TIME RESOLVED BUBBLE NUCLEATION IN POLYMER FOAMS

摘要

Foams are all around us, take many different shapes and can be used in many applications. In this study we are interested in improving the thermal insulation properties of foams, as an improved building insulation materials can save customers significant amounts of money in energy costs. In this study we are interested in improving the insulation performance of polymer foams used for thermal insulation, such as Styropor® or Styrodur®, which are polystyrene foams. A typical Styrodur® foam has a thermal conductivity of approximately 34 mW/m K in air at atmospheric conditions. In order to improve the thermal insulation properties of these foams we will reduce the average cell size of the foam. As the average cell size in a foam structure approaches the mean free path of gas molecules in air, the "Knudsen" effect begins to play an important role in determining the thermal insulation properties. When the cell size of a foam approaches the mean free path of a gas molecule, the thermal properties of the foam in air are comparable to the thermal properties of the foam in a vacuum, and the thermal insulation properties are therefore significantly improved. In order to reduce the average cell size of foams made by physical blowing an understanding of nucleation behavior of bubbles in polymers is required. We are therefore studying the fundamentals of nucleation and growth of bubbles in a polymer melt and measuring this growth using scattering techniques. The scattering techniques used in this study are high-speed static light scattering and high-speed x-ray scattering.