Controlled development of pores in polyethylene terepthalate sheet by room temperature chemical etching method

Abstract

In the present work, a room temperature chemical etching (RTCE) method has been explored for controlled development of pores in the chlorine ions (115MeV) bombarded polyethylene terepthalate (PET) (25μm) sheets. In this pore development method, a mixture of ethanolamine and NaOH is employed. The pore-size distributions in thus formed PET track-etched membranes have been obtained by the capillary flow porometry, and compared with the results of PET track-etched membranes subjected to widely used chemical etching (CE) at elevated temperature. Multiple pore size distributions have been observed with the CE method. However, with RTCE, pores with single narrow pore size distribution have been observed. To further improve the RTCE method, the chlorine ions bombarded PET sheets have been sensitized with UV radiation (254nm) for 1h, and subjected to RTCE. The average pore-size has been found to increase with UV-sensitization without affecting the nature of pore-size distribution, indicating the possibility of formation of the track-etch membranes with different pore sizes. Track etching studies show that both bulk-etch and track-etch rates increase in RTCE with respect to the conventional chemical etching. The ratio of the track-etch rate to bulk-etch rate governs the shape of the pores. The conical shaped pores with small cone angles are observed when track-etch rate is significantly higher than the bulk-etch rate. However, in the present case, VT is observed to be not very much greater than VB (VT/VB<100), showing the formation of double bowl pores or conical pores with large cone angles. This has been confirmed by the FEG-SEM observations.