Microfibers within fibers: A review

Abstract

Literature relating to the fundamental nature of the fibrous state is reviewed with the goal of illustrating evidence for the existence of a possibly fundamental morphological unit, the elemental microfiber or fibril. Following a short summary of the rather well documented situation in natural fibers, the problem of the microfiber in synthetic fibers is probed in terms of phenomena in solution and bulk polymeric systems. The reviewed literature indicates the existence of unique, elemental microfibers in synthetic fibers is largely tenuous; however, there is wide evidence of the existence of complex elongated structures axially aligned within macrofibers which future work may resolve into a central microfiber. The structural complexity appears to simplify for transformations occurring in high shear fields. This review covers articles through 1971, and it is notable that in 1971 approximately 100 articles of high relevance appeared in major journals.

Ultrafine formation of optically transparent polyacrylonitrile/polyacrylic acid nanofibre fibrils via electrospinning at high relative humidity

“…Tucker and George mentioned that PAN fibrils were usually 5-3500 nm in diameter [15]. Warner et al reported that PAN fibrils exhibit a periodic structure along the axis with an 8-10 nm diameter [16].…”

Fibrils separated from polyacrylonitrile fiber by ultrasonic etching in dimethylsulphoxide solution

“…8 Tucker and George mentioned that the PAN fibrils are normally in the range of 5-3500 nm in diameter. 9 Warner and Uhlmann reported that the PAN fiber exhibited a periodic structure along the fiber axis with 8-10 nm diameter. 4 Hinrichsen and Orth detected periodical structure of drawn PAN by small-angle X-ray scattering and observed the exposed periodical morphology by high frequency discharge of activated oxygen.…”

Correlation between fibril structures and mechanical properties of polyacrylonitrile fibers during the dry‐jet wet spinning process

“…To some degree, the fibril‐pore structures are regarded as a fundamental morphological unit of PAN fibers . The macroscopic properties of the PAN fibers are in part derived from their morphologies, which have the key influence on the mechanical properties.…”

“…19,20 To some degree, the fibril-pore structures are regarded as a fundamental morphological unit of PAN fibers. 21 The macroscopic properties of the PAN fibers are in part derived from their morphologies, which have the key influence on the mechanical properties. To date, many researches and methods have been carried to improve the understanding of the morphology of the fibrils structures and possible correlation between mechanical properties and the fibril structures of PAN fibers.…”