Study on polyurethane elastomer modification for improving low-temperature resistance of high-capacity polyurethane elastomeric bearing for bridges

Abstract

• Side methyl groups in PTGL hindered the crystallization of soft segments in PUE. • Shear modulus of PUE decreased with incorporating PTGL at subzero temperatures. • HPEB prepared with new PUE still exhibited high enough vertical bearing capacity. • Adding PTGL could significantly improve the low-temperature resistance of HPEB. Seismic isolation laminated elastomeric bearings are applied worldwide in bridges to reduce vibration and prevent collapse. Currently, the high-capacity polyurethane elastomeric bearings (HPEB) are favored in long-span bridges due to their super-high bearing capacity, low cost, and simple manufacturing process. However, there are many countries and regions in the world with extremely cold climates and are covered by ice and snow. At subzero temperatures, the stiffness of polyurethane elastomers (PUEs), which are an important component of HPEB, increases significantly, rendering HPEB ineffective in protecting bridges in cold regions from earthquake hazards. In this work, an attempt was made to modify the PUE as well as to improve the low-temperature resistance of HPEB by introducing 3-methyl-tetrahydrofuran/tetrahydrofuran co-polyether glycol (PTGL). Specifically, a series of microscopic characterization experiments (FT-IR, AFM, DSC, and DMA) were performed to study microphase separation and crystallization phenomena of the newly developed PUE. Moreover, the mechanical verification experiments were performed for the PUE and HPEB with different amounts of PTGL, including tensile, compression, and shear tests. All tests are performed at 23, 0, −10, and −20 °C temperatures respectively. The mechanical experiments demonstrate that the introduction of PTGL significantly reduces the shear modulus ( G ) and horizontal stiffness ( K h ) of HPEB at low temperatures, that is, improves the low-temperature resistance of HPEB. Therefore, this research is of great significance for the application of isolation bearings in cold regions.