Synthesis and Mechanical Characterization of Ambient-Dried and Hydrophobic Poly(isocyanurate-urethane) Aerogels

摘要

Aerogels are low-density, nanoporous materials with high specific surface area. Traditional aerogels are mainly based on silica with a wide range of engineering applications such as thermal insulation and vibro-acoustic dampening. However, silica aerogels suffer from an extreme fragility that confines their applications only to the space exploration projects. One approach to overcome this issue is to introduce a new class of aerogels with flexible building blocks named as polymer aerogel. In this presentation, a mass-producible synthetic protocol for the preparation of a hydrophobic polymer aerogel, poly(isocyanurate-urethane) aerogel, with densities as low as 0.28 g/cm3 and porosities as high as -77% along with rubber-like elastic behavior is introduced. The mechanical properties of the aerogels are systematically characterized at different loading and environmental conditions. These aerogels show high thermal stability up to 300 C with only less than 3% mass-loss while the glass transition was below or at room temperature at all densities. Notable dependencies in the mechanical behavior of the obtained aerogels have been observed with respect to bulk density and strain-rate. For instance, the aerogels were linear-elastically stretchable without any yielding up to at least 120% tensile strain. Furthermore, the aerogels were studied under cyclic loading-unloading compression tests, which pointed to a very repeatable and stable behavior with a negligible drop in maximum stresses and absorption energies after the second cycle. Dynamic properties of the aerogels have been also measured using multiple-frequency dynamic mechanical analysis at various temperatures and a split Hopkinson pressure bar system. The compressive properties at high strain rates were increased by orders of magnitude with respect to the quasi-static counter-results, indicating high strain rate dependency in this class of aerogels.