Surface modification of PIPD fiber using nitric acid treatment

The poly-pyridobisimidazole (PIPD) is a new rigid rod polymeric fiber, which has an exceptional compression strength that permits it to be an alternative to many other fibers. However, its inert surface and smoothness prevents its functional performance. In this work, an effective acid treatment using nitric acid in different conditions was applied on the PIPD fiber to improve its surface properties. A several measurements were carried out to quantify the effect of this treatment on the mechanical and surficial properties. The experimental results of the X-ray photoelectron spectroscopy (XPS) detected the generation of oxygen polar groups on the surface of the treated fiber. Consequently, the interface shear strength (IFSS) increases by 25%. The scanning electron microscopy (SEM) also showed the increase of surface roughness on the fiber after the nitric acid treatment, and the atomic force microscopy (AFM) supports this observation. Actually, the roughness of the fiber (Ra) was increased from 88.7 nm to 225 nm. This major improvement affects the surface tension (ST), it was increased by 40% and the surface wettability was considerably improved.