Effect of Low-Pressure Plasma Surface Modification on Filtration Performance of Chitosan Nanofibrous Respiratory Filter

Low pressure drop is highly desirable for respiratory filters. Surface activation plays an important role to enhance the filtration performance of respiratory filters. In this study, a three-layer composite respiratory filter was developed using a combination of polypropylene (PP) nonwoven layers and chitosan nanofibres (CSNF) with variable coating time (h) during the electrospinning process. To study the impact of surface activation on filtration performance, the outer surface of all the samples were modified using low-pressure plasma treatment. Filtration performance testing was conducted to determine the filtration efficiency (%), pressure drop (Pa), and quality factor (Q) results, before and after the surface treatment. The maximum values of filtration efficiency and quality factor achieved were 99.99% and 0.068, respectively. The lowest value of the pressure drop was 16.12 Pa. All the low-pressure plasma-treated samples showed higher filtration efficiency and quality factor compared to untreated samples due to a more effective capturing mechanism. However, pressure drop results indicated no significant difference. Furthermore, the decay of plasma treatment impact was analysed by using drop shape analysis method to measure the water contact angle on the surface of the samples. Results showed a gradual decrease in surface modification impact and the surface of the treated samples changed from hydrophilic to hydrophobic with the passage of time.