and 15% (w/w)), the peaks were observed to appear in three different groups. The thermal stability of the rigid PU treated with BA was investigated via thermogravimetric analysis and the limiting oxygen index (LOI) analysis. The electromagnetic interference shielding effectiveness (EMI SE) was measured via a system consisting of two anechoic boxes and receiving and transmitting antennas. Four different temperature zones were observed when examining the thermal behavior via differential scanning calorimetry. Single source flame test, UL94 test and cone calorimeter tests were performed to determine the ignition property of BA doped PU. It was determined that BA is a better fire retardant than other chemicals also for the low toxicity of the combustion products formed.