Usage of E-Polytetrafluoroethylene (e-PTFE) Membrane for Managing Trabeculectomy Flap- Related Over-Filtration Due to Unavailability of Scleral Patch Graft during Nation-Wide Lockdown

Scleral flap tears during trabeculectomy are difficult to repair in a predictable fashion. Donor scleral flap reinforcements are commonly preferred for managing trabeculectomy flap-related over-filtration, leading to shallow anterior chamber (AC). Due to the advent of COVID-19 lockdown, especially in the initial phases, eye banking activities almost came to a standstill, with almost no corneal and/or scleral tissue retrievals. Hence, in this manuscript we have presented a mini case series with follow-up of two of our cases; where Gore-Tex (e-polytetrafluoroethylene) implant was used as an alternative to scleral patch graft, for managing trabeculectomy flap-related over-filtration, with their pros and cons. Though Gore-Tex implant stability in both cases were contentious, it still served the purpose of managing the flap-related over- filtration and subsequent shallow AC.

Improvement of Polytetrafluoroethylene Membrane High-Efficiency Particulate Air Filter Performance with Melt-Blown Media

Polytetrafluoroethylene (PTFE) membrane filters are widely used in low-load application areas, such as industrial cleanrooms, due to their low initial pressure drop. In this study, melt-blown (MB) nonwoven was introduced as a pre-filtration layer at the front end of a high-efficiency particulate air (HEPA) filter to improve the filter performance of the PTFE membrane. Pre-filtration reduces the average particle size, which reaches the PTFE membrane and reduces the dust load on the HEPA filters. A comparative analysis of the HEPA filters by composite MB and PTFE was conducted. Regarding the MB composite on the PTFE, low-weight and high-weight MB composites were effective in increasing dust filtration efficiency, and the dust loading capacity of the PTFE composite with high-weight MB increased by approximately three times that of the PTFE membrane. In addition, the filter was installed on an external air conditioner in an actual use environment and showed a high efficiency of 99.984% without a change in differential pressure after 120 days.

Impact of heavy hydrocarbon impurities on polytetrafluoroethylene (PTFE) membrane stability

Membrane contactor technology has attained considerable attention as a promising technology to reduce CO2 content in natural gas. In this study, the main objective is to investigate the effect of heavy hydrocarbons impurities, often present in natural gas, on polytetrafluoroethylene (PTFE) hollow fibre membrane. The membranes were immersed for months in n-heptane, 1-decene, benzene and toluene, and analysed periodically through its surface morphology, composition, functional groups, hydrophobicity, and thermal stability. The characteristics of PTFE fibres remained unchanged even after long term exposure with heavy hydrocarbons. This study provides a better understanding of the robustness of using PTFE membrane fibre for CO2 removal in membrane contactor system.

Influence of Ultraviolet Radiation on the Properties of Polymer Microfiltration Membranes

To improve the parameters of the process of membrane separation of oil-in-water emulsions, the surface of thin-film membranes of nylon, cellulose acetateб and polytetrafluoroethylene (PTFE) was treated with ultraviolet (UV) radiation in the wavelength range 280–320 nm at a radiation power of 36 W, during 1–10 min. As a result of exposure to UV radiation, a change in the mass of the membranes was revealed depending on the treatment time. Thus, for membranes made of nylon and PTFE, an increase in weight is not significant, while for a membrane made of cellulose acetate, a decrease in weight up to 2.5% was found. An increase in the wettability of the surface layer of a PTFE and nylon membranes, as a result of their exposure to UV radiation, has been established. Changes in the supramolecular structure of the membranes were confirmed by the results of Fourier transform infrared spectroscopy: an increase in the intensity of absorption bands in the IR spectra in the range 600–3600 cm-1 was revealed. An increase in the intensity of the absorption bands of the IR spectra after the treatment of the nylon membrane with UV radiation is associated with the destruction of the defective regions of the surface layer of the membrane as a result of oxidative destruction. A decrease in the intensity of the absorption bands in the IR spectra of the PTFE membrane is observed over the entire spectral range. In addition, the expansion of the bases of the most intense absorption bands related to stretching vibrations of CF2 groups (1203 and 1150 cm-1) was revealed, which may be associated with the formation of the oxide group of the C–O bond. That is, the surface layer of the membrane is oxidized, which leads to an increase in the membrane wettability. UV radiation also influenced the main parameters of the membrane separation of the oil-in-water-emulsion: an increase of up to 7% in the specific productivity of membranes made of nylon and cellulose acetate, depending on the time of UV treatment with a decrease in the separation efficiency was established. When the PTFE membrane was exposed to UV radiation, a decrease in the specific productivity of the process by 14% was observed with an increase in the separation efficiency of the studied emulsion by 14%.