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 nanoadhesive is prepared by dispersing carbon nano-fi bers into ultra-high temperature resistant epoxy adhesive. Prior to fabrication of PBI, the surface of PBI is ultrasonically cleaned by acetone and then modifi ed 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 unmodifi ed and modifi ed 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 signifi cantly 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 fi bers 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.

UV Photo-Oxidation of Polybenzimidazole (PBI)

“…As with PS [23], the radiation absorbed by the aromatic groups had a total energy content in excess of that required for bond scission producing free radicals on the PBI surface by reaction (2). Reactions (3)(4)(5)(6)(7) illustrate the formation of carbonyl-containing compounds involving the R• free radical [23].…”

“…Poly 2,2'-m-(phenylene)-5,5'-bibenzimidazole, better known as polybenzimidazole (PBI), or meta-PBI, is a high-performance polymer consisting of benzimidazole units, as shown in the Figure 1. PBI has high thermal stability, chemical resistivity, and mechanical strength, making it suitable for many applications [1][2][3][4], such as in high-temperature fuel cells [1,2,5,6]; redox flow batteries [7][8][9]; protective thermal coatings [3], and aerospace industries, where PBI may be exposed to ozone and UV radiation [4].…”

“…Poly 2,2'-m-(phenylene)-5,5'-bibenzimidazole, better known as polybenzimidazole (PBI), or meta-PBI, is a high-performance polymer consisting of benzimidazole units, as shown in the Figure 1. PBI has high thermal stability, chemical resistivity, and mechanical strength, making it suitable for many applications [1][2][3][4], such as in high-temperature fuel cells [1,2,5,6]; redox flow batteries [7][8][9]; protective thermal coatings [3], and aerospace industries, where PBI may be exposed to ozone and UV radiation [4]. Interfacial properties are a key aspect for the optimization of fuel cell membrane electrode assemblies [10] and redox flow batteries [7][8][9] to increase the conductivity and uptake of the proton carrier; the concentration of the polar groups on the polymer backbone must be maximized [11].…”

Thermally Fast-Curable, “Sticky” Nanoadhesive for Strong Adhesion on Arbitrary Substrates

“…Several attempts have been made to reduce the adhesive thickness while maintaining the high adhesive strength by surface modification, such as pretreatment of the target substrate with e-beam or γ radiation or chemical modification. − However, the effect of such treatments is temporary in most cases. The chemical modification of the substrate often requires specific surface functionalities on the substrate, and the modification procedure might be quite complicated, which substantially limits its applicability to various kinds of substrate materials.…”