N Bhatnagar

Physico-chemical characteristics of high performance polymer modified by low and atmospheric pressure plasma

In this work, the effect of low pressure plasma and atmospheric-pressure plasma treatment on surface properties and adhesion characteristics of high performance polymer, Polyether Ether Ketone (PEEK) are investigated in terms of Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Atomic Force Microscopy (AFM). The experimental results show that the PEEK surface treated by atmospheric pressure plasma lead to an increase in the polar component of the surface energy, resulting in improving the adhesion characteristics of the PEEK/Epoxy adhesive system. Also, the roughness of the treated surfaces is largely increased as confirmed by AFM observation. These results can be explained by the fact that the atmospheric pressure plasma treatment of PEEK surface yields several oxygen functionalities on hydrophobic surface, which play an important role in increasing the surface polarity, wettability, and the adhesion characteristics of the PEEK/Epoxy adhesive system.

Electron beam modification of space durable polymeric nano-adhesive bonding of ultra-high temperature resistant polymer

Abstract This investigation highlights fabrication of ultra-high temperature resistant polymers such as polybenzimidazole (PBI) by high-performance nano-adhesive. High-performance nano-adhesive is prepared by dispersing carbon nano-fibers into ultra-high temperature resistant epoxy adhesive. Prior to fabrication of PBI, the surface of PBI is ultrasonically cleaned by acetone and then modified by atmospheric pressure plasma with 30, 60 and 90 s of exposure and low-pressure plasma with 30, 60, 120, 240 and 480 s of exposure. Surface characterization of the unmodified and modified PBI sheets is carried out by contact angle measurements and surface energy of the polymer is estimated. It is observed that the polar component of surface energy leading to total surface energy of the polymer increases significantly when exposed to atmospheric pressure plasma. Tensile lap shear strength of adhesive bonded PBI reveals that atmospheric pressure plasma is more useful than low-pressure plasma in terms of adhesive bond strength of PBI and increases further when fabricated by nano-carbon fibers dispersed epoxy adhesive. The nano-adhesive bonded PBI sheets are post-cured by electron beam radiation under the SLOWPOKE-2 nuclear reactor. Post curing under electron beam radiation further increases the adhesive bond strength considerably.