The micro response mechanisms of foamed polymer rehabilitation material under compression: From a closed cell view

Abstract

Non-aqueous reactive foamed polyurethanes are widely used in the non-excavation rehabilitation of infrastructures and fundamental engineering. However, the effect of a microscopic cell on the understanding of micro-mechanical properties of a polyurethane is not clearly stated. In this work, a molecular model of a polyurethane closed cell is established corresponding to the field emission scanning electron microscopy results. Molecular dynamics simulations were subsequently employed to investigate the effect of a closed cell on the micro-mechanical response of polyurethane during compression. Based on the layered non-affine displacement and internal structure variables, we find that the existence of cells reduces changes in the polymer chain structure, i.e., the bond stretching, bond angle bending, and dihedral angle rotation. This makes slippage of the polymer chain more violent, and the farther away from the centre of the cell, the greater the level of the polymer chain slippage. In other words, chain slippage plays a key role in reducing the mechanical properties of a polymer. What’ s more, it is found that the number of hydrogen bonds in the cell is significantly less than that in the elastomer, which also could reduce the mechanical properties of foamed polyurethane. This study provides an efficient route for studying the micro-mechanical characterization of foamed polyurethane.