Application of constant volume - variable pressure (time-lag) method to measure oxygen gas diffusion through polypropylene pipes

In this study, we have successfully applied constant volume - variable pressure method to measure oxygen gas diffusion coefficient of polypropylene-co-ethylene random copolymer pipes on the bases of Fick's laws of diffusion in cylindrical coordinates. Results showed that oxygen diffusion coefficient of polypropylene-co-ethylene random copolymer in the form of extruded plastic pipe is significantly different from thin films and sheets, mostly due to differences in plastic fabrication process yielding different orientation and crystallinity. Furthermore, long term oxygen diffusion coefficient of polypropylene pipes depends on the type of aging that the polypropylene pipes exposed during its service life. Oxygen transmission rate of single layer polypropylene pipes found higher than permissible value specified in building standards.