RESEARCH ARTICLE Investigation of wicking phenomenon and tensile in three-layer composite nanofibrous PA/PLLA yarn Zeinab Moghbelnejad 1 | Ali Akbar Gharehaghaji 1 | Maryam Yousefzadeh 1 | Farideh Hajiani 2 1 Textile Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran 2 Faculty of Applied Arts, University of Art, Tehran, Iran Correspondence Maryam Yousefzadeh and Ali Akbar Gharehaghaji, Textile Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran 1591634311, Iran. Email: yousefzadeh@aut.ac.ir and aghaji@aut.ac.ir Abstract One critical property of a nanofibrous structure is the wicking behavior in contact with liquids. This work's purpose is fabrication and investigation of tensile and wicking properties of a newly designed three-layer nanofibrous yarn consisting of polyamide 6/poly(L-lactic acid) (PA/PLLA) with a similar idea to Bobtex spun yarn structure in which adhesion between core (PA) and sheath (PLLA) is provided with a thin layer of polymeric thin film. The tensile strength and strain decreased 32 and 46%, respectively, in a three-layer yarn compared with two-layer, that is, yarn without the adhe- sion film. In addition, the ultimate strength of the three-layer yarn was higher than a PLLA yarn. The vertical wicking test for three-layer nanofibrous yarn reveals that at short times, capillary rise kinetics follow the Lucas–Washburn law while increasing the take-up velocity of the take- up roller in yarn fabrication leads to increasing the maximum height of water in yarn. KEYWORDS electrospinning, nanofiber yarn, tensile properties, three-layer structure, wicking 1 | INTRODUCTION Nanofibrous yarns can be used for drug delivery sys- tems, medical wound dressings, sutures, and many other applications. Nanofibrous yarns can be produced via various methods. For single-layer yarns methods include a dynamic liquid support system, water vortex, self-bundling electrospinning, a suction vortex, and rotating collection via needleless melt electrospinning, and others. [1–4] Methods for producing multilayer yarns include two opposite asymmetric nozzles, the air-flow twisting method, coaxial electrospinning, and Bobtex spinning in combination with electrospinning. [5–8] Multilayer structures can have good wicking properties and can be used for drug- loaded sutures, high-sensitive humidity sensors, and so forth. Wicking is defined as the spontaneous absorp- tion of a liquid by capillary forces in a porous system. [9] Wicking can be modeled by two approaches. The more conventional approach uses the Lucas and Washburn theory, which models the porous media as a bundle of aligned same radii capillary tubes. In the newer method, wicking is assumed as a single-phase flow through the porous system based on Darcy's law. Wick- ing is a function of the microstructure that exists inside the porous system, the characteristics of the liquid, and time. [10] Wicking has many technological applications in humidity sensors, geotextiles, filtration, suture yarns, and tissue scaffolds; however, there is a lack of information concerning different yarn structures. The liquid capillary rise equation can be described by the well-known Hagen-Poiseuille law as Equation (1). [11] Received: 22 August 2020 Revised: 14 November 2020 Accepted: 16 November 2020 DOI: 10.1002/pen.25601 Polym Eng Sci. 2020;1–10. wileyonlinelibrary.com/journal/pen © 2020 Society of Plastics Engineers 1