A novel apparatus based on a photoacoustic gas detection system for measuring permeation parameters of polymer samples

Gas permeability parameters of polymer samples were determined from measurements performed with a novel permeation apparatus, into which a room temperature diode laser-based photoacoustic (PA) system-as a sensitive and selective gas concentration measuring tool-was incorporated. The fully automatic and flow-through mode operation of the PA instrument makes it possible to perform the measurements on-line, i.e. sampling from the gaseous phase is eliminated. The system's performance was demonstrated by measuring methane permeation through rubber compounds used in flexible offshore pipes. The system proved to be capable of not only measuring the gas concentration throughout the entire permeation process with high precision, but also of following methane release from one type of rubber sample. A numerical fitting algorithm was introduced with which the measurement time required for the precise determination of permeability parameters can be reduced by a factor of 2-5.