Hybrid Silica Aerogels

Abstract

The ever-growing demand on single use food packaging materials made from expanded polystyrene (EPS) comes at a high price. Careless disposal at the place of consumption leads to environmental pollution. Driven by wind and collected by rivers, an incredible amount of EPS reaches the oceans. Large garbage patches are the shameful result which will outlive the responsible due to ultralow degradation rates. Aiming at the replacement of EPS products we are developing biodegradable hybrid aerogels from polymers and silica. The combination of a ductile polymer aerogel network that covers the brittle silica phase is a promising strategy to overcome the biggest drawback of silica aerogel when handled - dustiness. Hydrophobic silica aerogel in liquid phase was mechanically treated. The efficient breakdown of particles to submillimeter sizes was dust free and scalable. Resulting suspensions were thickened with polymer. With our focus on scalability, we employed different high throughput methods to produce hybrid gel bodies of various shapes. After solvent exchange to ethanol hybrid gels were supercritically dried with CO2. Following physisorption measurement practice hybrid aerogels showed high specific surface areas. A uniquely shaped hysteresis of investigated hybrid aerogels revealed dual mesoporosity. Scanning electron microscope investigations revealed a homogeneous polymer network in which silica particles were embedded. With our main development focus on insulation performance the heat flow method was used to measure the thermal conductivity of hybrid aerogels at values that are one third below of commercial EPS. Monolithic structures made from hybrid aerogels combine lightweight, thermal insulation and biodegradability. Our hybrid silica aerogels are a sustainable alternative to EPS.