Preparation of Ultrafine Polyurethane Fiber Web by Laser-Electrospinning Combined With Air Blowing Midori Takasaki, 1 Kentaro Hara, 2 Yutaka Ohkoshi, 2 Takayuki Fujii, 3 Hiroyasu Shimizu, 3 Masaharu Saito 3 1 Division of Domestic Science Education, Faculty of Education, Miyagi University of Education, Aobaku, Sendai 980-0845, Japan 2 Department of Advanced Textile Engineering, Faculty of Textile Science and Technology, Shinshu University, Ueda, Nagano 386-8567, Japan 3 KB SEIREN LTD, Sabae, Fukui 916-0038, Japan Thermoplastic polyurethane fiber webs were prepared using a laser-heated electrospinning process combined with air blowing. The effect of spinning conditions such as air flow rate and air temperature on fiber diameter and molecular weight was investigated. Although the average fiber diameter decreased with increased air flow rate at each air temperature, the diameter increased when the air flow rate was >15 NL min 21 . In addition, the fiber was comparatively thicker with an increase in the air tempera- ture. The variation in the fiber diameter tends to increase with the air flow rate, and a reduction in the molecular weight of the fiber by thermal degradation was sup- pressed. The thinnest and most uniform fiber with a diam- eter of 0.9 mm and a diameter coefficient variation of 15% was obtained at an air temperature of 25  C under an air flow rate of 15 NL min 21 . This fiber also had a minimum of decreased molecular weight. POLYM. ENG. SCI., 54:2605– 2609, 2014. V C 2013 Society of Plastics Engineers INTRODUCTION Thermoplastic polyurethane (TPU) fibers have a crosslinking structure of soft and hard domains and excellent flexibility, and thus exhibit significant potential as materials for clothing, sani- tary, and medical and industrial applications. In particular, non- woven TPU has been employed in sanitary applications including adhesive tape, diapers, and masks, and has been mainly produced using the melt-blowing process [1–4]. Melt blowing is an economic process for the formation of fine fibers by blowing hot air at high velocity; however, this process suf- fers from a high variation in fiber diameter. This results in non- woven containing uneven fibers, which can have a negative effect on products such as filters that require uniform fibers. Electrospinning, which is a spinning method used to form nonwoven from submicron- and nanofibers, has been actively investigated [5–24]. The electrospinning method is classified into solution and melt electrospinning. Although solution elec- trospinning requires a solvent, melt electrospinning can resolve issues of recycle cost and the toxicity of solvents because it is a solvent-free process. The melt electrospinning process involves heating of the polymer and equipment such as a mixing extruder with a screw [9, 10] and a syringe heated with a heater coil, cir- culator, and heat gun [11–15]. Zhmayev et al. [16] have demon- strated a gas-assisted polymer melt electrospinning process that provided polylactic acid fibers with submicron diameters. Laser-heated electrospinning (LES), which uses a CO 2 laser to heat the polymer, has also been reported [17–24]. The elonga- tional deformation of a molten polymer in a spin line generally tends to be unstable when the polymer is drawn with heating [25], so that a shorter heating time is preferred in the spin line. The LES method produces fine and uniform fibers and suppresses thermal degradation of the fibers because the fiber is drawn rap- idly by electrostatic forces while rapid and uniform heating is simultaneously applied by CO 2 laser irradiation. We have per- formed LES using various polymers and successfully obtained uniform and ultrafine nylon 6 and poly(L-lactide-co-e-caprolac- tone) fibers with average diameters of 1 mm and with a coeffi- cient of variation (C.V.) of <20% [22]. In addition, we have investigated the effect of LES conditions such as the applied volt- age, laser power, laser irradiation point, and the laser beam width on the diameter of TPU microfibers [24]. As a result, a TPU web could be fabricated from ultrafine and uniform fibers with an average diameter of 2.4 mm and a C.V. of 8%. In this article, we examine the LES process combined with air blowing (LES-AB) and investigate the effect of the LES-AB con- ditions (air flow rate, air temperature, laser output power, and applied voltage) on the average diameter of ultrafine TPU fibers, fiber diameter variation, and the molecular weight of the fiber. In particular, we focus on the effects of drag and cooling induced by air. The LES-AB process is expected to produce thinner and more uniform fibers while suppressing thermal degradation owing to the action of air drag in addition to electrostatic force. EXPERIMENTAL Materials TPU fibers (average diameter, 250 mm) supplied by KB Sei- ren were used for the LES-AB process. Laser-heated Electrospinning Combined with Air Blowing The LES-AB apparatus used in this study (Fig. 1) consists of a CO 2 laser system (PIN-30R, Onizuka Glass) and an electro- spinning system (NEU-010, Katotech) with concentric inner and outer nozzles. The TPU fiber was fed from the inner nozzle using a feed roller at a rate of 40 mm min 21 , whereas air was blown though the outer nozzle. The fiber was heated rapidly by laser irradiation (wavelength, 10.6 mm) and a high voltage was applied to the nozzle. The spun fibers were collected onto a Correspondence to: Midori Takasaki; e-mail: mitakas@staff.miyakyo-u.ac.jp, and Yutaka Ohkoshi; e-mail: yokoshi@shinshu-u.ac.jp Contract grant sponsors: KB Seiren, Ltd, Special Coordination Funds for Promoting Science and Technology of the project for “Innovation Creative Center for Advanced Interdisciplinary Research Areas” from the Ministry of Education, Culture, Sports, Science and Technology of Japan. DOI 10.1002/pen.23811 Published online in Wiley Online Library (wileyonlinelibrary.com). V C 2013 Society of Plastics Engineers POLYMER ENGINEERING AND SCIENCE—2014